diff options
Diffstat (limited to '35639-8.txt')
| -rw-r--r-- | 35639-8.txt | 6802 |
1 files changed, 6802 insertions, 0 deletions
diff --git a/35639-8.txt b/35639-8.txt new file mode 100644 index 0000000..046c28d --- /dev/null +++ b/35639-8.txt @@ -0,0 +1,6802 @@ +The Project Gutenberg EBook of Schweigger on Squint, by C. Schweigger + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Schweigger on Squint + A Monograph by Dr. C. Schweigger + +Author: C. Schweigger + +Editor: Gustavus Hartridge + +Translator: Emily J. Robinson + +Release Date: March 20, 2011 [EBook #35639] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK SCHWEIGGER ON SQUINT *** + + + + +Produced by Ian Deane, Josephine Paolucci and the Online +Distributed Proofreading Team at https://www.pgdp.net. + + + + + + + +CLINICAL INVESTIGATIONS ON SQUINT + +A MONOGRAPH + +BY + +DR. C. SCHWEIGGER, + +PROFESSOR OF OPHTHALMOLOGY AT THE UNIVERSITY OF BERLIN + +TRANSLATED FROM THE GERMAN + +BY + +EMILY J. ROBINSON + +EDITED BY + +GUSTAVUS HARTRIDGE, F.R.C.S. + +LONDON +J. & A. CHURCHILL +11, NEW BURLINGTON STREET +1887 + + + + +TRANSLATOR'S PREFACE + + +The subject of Squint is so interesting that we venture to think an +English rendering of this exhaustive monograph will be acceptable to +many ophthalmic surgeons and students. + +While adhering as far as possible to the spirit and style of the +original we have not hesitated here and there to give a somewhat free +translation. This has been partly necessitated by the difficulty of +finding an exact equivalent in English for all the terms used in the +original text. + +In the German Edition the old system of inches is used. We have (with +the consent of the author) altered these to the dioptric system. + + E. J. R. + G. H. + + + + +PREFACE + + +_Amicus Plato, amicus Socrates, magis amica veritas._ May my friends and +colleagues, whose views differ from mine, read the following +observations without prejudice. A fact, which does not agree with the +system, is generally worth more than theory, still it is very difficult +for even the most important fact to find recognition if it contradicts +received opinion. For theories and dogmas are narcotics, which are +necessary to men; some flatter themselves by composing them, while +others content themselves by satisfying their own craving for a creed. +Reasonably applied, they may be useful, but the boundary line is only +too easily over-stepped. It is the task of science to observe also +whether theories correspond with the progress of facts. The present +reigning theory on strabismus will have to submit to various +limitations; on the other hand, we are ready to leave to the scholastic +science of medicine and its followers certain dogmas which remain +unproved and which have nothing but the fact of their existence to +recommend them. + +The small compass of the following treatise proves that it was not +intended to exhaust the rich literature on the subject; I have only +referred to the same where it appeared to me necessary for the interest +of the work in hand. + +Above all, it has been my endeavour to treat the subject of this +treatise (which occurs so frequently in practice) in a way intelligible +to every physician, at the same time, however, to bring sufficiently +into notice those facts and views which are of value to my special +colleagues. + + C. SCHWEIGGER. + + BERLIN. + + + + +INDEX TO CONTENTS. + + +INTRODUCTION. PAGES + +Ordinary use of the word squint and its meaning. Apparent +squint. Paralytic and typical squint. Law of association. +Squint angle and linear measure of the deviation. +Permanent, periodic, latent, monolateral, and alternating +squint 1-8 + +CONVERGENT SQUINT. + +Donders' theory and the test of it by statistics. Limits +of error in the subjective and objective determination of +hypermetropia. Statistics of convergent squint. Hypermetropia +and favouring circumstances. Participation +of the accommodation. Preponderance of the interni +and insufficiency of the externi. Nebulæ of the cornea. 9-26 + +PERIODIC CONVERGENT SQUINT. + +In myopia, emmetropia, and hypermetropia. Intermittent +squint. Accommodative squint 27-35 + +CONVERGENT SQUINT IN MYOPIA 36-38 + +SQUINT FROM PARALYSIS OF THE ABDUCENS 39-40 + +HYSTERICAL SQUINT 41-43 + +DIVERGENT SQUINT. + +Absolute and relative divergence. Statistics of divergent +squint. Causes 44-49 + +DYNAMIC SQUINT, INSUFFICIENCY OF THE INTERNI AND +MUSCULAR ASTHENOPIA. + +Diplopia and power of overcoming prisms. Facultative +divergence. Dynamic absolute divergence. Parallel +strabismus. Relative divergence in myopia. Muscular +asthenopia. Dynamic relative divergence. Treatment +of muscular asthenopia 50-63 + +BINOCULAR VISION IN SQUINT. + +Single vision in squint. Theory of exclusion. Forms of +binocular vision in squint 64-74 + +VISUAL ACUTENESS OF THE SQUINTING EYE. + +The trial of vision and its results. Appearance, diagnosis. +Peculiarities and statistics of congenital defective vision. +Relation of the same to defective vision in squint 75-104 + +CURE OF SQUINT. + +Spontaneous cure. Voluntary loss of the habit. Cure of +convergent squint by means of convex glasses. Strabotomy. +Tenotomy. Advancement. Result of the +operation and choice of methods. After-treatment by +means of influence on the ocular muscles and on the +accommodation. Aim of more extended results of the +operation. Artificial strabismus. Operation for periodic +convergent squint. Strabotomy in homonymous diplopia. +Operation for squint after paralysis of the abducens. +Operation for divergent squint and for periodic divergence. +Degree of the result of the operation. Determination +on the age best suited for operation 105-141 + + + + +SQUINT + +INTRODUCTION + + +By squinting, in the German vocabulary, is understood every oblique +direction of the visual axes. We prefer that the eyes which turn towards +us should do so in a straight line, and feel it to be something ugly and +out of harmony, if anyone squints at us. Æsthetic feeling is, however, +too individual and uncertain a guide to be laid down as a foundation for +the decision of questions of medicine. Parents have repeatedly brought +to me children said to squint, when frequent and careful examination of +them showed normal position of the eyes and perfect binocular vision; +the over-anxious parents had taken mere physiological convergence or +side glances for squinting. + +On the other hand, cases appear in which such a strong semblance of +squinting is present, that at the first glance one cannot say whether +absolute fixation takes place or not. A very simple examination suffices +to determine these doubts:--Cause the patient to gaze at a certain point +on the horizon and cover first one eye and then the other. If the +covered eye remains stationary, no squint exists, but if it is observed +that when giving one eye its freedom and covering the other, the first +must make a movement in order to fix the object to be looked at, it is +only a question of discovering whether the squint does not simply ensue +from the covering up of the eye. We will return to these cases at +greater length, in order to occupy ourselves now with the fact, that the +examination above referred to proves the non-existence of strabismus, +while appearance still allows us to suspect its existence. + +This apparent contradiction finds its explanation in the fact that the +scientific notion of squinting is determined by the direction of the +visual axes. Strabismus is present when one eye only is directed to the +fixed point, while the visual line of the other eye deviates from it. + +But we cannot see the direction of the visual line, we can only judge of +it from the position of the cornea. It is exactly that line which joins +the point fixed with the centre of the fovea centralis. We can determine +the position of the cornea by a perpendicular line passing through the +centre of the cornea; this does not coincide with the visual line but +deviates from it about 5° outwards. In the case of parallel lines of +vision the corneæ are directed slightly outwards, a position which we +are accustomed to consider as the normal one. If the angle formed by the +above-mentioned perpendicular and the visual line is larger than usual, +_i. e._ if the corneæ move further outwards than usual, the unusual +appearance strikes us, and gives us the impression of a divergent +squint. The enlargement of this angle, which is usually indicated as +Angle a, is a peculiarity of the hypermetropic eye; and where we have an +apparent divergent squint we may expect to find also hypermetropia, +while an apparent convergent squint occurs occasionally in myopia of +high degree. + +If we turn now to those cases in which a real deviation of the visual +line occurs, we must first consider the cause, and afterwards +distinguish it from paralysis of the ocular muscles. The faulty position +may be constantly present or it may only occur when the paralysed muscle +is called into action. It is almost invariably combined with double +vision; sometimes the latter is the prevailing symptom, whilst the +faulty position of the eye is in no way obtrusive, and can only be +proved by careful investigation. + +In contrast to paralysis of the ocular muscles stands the typical +concomitant squint, in which the squinting eye normally accompanies the +movements of the other. Transitional forms may thus be brought about, in +some of which the paralysis recovers, with complete or almost complete +restoration of movement, but with continuance of the squint. On the +other hand, in concomitant strabismus, restriction of movement towards +the opposite side not unfrequently develops itself. + +This impairment of movement has its origin generally in a want of use. +Those who squint have less need for movement, since one of their eyes is +already directed obliquely. In divergent strabismus this is apparent, +but in convergent strabismus the squinting eye governs the field of +vision on the side to which it turns. When the fixing eye is turned +towards the side of the squinting eye in convergent strabismus, the +latter, it is true, makes a concomitant movement, which does not, +however, bring it by a long way to the limit of the movement of which it +is capable. The defect of motion is therefore generally present in both +eyes, and is usually most marked in the squinting eye. Often, indeed, +there is present at the same time a congenital or acquired insufficiency +of the antagonistic muscle, but that want of use has also much to do +with it, is shown by the improvement of mobility that often follows even +short practice. + +From the law of equal innervation, which governs the movements of the +eyes, it follows that the fixing eye lapses into the associated +deviation as soon as the squinting eye is directed straight forwards. +If, for example, a convergent squinting eye is put into fixation, an +innervation of the external rectus, with which just as strong an +associated contraction of the internal rectus of the other eye, is +called forth; the direction of the squint then, as well as the degree of +deviation, is transferred from one eye to the other. It is naturally the +same with divergent squint. + +Squinting upwards or downwards seldom occurs as a symptom by itself; +more frequently it is associated with convergent or divergent squint. + +According to the law of associated movements, when an eye squinting +upwards is put into fixation, the other eye should make a movement +downwards, as normally both eyes move together up and down, yet this is +not always the case. For example, when an upward deviation is present in +convergent squint, it not uncommonly follows that the secondary +deviation of the eye which usually fixes is also inwards and upwards; +only exceptionally in cases of deviation in height of the squinting eye +does the sympathetic movement take place without change of height. +Sometimes with deviation of height, I found combined a distinct rotation +of the eye, generally thus, that together with the movement upwards was +combined a rotation of the vertical meridian outwards and _vice versâ_; +in fixing the eye a rolling inwards was combined with the movement +downwards. The other eye then usually showed a similar rotation (thus +the meridian of both eyes rotated simultaneously to the right or left), +but the deviation in height was not always the same. + +The law of equal innervation requires in alternate fixation, first with +one eye, then with the other, that the same degree of deviation be +transferred to the non-fixing eye. When exceptions appear, and the +deviation in the two eyes is unequal, it is (provided the inequality has +not been caused by attempted operation, or is the result of paralysis), +usually to be explained by the fact, that an accommodative movement +takes place when we are expecting an associated one. For example, if +there is convergent squint and hypermetropia in both eyes, but more +hypermetropia in one than the other, in alternate fixation it will be +found that the least hypermetropic eye always undergoes the greatest +deviation, because in fixation with the more hypermetropic eye a +stronger effort of accommodation unites itself with a corresponding +innervation of the internal rectus, which is transferred equally to the +other and non-fixing eye. Thus it happens frequently in divergent +strabismus, when one eye is myopic, the other emmetropic. If the latter +fixes an object stationed near the "far point" of the myopic eye, the +internal recti and the accommodation act simultaneously; on the other +hand if the myopic eye fixes, it wants no accommodation and the +emmetropic eye sinks into divergence. + +With regard to the immutability of the squint; it must not be understood +that the squint angle always remains the same with the same individual; +in most cases the amount of deviation varies, the squint is now less, +now greater; it is desirable however, to know the bounds within which it +fluctuates. + +To determine the degree of the squint one can either ascertain the angle +of the squint, or use v. Graefe's so-called linear measure of deviation. + +The squint angle is that angle, which the visual line of the squinting +eye encloses with the direction it ought normally to take--it may be +measured with the aid of a perimeter. The patient's head is so placed by +means of a chin rest, that the axis of the squinting eye is in the +centre of the arc of the perimeter; a distant point in the centre of the +field of vision is fixed. Behind the patient is a candle, the reflection +of which is thrown into the squinting eye by means of a plane mirror; +now slide the mirror along the arc of the perimeter, till the reflection +on the cornea stands in the centre of the pupil of the eye which is +under observation. The point which the mirror occupies on the arc of the +perimeter, indicates the squint angle. In deviation in height of the +squinting eye, bring the arc of the perimeter into the corresponding +direction and so measure at the same time the degree of deviation in +height. Were the method more exact than it is, one would be able to +measure the angle formed by the visual line and the axis of the cornea. + +To find the linear measure of the deviation, cover the fixing eye and +allow the squinting eye to fix. Hold a millimetre measure close to the +under lid, so that a chosen portion of it stands under the centre of the +pupil; uncover the other eye and when the squinting eye returns to its +deviation, it can be seen over which point the centre of the pupil +stands, and the linear measure of the deviation is thus obtained. The +secondary deviation of the other eye is measured of course in the same +way. If, in consequence of amblyopia, the squinting eye possesses no +certain fixation, the measure may be so held that the _nil_ point of the +division coincides with the lower punctum, and then in unchanged +fixation the portion lying under the centre of the pupil is determined, +first in the sound and then in the squinting eye. + +The execution of one or other of these forms of measurement is in every +case to be recommended, and if their exactness is not as perfect as can +be desired, still, on the other hand it should be remembered, that for +surgical treatment, an exact measurement of the deviation does not +possess the importance sometimes assigned to it, as in most cases the +squint angle shows considerable variations. + +In a large number of cases these variations are so great, that a correct +position of the eyes alternates with a more or less considerable squint, +which as the case may be, appears seldom or often, sometimes only under +certain conditions, and sometimes quite unexpectedly (periodic squint). +In some cases stationary or permanent squint begins with the periodic +form, however, one must not conclude that periodic squint is invariably +the precursor of the permanent form. In by far the greater number of +cases periodic squint continues unchanged without ever becoming +permanent. + +The transition from squint to the normal condition is formed by those +cases, in which the proper position of the eyes is maintained by a +desire for binocular single vision, while the elastic tensions of the +muscles are such, that squinting sets in as soon as binocular single +vision is rendered impossible (latent squint). + +The squint is generally one sided (monolateral), for the eyes in this +case are usually of unequal value, and the best is always preferred for +use. The eye which has the acuter vision is always made use of when +something has to be carefully observed. But when the acuteness of vision +is equal, and one eye is emmetropic and the other hypermetropic, or if +both are hypermetropic but in varying degree, the most hypermetropic eye +is always the squinting one; for with a greater power of accommodation +it does not accomplish more than the emmetropic or less hypermetropic +one with slighter expenditure of strength. Why should a man strain his +accommodation when no advantage is thereby gained? + +In most cases the squinting eye has also an available power of vision +and is on that account used for fixing objects which lie in the +direction of its visual axis; it can also be made to fix objects in +front, this occurs as soon as the other eye is covered; it remains as +the fixing eye till the next blinking of the lids, or movement to +another object for fixation, or till both eyes are closed for a short +time, when it returns to its former deviation. + +A true alternating strabismus, _i. e._ alternate use of first one eye +and then the other to fix objects straight ahead, only occurs when both +eyes are of equal value as regards weakness and acuteness of vision, or +when one is more conveniently used for near, and the other for distant +vision. In these circumstances one eye is always short-sighted and is +used for near objects, while the other is emmetropic (or in less degree +near-sighted or long-sighted) and is preferred for distant things. The +reason for the alternation lies in the necessity for the act of vision +itself; it begins regularly whenever distant and near objects are +alternately fixed. Alternating squint is usually divergent, with short +sight on one side, still convergent strabismus may occur under these +conditions. + + + + +CONVERGENT SQUINT + + +To Donders belongs the merit of having pointed out the presence of +hypermetropia in about two thirds of all cases of convergent strabismus. +The fact is undeniable, the theories built upon it are doubtful. Donders +declares no other conclusion to be possible, than this, that the +hypermetropia is the cause of the squint. "To see clearly, the +hypermetrope must accommodate vigorously for each distance. In looking +even at distant objects he must overcome his hypermetropia by exerting +his accommodation, and in proportion as the object approaches him, he +must add to it as much accommodation as the normal emmetropic eye would +use. The inspection of near objects requires then a special amount of +exertion. There exists, however, a certain connection between +accommodation and convergence of the visual lines. The stronger one +converges the more one has to put into action the accommodation. A +certain tendency to convergence cannot then be absent during any effort +of the faculty of accommodation." + +Right as these conclusions may appear, and as they really are, as far as +emmetropia is concerned, they leave out of sight the fact, that the +connection between accommodation and convergence is an individual and +acquired one. The weak side of the theory lies in the fact, that that +relation between accommodation and convergence which is developed in +emmetropia in consequence of daily practice, is given as being in itself +normal and the one for all conditions of refraction. The relation +between accommodation and convergence depends on the state of +refraction, and alters with any of its changes in the course of life. In +proportion as myopia is gradually developed in originally existing +emmetropia, myopes learn to converge to the neighbourhood of their far +point without allowing their accommodation to come into action. With +hypermetropia it is just the contrary. By far the greater number of +hypermetropes learn to use their accommodation without difficulty, even +with parallel lines of vision, for they see distant objects clearly, +while they neutralise their hypermetropia by accommodation, without +sacrificing the parallelism of the visual lines. + +It is important to notice that Donders' theory makes convergent squint +appear as almost a necessary consequence of hypermetropia. According to +Donders, hypermetropes have to choose between the advantages of +binocular vision with an effort of accommodation corresponding to the +hypermetropia, and relief to the accommodation by too strong convergence +with the sacrifice of binocular fixation; and the decision will tend to +the latter condition, if circumstances exist which deprecate the value +of binocular vision. + +The demand for binocular fusion of the retinal images will be greater if +both eyes are of equal value; on the contrary it will be less, if the +retinal image or the visual acuteness of one eye is less perfect than +that of the other. Varieties of weakness; when one eye always receives a +clear retinal image, the other an indistinct one; lowering of the visual +acuteness of one eye by nebulæ, astigmatism or any other cause. +According to Donders all these furnish a reason why, in existing +hypermetropia, binocular fixation should be abandoned and convergent +strabismus developed. + +It cannot be denied that the relation existing between convergent +strabismus and hypermetropia may be as Donders represents it; the only +question is, whether it really is so. A theory may appear very +acceptable, and may rest on a firm physiological basis; it will, +however, be more perfect if it answers to facts. Physiological +possibility is not always pathological reality, for other unusual causes +besides physiological ones acquire value, and so things become +pathological. If Donders' theory is right, convergent strabismus must +really begin, as soon as double hypermetropia meets with causes which +depreciate the value of binocular vision. The theory may be tested then +by statistics, which confront the cases of hypermetropia and convergent +strabismus with those cases in which hypermetropia meets with Donders' +conditions and normal binocular vision still remains. + +The statistics, which I have collected, relate to all the cases which +have appeared in my private practice during the last ten years. The +number would be much more considerable if I had included the patients of +the University Clinic; however, the reliability of the single elements +of which the statistics are composed was to me more important than the +number. In my private practice I have myself examined every case with +reference to these statistics for at least five years. + +In a large clinic, where more than 5000 new patients annually come under +treatment, one must frequently content oneself by satisfying the demands +of the moment; thus the sources of inaccuracy in the statistics would be +augmented. + +Included in the statistics were not merely the cases which came under +treatment for squint, but all in which squinting was present or those in +which it could be objectively proved (for example, by scars left by +previous operations for squint), that squint had formerly existed. + +Further, in the following statistics, only those cases were included, +where an exact determination of the amount of error was possible; in +most cases this was also verified objectively with the ophthalmoscope. +In many cases, especially in children, the objective determination of +refraction alone is possible, and is practicable only with the greatest +difficulty and by the use of atropine. + +Those cases deserve particular mention, in which it remained doubtful +whether hypermetropia of slight degree or emmetropia was present. Even +in full visual acuteness it is not unusual that with weak convex glasses +(of less than a dioptre) binocular vision is just as clear as with the +naked eyes, while in monocular investigation convex glasses cause a +slight indistinctness of vision. Are we to recognise hypermetropia here +or not? Opposed to the objection that in covering one eye the +hypermetropia is more easily neutralised by accommodation, stands the +observation that binocular is, as a rule, clearer than monocular vision, +wherefore, in the usual method for testing the sight, unless special +precautions are taken, full binocular visual acuteness does not prove +the presence of absolutely distinct retinal images. These doubts arise +much oftener in lowered visual acuteness. All conclusions which we +derive from visual acuteness become very inexact as soon as it is +lowered. In such cases, in determining anomalies of refraction we are +accustomed to consider the strongest convex--relatively, the weakest +concave glass, with which the visual acuteness individually present is +reached, as the most correct expression of the hypermetropia or myopia, +and with good reason if it is a case of ordering spectacles, as all +sources of error in the method of examination are then avoided as far as +possible; but it is quite another question if in such cases an exact +measurement of the amount of error is required solely for diagnostic +purposes; investigation with the ophthalmoscope is then alone decisive +and furnishes proof at the same time of how unreliable the determination +of the error by testing the vision is, in cases of short sight. One can +realise this most readily in cases of myopia with congenital amblyopia; +one gets frequently with the most exact correction possible of the +objectively determined myopia no better visual acuteness than with a +very imperfect one. In one case, for instance, which I have repeatedly +examined in the course of years, the degree of myopia determinable by +means of the ophthalmoscope amounted to at least 6·5 D., while the +weakest concave glass with which the full visual acuteness of 5/24 was +attainable was 2·5 D. Under these circumstances, if one relies merely on +the trial of vision, the degree of myopia appears too small, that of the +hypermetropia, on the contrary, just as much too great. + +But even the ophthalmoscopic diagnosis of refraction has its limits of +error. It is a question of determining the conditions under which the +image of the fundus of the eye still appears distinct. We will except +those circumstances which prevent our obtaining a clear erect image of +the fundus of the eye, as, for example, high degrees of astigmatism, +nebulæ, &c.--even under normal circumstances the fundus of the eye does +not always present such sharply-defined lines, that one could form a +perfectly safe opinion from the clearness of the image. + +When we call the ophthalmoscopic diagnosis of refraction objective, we +only mean to say that we count the subjective opinion of the patient to +be of less value, than that of the physician who examines him. The +determination of the glass even, with which we believe we are able +distinctly to see the fundus of the eye, is also an objective one. +Whoever, for instance, is firmly convinced that convergent strabismus +depends on hypermetropia, will, in doubtful cases, very easily carry his +subjective conviction into the objective examination, and will still see +clearly the fundus of even an emmetropic eye with a weak convex +glass--the objective signs for the clearness of the image have no +absolutely defined limits. But apart from this, other sources of error +are possible. A person using the ophthalmoscope, for instance, who, +without knowing it--and such a thing may happen--possesses a slight +degree of latent hypermetropia, will find his own hypermetropia +everywhere, just also as a myope, who deceives himself slightly about +the degree of his myopia in the calculation of the ophthalmoscopic +diagnosis of refraction, lays rather too high a value on his own myopia. + +Finally it must be added, that if the ophthalmoscopic estimation of +refraction is to be exact, mydriasis by atropine is required, when, as +is known, even emmetropic eyes may show a slight degree of +hypermetropia. Enough, we must not over-rate the value of the objective +determination of the error of refraction, and I would estimate the limit +of error at half a dioptre at least. If the examination is rendered more +difficult, as is frequently the case with children, by a restless and +impatient demeanour of the patient, even the objective diagnosis may +afford very doubtful results; such cases were, of course, excluded from +the statistics. Moreover, ophthalmoscopic determination of the error in +convergent strabismus is specially difficult, for one cannot advise the +patient as to a suitable direction for the eye not under investigation. +It is generally best to keep the eye not under investigation closed. + +In practice it is immaterial whether emmetropia or a minimum degree of +hypermetropia is present; for statistics essentially devoted to +theoretical questions it seemed more suitable to unite these cases in a +separate group. + +Accurately taken, the statistics should give the condition of refraction +at the age at which the squint begins. But, if there is a thankless +task, it is that of examining the erect image in children from two to +three years of age. To furnish accurate results this method requires a +certain tractability on the patient's side, which is never present at +this age, and not always in adults. A number of the cases surveyed in +the following table also came under observation long after the squint +commenced, and in some short-sighted persons in particular, the degree +of myopia at the time when squinting began, may have been less than it +was at the time of the examination. + +Further, it seemed to me desirable to keep periodic, separate from +permanent squint; this, however, could not be accomplished with +exactness. It may easily happen that children with periodic squint +always squint just when one sees them, and in those cases which had +already been operated on when they came to be examined, it was quite +impossible to determine whether periodic or permanent squint had +formerly been present. Therefore I have represented separately in each +particular group the number of those previously operated on. + +In the following table the refraction of the fixing eye and the visual +acuteness of the squinting eye are given. In alternating squint the +refraction of the emmetropic eye was taken, as determining it for +insertion in the lower division of the statistics. + +A. Convergent squint with myopia: + 1. Slight myopia to M. = 1·75 D. + (_a_) Permanent squint 11 cases (3 previously operated + on). Anisometropia in 2 cases (one with M. + 1·25 D. of the fixing, M. 4 D. of the squinting eye; + the other with M. 1·25 D. of the fixing, H. 4 D. and + V. = 1 of the squinting eye). The examination of + the visual acuteness of the squinting eye showed: + V. more than 1/7 4 cases. + V. 1/12 - 1/18 1 case. + V. 1/24 - 1/36 1 case. + V. Less than 1/36 4 cases (among them + one with H. 2 D. + in the squinting eye.) + V. indeterminable 1 case. + + (_b_) Periodic squint 2 cases with very slight anisometropia + and good vision. + 2. M. 2 D. to M. 3 D. 11 cases, all permanent (6 cases + previously operated on), anisometropia with + good vision in both eyes in 2 cases (in both, the + less myopic eye squints). V. of the squinting + eye more than 1/7 in 6 cases. + V. 1/12 - 1/18 1 case. + V. 1/24 - 1/36 2 cases. + V. less than 1/36 2 cases (one with H = 5 D). + 3. M. 3·5 D. to 6 D. + (_a_) Permanent 11 cases (one previously operated + on). Anisometropia in 2 cases, of which one consisted + of alternating squint, while the other possessed + in the fixing eye M. 4 D., in the squinting one M. 7·5 + D. with good vision on both sides. + V. more than 1/7 7 cases. + V. 1/24 1 case. + V. 1/36 1 case (in fixation with this + eye; the visual axis shows a linear deviation of 2 mm. + The presence of emmetropia is detected with the ophthalmoscope). + Two cases were excluded from the statistics of vision, one on + account of congenital capsular cataract, covering almost the + whole pupil area, the other on account of choroiditis of the + macula lutea. + (_b_) Periodic squint 4 cases with good vision, + anisometropia in 2 cases. + 4. M. 6·5 D. and more. + (_a_) Permanent 11 cases, among them 9 with V. + more than 1/7, 2 excluded from the statistics, one on + account of complication with corneal nebulæ, cataract, + &c., the other possessed in the fixing eye M. 6·5 D. + V. = 10/70 and slight nystagmus, in the squinting eye + a smaller amount of sight not accurately noted, and + strong nystagmus in fixing with this eye. + (_b_) Periodic squint in 4 cases with good vision. + 5. Myopia with nystagmus and congenital amblyopia + on both sides, 2 cases (not included in the + statistics of vision). Altogether 56 cases, among + them 10 with periodic squint. + +B. Convergent squint in emmetropia, including simple + myopic astigmatism, 98 cases. + (_a_) Permanent 81 cases (13 previously operated + on). Visual acuteness more than 1/7 in 44 cases. V. + less than 1/7 to V. = 1/12 6 cases; V. less than 1/12 to + V. = 1/36 20 cases; V. less than 1/36 7. Excluded from + statistics of vision 4 (3 on account of complications, + 1 on account of lack of accurate information). + (_b_) Alternating convergent squint with emmetropia + in one, myopia in the other eye, 4 cases. The degree + of the myopia was 3·75 D., 5 D., 6 D., 12 D. + Vision good on both sides. + (_c_) Periodic squint 13 cases (in 6 of them the + refraction was objectively and subjectively determined + in mydriasis by atropine). No anisometropia worth + mentioning was present in any of these cases. Visual + acuteness more than 1/7 9 cases. V. < 1/7 to V. = 1/12 + 2. V. < 1/12 to V. = 1/36 1; one case with choroiditis + excluded. + +C. Convergent squint with doubtful hypermetropia to + H. = 1 D., including simple hypermetropic astigmatism, + 38 cases. + (_a_) Permanent 30 cases (5 previously operated on). + Visual acuteness more than 1/7 7 cases. V < 1/7 to + V. = 1/12 2. V. < 1/12 to V. = 1/36 5. V. < 1/36 2 cases. + 4 excluded (3 complicated with cataract, one on + account of impossibility of a trial of vision). + (_b_) Periodic squint 8 cases. V. more than 1/7 7. + V. < 1/7 to V. = 1/12 1 case. + +D. Hypermetropia 1 D. to 1·5 D. 37 cases. + (_a_) Permanent 23 (4 cases previously operated on). + V. more than 1/7 13, V. < 1/7 to V. = 1/12 3. V. < 1/12 + to V. = 1/36 3. V. < 1/36 3. One case excluded + (choroiditis of the macula lutea). + (_b_) Periodic squint 14 cases. V. more than 1/7 12. + V. < 1/12 to V. = 1/36 1 case. One excluded on account + of choroiditis. + +E. Hypermetropia 1·5 D. to 2 D. 61 cases. + (_a_) Permanent 41 (3 previously operated on). V. + more than 1/7 26 cases. V. < 1/7 to V. = 1/12 3; + V. < 1/12 to V. = 1/36 3; V. < 1/36 2; (7 cases excluded, + 2 as complicated, 5 on account of the impossibility of + testing the vision). + (_b_) Periodic 20 cases. V. more than 1/7 16; V. + < 1/7 to V. = 1/12 2; V. < 1/12 to 1/36 1; V. < 1/36 1 + case. + +F. Hypermetropia 2 D. to 3 D. 88 cases. + (_a_) Permanent 58 cases. V. more than 1/7 26 cases; + V. < 1/7 to V. = 1/12 5 cases (among them one with V. + = 1/12 in both eyes); V. < 1/12 to V. = 1/36 17; V. + < 1/36 4 cases. Six cases excluded as indeterminable. + (_b_) Periodic 30 cases. V. to 1/7 24; V < 1/7 to V. + = 1/12 3; V. < 1/12 to V. = 1/36 1; V < 1/36 1. One case + excluded as indeterminable. + +G. Hypermetropia 3 D. to 4·5 D. 54 cases. + (_a_) Permanent 35 cases (9 previously operated on). + V. more than 1/7 18 cases; V. < 1/7 to V. = 1/12 1 case; + V. < 1/12 to 1/36 9; 7 cases excluded. + (_b_) Periodic 19 cases. V. more than 1/7 14; V. + < 1/7 to V. = 1/12 1; V. < 1/12 to V. = 1/36 3; V. < 1/36 + 1 case. + +H. H. 5 D. and more, 16 cases. + (_a_) Permanent 9; V. to 1/7 3; V. < 1/7 to V. = 1/12 + 3; V. < 1/12 to V. = 1/36 2; V. < 1/36 1 case. + (_b_) Periodic 7; V. to 1/7 4; V. < 1/7 to V. = 1/12 3 + cases. + + +_Table of Refraction and Acuity of Vision in Convergent Strabismus._ + +[Transcriber's note: Key created to make table fit page] + +KEY: +A: Permanent +B: V. to 1/7. +C: V. < 1/7 to V 1/12. +D: V. < 1/12 to V. 1/36. +E: V. < 1/36. +F: Excluded. +G: Periodic. +H: V. to 1/7. +I: V. < 1/7 to V. 1/12. +J: V. < 1/12. to V. 1/36. +K: V. < 1/36. +L: Excluded. + +--------------------+---+----+---+----+----+----+----+----+----+----+----+---- + Convergent | | | | | | | | | | | | + strabismus. | A | B | C | D | E | F | G | H | I | J |K | L +--------------------+---+----+---+----+----+----+----+----+----+----+----+---- +Myopia | 44| 26 | 2| 4 | 7 | 5 | 10 | 10 | -- | -- | -- | -- +Emmetropia | 85| 48 | 6| 20 | 7 | 4 | 13 | 9 | 2 | 1 | -- | 1 +H ? to H. 1 D. | 30| 17 | 2| 5 | 2 | 4 | 8 | 7 | 1 | -- | -- | -- +H. 1 D. to H. 1·5 D.| 23| 13 | 3| 3 | 3 | 1 | 14 | 12 | -- | 1 | -- | 1 +H. 1·5 D. to H. 2 D.| 41| 26 | 3| 3 | 2 | 7 | 20 | 16 | 2 | 1 | 1 | -- +H. 2 D. to H. 3 D. | 58| 26 | 5| 17 | 4 | 6 | 30 | 24 | 3 | 1 | 1 | 1 +H. 3 D. to H. 4·5 D.| 35| 18 | 1| 9 | -- | 7 | 19 | 14 | 1 | 3 | 1 | -- +H. 5 D. and more | 9| 3 | 3| 2 | 1 | -- | 7 | 4 | 3 | -- | -- | -- +--------------------+---+----+---+----+----+----+----+----+----+----+----+---- + |325|177 | 25| 63 | 26 | 34 |121 | 96 | 12 | 7 | 3 | 3 +--------------------+---+----+---+----+----+----+----+----+----+----+----+---- + +According to this the percentage of the hypermetropia (including +doubtful cases) amounts to 66 per cent. Dr. Isler in his dissertation, +'The Dependence of Strabismus on Refraction,' gives the percentage of +hypermetropia in convergent squint as 88 per cent.--a great difference, +which can, however, be partly accounted for. Isler found in +hypermetropia of 2 to 10 dioptres squinting in 75 per cent.; in my +statistics H. 1·5 D. to the highest degrees of hypermetropia are +likewise represented by 75 per cent. As the difference between H. 2 D. +and H. 1·5 D. amounts to only half a dioptre, the results of the +statistics agree perfectly within these limits; the difference lies only +in the slighter degrees of hypermetropia, for the diagnosis of which +refer to pp. 12 to 14. + +The influence of hypermetropia is very apparent in the percentage of +periodic squint. While in myopia, emmetropia, and slight hypermetropia, +the sum total of permanent as compared to periodic squint is as 100: +19·5, this number mounts in hypermetropia of 1 D. to H. = 3 D. to 52·5 +and in the higher degrees to 59 per cent. Despite the small number of +cases it is probably no mere accident that in the highest degrees (of H. += 5 D. and more) this percentage is calculated at 77·7. + +But just this undoubted favouring of periodic squint by hypermetropia, +helps to show that this condition is one of the causes of squint, but +not the only one, for in periodic squint just those conditions are +wanting which induce a permanent deviation. + +It is further proved by the table that in convergent strabismus, myopia +appears just about as frequently as the higher degrees of hypermetropia +(of 3 dioptres and more). The fact that these are not so strongly +represented in convergent strabismus, as one would have expected +according to his theory, had also struck Donders. "This cannot be +wondered at," he continues, "the power of accommodation, even with +increased convergence, does not here suffice to produce clear images. +One gains much better ideas by practice from imperfect retinal images +than by correcting, as far as possible, the retinal images by a maximum +of accommodation." I can concede neither to the facts on which the +theory is based nor to the theoretical structure itself. + +An additional statistic which I drew up of the cases of hypermetropia +which occurred during one year in my private practice, showed that the +higher degrees are rare in the same proportion as cases of convergent +strabismus are, with the corresponding degrees of hypermetropia. +Further, however, I maintain that as a rule, at the age when squint +usually begins, the accommodation really suffices to overcome even high +degrees of hypermetropia. In all cases where we find full acuity of +vision without correction of extreme hypermetropia--and this is +frequently the case in young persons who do not squint--we may assume +that the accommodation perfectly suffices to produce clear retinal +images, without excessive convergence. In full acuity of vision even +high degrees of hypermetropia are no trouble to children. Asthenopia, +which occurs in children in connection with hypermetropia, is nearly +always accompanied by defective vision. Were the increased demand on the +accommodation really the cause of convergent strabismus, asthenopia +would be far more common than it is among hypermetropic children who do +not squint. + +One can assert, with far greater right, that a sufficient ground for +squint is not given by slight degrees of hypermetropia, for the latter +are accommodatively overcome and binocular fixation retained by youthful +persons without any difficulty, even when the additional motives +enumerated by Donders are present. I have endeavoured to obtain a +foundation for the depreciating influence of these circumstances +favorable to squint, for I counted in my private practice, at the same +time with the cases of squint, those cases also in which, despite those +conditions which lessen the value of binocular vision, squinting was not +present. Taking notice then of those cases in which the hypermetropia of +the better or less hypermetropic eye amounted to at least 1·5 D., in +order to allow the influence of the hypermetropia to be more +conspicuous. The patients from which the above-cited 219 cases of +convergent strabismus with a hypermetropia of at least 1·5 D. are drawn, +comprised also 117 cases in which, with the same degree of hypermetropia +and simultaneous difference of refraction or monocular amblyopia, no +convergent squint was present; of these cases 101 had acuity of vision +to 1/7; less than 1/7 to V. = 1/12 7, and V. less than 1/12 to V. 1/36 9 +cases. The percentage 219: 117 = 100: 53, which is yielded for the +middle and higher degrees of hypermetropia, is not exactly convincing +for the accommodative theory of squint; it would be placed still less +favorably if we were to include the lowest degrees of hypermetropia in +the statistics. + +In face of these facts I do not consider it a happy question, that of +seeking after "reasons for the prevention of squint." We do not want to +quarrel with Donders over the question why all hypermetropes do not +squint. Here, of course, I quite agree with Ulrich that squint does not +occur if the necessary muscular conditions are absent. The identity of +the fields of vision, on the other hand, seems to me to be of no +importance for the age at which squint usually commences. This identity +presupposes the habit of binocular fusion; but convergent squint arises, +as a rule, before this habit is acquired. But even if binocular fusion +were already learnt, it is given up with astonishing rapidity by +children as soon as squint develops itself (see Case 16). The fixed +habit of binocular fusion and the identity of the fields of vision +dependent on it, is contracted only when squint does not occur, +notwithstanding the presence of conditions favorable to it. + +However, the number of cases is so considerable in which, despite the +presence of the causative motives suggested by Donders, no convergent +strabismus is present, that the co-operation of other causes is +necessary for the production of squint, and the first thing we do is to +think of those causes which lead to squint even without hypermetropia. + +The attempt has really been made to attribute the commencement of +convergent strabismus to the accommodation even in emmetropia, and +offers fresh proof how easily facts are overwhelmed by theories. Donders +originally gave it as his opinion, that loss of power or paresis of the +accommodation produces strabismus just as little as the decrease in the +amount of accommodation which comes with increase of years; a year +later, because he could not agree with Donders' theory, Javal declared +the principal cause to be due to weakening of the accommodation and not +the refraction, but without producing any other ground for the assertion +than that of his own good pleasure. Afterwards, Donders sought to +explain the occurrence of convergent strabismus in emmetropia by paresis +of accommodation, which must indeed, according to his theory, produce +the same result as hypermetropia. + +I content myself by reminding my readers, that at the age when +convergent strabismus usually arises, between the second and third year +of life, a determination of the near point is utterly impossible; a +foundation in fact is therefore wanting to the theory. But, further, if +paresis of accommodation really had the significance assigned to it, +atropine, which is so frequently used in the ophthalmic treatment of +children, would be followed by convergent strabismus. This is still more +the case with diphtheritic paralysis of accommodation, which is present +more frequently than we are aware of, for it is only a trouble to +children in the schoolroom, in younger children it passes through its +natural uninterrupted course of recovery unobserved, in hypermetropia as +well as in emmetropia. If the accommodation were really of great +importance in the occurrence of squint, convergent strabismus would +frequently be an after symptom of diphtheria, which, as is known, is not +the case. The few cases of squint which I have seen after diphtheria, +had their origin in paresis of the external rectus, which was proved by +the objective defect in movement, as well as by the disappearance of the +squint, with the recovery of the paralysis of the abducens. + +That the accommodation can play a part, is shown by the rarity of +periodic accommodative squint, but for the great majority we must seek +the chief cause of squint in emmetropia and myopia, in elastic +preponderance of the internal recti and insufficiency of the externi, +and it is apparent that the same causes will also be influential in +hypermetropia. + +In hypermetropia, if one causes fixation at about 30 cm. and then covers +the eye with the hand, it frequently deviates inwards. Donders infers +from this, that most hypermetropes prefer to sacrifice comfortable and +clear vision in order to retain binocular vision. Now, it is easy to +convince oneself that youthful hypermetropes see distinctly even without +correction of their hypermetropia, and we may assume that they see +comfortably if they do not complain of asthenopia; but that is by no +means always the case, for the appearance of asthenopia is conditional +on the relation of the degree of the hypermetropia to the amount of the +accommodation, which, apart from a few other causes, depends chiefly on +the age of the patient. + +Just as we refer the deviation outwards of the covered eye to +insufficiency of the interni or preponderance of the externi, we may +conclude an inward deviation of the covered eye to be due to +insufficiency of the externi or preponderance of the interni, and this +all the more, as in hypermetropia the covered eye very frequently +remains in fixation, and falls away exceptionally into relative +divergence. + +Just as in myopia even in the lesser degrees, insufficiency of the +interni or preponderance of the externi is not rare, so in hypermetropia +insufficiency of the externi or preponderance of the interni appears to +be frequent; and if this disturbance of the muscular balance be followed +even in myopia or emmetropia by convergent strabismus, this will of +course happen still more easily if at the same time hypermetropia, or +even without hypermetropia, the remaining favouring conditions mentioned +by Donders are present. Of course I do not deny the effect of the +hypermetropia and of those other favouring conditions, but only wish to +draw attention to the fact with reference to them, that as a rule they +do not of themselves suffice to produce convergent strabismus. + +Nebulæ have always been regarded as one of the causes of squint; here I +quite agree with Donders that they may operate, firstly, as general +causes of weak sight; secondly, through this, that the irritated +condition, combined with the keratitis, may produce a spasmodic, +afterwards a trophic shortening of the muscles; but this seldom happens. + +Whether nebulæ are found rarely or often in squint, depends in great +measure on the statistic materials which are worked out. In my +statistics they do not occur in any quantity worth mentioning, because +in private practice purulent ophthalmia keratitis, and in short, the +whole army of external inflammations of the eye is much rarer, than in +that portion of the populace which fills public clinics. Further, it is +to be observed that the mere occurrence of nebulæ in squint proves +nothing--even squinting eyes may develop keratitis. We must at least +require to be assured that the squint began after the keratitis. + +Among the causes which promote the occurrence of squint, Donders +mentions also conditions which diminish convergence. We have ascribed a +very important _rôle_ to the muscles, and have only to occupy ourselves +here with the relation between the visual line and the axis of the +cornea, which we have already mentioned on page 2. Donders has measured +the angle _a_ in ten cases of hypermetropia with convergent strabismus, +and from the comparison with hypermetropic non-squinting eyes draws the +conclusion, that in similar degrees of hypermetropia a higher amount of +_a_ specially disposes to strabismus. I will not repeat here the witty +deduction by which Donders seeks to point out that a higher value of a +must be followed by insufficiency of the externi and preponderance of +the interni; the concession is enough that these circumstances exist and +are the cause of the squint. + + + + +PERIODIC CONVERGENT SQUINT. + + +The opinion is prevalent that convergent strabismus usually begins in +the form of periodic squint, and that a permanent deviation is developed +in this way only. In many cases it may be so; on the other hand I have +sometimes seen convergent strabismus arise suddenly, without a +preliminary stage of periodic squint. This question, however, is of no +special interest. It is more important to note that periodic squint +frequently continues to exist unchanged, without ever becoming +permanent. + +Like the whole doctrine of strabismus, opinions on periodic squint have +been governed by Donders' theory, regardless of facts, but as the +accommodation frequently exercises a perceptible influence, it is +judicious to consider first of all the cases in which this does not +happen. + +Convergent squint in myopia begins as a rule with periodic squint, and +may continue to exist in this form: some patients who would not be +operated upon have been under my observation for years; sometimes a +correct position was retained for a long time, and sometimes strong +convergent squint was present, proving that accommodation had nothing +whatever to do with it. In myopia of higher degree the accommodation is +scarcely used--unless concave glasses are worn; still periodic squint +occurs under these circumstances. For example: + +CASE 1. Miss B--, æt. 22, possesses in both eyes myopia of 6·5 D. with +full visual acuteness and without posterior staphyloma. A concave +eyeglass of 4·5 D. is used off and on for distance, and the eyes have +never been over-exerted in looking at near objects. For a long time +tendency to convergent squint, which is combined with diplopia, has +existed on the left side. The eyes generally have a perfectly normal +position, but occasionally convergent squint occurs, remains in +existence a few hours, perhaps for a whole day even, and disappears +again. The deviation here amounts to 4 or 5 mm. As the patient did not +wish for an operation, I have been able to observe the condition for +years without any change in it or without the squint becoming permanent. +The cause of periodic squint is certainly not to be sought for here, in +the accommodation. + +Many cases of convergent strabismus with myopia constantly offer such a +peculiar phase of the defect, that one has accepted the statements which +ascribe to short-sightedness a determining influence on this form of +squint, without asking for further proof. It may, therefore, be useful +for our purpose to cite a few cases of periodic convergent strabismus +with emmetropia. For instance: + +CASE 2. Louise S--, æt. 6-1/2, came under treatment for follicular +conjunctivitis, convergent strabismus appearing simultaneously on the +right side; the investigation showed the acuity of vision of left eye = +5/12, right V. = 5/36, the ophthalmoscope, and also mydriasis by +atropine, proved the presence of emmetropia. The squint had first been +observed when the child was about two years old, then it disappeared +spontaneously and returned again three or four months ago. + +In the course of treatment, which extended over about six months, the +child came repeatedly into my consulting room, sometimes with squint, +sometimes without, in the periods during which correct fixation existed, +no squint occurred even when working. Examination with the stereoscope +showed no normal binocular fusion even during normal position of the +eyes. + +CASE 3. Vera von K--, æt. 6; tendency to convergent strabismus, mostly +on right side, has existed one and a half years. Normal position as a +rule, on covering the eye immediate convergence, with a deviation of 5 +mm.; with additional aid of a red glass and weak prisms deviating in a +vertical direction, homonymous diplopia is very easily provoked. Visual +acuteness on both sides 5/12, the left slightly better than the right; +emmetropia in mydriasis by atropine. A year later a repeated examination +gave the same result. + +The cause of periodic squint in these cases can only be sought in the +bearing of the ocular muscles; an elastic preponderance of the interni +existed, which ceased, as a rule, on using the externi. A special +influence of the accommodation was not traceable, which does not of +course prevent this from acting differently in other cases. But in +periodic squint it may frequently be observed that the deviation +commences under influences which have nothing to do with the +accommodation, but, on the contrary, under those which weaken the +muscular energy generally, for example, fatigue, anxiety, &c. + +Like convergent squint generally, the periodic form is also more +frequent in hypermetropia than in emmetropia or myopia, and we admit +that in hypermetropia the strain on the accommodation has more influence +in producing the deviation. But as the appearance of periodic squint in +emmetropia or myopia is proved without participation of the +accommodation, solely on the ground of the muscular forces--so the +presence of the same forces in hypermetropia ought not to be ignored. + +It happens, indeed, that in considerable degrees of hypermetropia a +slight convergent deviation occurs only from time to time, the cause of +which, on closer investigation, can only be sought in the ocular +muscles. For example: + +CASE 4. Paul F--, was first introduced to me in 1872 as a child of three +years and two months, with a tendency to convergent strabismus on the +right side of two months' standing, which was sometimes greater, +sometimes less, and sometimes was not present at all. In 1877 I saw him +again suffering from conjunctivitis, without perceiving any squint; no +examination respecting it was made. In 1880 his elder brother came under +treatment for apparent myopia, which with the ophthalmoscope proved to +be hypermetropia, and my attention, being again drawn to the eyes of the +family, I requested the younger brother to come for examination. At +first sight the position of the eyes appeared to be quite normal, on +more careful inspection slight convergent squint of the right eye showed +itself occasionally. On both sides apparent emmetropia or very slight +hypermetropia, acuity of vision on left side 5/9, on the right 5/18, +ophthalmoscopic diagnosis of refraction was impossible on account of +restless fixation. + +With the addition of a red glass diplopia cannot be produced, the left +field of vision is observed in the stereoscope, then the right one on +covering the left eye; never both together. In mydriasis by atropine +hypermetropia of high degree (about 4 dioptres) is ophthalmoscopically +detected on both sides, with convex 4·5 D., V. = 5/9 with slight +convergent deviation of the right eye. + +What has here prevented the transition to permanent squint with a +deviation corresponding to the great strain on the accommodation? That +the accommodation was really in action is proved simply by the apparent +emmetropia and the school-work, that no retention of binocular single +vision took place is shown by the proved incapacity for binocular fusion +of the retinal images. Nothing then remains but to accept the fact that +in the ocular muscles inducement was only given for a slight periodic +squint, not for a permanent one answering to the amount of accommodation +used. + +As further proof that periodic squint may occur even in hypermetropia +quite independently of the accommodation, I should like to cite a case +of intermittent convergent strabismus which a number of other oculists +have seen besides myself. + +CASE 5. Sophie S--, æt. 7-3/4, has suffered for two years from a strong +convergent squint on the left side, occurring every other day. The +deviation amounts to 7 mm. (the same deviation is transferred to the +left eye, when the right is put into fixation). On the intervening days +the position of the eyes is quite normal, on covering one only a slight +deviation takes place. The visual acuteness amounts to 5/12 on the left, +5/24 on the right, ophthalmoscopically with atropine hypermetropia of +two dioptres. Quinine has been given without avail, a convex glass of 2 +D. also, which has been worn for the last half year, has not affected +the deviation. + +Diplopia was not present--on the intervening days free from squint, with +the aid of a red glass, homonymous diplopia could be detected without +perceptible deviation, still it was impossible to bring about a union of +the double images by prisms. In the stereoscope the left field of vision +was first inspected, then both, still fusion of the fields of vision was +not traceable. The statements, moreover, as indeed could not be expected +otherwise in a child of such tender age, were not free from +contradictions, but the existence of normal binocular vision was very +doubtful. I therefore performed tenotomy of the left internal rectus, +after which normal position continued to exist on the following squint +days. After three quarters of a year I saw the child again; the squint +was perfectly cured, even on looking down, convergence was no longer +present. Whether a permanent cure was thus obtained, seems to me +doubtful, owing to the rare peculiarities of this case. + +Mannhardt also describes a similar case of intermittent squint; that of +a girl aged eight years, in whom periodic convergent strabismus had +begun four years previously, and for two years had occurred regularly +every other day. On undecided vision the eyes were normally placed, but +as soon as a near or distant object was fixed, a considerable deviation +inwards of the left eye occurred. Under the covering hand both eyes +deviated inwards equally. On the non-squinting days strabismus could in +no way be produced even by fixation of the nearest objects, only under +the covering hand a deviation inwards ensued. The squint could not be +removed by quinine, but only by correction of the hypermetropia of 3 D. +In any case, then, hypermetropia was one of the causes of the squint, +but not the only one, as it cannot operate on alternate days only. + +Javal, who tries to make this case coincide with his theory, accepting +an intermitting paresis of accommodation as the cause of squint, is +manifestly in error, as Mannhardt particularly mentions that acuity of +vision, refraction and accommodation remained perfectly equal on both +days. + +If it is thus proved, that also in periodic inward squint the deviation +may occur quite independently of the accommodation, on the other hand it +is apparent, that if once a tendency to squint exists, a +disproportionately strong convergence may very easily unite itself with +the accommodation. Particularly of course in hypermetropes, who are able +to fix nothing without using their accommodation, a remarkable +fluctuation of the squint angle very frequently takes place. Sometimes +the deviation is exceedingly strong, sometimes so slight that it seems +to be absent. It is usually impossible to determine if it is really +absent, for as soon as we single out a point for fixation to make the +investigation feasible, strong deviation sets in. If in such cases we +perfectly atropise both eyes, restore the attainable acuity of vision by +neutralisation of the hypermetropia with convex glasses, and yet, +nevertheless, as is generally the case, the customary strong convergence +takes place on fixation of a distant object, there can be no talk of a +strain on the accommodation; at most we can say, that the impulse for +accommodation, habitually united with the intention to see distinctly, +and the too strong convergence combined with it, also takes place, +though by paralysis of the accommodation the participation of the same +has become impossible. As accommodative squint those cases are chiefly +indicated in which the deviation only takes place when there is a claim +on the accommodation. In most cases of this kind hypermetropia is +present. I have occasionally seen periodic accommodative squint with +emmetropia of the fixing eye. + +CASE 6 may serve as an example: H. B--, æt. 15, shows a considerable and +very varying periodic inward squint. Sometimes correct position is +present, sometimes strong deviation, indeed the latter only occurs on +looking at distant objects, while for near ones correct position of the +eyes generally takes place. The examination showed for the right eye +hypermetropia 1·5, for the left myopia 3·5 D.; full acuity of vision on +both sides. The squint occurring in the left eye on looking at distant +objects was therefore accommodative; the effort of the accommodation +necessary for correcting the hypermetropia united itself to an +excessively strong innervation of the interni, as the interests of +binocular vision came but slightly into consideration on account of the +myopia in the left eye. For near objects the myopic eye is used without +accommodation and therefore also without convergent strabismus of the +right. But if one caused a point about 25 cm. distant to be fixed first +with the right (hypermetropic) eye while the left was covered and then +caused fixation to be transferred to the left, the accommodative +convergent strabismus induced was alternately transferred to the left +eye and continued, although the left eye fixed without any effort of the +accommodation on account of its myopia. Double tenotomy of the interni +and correction of the hypermetropia effected the cure of the squint. + +The clearest cases of accommodative strabismus are those in which +usually a correct position and sometimes even binocular fusion is +present, while squint occurs only during the strain on the accommodation +necessary for distinct vision. + +CASE 7. Miss Bertha v. Pr--, æt. 27, shows strong accommodative squint +of the right eye, said to have been observed by her parents when she was +fifteen months old. Correct position of the eyes is generally present +with indistinct vision; the endeavours to see clearly immediately causes +striking convergence of the right eye. On the left hypermetropia 3·5 D., +vision normal; on the right the same degree of hypermetropia, vision not +more than 1/12 of the normal, no ophthalmoscopic report. On correction +of the hypermetropia and with aid of a red glass crossed diplopia +immediately appears, which is corrected by a prism of 5° base inwards; +prisms of 12° with the bases inwards are overcome on fixation of an +object about 12 ft. distant by divergence. The elastic tension of the +ocular muscles necessitates then a preponderance of the externi, and an +effort of the accommodation necessary to overcome the hypermetropia, +which on account of the congenital amblyopia of the right eye unites +itself with excessive convergence. Had the elastic tension of the ocular +muscles made a preponderance of the interni a condition, permanent +convergent squint would have been the result, and one would have called +the weak sight of the right eye amblyopia from want of use. + +Typical accommodative squint occurs quite independently of the will on +each effort of the accommodation, and is not combined with diplopia. It +is otherwise in those cases of hypermetropia of high degree in which +patients voluntarily call forth convergent squint, and retain it for a +short time for the purpose of distinct vision. They are then perfectly +conscious of the squint, and perceive also as a rule the double images +which occur at the same time; I have seen such cases in adults who could +only produce the accommodation necessary for distinct vision by the aid +of a too strong convergence; they, however, only now and then made use +of this help. Although differing much from the typical form, these cases +of voluntary accommodative squint were also included in the statistics. + +In involuntary periodic (even if not accommodative) squint, the patient +as a rule is not conscious of the occurrence of the false position; that +exceptions to this occur Case 1 has given us an instance. + + + + +CONVERGENT SQUINT IN MYOPIA. + + +For the ætiology of convergent strabismus it is of interest to ascertain +the age at which it is developed, and one of the first results we obtain +is the exceptional position which the union of myopia with convergent +strabismus takes in this category. Of the 56 cases contained in the +above statistics I possess reliable information of the time of +commencement in 11 cases; the squint was twice observed before the +fourth year of life, once between four and ten years of age, eight times +between the tenth and thirty-third years of life. + +I must first state prominently with regard to the connection of myopia +with convergent squint that I see no reason for holding short sight to +be the cause of the squint, as v. Graefe does. + +A specially severe strain of the eyes, as v. Graefe assumes, was not +traceable in the cases observed by me. Excessive convergence and strain +on the accommodation is often enough present in weak sight, for example, +in astigmatism without the existence of squint; were short sight in +general an inducement to convergent squint these cases would appear much +oftener than they actually do, owing to the frequency of myopia. In my +opinion the cause of their rarity lies in the fact that myopia is +frequently combined with insufficiency of the interni and preponderance +of the externi, but only rarely with the reverse condition of the +muscles. If, however, a preponderance of the interni develops itself +together with the myopia, convergent strabismus is easily produced, for +without correction of the myopia by spectacles, the desire for retaining +binocular single vision for everything beyond the far point is lessened +by the indistinctness of the retinal images. Within the range of their +field of distinct vision these squinting myopes frequently retain +binocular vision, while the capacity for accepting parallel rays or +retaining them for long, is lost. + +Strictly speaking, the periodic squint present in these cases is of a +peculiar kind, for the binocular single vision present within range of +the convergence excludes the notion of squint; the latter only occurs +when an object lying outside the point of convergence is fixed. +Moreover, according to the common use of language, I have only used the +expression periodic convergent squint for the change between a parallel +direction of the visual axes and pathological convergence. + +As squint in myopia usually commences at an age when binocular fusion +has already become a fixed habit, diplopia regularly takes place with +it, but patients become more easily accustomed to this than in paralysis +of the ocular muscles, because the retinal images are indistinct and the +double images in the field of vision always keep at about the same +distance, while in paralysis of the ocular muscles the distance is +constantly changing. + +The myopia, in these cases, is not the cause of the squint, but only a +favouring circumstance. If the same preponderance of the interni is +developed at the same age in emmetropia, squint is not so easily caused, +as the distinct retinal images present in the whole field of vision +render it easy to retain binocular single vision. Therefore we see the +same form of squint arise less often in emmetropia (see Case 45) when +childhood is past, than in myopia. As a rule preponderance of the +interni in hypermetropia leads eventually to convergent squint even in +childhood. + +In emmetropia and hypermetropia convergent strabismus seldom arises +after the tenth year (paresis of the abducens of course excepted), +therefore in my investigations as to the time of commencement of typical +squint I have only considered those patients who came under my treatment +before their tenth year. We must rely for the most part on the vague +statements of the parents, which lose in exactness in proportion as the +origin of the squint is of distant date; moreover, I have myself seen a +great many of the children before they were four years old. In this way +I have collected reliable information respecting the origin of the +squint in 193 cases, and of these (_a_) 88 cases occurred in children +one to three years old, (_b_) 53 in children three to four years old, +(_c_) 35 cases in children of over four years of age. It is thus at once +seen that in the great majority of cases, convergent strabismus +commences in children under four years of age, who have not yet begun to +read and write, and have no inducement to use their accommodation +severely, and still less continuously. + + + + +SQUINT FROM PARALYSIS OF THE ABDUCENS. + + +Convergent squint as a result of paralysis of the abducens is not very +often seen. It is first to be observed that a convergent squint, +including the whole field of vision, occurs by no means in all cases; in +about half the cases binocular fusion is retained towards the healthy +side, diplopia then only occurs when the weak abducens is exerted beyond +its strength. In those cases in which convergent squint is present in +the whole field of vision paralysis of the abducens cannot be the sole +cause, but some other cause than the most apparent one must co-operate. +An insufficiency of the externi of previous existence, or an elastic +preponderence of the interni may be considered. I have not been able to +persuade myself of the fact that hypermetropia can play any part +therein. + +In by far the greater number of cases paralytic convergent squint +recovers together with the paralysis of the abducens, the field of +single vision transfers itself gradually from the healthy side to the +side of the weak abducens, and at length governs the whole field of +vision. In proportion as the muscle again fulfils its normal functions, +the habit of binocular fixation regains its power, and it seldom happens +that the elastic tension of the muscles has so changed during paralysis +that the desire for binocular single vision does not suffice to overcome +it. Case 48 furnishes an example of the fact that although the squint +occurred as a consequence of paralysis of the abducens, it certainly +remained in existence after healing of the paralysis on account of +previously existing insufficiency of the externi. + +Congenital paralysis of the abducens seems more frequently to have +convergent squint as a result. If, for example, convergent squint is +observed in the first year of life, and we find a complete defect of +motion on the part of one abducens when the children become old enough +to be examined, we may certainly assume that the case is one of +congenital paralysis of this muscle, or at least that the paralysis +originated soon after birth. Doubtless, however, cases appear, of +congenital paralysis of the abducens without squint, and as these cases +are so rare I will describe two which I observed in adults. + +CASE 8. Miss H--, æt. 17, has nominally since her birth a considerable +defect in the outward movement of the left eye. On looking to the left +homonymous diplopia is present, on looking to the front and the right +binocular single vision and no squint; on both sides emmetropia and full +acuity of vision. + +CASE 9. Mr. V. W--, æt. 24, has likewise congenital paralysis of the +left abducens. No squint, but as soon as the left eye is used for +fixation in the left direction there occurs in the right one a strong +secondary movement inwards. + + + + +HYSTERICAL SQUINT. + + +In the hysterical form we see rather a rare variety of convergent +squint, which is conditional on contraction of the interni through +restriction of movement of the externi. Hysterical symptoms may at the +same time appear in the eyes or elsewhere, still this does not always +happen. As these cases are rare I will relate a few of those I have +observed. (These cases are not included in the above statistics.) + +CASE 10. Anna R--, æt. 20, came under treatment in February, 1878, +stating that on the previous day she perceived blindness of the right +eye on waking; in the afternoon she felt particularly weary, and after +she had slept about an hour woke with blindness in both eyes. No +perception of light, good pupillary reaction, ophthalmoscopic report +normal. Patient was treated with copious enemata and dismissed on the +fifth day cured. + +In February, 1880, she again came under treatment with blindness of both +eyes, also perceived the previous day on waking. Convergent strabismus +was present at the same time, of such a degree that the eyes converged +to a point 10 to 20 cm. distant. The outward movement was suspended in +both eyes. The attempt to turn the eye outwards is accompanied by short +convulsive movements, and followed by an immediate rebound to the +convergent position. She asserts her inability to see the movements of a +hand before her eyes, is able, however, to move about in a strange room, +unsteadily certainly, but with avoidance of obstacles; she sits down on +a chair indicated to her, &c. The position of the eyes proves that there +was no simulation in all this; it would be impossible for any person to +simulate a strong convergent squint continuously for four to five days. +Eight days after her admission the patient was dismissed with normal +movement of the eyes and good vision. + +CASE 11. Miss Antonie E--, æt. 15, who has been treated by her family +physician for various hysterical disturbances, suffered since the middle +of December, 1879, from convergent strabismus with permanent but very +varying deviation, which is at times very slight, and sometimes amounted +to more than 7 mm. The movement outwards is in both eyes rendered +difficult, still the outer edge of the cornea is brought to the outer +angle of the lids with trouble and twitching movements. Homonymous +double images are present, their mutual distance is alike in the whole +field of vision, but is (six or eight weeks after the commencement of +the squint) signified as being slight; at the same time a difference in +height is present, the image of the left eye stands lower, prism 30°, +base outwards, places the images just above one another. Nystagmus +occasionally occurs in monocular fixation (with exclusion of the other +eye). In due course a gradual improvement set in, the deviation and the +distance apart of the double images became slighter, the outward +movement better, and in the middle of April, 1880, four months after the +trouble began, no squint and no diplopia were present, the outward +movement normal, facultative divergence = 0. + +The hysterical character of the visual disturbance showed itself when +the vision was tested. I will first observe that repeated investigations +with atropine showed emmetropia, while in the first investigation on the +left side, No. 36 at 5 m. was not recognised with the naked eye, but +only with weak concave glasses (with - ·5 D. V. = 5/18). With the right +eye No. 0·8 was read fluently, from 0·75 she asserted she was unable to +recognise a word, with - 2 D. V. = 5/36. It would be wrong to conclude +from this myopia or spasm of the accommodation, for here, as in most +cases of hysterical weak sight, it could be shown that whatever glass +one chose to hold before the patient's eyes, was followed by an +improvement in the statements. The same improvement in visual acuteness +was repeatedly obtained in this case by a weak prism (3°), held before +the fixing eye during monocular examination, and in the end, V. 5/12 was +obtained for the right eye, as against 5/6 with a prism of 3°. + +Finally, on May 1st, full visual acuteness was present on both sides. +Field of vision and sense of colour normal. + +CASE 12. Mrs. B--, æt. 30, previously treated for various hysterical +disturbances, has complained for about eight days of disordered vision, +the binocular nature of which was proved as patient had herself observed +that on closing one eye she could at once see clearly. Near objects to +15 cm. are seen distinctly. With all this, at the first examination it +was impossible to produce diplopia, either with the aid of a red glass +or prisms, &c., the images of first one eye, then the other were always +seen by turns. A few days later, on repeating the examination, double +images were perceived, they were homonymous with slight difference in +height (image of the right eye lower), the lateral displacement is +corrected by a prism of 28°. Micropsia of one image was also perceived. +On both sides the outward movement is rather difficult. Full visual +acuity on both sides--in the first examination slight myopia - ·75 D. is +specified, afterwards emmetropia. The visual disturbance was removed by +goggles with faintly ground glass on the right side--preparations of +iron, bromide salts, shampooing with cold water and electricity were +used. In six weeks' time binocular single vision was again restored; the +facultative divergence = 0. With red glass and vertically deviating +prisms homonymous diplopia corrected by prism 3°. Field of vision and +sense of colour remained normal throughout. + + + + +DIVERGENT SQUINT. + + +If we want to draw a comparison between convergent and divergent squint, +we must consider only absolute divergent strabismus, for convergent +strabismus does not offer a parallel to relative divergent squint. In +absolute divergent squint the direction of the visual axes is such that +they would meet behind the patient's head; in the relative divergent +squint the axes of vision are parallel or slightly convergent, but they +do not cross at the point fixed by the one eye, but at a greater +distance off. + +If we then only compare that which admits of comparison, we first find +out that divergent squint is rarer than the convergent form, and the +cause contained in the ocular muscles is here brought to light still +more clearly than there. + +We must next distinguish between permanent and periodic squint, and we +see the latter so frequently continue as such, that we must not consider +the transition from this variety to the permanent one to be the rule. + +In 183 cases of absolute divergent strabismus which appeared in my +private practice in the same space of time as the cases of convergent +squint above discussed I have been able to obtain exact determinations +of the refraction and visual acuteness. The weakness of the fixing eye +was the test for classing them among the statistics, and in patients who +had been long under observation, the first certain determination of +refraction, which was necessary, as several children are included who +came under treatment with divergent strabismus and emmetropia whilst +myopia developed itself later. + + +A. Divergent squint with hypermetropia. + +(_a_) Permanent 4 cases. Visual acuteness of the squinting eye more than +1/7 1 case, V. less than 1/36 1 case, 2 excluded, one on account of +complication with detachment of retina, the other on account of +impossibility of testing vision. + +(_b_) Periodic squint 5 cases. Among them 3 with double hypermetropia, 2 +with emmetropia in one, and hypermetropia in the other eye. Visual +acuteness of more than 1/7 in 3 cases; V. = 1/9 1 case; V. = 1/36 1 +case. + + +B. Divergent squint in emmetropia. + +(_a_) Permanent 32 cases. Among them 10 with alternating strabismus and +anisometropia of at least 2 D. And in 9 cases emmetropia in one, myopia +in the other eye; once simple hypermetropic astigmatism in one, with +myopic astigmatism in the other eye. Visual acuteness of both eyes in +these 10 cases more than 1/7. In the 22 cases of monocular squint the +visual acuteness of the squinting eye amounted 8 times to more than 1/7 +-, 10 times 1/12 to 1/36 (in 1 case V. = 1/36 with nystagmus of the +squinting eye when put into fixation). V. less than 1/36 in 3 cases; 6 +cases excluded on account of complications. + +(_b_) Periodic squint 28 cases. Among them 5 with anisometropia of at +least 2 D. (emmetropia in one, myopia in the other eye). Visual +acuteness of the squinting eye more than 1/7 in 27 cases, less than 1/7 +to V. = 1/12 in 1 case. + + +C. Divergent squint in myopia to M. = 2 D. + +(_a_) Permanent 24 cases (among them 6 with anisometropia of at least 2 +D.). Visual acuteness of the squinting eye more than 1/7 in 15 cases. V. +less than 1/7 to V. = 1/12 2; V. less than 1/12 to V. = 1/36 3; V. less +than 1/36 2 cases; 2 cases excluded on account of complications (one on +account of atrophy of the optic nerve, the other on account of posterior +polar cataract). + +(_b_) Periodic squint 23 cases. Among them 10 cases with anisometropia +of at least 2 D. Visual acuteness more than 1/7 in all 23 cases. + + +D. Divergent squint in myopia 2 D. to M. = 4 D. + +(_a_) Permanent 17 cases. Among them 2 with anisometropia of more than 2 +D. V. to 1/7 9 cases. V. < 1/7 to V. = 1/12 1 case. V. < 1/12 to V. = +1/36 2 cases. V. < 1/36 1 case. Four cases excluded (2 with choroiditis, +1 with congenital cataract, 1 with traumatic cataract). + +(_b_) Periodic 8 cases. Among them 4 with anisometropia of at least 2 D. +V. to 1/7 7 cases. V. 1/36 1 case. + + +E. Divergent squint in myopia 4 D. to M. 6·5 D. + +(_a_) Permanent 10 cases. V. more than 1/7 in 5; V. less than 1/36 in 3 +cases, 2 excluded (one on account of large anterior synechia, one on +account of choroiditis of the macula lutea). + +(_b_) Periodic 9 cases. Among them one with anisometropia of more than 2 +D. V. more than 1/7 5 cases. V. = 1/9 1 case; 3 cases excluded on +account of complications. + + +F. Divergent squint in myopia more than 6·5 D. + +(_a_) Permanent 8 cases. V. more than 1/7 4 cases, 4 excluded on account +of choroiditis of the macula lutea. + +(_b_) Periodic 10 cases. V. to 1/7 9 cases; V. = 1/12 in one case. + + +_Table of Refraction and Visual Acuteness in Divergent Squint._ + +[Transcriber's note: Key created to make table fit page] + +KEY: +A: Permanent. +B: V. to 1/7. +C: V. < 1/7 to V. = 1/12. +D: V. < 1/12 to V. = 1/36. +E: V. < 1/36. +F: Excluded. +G: Periodic. +H: V. to 1/7. +I: V. < 1/7 to V. = 1/12. +J: V. < 1/12 to V. = 1/36. +K: V. < 1/36. +L: Excluded. + +-------------------+---+----+----+----+----+----+----+----+----+----+----+--- + | A | B | C | D | E | F | G | H | I | J | K | L +-------------------+----+----+----+----+----+----+----+----+----+----+----+-- +Hypermetropia | 4| 1 | -- | -- | 1 | 2 | 5 | 3 | 1 | 1 | -- | -- +Emmetropia | 37| 18 | -- | 10 | 3 | 6 | 28 | 27 | 1 | -- | -- | -- +Myopia to M. 2 D. | 24| 15 | 2 | 3 | 2 | 2 | 23 | 23 | -- | -- | -- | -- +M. 2 D. to 4 D. | 17| 9 | 1 | 2 | 1 | 4 | 8 | 7 | -- | 1 | -- | -- +M. 4 D. to 6·5 D. | 10| 5 | -- | -- | 3 | 2 | 9 | 5 | 1 | -- | -- | 3 +M. more than 6·5 D.| 8| 4 | -- | -- | -- | 4 | 10 | 9 | 1 | -- | -- | -- +-------------------+---+----+----+----+----+----+----+----+----+----+----+--- + |100| 52 | 3 | 15 | 10 | 20 | 83 | 74 | 4 | 2 | -- | 3 +-------------------+---+----+----+----+----+----+----+----+----+----+----+--- + +It follows then from this, that periodic absolute divergent squint is +just about as frequent as the permanent form and that both become more +rare as the degrees of myopia increase. As, however, in spite of this, +myopia is present in about 60 per cent. of all cases, the connection can +be no other than this, that myopia frequently unites itself with +insufficiency of the interni and preponderance of the externi; in this +respect, as in every other, myopia and hypermetropia are directly +opposed. + +The setting up of a "hypermetropic divergent strabismus," dependent on +hypermetropia, seems to me only to show how much people have been +carried away by the idea that the cause of the squint must be given by +the state of refraction. Isler claims 17 to 29 per cent. of the cases +for hypermetropic divergent strabismus; of these, however, the half +possess only slight hypermetropia of 2 D. or less, which perfectly +agrees with the fact that the same observer has also found in convergent +squint a remarkably high percentage of the lower degrees of +hypermetropia. + +Whether squint originates in the permanent or periodic form depends +chiefly on whether the movement of convergence is retained or lost. +There are cases of considerable divergent squint, in which the near +point of the convergence is scarcely removed, while on the other hand, +the physiological innervation for convergence may be lost, without +absolute divergence ever being brought about. In a number of emmetropic +or slightly myopic cases with absolute preponderance of the externi, the +physiological connection between accommodation and convergence is +maintained in a relaxed way; thus, for example, it is impossible to +converge voluntarily to a large object, as, for instance, a pencil held +in the vertical line, while accurate convergence immediately follows on +reading at the same distance; in other cases accommodation can be +exerted to the near point, without inducing the slightest impulse to +convergence. This circumstance is worthy of consideration for the +prognosis of the operation. A mere relaxing of the tie between +accommodation and convergence may be strengthened by practice, but if +the impulse to innervation is completely lost, it will scarcely be +possible to restore it again; as after complete laying aside of absolute +divergence the relative form still continues to exist. + +Those cases deserve special consideration in which emmetropia is present +in one eye, in the other myopia. Slight degrees of one-sided myopia +reconcile themselves with the continuance of a normal binocular act of +vision. If the far point of the myopic eye lies at an inconvenient +proximity even for reading, then, as a rule, the emmetropic eye is used +for near as well as distant objects; if, on the contrary, the degree of +myopia answers to a range of vision convenient for working, and visual +acuteness is normal, then the temptation to use the emmetropic eye only +for distance and the myopic one only for near objects is so +overpowering, and the advantages on the other hand which would be +offered by clinging to binocular vision so slight, that a convenient +monocular vision is generally preferred. Even for objects which lie +nearer the eye than the far point of the myopic, and at the same time +farther than the near point of the emmetropic eye, for which, therefore, +both eyes could secure clear retinal images, binocular vision is not +used. In cases in which the patient can read with proper binocular +fixation, if one covers all but one line and then makes with prisms +double images standing one above another, it is the myopic eye alone +which almost invariably shows a clear retinal image. + +The usual result of this is, first a relaxing of binocular vision, and +as together with this the motive for convergence, namely, the effort of +the accommodation ceases, the conditions for the commencement of +divergence are produced. Still the elastic tension of the ocular muscles +decides even here; if the interni preponderate, convergent squint +results, when the myopic eye is used for near objects, the emmetropic +for distant ones. If the externi preponderate, then permanent or +periodic divergent strabismus is caused. Nevertheless, in a remarkable +minority of cases the elastic tension of the ocular muscles is so +regulated that, despite relaxation of binocular fusion, neither +convergent squint nor absolute divergence occurs, but simple relative +divergence remains with employment of the myopic eye for near objects. + + + + +DYNAMIC SQUINT, INSUFFICIENCY OF THE INTERNI AND MUSCULAR ASTHENOPIA. + + +The habit of binocular single vision, when it has once reached its +normal development, governs the movements of our eyes to a great degree; +the desire to avoid double images makes itself continually felt; and +where this is not possible, an uncomfortable feeling of uncertainty +arises at every movement of the body. Double images are prevented as far +as possible by movements of the eyes, which we must designate as +voluntary when we are conscious of their occurrence. + +If we follow a moving object with the eyes, the latter make +corresponding movements in order to keep the image in the centre of both +retinæ. For example, if we look at a distant object which approaches in +the direction of one visual axis, this eye will necessarily remain +still, while the other will be put into convergence in proportion as the +object advances. If this did not happen, if this eye remained also +immovable, the retinal image would deviate outwards more and more from +the macula lutea and diplopia would arise. In order then to avoid +diplopia the macula lutea moves to where the retinal image is formed. We +can, however, move the images on the retina by the aid of prisms without +movement of the object. If, for example, we hold a prism before the eye +so that the base lies towards the temporal side, the retinal image will +be displaced towards the base of the prism, outwards then from the +macula, and double images will occur, which are at once removed by a +distinctly perceptible inward movement of the eye. In this way, by means +of a prism applied with the base inwards, outward deviation may be +produced, and even in a modified way deviations in height of the visual +axes by means of prisms with the base upwards or downwards. Here the +force of habit is apparent, for in the daily use of our eyes we +continually practise the inward movement of the visual axes; we can also +easily restore the customary degree of convergence by means of prisms +with the bases outwards; physiologically indeed, it is quite immaterial +whether an object is in a proximity to our eyes attainable by +convergence, which causes double images until it is binocularly fixed, +or whether by the aid of prisms we bring the retinal images of a distant +object to parts of the retinæ which do not correspond. If we look at a +distant object fixed with parallel visual axes, under normal +circumstances, prisms of 6° to 8° with the base inwards can be overcome, +that is to say, as in weak prisms the deviation is equal to about half +of the prism, an absolute divergence of the visual axes of 3° to 4° may +be produced by which the double images are blended. It is immaterial +whether we apply a prism of, say 8° to one eye, or prisms of 4° with the +bases inwards to both. The facultative divergence thus attainable +remains the same, which speaks for the fact, that this monolateral +movement attainable by prisms is also combined with double innervation; +and of course in the eye remaining in unmoved fixation, with impulses to +innervation which are reciprocally abolished. + +In the physiological use of our eyes we certainly never have occasion to +practise absolute divergence, but we constantly practise the transition +from the inward to the outward movement of the eyes, and experiments +with prisms teach us, that the innervation of the externi therewith +connected may even be carried somewhat beyond the physiological limits +of parallelism. Moreover, the extent of the "facultative" divergence +attainable by prisms shows a considerable latitude. + +The case is similar with deviation in height of the visual axes. In +looking upwards or downwards the innervation of both eyes is usually +precisely the same, but on looking at any point when holding the head +obliquely, the difference in height of the eyes then present must be +balanced by a corresponding difference in the direction of the visual +axes. The same thing happens, if we hold a vertically deviating prism in +front of one eye in binocular vision; prisms of 2° to 3° may then be +overcome by difference in height of the eyes; rarely is a much greater +difference in height of the visual axes attainable. I have seen this +particularly in those cases where facultative divergence also was +greater than usual. + +It happens especially in myopia that prisms of considerably more than 6° +to 8° are overcome by divergence, and certainly without causing any +inconvenience. Among the cases presented for examination, those, of +course, are most numerous where the patients have some complaint to +make, even if this have quite a different cause. In any case a divergent +position of the axes of vision corresponds to the balance of the +muscles, and this does not generally occur, for this reason, because +retaining binocular single vision necessitates a parallel or convergent +position of the eyes. Frequently, however, even a slight impediment to +binocular fusion, such as the application of a red glass to one eye, +suffices to procure preponderance in the elastic tensions of the +muscles, and to cause the fixed point to appear double. We can put a +stop to binocular single vision still more surely by applying to one eye +a prism with the base upwards or downwards. If the double images of a +point 4 to 5 meters distant show a crossed lateral position besides the +difference in height caused by the prism, we may assume that an +absolute divergent position of the eyes corresponds to the elastic +tension of the muscles; and the measure of the deviation will be given +by those prisms which, placed with the bases inwards before one or both +eyes, bring the double images perpendicularly over one another. As a +rule, in these cases the degree of divergence which occurs on cessation +of binocular single vision, is almost as great as the facultative +divergence, which may be reached in the interest of binocular single +vision. + +V. Graefe designates as "dynamic squint" that condition in which the +position of divergence corresponding to the state of tension of the +muscles does not occur because binocular vision is retained. Without +clearly defined limits these conditions pass on into periodic squint, +when either diplopia occurs together with the divergence, or the habit +of binocular fusion becomes less frequent or is quite forgotten, while, +however, according to the varying state of the muscles sometimes normal +position, sometimes divergence, is present. A correct position of the +eyes is quite possible even without binocular fusion, then only the +regulator is wanting, which, in the varying play of the muscular forces, +ensures the balance of position and movement. + +The older ophthalmologists had a parallel strabismus and probably +understood by that, what we now designate as relative divergence. The +connection between relative divergence and myopia, pointed out by +Donders, is universally admitted; on the other hand, in more modern +literature we scarcely find any intimation of the fact that a parallel +squint occurs, which is quite independent of myopia, and rests solely on +the fact that the impulse of innervation for convergence is lost. A few +examples may explain this condition. + +CASE 13.--Auguste T--, æt. 28. On the left emmetropia, V. 12/20. On the +right the visual acuteness is variously given, but certainly does not +amount to more than 1/5 nor less than 1/10 of the normal. +Ophthalmoscopic report normal. The left eye is naturally the fixing one, +the right always remains parallel--for near objects double images are +present. A convergent movement is not attained, either for near objects, +or by means of prisms with bases outwards for distant ones. Prisms with +the bases inwards are not overcome; with vertically deviating prisms the +double images of distant objects stand perpendicularly above one +another. + +CASE 14.--Ludwig v. K--, æt 32, has complained of diplopia repeatedly +for fifteen years. Statement in August, 1877: Convergence to a pencil +held before patient on the median line is only retained to about 50 cm., +nearer, crossed diplopia occurs. In reading, binocular fixation is +possible with an effort at a nearer point. The facultative divergence +does not amount to more than 3°; even by convergence to a distance of 4 +mtr. prisms of 3° only are overcome. Emmetropia and full visual acuity +on both sides. In Sept., 1880, three years after, the statement remained +unaltered. Patient has only used the prismatic spectacles then +prescribed off and on, as the symptoms are sometimes more troublesome, +sometimes less so, and he exerts his eyes but little on the whole. + +A restriction of movement of the internal recti did not exist in these +cases; the absence of the convergent movement is not then to be set down +to the interni not possessing the proper power for acting, but only to +the fact that the impulse for their simultaneous innervation was +wanting. We frequently find this absence of innervation in divergent +squint, and then generally consider it to be a consequence of the +squint, which, however, as the above cases show, need not necessarily be +the case. If preponderance of the externi is at the same time present, +absolute divergence is the result, but not always permanent squint, +frequently only the periodic form. The anomaly of innervation may also +usually be proved in such cases, in that after the removal by operation +of the absolute divergence it continues to exist in the relative form; +it can indeed happen that for a few days after the operation convergent +squint is present for distance, together with relative divergence for +near objects. + +The highest phases of this anomaly, as represented in Cases 13 and 14, +are seldom seen. Slighter degrees, which, like so many other things, are +usually designated as "insufficiency of the interni," are more +frequently met with and are combined with asthenopia. On the one hand, +in looking at near objects a tendency exists to the formation of double +images, which are removed by the action of the interni; on the other +hand, however, the habit of binocular single vision is relinquished on +account of the frequent diplopia. In all forms of squint we see that +binocular fusion is forgotten; still it seems more natural to assume +this to be the result, and not the cause of the squint, as Krenchel +does. + +Another form of relative divergence is that which is brought about in +consequence of extreme myopia. The change in form of the myopic eye +diminishes its mobility, associated movements of the eyes may be +replaced by turning the head, but this is not possible for the movement +of convergence. Further, in extreme myopia the far point is generally +used for reading, &c., and sometimes even a somewhat greater distance, +because on account of the close proximity of the objects the retinal +images are so large that they are sufficiently clearly recognised even +if they are not quite distinct. At all events accommodation certainly +does not take place, hence one motive favouring convergence is removed. + +Finally, however, such considerable convergence as clear vision demands +in high degrees of myopia, would be difficult even for a normally +movable eye. Reasons enough therefore exist for giving up binocular +fixation and using only the more convenient eye for reading, without +effort to the accommodation and convergence. In myopia of high degree +patients almost always read with relative divergence, and these myopes +do just what we must advise them to do, they avoid strain of the +accommodation and convergence of the visual axes and thus keep well. + +Notwithstanding that this condition necessarily results from the nature +of extreme myopia, it is frequently held to be pathological, which it +certainly is not in itself. At most, the short-sightedness and change in +form of the eye are pathological; the relative divergence on the other +hand is simply a harmless result of the above conditions. + +No doubts whatever exist about this relative divergence. The theory that +the demands on the working eye must be very much increased is quite +unfounded. If any harmful influence were to be feared for the fixing +eye, one would observe the same in convergent squint, when, as a rule, +one eye only is used for fixation even after operation. + +In convergent strabismus, however, no one, at least no ophthalmologist, +thinks of entertaining such fears for the eye used in fixation, and +where is the physiological basis of this whole idea to be found? Is the +visual purple more active in monocular than in binocular vision, or what +physiological activity is thereby taxed in increased degree? + +I have found no confirmation of Alfred Graefe's theory that in myopia +the eye chiefly used in fixation is frequently affected with choroiditis +of the macula lutea, &c., but have only observed that patients to whom +this happens seek the advice of a physician more eagerly than when the +same intra-ocular troubles befall the other usually neglected eye in +connection with myopia. + +Muscular asthenopia undoubtedly occurs; it is only a question whether it +is as frequent as it is diagnosed. It has its foundation in that the +convergence necessary for reading, writing, &c., can only be sustained +by an effort of the internal recti, which exceeds their strength, and +finally results in painful fatigue of the muscles, just as accommodative +asthenopia depends on painful fatigue of the muscles of accommodation. +The similarity reaches still further. We occasionally find that despite +considerable degrees of hypermetropia no asthenopia occurs even in +persons who strain their eyes; while, on the other hand, asthenopic +troubles appear in hypermetropia which are not removed by correction of +the refraction and must consequently have some other motive. Yet still +more is this the case with those disorders, of which muscular asthenopia +may be supposed to be the cause. Notwithstanding the existence of a +considerable preponderance of the externi, muscular asthenopia may be +entirely absent. If we find, for example, that as soon as we do away +with binocular single vision absolute divergence occurs even on looking +at a distant fixed point, and that prisms of 12° to 30° are overcome by +divergence, we may safely assume that the elastic preponderance of the +externi must be overcome in reading, &c., in the interest of binocular, +single vision by a stronger muscular effort of the interni, which is, +however, very frequently accomplished without fatigue. Asthenopic +disorders are also frequently present together with preponderance of the +externi, which continue to exist despite the removal of the same by +operation, and must consequently have some other cause. The diagnosis of +accommodative asthenopia is as a rule confirmed _ex juvantibus_; this +cannot be asserted for the muscular form. + +For example, Case 15.--Mathilde F--, æt. 21, has suffered from +asthenopic disorders for three years. The investigation at the beginning +of January, 1880, shows: On the left, myopia 4 D., V. = 5/18, No. 0·3 is +read at 10 cm.; on the right, myopia 6 D., V. 5/24, 0·3 is read with +difficulty, cylindrical glasses cause no improvement. Patient converges +to about 8 cm., on exclusion absolute divergence of 3 to 4 mm. follows, +with slight upward deviation of the right eye. + +On correction of the myopia the facultative divergence amounts to = 26°. +Here one might easily have concluded the asthenopia to be a result of +fatigue of the interni, but this opinion was refuted by the effect of +the treatment. The double tenotomy of the externi performed on January +2nd was first followed by convergent squint with homonymous double +images, which were united by a prism of 12° with the base inwards. In +the course of a few days single vision was again restored. A fortnight +after the operation, on correction of the myopia, patient could see +singly to 3 mtr.: towards both sides homonymous double images were still +present, and in fixation to 30 cm. relative divergence on exclusion of +one eye. Six months after the operation, on correction of the myopia and +application of red glass to one eye, crossed double images occur close +together, which become homonymous by means of a prism of 3° with the +base inwards. Patient sees double images always, without being much +disturbed by them, yet they cannot be united by means of prisms. The +habit of binocular single vision has also gradually been lost. In +reading (without correction) a movement of convergence takes place (it +cannot be determined whether this answers exactly to the distance of the +object). If, on the other hand, one asks the patient to fix binocularly +larger objects, such as a pencil close to her, she is unable to do it, +relative divergence occurs then, as well as on exclusion of one eye. The +asthenopic disorders remain unchanged and are not removed even by +prismatic spectacles. Despite all reasons then for the supposition the +asthenopia was certainly not of a muscular nature. + +The uncertainty as to diagnosis is still greater in those cases which, +according to v. Graefe, were to be designated as dynamic relative +divergence; cases in which with parallel visual axes a disturbed +balance is not present but occurs on convergence in such a way that the +interni only perform their destined work with difficulty, and are +nevertheless urged on in the interest of binocular single vision, till +they give way in painful fatigue. + +According to v. Graefe the diagnosis of this condition must be carried +out in the following way. First of all the convergence must be fixed on +a near object in the median line; if one eye remains behind in the +movement it may be accounted for in various ways, for example, the +impediment of movement caused by the change in form of the eye in myopia +or the faulty innervation of the interni mentioned on p. 54. In both +cases for the most part no dynamic, but manifest relative divergence is +present in viewing near objects. It may also happen that the patient +does not converge sufficiently, merely because accommodation is absent. +This experiment does not then prove the presence of dynamic relative +convergence, and v. Graefe came to the conclusion, therefore, that a +normal position of the eyes obtained only by the habit of binocular +single vision must be relinquished so soon as we cause binocular single +vision to cease. Just as under these circumstances dynamic absolute +divergence is manifested in the observance of distant objects, so must +this be the case in dynamic relative divergence in the observance of +near objects. One eye is first excluded while looking at an object about +25 cm. distant, to determine whether it still remains in a proper +position for fixation. We have reason to believe that the position which +occurs in the excluded eye answers to the given conditions of tension of +the muscles. Still it is not necessary to cause binocular vision quite +to cease, it is sufficient and even more advantageous, simply to make +binocular single vision impossible, which we are able to do by means of +prisms. If, for example, a point be fixed lying at the usual distance +for work of 25 to 30 cm., or, according to v. Graefe, a large spot +intersected by a vertical line, and one then applies a vertically +deviating prism to one eye, the influence of binocular single vision on +the ocular muscles is removed, as the fusion of the double images +standing above one another is impossible; and nothing prevents the +assumption of a relative position of divergence instead of a proper +convergent one; as a result of this the double images show a crossed +lateral position as well as the difference in height produced by the +prism. The extent of this lateral deviation may be measured by means of +prisms, which being applied to the eyes with the bases inwards place the +double images again perpendicularly above one another. Von Graefe holds +it to be of importance to determine the strongest prisms which can be +overcome for the given distance by means of convergence and by the +outward movement of the eyes. + +On the strength of this method of inquiry there is a prevalence of +opinion that the asthenopic disorders common in myopia are caused by +over-exertion of the ocular muscles; indeed people believe this so +strongly that they assume the presence of muscular asthenopia even in +individuals in whom the habit of working with relative divergence is +already firmly rooted. Relative divergence may perchance cause annoyance +through double images, though this really seldom happens, but it can +never cause muscular asthenopia, for the internal recti muscles protect +themselves by means of relative divergence from any stronger exertion. + +Asthenopic disturbances are certainly frequent in myopia, but the above +method of inquiry does not at all prove that their cause lies in the +ocular muscles, for those appearances from which one concludes dynamic +relative divergence and muscular asthenopia, are found in almost all +myopes, even when the latter have no asthenopic troubles, for they owe +their origin to the nature of the myopia. Myopes learn to converge to +the distance of their far point, without exerting the accommodation; if +we now cause a point at this distance to be fixed and then exclude one +eye, or make binocular fusion impossible by means of vertical prisms, +what imaginable reason is there for the excluded eye to remain in proper +fixation? In emmetropia the habitual relation between accommodation and +convergence will be able to ensure that the excluded eye also remains +covering the fixed object, convergently as well as accommodatively; in +myopia, every discretionary relative divergence up to parallelism of the +lines of vision is perfectly justified, because no effort of the +accommodation takes place. How in the world can it be held to be +pathological that a movement of convergence does not occur, when one has +just artificially removed all those physiological conditions which could +possibly have brought it about? If one now likes, as v. Graefe proposes, +to determine the prisms, which can be overcome by means of the outward +movement, there is no doubt about the fact, that with the aid of prisms +the lines of vision may be made parallel or even divergent, the retinal +images indeed, always retaining the same distinctness, in so far as they +are not injured by the prismatic diffusion of colours. There is just as +little reason why the convergence usually attainable should not also be +restored by the aid of prisms with the bases outwards, the retinal +images are not only impaired by the prisms, but the accommodation united +with the convergence, no longer corresponds to the real distance of the +fixed point. + +Enough, all these incidents, which are to prove the presence of muscular +asthenopia in myopia, occur when the investigation is carried out as +usual in the region of the far point, entirely on a physiological basis, +and must not therefore be held to be pathological without further proof. + +The proof of muscular asthenopia in slight degrees of myopia, +emmetropia, or hypermetropia, is somewhat more certain; a deviation from +physiological laws is certainly present, if we find that the +corresponding convergence does not unite itself with the accommodation +for a near object, we must be quite sure that an exact accommodation for +the fixed point is also really present. It by no means follows because +one causes a large black spot to be observed at a distance of 25 to 30 +cm., that an exact accommodation takes place; one can see these things +even with circles of diffusion, the retinal images are already dimmed by +means of the prisms, and one can easily convince one's self that, on the +renunciation of clear retinal images, normal eyes can reach every +attainable convergence or relative divergence by means of prisms. +Insufficient accommodation and defective convergence are, however, +easily caused by all painful sensations situated near the eye, which +make the accommodation uncomfortable and fatiguing. This applies to +every common head- or tooth-ache, and in the same manner to disturbances +arising in the conjunctiva, or which depend on the stretching of the +collective tunics of the eye in myopia, or which allow any other +so-called "nervous" origin to be suspected. + +We must place the same claims to the diagnosis of muscular asthenopia as +to that of the accommodative form. Just as the latter is only detected +if convex glasses really give the expected relief, so the proof of +muscular asthenopia is only furnished when relief to the interni is +brought about by means of the appropriate remedies. For myopes, who do +not fall back on the aid of relative divergence, notwithstanding that +they possess a clear field of vision only attainable with difficulty +through convergence, it is the simplest plan to remove the far point to +about 25 to 30 cm. by specially adapted concave glasses. If only slight +myopia or none at all is present, but the relation between accommodation +and convergence is disturbed, the latter can be corrected by means of +prisms with the bases inwards--to be sure, only in a slight degree, as +prisms of more than 4° are scarcely suited for spectacles, partly on +account of their weight and partly on account of the diffusion of +colours. Prisms may be ground with concave or convex surfaces, according +to the requirements of refraction or accommodation. + +Finally, if an elastic preponderance of the externi can be proved by +means of considerable facultative divergence, the same may be lessened +by tenotomy of one or both externi; still after my own experience I +cannot advise the performance of this operation unless prisms of at +least 16° are overcome by absolute divergence, for I have seen many +patients in other practices who have acquired convergent squint and +diplopia for distance as the sole result of the operation, while the +asthenopic troubles for near objects continue. The proof that it is not +a case of muscular asthenopia is sometimes only obtained by the +operation. + + + + +BINOCULAR VISION IN SQUINT. + + +The fact that those who squint do not as a rule have diplopia, while +squints depending on paralysis of the ocular muscles are combined with +diplopia, was difficult to explain as long as the view was adhered to of +identical retinal areas founded on anatomical construction. The first +explanation hit upon was that a false identity became established, an +inequality of the retinæ; were this the case diplopia must of necessity +occur on correction of the squint by tenotomy. + +Commencing with the assumption of a congenital identity which led under +all circumstances to the occurrence of diplopia as soon as the images of +the same object fell in both eyes upon non-identical points of the +retinæ, the hypothesis was next advanced that the image of the squinting +eye was not perceived, that a constant suppression of the sensations in +the squinting eye took place. Suppression of sense-impressions does take +place; as soon as our attention is entirely engrossed upon anything, we +are in a position to disregard the impressions upon all other organs of +sense; they do not reach our consciousness. That visual sensations are +easily disregarded may be proved by experiments. Hold a small plane +mirror obliquely before one eye, with the brim pressed into the angle of +the nose so that the objects lying at the side and behind are seen in +the mirror. If the other eye is now used to read with, it is quite easy +to disregard the objects seen in the mirror provided that our attention +is not attracted to places by a particularly bright light. No doubt +those who squint also possess this physiological power, and it is +therefore certain that they make use of it under certain circumstances; +but the suppression theory necessitates that they should constantly and +always do so, since diplopia is bound to occur directly they do not do +it. + +The absence of double vision is in fact the only evidence that can be +adduced in favour of the exclusion theory; this negative fact, however, +proves nothing, and is, moreover, capable of other explanations, as soon +as one abandons the theory of congenital retinal identity. The +examination of those who squint demonstrates the untenability of this +theory. People who squint seldom complain of diplopia, but double images +can be rendered apparent in a comparatively large proportion of cases, +usually with the greatest ease, by covering the best eye with a red +glass and squinting with a vertically deviating prism. Many squinters +now admit the presence of double images, but their position by no means +corresponds to the identity theory, their lateral displacement is far +too slight, or patients find themselves unable to localise the position +of the image. It sometimes happens that alternating vision with both +eyes is mistaken for diplopia, the images are then invariably specified +as homonymous; however, with attention it is easy to distinguish this +alternating vision from the simultaneous perception of two images of one +and the same object. + +There can be no doubt that in most cases the position of the double +images does not correspond to the principle of identity, and just as +little doubt that one to whom double images are easily made apparent +cannot possess the confirmed habit of always suppressing the image of +the squinting eye. A certain number of cases remain in which it is +impossible to produce diplopia; that these, however, do not constantly +suppress the image of the squinting eye may be proved in the very simple +way I have indicated. An object of fixation is placed in a darkened +room, on one side of and behind the squinting eye is placed a small +flame, the reflection of which, by means of a plane mirror before the +squinting eye is thrown upon its retina. The reflection of the flame is +seen on the cornea of the squinting eye, by slight rotation of the glass +it can be brought into the area of the pupil, and at the same instant +the patient sees the light, the reflection of which can easily be made +to coincide with the image of the fixation object seen by the other eye. +The experiment has then an entirely objective basis, it always succeeds, +a fact on which I lay special stress, even in eyes whose vision is very +defective; therefore here also the habit of suppression of the retinal +images of the squinting eye is not present. + +That the squinting eye really possesses its full share of the visual +field can easily be proved (especially in divergent squint) by the aid +of a perimeter. The best eye is covered with a red glass, so that the +objects projected from the fixation point, as well as the excentric +field of vision of this eye, appear red. As soon as the test object +moves towards the side of the squinting eye and enters the visual area +covered by the latter, it appears in its natural white colour, and this +in most cases before it has reached the centre of the retina of this +eye. + +Another proof that the squinting eye is really used for vision appears +to me to lie in the fact that persons who squint, provided of course +that the vision of the eye concerned is not very defective, do not show +that uncertainty in the estimation of distance, which is apt to prove so +troublesome to those who have only monocular vision. + +[Illustration: FIG. 1.] + +If, then, the view of the constant suppression of the retinal images of +the squinting eye is untenable, how is it to be explained that squint as +the result of paralysis of the ocular muscles causes diplopia, while +concomitant squint does not? The answer to this question is clear as +soon as we abandon the supposition of a congenital retinal identity, and +look instead upon the relation of the eyes to each other as harmonious; +identity, or co-ordination as something acquired. Central fixation is +congenital and depends upon anatomical conditions, for as the macula +lutea is anatomically the most perfect part of the retina, it is natural +that the new-born child soon learns to place this part of the retina +opposite objects which attract its attention, and therefore those +relations of the eyes to each other are naturally developed. For +instance, if both eyes (Fig. 1) are directed to the distant point _a_, +the image of point _b_, situated at the same distance, will fall on the +inner half of the retina of the left eye; the left eye will now learn by +experience to refer inner retinal images to objects lying to the left of +the fixation point; at the same time, however, with binocular fixation, +the right eye learns to seek the images of the temporal half of its +retina in the left field of vision, and _vice versâ_. From this it is +easy to trace the laws of binocular diplopia. For example, let _a_ in +Fig. 2 be the fixation point, while at the same time the image of _b_ +belongs in both eyes to the temporal half of the retina. Now, as we have +already seen, the right eye has learnt to refer temporal retinal images, +to objects lying to the left of the fixation point, while for the same +reasons the left eye projects temporal images to the right. While then +point _a_ is seen binocularly singly, point _b_ appears double, and +certainly the image of the right eye is projected to the left of the +fixation point, and that of the left eye to the right of it, in other +words, crossed diplopia is present. But the eyes are divergent relative +to point _b_; double images then which occur as a result of divergence +(whether relative or absolute) must appear crossed, and one will easily +be able to infer that for the same reasons those double images which +occur in consequence of convergence, must be homonymous. All this, +however, only with the presupposition, that the habit of binocular +fixation is already fully developed; any disturbance of the same, in +whatever way (by prisms, mechanical displacement of the eyes, paralyses +of the ocular muscles, or by those forms of squint which arise after +childhood is past) causes the double images to illustrate the law above +explained. Certainly diplopia may be absent even then, but only in very +rare instances. Now and then this happens in objectively proved ailments +of the ocular muscles, where the patients complain of disturbed vision, +which disappears immediately on the exclusion of one eye (see Case 12), +a method of relief they usually discover for themselves; thus the +indistinct vision is seen at once to be a disturbance of binocular +vision. Many such patients learn to see the double images which formerly +escaped them, after they have been instructed how to do so during the +examination. With others, all efforts are in vain, it is impossible to +render them conscious of the double images, notwithstanding that the +presence of the binocular disturbance of vision proves that the habit of +binocular fixation exists. This apparent contradiction is explained, if +one reflects that the physiological basis of vision rests on a series of +conclusions. The first thing which strikes us as a result of binocular +fixation is, that the images of the centres of the retinæ may be +referred to one and the same region of the room, and this experience +will be retained, even if the images on the centres of the retinæ +represent different objects in consequence of paralysis of the ocular +muscles; the images are notwithstanding referred to one and the same +part of the room, all objects are thrown together promiscuously, and the +consequent embarrassment is of course removed directly one eye is shut. +The experience of those patients whom it is impossible to render +conscious of double images, despite the habit of binocular fixation, +reaches up to this point. A second conclusion belongs to diplopia, and +for that it is necessary to seek out from the confusion of objects, the +two retinal images belonging to one and the same object, and the +majority of people, though not all, take this second step also. It is +seen at the same time that the opinion held by Donders, that diplopia is +absent in squint, does not suffice, for this reason, because the image +in the deviating eye is too excentric. What becomes then of the image +lying in the centre of the retina? + +[Illustration: FIG. 2.] + +The absence of diplopia in squint may be explained quite simply by the +fact that the habit of binocular fixation has not been learnt or has +been forgotten; one can learn nothing that cannot be again forgotten. +The normal fusion of the visual fields can only develop in consequence +of binocular fixation, and diplopia is only possible when some kind of +binocular fusion exists. If no binocular fusion exists, then all +possibility of diplopia is excluded. And why should those who squint +from their earliest childhood not see well with both eyes, but yet with +each separately, just as is the case with animals with laterally placed +eyes? For example, in Fig. 3 there is convergent squint of the left eye, +the right eye fixes the point a, whose retinal image is cast at _a_' in +the left eye; the direction outwards in which these images are projected +is discovered by drawing a straight line from _a_ to _c_ (the optical +centre of the eye); suffice it to say that point _a_ is seen by each eye +in the direction in which it really stands. + +[Illustration: FIG. 3.] + +But although both eyes see at the same time, yet the close relation +which in binocular fixation develops between the centres of the retinæ +does not occur in squint; firstly, because the retinal area in the +squinting eye which corresponds to the fixation point is too excentric, +and secondly, because the angle of the squint often changes. In +binocular fixation, the fixation point of one retina answers to the +corresponding point of the other; in squint, on account of the varying +size of the squint angle, if a like relation develops between the eyes, +the fixation point of one retina must correspond to a larger area of the +other. Possibly this explains a fact that is often to be observed. In +those cases of squint where diplopia can easily be caused by covering +one eye with a red glass and the other with a vertically deviating +prism, the double images disappear on rotation of the prism round the +axis of vision, as soon as the angle of the prism reaches an angle of +about 45°. The occurrence of double images shows that there exists for +the upper and lower parts of the retinæ a community of vision by no +means coinciding with the identity principle. The disappearance of the +diplopia can be explained by the fact that the variations of the squint +angle take place chiefly in the horizontal direction. Therefore the area +in the squinting eye that corresponds to the fovea centralis of the +fixing eye must be more extensive in the horizontal than in the vertical +direction. Alfred Graefe has designated this phenomenon as "regional +exclusion." Whilst then a sort of community of vision exists for the +upper and lower parts of the retinæ, the sensations of the retinal area +lying in the horizontal plane of the macula lutea of the squinting eye +must be suppressed. The physiological occurrence of a suppression of the +retinal images, as far as we are able to investigate it, always refers +to the whole retina; however, the possibility of a "regional exclusion" +should not be excluded to begin with; but in the inductive sciences it +is for us to ask first, whether an incident really happens, and not +whether it is possible. The fact from which Alfred Graefe draws his +inference is not, as we have just seen, to be explained in any other +way, and the ophthalmoscopic test described on p. 65 proves that also in +these cases of "regional exclusion" both eyes are used for vision. + +In many cases of periodic squint the condition of binocular vision is +very interesting. Binocular fusion may be quite absent even in normal +position of the eyes; on the other hand the non-occurrence of diplopia +in squint does not prevent the occurrence of perfect binocular fusion +with a normal position. In periodic outward squint I have sometimes seen +binocular fixation without the existence of binocular fusion; the +excluded eye deviates outwards, but as soon as it is free it puts itself +into fixation, whilst neither with prisms nor stereoscope can anything +other than alternating vision be proved, _i. e._ neither binocular +diplopia nor fusion. + +If squint arises when the habit of binocular single vision has become +confirmed, diplopia is always present, at least at first; even children +of six to seven years old make this statement uninvited, but they soon +get accustomed to the new relations, and after a short time it is +impossible to make them see double images (see Case 42). Habits cling +more closely in adults, therefore that form of convergent squint in +particular, which usually develops quickly in myopia of average degree, +causes annoying diplopia to last for a longer time. For just when these +patients want to employ binocular vision in order to estimate distance +correctly, diplopia occurs to hinder and confuse them. + +It is otherwise with the relative divergence which is developed in +consequence of myopia. At first diplopia is present here for a short +time; in this case circumstances are specially favorable to a temporary +suppression of the deviating eye; the fixing eye receives large distinct +images to which the attention is directed. Meanwhile the relatively +divergent eye is usually turned to other more distant objects that +furnish indistinct retinal images, from which the attention is easily +diverted. The habit of suppression may become so dominant that binocular +fixation continues to exist for distant objects and the presence of +binocular fusion is easily traceable, while for near objects, which are +monocularly fixed with relative divergence, it is impossible to render +the patient conscious of the images of the deviating eye. + +Considerable squint is by no means necessary for the cessation of normal +binocular single vision; slight, frequently recurring deviations are +quite sufficient, as in those cases where want of control renders +physiological innervation for convergence more difficult. Double images +are present here, although not in a troublesome way, as is usual in +relative divergence, but binocular single vision does not exist even for +distance. The reason for this does not lie in the impossibility of +fixing the same object simultaneously with both eyes, for the +objectively proved deviation may be extremely slight. A union cannot be +obtained even by prisms. If crossed double images are present close +together, a prism of a few degrees base inwards suffices to make them +homonymous. The habit of binocular single vision is lost, in consequence +of that disturbance to the innervation of the interni which is +designated as insufficiency of the same. + +The stereoscope, as well as the prism, is useful for testing binocular +single vision, especially when it is suitably modified for the purpose. +The prismatic glasses usually attached to stereoscopes are here quite +superfluous. The advantage of the prismatic deviation consists solely in +the fact that the centres of the images fixed for the macula lutea on +each side can be removed farther from one another than the distance +apart of the eyes amounts to, so that a greater extension of the visual +area is rendered possible. Ordinary stereoscopic pictures are quite +useless for testing binocular vision; it is a question here of employing +diagrams, which contain on the one hand very prominent identical figures +stimulating binocular fusion but which, on the other hand, offer for +each eye special attractions not present in the visual field of the +other. Further, it is desirable to regulate the stereoscope so that the +glasses are not firmly inserted, but that glasses from the trial case +may be applied according to the condition of refraction of the patient +and the distance of the stereoscopic images. + +The stereoscope is generally used with the greatest advantage in those +cases where there is no conspicuous deviation, and by testing binocular +vision conclusions may be drawn as to whether normal binocular fusion +exists or has disappeared in consequence of the squint. + +It is desirable to use both methods of investigation, that with the +stereoscope as well as prisms, as each test has its own value. One who +at once combines the stereoscopic fields of vision certainly has +binocular single vision; in other cases this is only so far lost that +the stereoscopic combination does not take place at once but only after +some trouble. Care must be taken, especially when one eye has defective +vision, that the corresponding visual field contains objects +sufficiently large and easily recognisable, as very small objects which +do not correspond to the lowered visual acuity are easily overlooked. It +sometimes happens that both fields are seen at the same time, but that +there is no fusion; finally it happens frequently that there is complete +suppression of one visual field. In testing with prisms it may appear +doubtful as to whether binocular fusion or suppression of one eye +exists; however, the stereoscope at once gives us certain information. +It must not be forgotten that the altered relations between the eyes, +which are always possible in squint, also appear at the same time; he +who sees double with prisms, may yet be able completely to suppress the +stereoscopic visual field of one eye. Binocular fusion, suppression of +the squinting eye and simultaneous vision with both eyes without +binocular fusion can alternate in the same individual. Von Kries has +come to the same conclusion, and if our colleague is unable to explain +all the phenomena of binocular vision that he could observe in his own +case, we need not be astonished if we sometimes hear from our patients +statements that appear incomprehensible and unphysiological. + +At any rate it is evident that the absence of diplopia in squint can +easily be understood, without adopting the arbitrary idea of a constant, +habitual suppression of the image of the squinting eye. + + + + +VISUAL ACUTENESS OF THE SQUINTING EYE. + + +Whether the state of refraction or the condition of the muscular +equilibrium is held to be the chief cause of squint, defective vision of +one eye will always have to be acknowledged as one of the most important +favouring circumstances; in order to cure squint it is important to have +regard to the visual acuity of both eyes, and not only to the defective +condition. But this is no easy matter. + +First it is to be observed, that most cases arise at an age when an +objective determination of refraction is possible, but when the visual +acuteness cannot be determined. Even in children who have received +slight instruction, it is frequently difficult to distinguish whether +imperfect knowledge of the letters or faulty visual acuteness is the +cause of the non-recognition of the test-letters; when testing the +vision of children it is often better to use figures than letters. + +Further, in these cases it is much to be desired that the habit of +determining the refraction and visual acuteness at the same time should +be discontinued, particularly in reduced visual acuteness, as the +test-tables only contain a few letters, which have to be recognised at a +distance of 5 to 6 metres. If they have once been read with one eye it +may easily happen that in testing the second eye they are repeated from +memory, without being clearly recognised; even a child soon learns the +few letters by heart. Therefore, when it has been a case of determining +the visual acuteness I have always conducted the examination at a +distance of one metre, as the choice of letters or figures which can be +employed at this distance is much larger than for greater distances. In +every case the reading of test-letters must be used as an additional +means of examination. We must never forget that the test of vision is a +perfectly subjective examination, and that we are obliged first of all +to accept the statements of patients as they are given without knowing +what they are worth. I have met with patients in the most highly +educated classes of society who, in intra-ocular troubles, for example, +hæmorrhage of the retinal artery in the macula lutea, could not +distinguish the largest type in the first examination, and the next day +(perhaps with slight difficulty) could read small print. + +Such inaccuracies may continue to exist during repeated examinations and +for long periods. One of my patients, for instance, who first came under +treatment in the year 1873, had extreme myopia in the left eye with good +visual acuity; with the right eye, which was also myopic, and had +suffered for several years from choroiditis of the macula lutea he could +read only No. 20 Snellen, and a year later 7-1/2 was read with +difficulty, word by word. Choroiditis of the macula lutea gradually +developed in the left eye, and in the same proportion the statements as +to visual acuteness of the right eye improved, so that finally at the +end of 1881, 0·5 was read with difficulty with this eye, while the left +still sufficed to read 0·4 (at about 5 cm.). As I tried to comfort the +patient, who was very anxious about his left eye, with the fact that the +right eye had considerably improved in the course of the year, he +replied that he might previously have seen just as well with the right +eye if he had only taken the trouble, this was certainly my own opinion. + +The attention and intelligence shown by patients during examination +materially influences its results, and one should never hold the first +trial of vision to be conclusive. We must always remember, however, that +all conclusions drawn from visual acuteness become more unreliable in +proportion as the latter is slight. We must attend to some peculiar +difficulties in testing the vision of those who squint or we shall be +liable to make great mistakes. When testing the squinting eye, +particularly in children, it is not sufficient merely to cover the other +or to hold the hand over it, for they know how to bring the usual eye +into fixation by holding the head on one side or peeping between the +fingers; we must keep it carefully closed with a bandage. + +It is still more frequently the case that visual acuteness is stated to +be less than it is in reality. The result of always using the better eye +for fixation is, that fixation is not learnt with the weaker one. Even +where there is no squint we see very frequently that in one-sided +hypermetropia the accommodation is only used in that proportion which +has become habitual to the emmetropic eye and does not therefore suffice +to produce clear retinal images, while good visual acuteness is obtained +by means of the correcting convex glasses. In the case of squinters +(even without difference of refraction) it happens very frequently that +the first statements as to the visual power are considerably below the +truth. Patients who assert that they can only read the largest print +with difficulty, frequently read smaller, and even the smallest type +without more trouble, and we must be careful to ascertain this at first. +Accurate reports are usually obtained more quickly by means of convex +glasses or eserine. In any case insufficient accommodation is, according +to this, one of the difficulties, but not the only one, which has to be +overcome before the squinting eye can be put into fixation. We can +understand that the innervation necessary for distinct vision can be set +aside even without loss of visual acuteness, just as we see the movement +of convergence disappear without the interni losing their capacity for +contraction. + +In order to explain the relation between squint and defective vision, +we must first consider the question hitherto neglected, or what is +worse, answered with preconceived opinion, as to whether the same form +of defective sight which is so common in squint also occurs without +squint. No one doubts the existence of congenital amblyopia, +nevertheless it has received but little attention in the handbooks on +ophthalmology. Leber, for instance (in the well-known compilation, vol. +v), does not mention it at all. + +A more or less considerable reduction of visual acuteness, with good +field of vision, normal sense of colour and normal ophthalmoscopic +condition, are characteristic of congenital amblyopia. Colour-blindness +may of course be present at the same time. I also hold as probable the +very rare occurrence of congenital defects of the visual field in good +central vision, but I will reserve for the present the few observations +I possess on the subject. + +Together with congenital defective vision we must consider the +depreciation in visual acuteness usually present in nystagmus, although +it might be asserted that it can neither be the cause nor the result of +the nystagmus, for we find very considerable degrees of congenital +defective sight in both eyes without nystagmus, as well as nystagmus +with remarkably good visual acuteness. Not to complicate the question, +however, I have excluded all cases of nystagmus from the following +investigation. All cases of myopia of higher degree (_i. e._ of more +than 6 D.) have also been excluded, as in such cases for various +well-known reasons the full visual acuteness is never present. In the +case of individual patients who remained for years under my observation +I have been able to convince myself that visual acuteness decreased in +accordance with the increase of myopia; on the other hand, however, it +appeared to me very probable that just those cases of myopia, which from +the beginning do not possess full visual acuteness, have a special +tendency to increase quickly. + +For instance, if the examination of a hypermetropic eye, whose defect +can be exactly determined by means of the ophthalmoscope, shows very +faulty visual acuteness which is but slightly or not at all improved on +correction of the hypermetropia, it is clear that the cause of defective +sight is not to be sought in the hypermetropia. It is just the same with +astigmatism. In defective vision with astigmatism proved by means of the +ophthalmoscope, how frequently it is the case that not even the +slightest improvement can be obtained with cylindrical glasses. This is +usually attributed to the presence of an irregular astigmatism situated +near the asymmetric meridian. If we illuminate the eye by means of a +plane mirror, and observe one spot on the pupillary area which looks +sometimes bright, sometimes dark, during slight rotations of the glass, +this appearance can only be caused by the above-mentioned irregularity +of the refraction of light, and it will be easy to determine whether the +same takes place in the cornea or in the lens. But if this appearance is +not present then irregular astigmatism cannot be proved. It is purely +intentional, or a play upon words, if we refer an existing defective +sight to an optic cause which cannot be proved. For instance, if +haziness of the cornea exists, it is not difficult to learn to estimate +by practical experience whether the amount of visual disturbance +corresponds to the optic irregularities caused by the opacities and +irregular refraction of the cornea. Slightly nebulous corneæ with +disproportionately bad vision were therefore included in the following +statistics; however, they do not influence the result as there are only +ten cases in all. On the other hand, considerable opacity of the corneæ +or cases which were complicated with anterior synechia, &c., were +excluded from the statistics. + +If then we find defective vision, the development of which has not been +noticed by the patient, together with normal ophthalmoscopic condition +and full visual field, and if it is further seen that the condition +remains unchanged for years, we have every reason for considering the +defective sight to be congenital. The statements of patients must of +course be received with caution. If congenital amblyopia of moderate +degree exists in both eyes, patients do not usually know that it is +possible for anyone to see better; if the congenital defect is one +sided, it is generally only casually noticed on closing the better eye. +We can scarcely doubt that it is a case of congenital amblyopia if it +happens in children. Acquired defective sight without ophthalmoscopic +cause seldom occurs among children. I have seen a few cases as a result +of severe cerebral disease (hydrocephalus, for example); so-called +anæsthesia retinæ, or amblyopia marked by contraction of the visual +field is not quite so rare. It is easy to avoid confounding both these +cases with congenital amblyopia. + +One must be more careful about drawing conclusions with regard to +adults, for on the one hand it happens that gradually developed +monocular visual disturbances are only accidentally observed by patients +after they have reached a high degree, and it is very difficult then to +persuade these attentive observers that it is not a case of sudden +blindness of one eye. (Only a few people seem to be really aware that +they have two eyes, and still fewer appear to suspect the existence of a +visual field.) + +In all these cases opportunity is hardly given for mistakes with +reference to the diagnosis of congenital amblyopia, as slowly developed +monocular defect scarcely occurs without ophthalmoscopic cause. On the +other hand, ophthalmoscopic symptoms (such as hæmorrhage of the retinal +artery in the macula lutea) may disappear without leaving a trace, while +defective vision remains. The law of habit, however, usually helps us +here. In congenital monocular defect patients are generally accustomed +to this condition, and only notice it when special claim is made on the +visual faculty of this eye,--he, on the other hand, who is accustomed +to see with two equally good eyes, may not observe a gradually occurring +blindness of one eye, if his talent of observation be faulty, but I have +never had reason to suppose that a rapid depreciation of the central +visual acuteness of one eye is also overlooked. Rapidly occurring +monocular visual disturbances are noticed, whether detected with or +without the ophthalmoscope. + +Two peculiarities appear in isolated cases of congenital amblyopia, +which may render the testing of vision difficult: rapid fatigue of the +retina, and depreciation of the central visual acuteness in such a way, +that an adjoining part of the retina possesses a better visual faculty +than the centre. + +Rapid fatigue of the retina occurs in comparatively good visual +acuteness. For example: + +CASE 16.--Mr. W--, æt. 35, came under treatment for conjunctivitis. In +testing the vision, emmetropia (or doubtful hypermetropia) was found on +the left, V. = 5/6. Refraction of right eye similar to that of left, V. += 5/18 to 5/12, but with rapidly occurring fatigue of the retina. +Patient had observed this fifteen years before, when shooting during his +period of army service. Position and movements of the eyes are normal. + +This peculiarity occurs more often in higher degrees of defective +vision. For example: + +CASE 17.--Mrs. von G--, æt. 60, has always seen badly with the left eye. +On the right H. 1·25 D., V. 5/12. On the left with + 2 D., V. 1/12 with ++ 5 D. words of No. 1·75 were recognised; but the visual acuteness above +stated is only present at the first moment; after a few seconds +everything disappears in a fog. The left eye has a slightly conical +nebulous cornea, detected only on focal illumination, which does not, +however, cause the slightest irregular astigmatism, and cannot, +therefore, serve as explanation of the defective sight. + +This rapid fatigue, which only permits the visual acuity present to be +estimated for a short period at a time, may easily result in the visual +acuity being supposed to be worse than it is. + +The other phenomenon above mentioned, which occurs in defective vision +without being actually a necessary symptom, is the depreciation of the +central visual acuity, which we designate as central scotoma in acquired +amblyopia. It should be remembered that the visual acuteness which we +determine under these conditions is something different from what we are +usually accustomed to designate by this idea. When we simply talk of +visual acuity we always imply the central visual acuity; however, in +cases where the centre of the retina is so injured in its function, that +the peripheral parts lying near are too often called into requisition, +we do not determine the central visual acuity at all, but that of the +nearest and at the same time best, excentric part. We cannot prevent +patients from using that part of the retina which seems best to them for +recognising the test objects. In such cases (just as in acquired central +scotoma) continuous print is read badly, and with more trouble than one +would expect from the visual acuteness which is specified in the +recognition of single letters. Of course spelling and reading are two +different things; the excentric visual acuity may perfectly suffice for +the recognition of single letters, central and also excentric visual +acuity is necessary for reading. There are patients who, despite full +visual acuteness, are unable to read continuously, as soon as a defect +in the right half of the visual field extends close to the fixation +point. To read fluently, the excentric vision must work on in advance +for the width of several letters, but if the first letter is seen +excentrically, the excentric visual acuteness rapidly sinking in a +physiological way, does not suffice for the following ones. + +When testing the vision these circumstances should be carefully +regarded. The apparent contradiction between the visual acuteness +specified with test-letters, and the uncertainty in reading continuous +print, may be taken for simulation (I have seen some sad examples of +this in acquired central scotoma), and, on the other hand, if in the +form of defective vision now under discussion we content ourselves by +merely employing reading tests, we take the visual acuteness to be worse +than it is, or than we find it later when single test-letters are used, +for even though excentric, it is yet always visual acuteness. The +excentricity of that part of the retina put into fixation is usually so +slight, that the oblique direction of the visual axis cannot be seen +with the naked eye; if considerable and extensive defect of the centre +of the retina is present, either varying fixation occurs, sometimes +parts lying to the nasal and sometimes to the temporal side are put into +fixation; or excentric fixation exists; an inner retinal area but +sometimes also a temporal then usually has comparatively the best visual +acuteness. + +A third peculiarity which sometimes occurs in extreme degrees of +congenital amblyopia, is monocular nystagmus of the weak eye. This +trembling may be so slight that it is only observable during +investigation with the ophthalmoscope; in other cases it is most marked +as soon as the weak eye is put into fixation by exclusion of the sound +one. + +Cases of congenital amblyopia in both eyes, where no explanatory cause +can be traced, and no nystagmus is present, are rare, but all the more +interesting. For instance: + +CASE 18.--Mr. F--, æt. 56, has seen badly from childhood; the visual +acuteness of each eye singly examined amounts to 1/18 to 1/12, binocular +1/12. No. 0·75 is read with difficulty at 8 cm. Ophthalmoscopic +condition is normal. In mydriasis by atropine hypermetropia of 3 to 4 +dioptres results. With convex 3· 5 D. on the right V. 1/18 to 1/12, on +the left V. 1/12, binocular V. 1/12 to 1/9, with convex 6 D. still only +0·75 can be read, but more fluently than with the naked eyes. + +Normal binocular fusion may continue to exist even in extreme degrees of +monocular weak sight; I have observed it up to a visual acuteness of +1/24. The stereoscope is well adapted to prove binocular fusion in these +cases; only we must then take care that sufficiently large letters are +present in the visual field of the defective eye, so that they may +easily be recognised with the existing visual acuteness. Binocular +fusion is naturally rendered still more difficult if the weak-sighted +eye is at the same time hypermetropic to a high degree, as it then +receives simultaneously indistinct retinal images on account of the +difference of refraction; and yet in the above table there are 117 cases +with hypermetropia of at least 2 D. in the better eye, and faulty visual +acuteness in the other, 7 with visual acuteness of less than 1/7 to V. +1/12, and 9 with less than 1/12 to V. 1/36. + +In the highest degrees of congenital defective vision, binocular fusion +cannot as a rule be proved; partly because the methods of investigation +by which we are able to prove binocular fusion presuppose the existence +of a sufficient visual acuteness. On the other hand, it cannot be +expected that normal binocular vision can be learnt with such a large +amount of monocular defective vision. If the relative strength of the +muscles is normal, so also are the position and movements of the eyes, +if elastic preponderance on the part of the muscles is present, which in +monocular defective vision of considerable degree is no longer governed +by binocular fusion, and this is frequently the case, squint is +developed. + +Sometimes other congenital anomalies are present at the same time with +congenital defective vision (for example, congenital dermoid growths on +the edge of the cornea), and undoubtedly hereditary influences play a +considerable rôle therein. + +In order to determine the relation of congenital defective vision +without squint, to defective vision with squint, I have taken those +cases where congenital defective vision without squint was observed, +together with the cases of squint, from the diaries of my private +practice for the last ten years. I have personally investigated every +case, and the observations on each were carefully examined before being +included in the statistics; all cases with myopia of six or more +dioptres, all cases of double nystagmus, and, finally, all those cases +where the previous existence of squint might be suspected, were +excluded, as above stated. I must also remark that before the last ten +years I had not begun to collect these cases. In order to find monocular +congenital defective vision one must seek for it, as patients usually +come under treatment for quite different disorders, and in the +consulting-room there is not always time carefully to investigate what +possesses interest for us but none for the patient. In cases of squint +the opportunity for investigating the power of vision does not escape us +so easily, and yet the same list, which contains among 629 patients 177 +cases of squint with a visual acuteness of 1/8 to less than 1/36, +furnished at the same time 98 cases with undoubted congenital defective +vision of the same high degree without squint, which I place together in +the following review. + +Cases of congenital amblyopia with visual acuteness of 1/7 are so +frequent, that I have not drawn up special statistics of them. I was not +anxious to collect a large number of cases but only material for +evidence. I have therefore divided the 98 cases I observed into 3 +groups. (1) Cases with visual acuteness of less than 1/7 to V. 1/12; (2) +V. less than 1/12 to V. 1/36; (3) visual acuteness less than 1/36. The +limits between these groups are of course not very sharply defined, for +what is designated as "measurement" of visual acuteness contains, even +if we accept the statements of patients as trustworthy, not an +inconsiderable number of sources of error; and we often find a +remarkable absence of conformity in the analysed causes of congenital +amblyopia, according as we seek to determine the visual acuteness by +means of single test-letters or by reading printed matter. In a case of +visual acuteness of 1/12 No. 0·75 with convex 6 was the smallest type +that could be read, and that with difficulty, larger type was usually +required; and in one case where at first only single words of No. 2·25 +were read with difficulty--this test was on that account repeated in +myosis by eserine--No. 1·75 was finally the smallest print which could +with the same difficulty be deciphered. In the division of the groups +here arranged the best visual acuteness ascertained in the various +examinations was always used as the basis. + +A. Vision less than 1/7 to V. 1/12 38 cases. The examination of the +better eye showed: + + + (_a_) Emmetropia in 18 cases. A determination of refraction, + mostly ophthalmoscopic, of the weaker eye is submitted in 11 + cases, which divide themselves into, 4 with emmetropia, 3 + with hypermetropia (of H. 2 D. and 2·25 D.), 3 with + hypermetropic astigmatism, I with myopic astigmatism. + + (_b_) Myopia in 5 cases (3 of M. 1 D. to 1·5 D., 2 of M. 4·5 + D. and 4 D.), the condition of the defective eye was + determined in 3 cases, and was twice hypermetropic, once + astigmatic. + + (_c_) Hypermetropia in 8 cases, hypermetropic astigmatism in + 3. In 4 cases an exact determination of refraction even of + the better eye was for some reason impracticable. + +There are 4 cases in this group where the visual acuteness in both eyes +did not exceed the above-stated small amount, and one which was +interesting from another point of view. + +CASE 19.--Max L--, æt. 8-1/2, recognises No. 24, and a few letters of 18 +at 5 metres with the better eye with convex 6 D.; at 1 metre V. 1/4 to +1/3, the left eye recognises only No. 60 at 5 m. with + 6 D. at 1 m. No. +0·75 is read with difficulty. If we exclude one eye it lapses into now +less, now greater convergence, and still no squint is present, but +diplopia as well as binocular fusion can be proved by the aid of prisms. +The theory of Donders that squint is less frequent in hypermetropia of +high degree because too strong convergence would not suffice to furnish +clear retinal images, is scarcely tenable in the face of such cases. If +indistinct retinal images are added to a visual acuteness of only 1/3 to +1/4 still, even with faulty accommodation, it is difficult to believe +how a child could learn to read if it did not hold the book close to its +eyes, which was not the case here, and indeed seldom happens. Therefore, +in spite of defective vision the accommodation must have sufficed, +without sacrificing binocular fusion, whilst in all probability +accommodative convergence followed on exclusion of one eye. + +B. 48 cases had visual acuteness from 1/12 to 1/36. The better eye was-- + + (_a_) Emmetropic in 16 cases; in 6 of them the refraction of + the defective eye was determined, which showed in one case + emmetropia, 3 hypermetropia, 2 astigmatism. + + (_b_) Myopia of the better eye was present in 7 cases (in 3 + myopia of 1 D., in 4 M. 3 D. to 6 D.). + + (_c_) Hypermetropia in 18, astigmatism in 4 cases. In 3 + cases the condition of the better eye was, for some reason + or other, indeterminable. + +In this group I should like to point out the following cases as worthy +of attention: + +CASE 20.--Margarethe T--, æt. 16, has hypermetropia 2 D. in the right +eye, V. 5/6, in the left the ophthalmoscope shows with an otherwise +normal condition a higher degree of hypermetropia, with + 6·5 D., V. +1/18, with + 10 D. No. 3·0 is read. No spectacles have been used until +now; for the past few years school tasks have been performed with a +certain effort, only during the last year the asthenopia has increased. +Squint is not present, and with prisms as well as with the stereoscope +(by the use of objects, whose size corresponds to the defective sight on +the left side) binocular fusion can be proved. + +The case is the same as regards divergent strabismus. + +CASE 21.--Mr. H--, æt. 28, has myopia 6 D., V. 6/9 in the right eye; the +left eye has always been weak sighted, emmetropia is detected with the +ophthalmoscope, with normal fundus, V. 1/18. No squint, binocular fusion +can be proved with prisms. + +CASE 22.--Mr. B--, æt. 47, has hypermetropia 5 D., V. 5/9 in the right +eye. Left eye with + 5 D., V. 1/18 (a few letters of 12 also were +recognised at 1 m.). It seems, however, that the patient is not able +exactly to indicate the position of the retinal images of his left eye, +he does not know, as he expresses himself, "whether the letters stand +here or there." Patient observed the defective sight long ago; the +ophthalmoscopic condition is normal. Patient really comes on account of +his son, aged 7-1/2, in whom hypermetropia of 3·5 dioptres is detected +with the ophthalmoscope, right eye with + 3·5 V. 5/9. Left eye has +convergent squint, V. 1/36, No. 3·0 is read with + 6·5 D. + +The hereditary tendency is seen also in the following case: + +CASE 23.--Mrs. S--, æt. about 46, on the left H. 4 D., V. 5/18 to 5/12, +has used no spectacles until now, and reads No. 0·75 without glasses at +about 15 cm. R. with + 4 D., V. 1/18, with + 6·5 D. large letters of No. +5·0 are recognised. + +Two sons, present at the same time, are hypermetropic. One has in either +eye V. 1/4, the other a slighter degree of congenital amblyopia. + +CASE 24.--Johanna L--, æt. 4, came under treatment for a congenital +fibroma covered with hair, about the size of a cherry-stone, situated on +the outer corneal margin of the left eye, which was removed. Three years +later, when the child had learnt to read, emmetropia and full visual +acuteness was observed in the right eye, with the left No. 4·0 only is +read with difficulty. The ophthalmoscope shows a slight degree of +irregular astigmatism of the cornea, which in no way explains the +defective vision; the image of the fundus is perfectly clear and quite +normal. + +CASE 25 afforded me a not altogether pleasant surprise. Martin M--, æt. +58, has matured cataract in the right eye, with perfectly satisfactory +light reflex, proper projection, &c. On the left progressive cloudiness +of the lens has begun. The course of operation and cure were regular in +every respect, but the power of vision finally was so small that with a +clear pupillary area, and otherwise normal condition, only single words +of No. 3·0 were recognised with difficulty at 10 to 15 cm. with convex +20 D. For the first time the patient remembers that he noticed the +defective sight in his right eye at the age of sixteen, and was for this +exempt from army service. The operation performed later on the left eye +procured satisfactory vision. + + +C. Visual acuteness of less than 1/36 12 cases. + +Determination of refraction of the better eye is given in 6 cases, and +showed twice emmetropia, twice slight myopia, twice hypermetropia. I +only possess an exact ophthalmoscopic determination of the condition of +the defective-sighted eye in one instance with H. 2·5 D. + +This group is of special interest in that it represents the extreme +degrees of congenital amblyopia, and, on the other hand, because it +contains 5 cases of children under 10 years of age. + +CASE 26.--Constanze von M--, æt. 9-1/2. Defective vision on the left +side had been noticed long before by the child's parents. On May 1, +1879, emmetropia was observed in right eye, V. 5/12 to 5/9. No. 0·4 is +read at 15 cm. On the left, only movements of the hand are seen, fingers +cannot be counted even when close to the eye; the visual field is good, +that is, on moving the hand in the periphery of the visual field the +child sees "something" without being able to state what it is. Reaction +of the pupils as rapid and equal as usual. The ophthalmoscopic condition +(even with dilated pupils) is perfectly normal. All tests for simulation +were of course applied. + +On account of the importance of the case, I suggested another +examination a year and a half later, on the 22nd December, 1880, which +showed precisely the same result as the former one--optic disc, macula +lutea, &c., perfectly normal, the ophthalmoscopic determination of the +refraction shows H. 2·5 D. + +The child's father also possesses in the left eye a slight degree of +congenital defective sight, observed for many years, with normal +ophthalmoscopic condition; No. 0·5 is read with + 6·5 D. at 10 cm. + +CASE 27.--Tina S--, æt. 6. The defective sight of the left eye had been +remarked some months previously; report on July 16th, 1878: R. full +visual acuteness, L. movements of the hand are scarcely visible. The +child cannot count fingers. Normal ophthalmoscopic condition. Eserine +and separate use were prescribed. On September 9th, 1878, fingers were +counted with the left eye at 1·5 m., single words of No. 4·0 were +recognised, No. 3·5 with convex 6·5 D., but always with oscillating +fixation. The improvement in the child's statements may be referred to +the fact that she had meanwhile learnt to form right conclusions from +the very imperfect sensual impressions of her left eye. + +CASE 28.--Frank J--, æt. 10. Left eye. V. 10/50 to 10/40, No. 1-1/2 +Snellen is read at 4 inches. On the right, nystagmus on fixation, +fingers are counted at 5-6 feet. The ophthalmoscopic condition is +normal. A sister of the boy squints. + +CASE 29.--Ernest G--, æt. 8, has slight nebulæ on both corneæ. On the +left V. 15/40. On the right, fingers are counted at 4 inches with visual +axis deviating inwards. + +CASE 30.--I operated on Moritz L-- for congenital cataract before he was +a year old in 1869 by means of a needle operation. In June, 1877, a thin +ophthalmoscopically transparent secondary cataract appeared in both +eyes; on the left, with convex 12 D. V. 3/24 to 3/18, with convex 16 D. +No. 0·4 is read at 10 cm. On the right, with convex 12 D., fingers are +counted with difficulty at about 1 m., with inward deviation of visual +axis. + +CASE 31 is also worthy of note. Carl H--, æt. 22, shows quite a number +of congenital anomalies on the left side of the face, harelip, deformed +nostril and a skin defect on the inner corner of the eyelid. There is a +congenital dermoid growth of the size of half a pea situated on the +inner lower corneal margin. A slight irregularity in the curve of the +cornea near the dermoid is detected with the ophthalmoscope; the fundus +of the eye is perfectly normal. Fingers are not counted further off than +a metre with visual axis deviating inwards. The right eye is emmetropic +(perhaps slightly hypermetropic), and has full visual acuteness. There +is no squint. + +It is customary to "explain" these cases of monocular amblyopia by +previously existing squint, and one is quite satisfied if by the +examination of patients it is only possible to prove that they have +occasionally squinted, although the advocates of the amblyopia ex +anopsia disallow the presence of the same under these conditions, that +is, in periodic squint. Of course a theory which cannot exist without +the assertion that occasional alternation suffices to hinder the +development of defective vision caused by disuse, cannot possibly hold +periodic squint to be the cause of it. Certainly permanent squint may +also disappear, but this much I have been able to determine, that this +seldom happens before the twelfth year of life, and one may surely +reckon that children in whom permanent squint is developed at the usual +early period of life, still squint at the age of ten years. Cases 24 and +26 to 30 can under no circumstances be explained by previous squint, +notwithstanding that they represent the extremest degrees of amblyopia, +but the question is undoubtedly that of congenital defective vision; +moreover I have excluded from the statistics of congenital amblyopia all +cases in which the previous presence of squint could even be supposed. + +A table of the cases above described with reference to the defective +condition is interesting; when a determination of refraction existed for +the weak eye I have given it, and when this was not the case I have +stated that of the better eye, thus it is seen that among 85 cases in +which the refraction was determined, hypermetropia (including +hypermetropic astigmatism) was present in 39. Hypermetropia was found +then in 47 per cent of all the cases. The percentage would probably be +higher, if all weak-sighted eyes had been examined from the beginning as +to their state of refraction, but as I only learnt to know the relation +between hypermetropia and the higher degrees of congenital amblyopia +from my statistics, I did not take notice of this relation when +investigating individual cases. + +How does congenital amblyopia now stand in relation to that disturbance +of vision which we observe in squint? I see no difference; whether +squint is present or not, the form of defective vision is precisely the +same, and nothing happens in the combination with squint which could not +also be proved without it. The relation to hypermetropia, which is +proved with congenital amblyopia, also appears in squint. + +A collective table of cases of convergent and divergent squint included +in the statistics (pp. 19 and 47) shows: + + (_a_) In myopia, emmetropia, and doubtful hypermetropia, + with convergent and divergent squint together + 329 cases. Among them: + Visual acuteness to 1/7 239 + " less than 1/7 to V. 1/12 19 + " " 1/12 to V. 1/36 46 + " " 1/36 25 + Defective sight of higher degree than 1/7, 27·3 per + cent. + + (_b_) In hypermetropia 1 to 3 D., including the few cases + of hypermetropia with divergent squint, 177 cases. + Among them: + Visual acuteness to 1/7 121 + " less than 1/7 to V. 1/12 17 + " " 1/12 to V. 1/36 27 + " " 1/36 12 + Defective sight then, 31·6 per cent. + + (_c_) In hypermetropia 3 D. and more, 70 cases with convergent + squint, with: + Vision to 1/7 39 + V. < 1/7 to V. 1/12 8 + V. < 1/12 to V. 1/36 14 + V. < 1/36 9 + Defective sight then, 44·2 per cent. + +This regular increase of defective sight with the increase of the +hypermetropia can be no mere accident, and speaks strongly for the +identity of defective vision in squint with congenital amblyopia. Were +defective vision caused by the squint the various states of refraction +would show no difference in the percentage of defective vision. + +Further, the circumstance is worthy of remark that among 198 cases of +periodic squint (convergent and divergent) which are applicable for the +statistics of visual acuteness-- + + 170 possess V. to 1/7. + 16 " V. < 1/7 to V. 1/12. + 9 " V. < 1/12 to V. 1/36. + 3 " V. < 1/36. + 14·2 per cent. then of defective vision of considerable degree. + +That defective sight on the whole plays an influential part as a cause +of squint is doubted by no one, indeed we see blind eyes lapse into +squint as soon as the conditions necessary to it are supplied by the +muscles. Of all the prevailing causes present defective vision will be +the more decisive in proportion as it is of high degree; for the motive +which despite the presence of favouring circumstances can prevent the +real occurrence of squint, binocular vision, becomes less efficacious as +the defective vision becomes more considerable. As binocular fusion +takes place frequently in periodic squint, for a time at least, that is +as long as proper fixation lasts, one can understand that periodic +squint exists chiefly in cases where the visual faculty of both eyes is +good. Even the highest degrees of congenital amblyopia are not excluded, +for periodic squint appears where the faculty of binocular fusion has +been completely lost. Further, that considerable congenital defective +sight is more frequent with than without squint, may be accounted for +quite simply by the fact that, in extreme degrees of it, binocular +fusion cannot be learnt at all, while in the lesser degrees it is more +easily forgotten again. + +If defective vision is undoubtedly one of the causes of squint, we must +seek for the grounds upon which it has been taken to be a consequence of +squint, and described as amblyopia ex anopsia. I will not inquire to +whom the honour of this invention belongs. I do not want to write a +history of mistakes but only to examine the basis of the views now +current. The most complete record of the same may be found in the +well-known journal on the 'Cure of Eye Diseases,' vol. v, p. 1011. +Leber, who does not seem to recognise the existence of congenital +amblyopia, has shown quite a special predilection for amblyopia ex +anopsia. + +Amblyopia from want of use, which formerly included all possible +disturbances to vision, great and small, is now only accepted in two +cases, for squint and congenital cataract, if the latter is not operated +on very early in the first or second year of life. + +The fact is simply this, that in congenital cataract even the most +successful operation is frequently deceiving as to its issue without +ophthalmoscopic report; this is the more disagreeable as the most exact +reflection test before the operation fails to prove the existence of +this defective sight. But does it follow from this, that congenital +cataract has induced defective sight from want of use? We find the same +defective vision also in congenital defective development of the +transparent lenses (so-called luxation of the lens). On the whole, we +often find several congenital defects in the same individual. The very +circumstance that the cataract is congenital makes it probable that the +defective sight is so also, or are we to take congenital cataract as +being a guarantee against congenital amblyopia? + +Von Graefe, who first considered this defective sight to be congenital, +designated it in his later lectures as originating from want of use, +probably in order to advise the earliest possible performance of an +operation. There is no mention of his having brought forward evidence +for this assertion; that the great master himself said it was enough, +and the host of believers felt themselves to be the happy possessors of +a new dogma. + +A number of children appeared in my practice, in whom congenital +cataract was needled by von Graefe in the first or second year of life +with recovery of transparent media, who showed, however, the extremest +degrees of defective vision when they were sufficiently intelligent to +have their vision tested. Whoever is interested in this can find a +number of such cases in the Royal Institution for the Blind at Steglitz, +which I am accustomed to visit several times a year by request of the +committee. On p. 91 I have related a case of monocular congenital +defective sight in congenital cataract of both eyes. + +Everywhere then the principle holds good, that whoever makes an +assertion must be prepared to verify it; amblyopia from non-use is +denoted as an inherited trouble, and still not a single observation +exists which furnishes proof that an eye of previously ascertained good +visual acuteness has become amblyopic in consequence of disuse, a fact I +drew attention to ten years ago. Leber replies to this, he remembers "to +have seen patients with complete amblyopia in the squinting eye, who +stated that its visual faculty had been found to be good during an +examination instituted years before." Is this intended as an +observation? By that I mean is it a proof of facts, for the +trustworthiness of which he holds himself responsible: in the handling +of scientific questions I do not place the least reliance on the dim +recollections of unnamed individuals. Even in personally conducted +examinations we must be on our guard to avoid mistakes, and now we are +confronted with mere recollections of tests of vision! + +By means of the above observations the theory that "the peculiar variety +of monocular amblyopia which is so frequent in monocular squint is +hardly observed without squint" is sufficiently disproved. + +Leber seeks to enfeeble Alfred Graefe's statement that the presence of +extremely defective vision may sometimes be proved at a very early age, +in children who have only squinted a short time (the rapid development +of amblyopia in consequence of the squint really appears incredible), by +the assertion "that just at the earliest age, when the activity of the +optic nerve is not yet sufficiently strengthened by use, the conditions +for producing amblyopia from non-use are most favorable with complete +exclusion of one eye," but complete exclusion of the squinting eye does +not take place even in extremely defective sight, as can easily be seen +by the mirror test (p. 66) I described fourteen years ago. Which +activities of the optic nerve apparatus are strengthened then by use? +Perhaps visual acuteness? The physiological conditions of this are only +to be sought in the anatomical structure, and the physiological +arrangements of the retina or the visual organs, which cannot be changed +much by use. What we can learn from the visual act relates solely to the +conclusions which we are able to draw from sensual impressions; but +visual acuteness, _i. e._ the faculty for the recognition of distinct +points, is an anatomical, physiological gift, and not a thing to be +acquired. + +The opposing observation, that squint, even of monolateral character +dating from earliest childhood, continued to the middle and later years +of life, can still exist with very good visual faculty, may easily be +explained by alternation from time to time. If that is so indeed, if +squint begins during the presence of good visual acuteness, and nothing +further is necessary to its maintenance than alternation from time to +time, why should defective vision from non-use ever be developed? With +good visual faculty on both sides alternations also occur from time to +time. + +Still more convincing are those cases which are numerous where the +visual acuteness of the squinting eye only amounts to about 1/7 to 1/12, +and where, on this account, there is no alternation. Were this defective +sight acquired through non-use it must of necessity be progressive; it +must exist in proportion to the duration of the squint. A moderate +experience will suffice to show that this is not the case. And further, +defective sight must continue progressive even after removal of the +squint by operation, for by the operation nothing is changed in the +relations of the binocular vision present in squint, which are dismissed +with the one word, "suppression," by the advocates of defective vision +from non-use. + +Moreover, suppression may exist for years without the slightest +disadvantage to the visual faculty. + +CASE 32.--In November, 1873, I operated on Fritz F-- for a slight +divergent squint of the left eye. Slight hypermetropia was present on +both sides, and nearly full visual acuteness. In October, 1880, +perfectly normal position of the eyes showed itself with the same visual +acuity and emmetropia in both eyes; at the same time, however, the boy +affirmed that when reading he could never see with his left eye but only +with the right; in reality only the right visual field was perceived in +the stereoscope. + +The second reason brought forward is, that the variety of amblyopia from +non-use is quite a peculiar one; "it consists of a functional +disturbance of those parts of the retina whose images belong to the +common V. F., and are suppressed in squint in order to render vision +distinct--the macula and the temporal and only a part of the nasal +halves of the retina." Does this hold good for all cases of amblyopia in +squint, or do those cases only belong to amblyopia from non-use where +excentric fixation takes place with an inward deviating visual axis? It +would be difficult to draw the line. I have seen a case in which the +squinting eye possessed a visual acuteness of 5/36 together with +excentric fixation and nystagmus; however, I attach no value to isolated +cases. We frequently find excentric fixation with a visual acuteness of +1/12 to 1/36. Further, those cases cannot possibly be regarded as +results of squint, which possess unsteady oscillating fixation or +rapidly trembling nystagmus, which occurs as soon as the squinting eye +fixes. But this conclusion is false, even for the excentric fixation +with visual axis deviating inwards; if it were right the angle at which +the eye deviates inwards on fixation in convergent squint would always +be greater than the squint angle. Those cases are, of course, more +remarkable where this is not the case; however, on close investigation +those cases are more frequent where the angle of deviation is about the +same size or smaller than the squint angle, and is fixed with a part of +the retina which undoubtedly belongs to the common visual field. + +On p. 91 I have described two cases of excentric fixation in children +who had never squinted, and it is only necessary to take a little +trouble to repeat the mirror test which I described, to be convinced +that squinting eyes have not lost the power "of using those parts of the +retina," even if they are amblyopic to an extreme degree; without the +slightest doubt the reflection is perceived as soon as it falls on the +retina. + +Value is attached to the improvement produced by the separate use of the +squinting eye. According to my experience no higher visual acuity can be +attained by use of the amblyopic eye, than that which is best detected +by the aid of eserine in the first examination, if it is only carried +out thoroughly enough. No doubt if we proceed otherwise, and rest +content with whatever statements the patient likes to make, without +giving ourselves any more trouble, we may expect the most superficial +diagnoses to show the most astonishing therapeutic results, as, indeed, +often happens. And now, talking of strychnine injections! When two +celebrated ophthalmologists occupy themselves simultaneously with the +therapeutics of strychnine, one of whom obtains the most astonishing +results in atrophic troubles of the optic nerves, but, on the other +hand, obtains no real improvement in "amblyopia from non-use," while the +other can show brilliant success in the last-named form of defective +vision, and, on the other hand, none in atrophy of the optic nerves, we +may perhaps conclude that both are right, if even really on the negative +side, and that the circumstances are the same in the tests of vision. +Again, we must examine more closely some of the cases, in which +strychnine injections showed a brilliant result. (Anyone interested in +the original work can read up the 'Vienna Weekly Medical News' for the +year 1873.) + +"1. Wilhelm H--, a strong healthy boy, æt. 12, complains of defective +vision. Right eye has nothing abnormal in its outward appearance, and +just as little in the fundus. V. 16/100, H. 2·5 D., Snellen IV-I/II; is +the smallest type he reads at 3 to 7 inches. With + 10, I-I/II is read +at 4 to 6 inches. Left eye V. 16/70. H. 2·75 D. II-I smallest type +legible at 3 to 12 inches. With + 4 D. I-I/II is read at 4 to 6 inches. +On March 14th, 1872, first injection of strychnine with 0·002 gr. in the +temples. An hour later V. of right eye 16/70, left unchanged. On March +23rd, 1872, after one injection daily, V. of each eye is 16/50." + +Patient shows then in the right eye visual acuity 16/100, with manifest +hypermetropia 2·5 D.; in all probability the total hypermetropia really +present was higher, and was scarcely corrected by means of convex 4 D. +If the patient now reads No. I-I/II Snellen with + 4 D. at 6 inches, +this proves a visual acuity of 1/3 during the first investigation before +the strychnine injection, and shows that the estimate of 16/100 was +inaccurate. At the close of the treatment, only a visual acuity of 16/50 +(almost exactly 1/3) is specified for distance. The result seems to me, +then, to be this, that the patient during repeated examinations has +gradually learned to make more accurate statements, indeed, with a boy +twelve years old one can scarcely expect it to be otherwise. + +"4. Paul A--, æt. 18, was operated on ten years ago for internal squint +of the right eye, and dismissed with + 2 D. for distance, and + 6·6 D. +for near use. He now complains of decrease of his visual acuity. The +eyes are normal externally and internally. Hyperopic formation in a high +degree. Right eye V. 1/20, with and without convex glasses, without +glass only VIII-I/II with difficulty, with + 6 V-I/II the smallest. Left +eye appears emmetropic, but is decidedly hyperopic. V. 5/4. Glasses are +rejected; I-I/II is read fluently at 6 to 12 inches. After one injection +the right eye recognises III-I/II with + 6, after the second II-I/II, +after the eighteenth I-I/II with difficulty. The visual acuity, however, +remains at 1/20, and is not changed after six months, although latterly +patient daily practised with + 3 D." + +Visual acuity of 1/20 suffices to read III-I/II at 2·5 inches, II-I/II +at 1·5 inches, and I-I/II at about 1 inch; clear, retinal images are +then scarcely obtainable, but we know what hypermetropes can do in that +case; besides this, if the patient is examined for weeks by Snellen's +method, he may get so far as to realise fairly well "the strange fate of +that man" of I-I/II, despite larger diffusion circles; in any case +vision remained at 1/20, despite strychnine and separate use. + +In extremely defective vision little importance should be paid to the +fact of slight diversity in the statements, as where visual acuity +amounts only to about 1/36, or where fingers are counted at a distance +of 1 to 2 metres, it is quite immaterial, as far as the usefulness of +the eyes is concerned, whether fingers are counted at a half or a whole +metre, and we ought never to forget that all conclusions which we draw +from the state of the visual acuity, are unreliable in proportion as the +latter is lowered. Indeed, on repeated examination of such cases we +frequently find considerable fluctuation in the statements of the +patients, therefore we ought not to expect accurate statements for very +inexact sensual impressions. + +By separate use, even in extremely defective vision, no improvement in +visual acuteness is developed, but only a more complete acquirement of +the power of deducing right conclusions from imperfect sensual +impressions. That which has been most unscientifically designated as +"suppression of diffusion circles," depends solely on this method of +use. As with indistinct retinal images so with facial impressions which +are insufficient, one can never learn to recognise larger objects +aright. + +We must never forget that vision is a conclusive act acquired by +practice; whoever sees well with one eye, and is weak sighted with the +other, acquires this end only for the sensual impressions of the better +eye, and must first collect experience for the defective eye, before he +can use it. + +Leber has recently joined those cases which are described as blindness +through blepharospasm, to amblyopia from disuse. First, I wish to +observe that blepharospasm is not a necessary cause; I have seen the +same disturbance of vision follow severe double blenorrhoea, which +destroyed one eye but left the other uninjured. These children are +always of an age which renders any trial of vision impossible, and we +are therefore obliged to draw conclusions as to visual power from the +movements of the body. If children move as though they were blind, it +need not necessarily follow that they are so in the common meaning of +the word. The art of vision is a difficult one, the acquisition of which +begins with the earliest days of life; we do not call every person blind +who does not see what is before his eyes, because he does not understand +how to see it. A child who has only imperfectly learnt the conclusive +act of vision, and forgotten it again during a continued disuse of both +eyes, will not know how to use perfect visual acuity, and will move like +a blind person till he again learns to estimate the relations between +his retinal images and the things of the material world, which happens +in a very short time. + +After this digression let us turn again to amblyopia from disuse, and to +the last trump which is played for it. "Those cases are very remarkable +where an immediate improvement occurs after tenotomy in amblyopia of +high degree, which according to this is certainly produced and +maintained by the squint." As proof a case is cited by Knapp, who +describes it in the following words:--"The improvement in visual power +varied very much. In many cases it was indefinable, in others very +pronounced; for example, in one case, where it was very great before the +operation, only No. 16 Jaeger could be read at 1 inch, while after it +No. 2 was read at 8 to 9 inches." + +And we are to believe wonders on the strength of this scanty +communication! It is an every-day experience that a person who squints, +who has just asserted his inability to read the largest type, +immediately afterwards reads smaller and the smallest type, and it would +at least first have to be determined that all endeavours to produce a +better visual result before tenotomy were unsuccessful; but as the +communication stands, the conclusion as to the effect of tenotomy is +quite a superficial _post hoc ergo propter hoc_. Moreover, I had this +case in view when I spoke on this matter in the first edition of my +'Handbook:'--"The frequently repeated assertion that a considerable +improvement of vision may occur as a direct result of tenotomy, is so +little in accordance with all the laws of physiology, that inquiries +must be instituted _ad hoc_, and carried out with the most perfect +exactitude. Only trials of vision which are carefully carried out and +repeated several times before the operation, and which have regard to +visual acuteness for distance as well as for near objects, the latter +indeed by the aid of convex glasses or Calabar extract, can be +recognised as proving anything in face of such a perfectly improbable +assertion. In the course of examinations so instituted I have not myself +found that tenotomy exercises any direct influence on visual acuity." + +I would not have given so much space to this explanation had not a +principle been in question. The occurrence of amblyopia as a result of +non-use has been deductively constructed and is not inductively proved +by observation. It is just an article of faith, and in science we cannot +rely on such things; we must not depart from the inductive method. + + + + +ON THE CURE OF SQUINT. + + +Therapeutic investigations have their safest and most instructive basis +in observation of the course of a disease as it appears without +complications, and with no unusual symptoms; we can only arrive at a +certain decision as to the extent of our therapeutics when we know +exactly what will happen without skilled assistance. When squint is once +present it is seldom complicated by fresh symptoms; on the other hand, +spontaneous cures unquestionably take place. We must certainly not rely +simply on the statements of patients themselves. On p. 1 we have seen +what mistakes occur, even when it is a question of whether squint is +present or not. How little such vague statements are worth is seen by +the fact, that the question as to the direction of the previous squint +very seldom finds a satisfactory answer; as a rule it is impossible to +determine whether periodic or permanent squint has been present. + +If we undertake the task of converting the statements of patients as to +previous squint into observations, in order to confirm the statements +from the objective material, we must first prove whether the squint +cannot by some means be still produced (by excluding the eye or by +raising or lowering the eyes). Thus the condition of binocular vision +offers us valuable guides. If we find that binocular fusion does not +exist with available power of vision on both sides, but that the same +conditions of sight appear in the eyes as we have learnt to attribute to +squint, there is no reason for doubting the statements about a +previously existing squint. It is otherwise in those cases of extreme +amblyopia where normal binocular vision is never expected, or at least +cannot be proved on account of the enormous difference between the two +eyes. + +If we discover the existence of normal binocular fusion, squint may +nevertheless have been present at a former time, for in many cases, of +periodic squint particularly, the habit of binocular fusion is never +quite lost. + +That squint can disappear of itself is unquestionable; how often this +happens it is difficult to say. The fact that in ophthalmic practice we +see many more squinting children than adults is best explained by +this,--that squinting children are brought to us by their parents, while +adults who still squint have usually given up any desire for a cosmetic +improvement, and only come under treatment accidentally or on account of +other ailments; lastly, a considerable number of cases are cured by +operation. If the squint has disappeared we only discover by accident +that it was ever present. The fact of its previous existence may usually +be determined by other signs more positive than mere statements from +memory; with reference, however, to the age at which the spontaneous +cure takes place we are left to depend almost entirely on the patient's +statement. As far as I have been able to determine, the period from the +ninth or tenth up to the sixteenth year seems to offer the most +favorable conditions. + +We rarely have an opportunity of watching the disappearance of squint, +still I have observed two cases in which a permanent convergent squint +disappeared after about a year. In both cases the squint had arisen in +young people (of eight and nineteen years of age) in the course of +irido-choroiditis which terminated in blindness, and disappeared with +the sight. The fixing eye was emmetropic in one case, in the other the +condition of error could not be determined owing to nebulæ of the +cornea. + +We more frequently see periodic squint disappear. + +CASE 33.--M--, a boy æt. 10, was first examined by me in April, 1873; +the right eye has hypermetropia 4·5 D., and almost full visual +acuteness, the left has convergent squint, and recognises No. 6-1/2 +(Snellen) with convex 10 D.; V. = 1/18 at 1 metre. (The boy's father +also squints with the left eye, which is amblyopic to a high degree (V. += 1/36), right eye has emmetropia, and full visual acuteness). The +prescribed spectacles (convex, 4·5 D.) were used for working, but not +continually; still three years later, in 1877, the deviation was +considerably less and only occurred occasionally. In March, 1880, +nothing more was seen of the squint, only slight convergence still +recurred on excluding the left eye. Patient now wears convex 4·5 D. +constantly. + +On account of the importance which the disappearance of squint possesses +in hypermetropia I will describe a few more cases which belong here. + +CASE 34.--Mrs. B--, æt. 32, has on the left H. 1·5 D., V. 5/9; on the +right H. 1·5 D., V. 5/12, binocular vision (H. =·75 D., V. = 5/6 to +5/9). Asthenopic troubles are the cause of her present complaint. She +says she squinted with the right eye as a child till her eighth or ninth +year; the present position of the eyes is quite normal; ordinary type is +read at the usual distance with normal fixation without glasses. +Particularly keen fixation is rarely followed by squint, which may be +produced by excluding the right eye; the latter then deviates about 5 +mm. inwards and slightly upwards; the secondary deviation of the left +eye is rather less. Only the left visual field is seen in the +stereoscope. + +CASE 35.--Mrs. W--, æt. 31, has on the right H. 3·5 D., V. 5/9, on the +left V. = 1/16 with + 4 D., single words of No. 0·8 are read (mother and +aunt have also congenital weak sight in this eye). Position and movement +of the eyes are perfectly normal, exclusion of the left eye is followed +by slight relative divergence. In answer to my question whether she had +not previously squinted, patient replied that she did not know, it had +always been a matter of dispute in her family; as, however, only the +right visual field was seen in the stereoscope, we may be sure that +squint had been present and that binocular fusion had been lost in +consequence. + +CASE 36.--Mrs. G--, æt. 49, report in March, 1876: On the right H. 3 D., +V. 10/10, on the left H. 4 D., V. 10/40; a previously existing squint +had disappeared of itself; the position of the eyes appears perfectly +normal, but binocular fusion is not present; with red glass before one +eye and a prism deviating in a vertical direction before the other, +patient does not see double, but first with one eye and then with the +other. The squint as well as its disappearance occurred however, at a +time when it would have been regarded as an error to allow children to +use convex glasses. + +CASE 37.--Miss H--, governess, æt. about 30, came under treatment for +asthenopic disorders; on both sides hypermetropia 2·5 D., visual +acuteness 5/18. She owns to have squinted as a child,--it had often been +remarked when she was at school. The squint gradually disappeared, but +still occurred sometimes on keen fixation. The usual position of the +eyes appears perfectly normal, and gives no suspicion of squint; +convergence occurs on exclusion, sometimes with downward deviation of +the right eye. With the aid of a red glass changing fixation is easily +produced even without prisms, but never diplopia. At first only the left +visual field was seen with the stereoscope; then the right on exclusion +of the left eye; never both at the same time. According to this the +condition of binocular vision speaks entirely for the fact, that squint +had existed long enough to prevent the development of a normal binocular +visual act, and the squint had disappeared without the help of convex +glasses in spite of the hypermetropia. + +CASE 38.--Bertha W--, æt. 18, reads with the naked eye on the right No. +0·75 at 10 cm., on the left only 1·75 at the same distance; +hypermetropia of 6 D. is detected with the ophthalmoscope, with + 5·5 +the visual acuteness of the right eye amounts at 1 metre to 1/9 (if the +test-letters had contained No. 8 or 7·5, that would probably have been +recognised also), on the left with + 5·5 D., V. = 1/12, with + 6 D. No. +0·8 is read with difficulty. Patient admits to have squinted as a child; +no squint is present now; binocular fusion can be detected with prisms +and she only squints now and then on the left side to assist vision, +with which, patient states without being questioned, diplopia is +combined. Spectacles have not been used till now. + +I could cite several more such cases, but they would prove no more than +these. At any rate the fact is settled that squint can disappear +spontaneously, and without the aid of convex glasses even in high +degrees of hypermetropia. + +Wecker's announcement that "this spontaneous cure goes hand in hand with +the progressive decrease of the accommodation, and depends on the fact +that the squinter, on the strength of this progressive decrease, +renounces more and more the aid which he finds in the increased +convergence during the act of accommodation," only proves to how great +an extent one may be prejudiced by theories. A limitation of the +accommodation must necessarily increase the claims which are made on it, +and can only afford inducement for calling forth all the help possible +to support the accommodation. + +The fact that squint spontaneously disappears after normal binocular +fusion is completely and permanently lost, and in individuals who +accommodate without the occurrence of a too strong convergence, +notwithstanding their hypermetropia and without the help of the +controlling influence of binocular single vision, seems to me quite +irreconcilable with Donders' theory. Every motive for the same, +hypermetropia, difference of refraction, monocular defective vision, +&c., may not only be present without the occurrence of squint, they do +not even prevent the spontaneous recurrence of a squint already cured. +Of course I will not affirm that the causes made so prominent by Donders +exercise no influence on the origin of squint, but will only emphasize +the fact, that other causes exist which possess a greater influence, and +which we can find only in the ocular muscles. + +We have no experience as to whether this spontaneous cure occurs in +myopia with divergent squint. This is not to be wondered at, as +hypermetropia is present in the great majority of cases of squint, and +the observations as to spontaneous cure are also rare in these. But I +can vouch for one case where a slight absolute divergent squint, with +crossed diplopia, which I treated shortly after its origin in a youthful +myope, with prismatic spectacles, soon disappeared, and remained +permanently cured. + +The inclination to preponderance of the interni appears to be peculiar +to youth, while later on circumstances change in favour of the externi, +and that seems to me the chief ground for the spontaneous cure of +convergent squint. The cure is not always complete; deviation still +occurs on exclusion, or on particularly keen fixation; sometimes, +however, also under conditions which can only be put down to a change in +the elastic tensions of the muscles. The following is an interesting +illustration of this: + +CASE 39.--Miss S--, æt. 20, states that she squinted frequently as a +child from her fifth to her tenth year; the squint gradually +disappeared, but returned again from time to time during the last half +year without apparent cause. The examination showed normal position of +the eyes, slight convergence only on exclusion. Visual acuteness on the +right 5/6, with atropine ophthalmoscopic and functional emmetropia, the +visual acuteness is lowered to 5/12 by convex 1 D.; on the left +hypermetropia 7 D., visual acuteness 5/18; the same degree of +hypermetropia is found with the ophthalmoscope. + +Crossed diplopia with a difference in height is distinguished with the +aid of a red glass, the difference being corrected by a prism of 4°, +with the base downwards before the right eye; a prism of 4° with the +base inwards suffices to place the double images immediately above one +another. Spontaneous diplopia does not take place; only the right visual +field is seen in the stereoscope. As patient lived in Brandenburg and +only came to consult me occasionally I never had an opportunity of +seeing the squint till she decided to stay here for some time. It was +then seen that a peculiar oscillating deviation of the left eye of about +4 mm. inwards often occurred. As the previous spontaneous disappearance +of the squint and the crossed diplopia made one fear that tenotomy of +the internus might be followed by divergence, instillations were used in +order to make a more exact measurement of the deviation,--by this means +the condition was so improved in the course of a few weeks, that +deviation no longer occurred even on exclusion of the right eye. + +The spontaneous cure of squint may, however, be quite complete; indeed I +have seen one case where convergent squint became divergent. + +CASE 40.--A young lady, slightly over twenty years of age, showed on the +right M. ·75 D., V = 10/10, on the left H. 1·5 D., V. 10/40 to 10/30, +and slight divergent squint on the left side. Crossed diplopia could be +produced with a red glass, tenotomy of the left abducens sufficed to +correct it. I had not concealed my doubts as to her statement that she +had previously squinted inwards, but they were quite dispelled by a +photograph taken about twelve years before, in which decided right +convergent squint could not be mistaken. There is something to be said +for the fact that it may have been a periodic squint, which occurred +during the taking of the picture, as the photographer would have taken +pains to hide a permanent squint in some way. + +Conscious suppression of squint happens now and then, although very +rarely. + +CASE 41.--Miss A. L--, æt. 27, is stated to have commenced to squint in +her first year, until at the age of eighteen she took pains to cure the +habit, and with perfect success as far as regards the position of the +eyes; the only disagreeable symptom was that she could no longer read +with the naked eye. Spectacles were therefore prescribed for her, convex +5 D., but even they did not quite remove the trouble in reading; it was +now a disagreeable, painful sensation to have recourse to squint in +order to see more clearly. It was easiest to read with greatly lowered +field of vision and with the help of a convex eyeglass as well as the +spectacles. During the examination I found on the right hypermetropia +5·5 D., visual acuteness 5/12 to 5/9, on the left with + 5·5 D., V = +1/12. With convex 6 D. No. 0·5 was read at 12 inches from the glass, but +not nearer, with normal fixation on both sides. The binocular near point +(if we may employ this expression in the absence of normal binocular +fusion) was considerably removed without the existence of paresis of the +accommodation, despite the over-correction of the hypermetropia. It was +rather a question of the same disposition of the relative amplitude of +accommodation as I have previously described in a similar case. By +methodical practice of binocular vision, I had taught an intelligent boy +to fix binocularly, not only for distance, but also for near objects, +but here again the relative amplitude for accommodation was diminished, +so that with correct binocular fixation he could only read with convex +glasses, which greatly over-corrected the hypermetropia. Finally, the +normal amplitude of accommodation was restored by tenotomy of the left +internal rectus, and when I saw the patient twelve years later I was +able to satisfy myself that both were perfectly preserved. In the case +of Miss L--, I believed I ought to give up all thoughts of an operation; +the position of the eyes could not be improved, convex 5·5 D. eyeglass +perfectly sufficed for distance, and convex 7 D. spectacles for reading. +It seemed to me senseless to perform tenotomy merely to enable her to +use the same glass for distance and for near objects, without any +possibility of a cosmetic improvement. Moreover the condition of +binocular vision quite confirmed the statements as to the previous +squint. Diplopia could only be produced now and then with the help of +prisms and red glass, at first the right visual field only was seen in +the stereoscope, on closer observation also the left, but without +binocular fusion. + +Besides, the proved decrease of the relative power of accommodation in +both these cases, marked by a voluntary suppression of the squint, does +not appear in those cases where squint disappears of itself, the state +of the accommodation, therefore, shows nothing unusual. + +The spontaneous cure of squint teaches us two important facts, firstly, +that the conditions of tension of the ocular muscles may change in the +course of time, and secondly, that normal binocular fusion of the +retinal images is not necessary for a correct position of the eyes; +neither the spontaneous nor the operative cure of squint presupposes the +presence or the restoration of a normal binocular fusion. If this were +the case the operation for squint would not be of much use. + +Observation of these cases further teaches, that treatment with convex +glasses has prospects of success, particularly in periodic squint with +hypermetropia, if squint can disappear spontaneously even without +correction of the hypermetropia. At the same time, however, it appears +that we need not form hasty conclusions about it. Periodic squint +frequently arises during the earliest years of life, and everyone +(perhaps with the exception of a few ophthalmologists) will at once +reject the idea of allowing children of two to three years old to wear +spectacles; constant wearing of spectacles even by older children seems +to me not to be without risk as long as there is any chance of their +falling when running, playing, &c., in which case the eyes as well as +the spectacles would be in danger. As a rule I only order children to +wear convex spectacles when they are distinctly indicated, and then only +during sedentary occupations, when working and eating. Of course, +exceptions may be made according to the individuality of the child, and +the care with which it is looked after at home. + +We are more rarely able to remove permanent convergent squint by means +of convex glasses than the periodic form; that it is possible, however, +I should like to show by an account of a patient, who offers, besides, +other interesting peculiarities. + +CASE 42.--Marie S--, æt. 6, came under treatment on November 28th, 1878, +for recent superficial marginal keratitis of the left eye, which was +treated first with atropine; a few days later slight blepharitis +appeared also. On December 9th, atropine was discontinued; on the 14th, +the position of the eyes was still quite normal; on the 19th, permanent +convergent squint of the left eye was present. Squint had never been +observed in the child before. Double images were voluntarily announced +without my having inquired for them, they were homonymous and moved +further apart at both sides of the visual field. On December 28th, the +squint still remained the same, the double images were, however, +scarcely noticed by the child, so quickly do the relations of the +corresponding points of the retina change even in the sixth year. Both +eyes were atropinised for the better determination of the error, when a +slight degree of hypermetropia was shown by the ophthalmoscope, at most +1·5 D.; certainly a higher degree was specified when the vision was +tested, namely, on the right H. 2·5 D., V. = 5/12 to 5/9, on the left H. +1·75 D., V. = 5/18, probably, however, the objective determination was +more exact than the child's statements. If a child of six knows its +letters and figures sufficiently well to undergo a visual test, that is +as much as we can expect; in any case, however, the forms of the +letters and figures which we use for the visual test are not easy to +children, and the more objective the way in which the child comprehends +the examination, the less it perplexes itself by guesses, but only names +the letters which it really distinctly recognises, the less deficient +are the reports as to the visual acuteness; the proportionately larger +retinal images are still recognised, even if they are no longer quite +distinct, but consist of diffusion circles as a result of +over-correction of the hypermetropia. That these observations were right +for the case in point, is seen by the fact that eight days later, after +the effects of the atropine had passed off, the child could see better +with the naked eyes than with convex glasses, and that finally, when it +had become accustomed to the forms of the letters and figures employed, +V. = 5/9 was announced on the right, and V. = 5/12 on the left. + +Mydriasis by atropine had no influence whatever on the squint, +therefore, on December 31st, convex spectacles 2 D. were prescribed for +permanent use. On January 4th, the linear deviation still amounted to 4 +mm.; on January 15th, convergence was no longer discernible for +distance, with red glass double images occurred at once; on January +21st, no squint was present, and binocular fusion was again restored; +prisms immediately caused double images, the facultative divergence was += 0. I thought it prudent to order the spectacles to be worn till the +middle of March, when they were discontinued; squint has not appeared +since then. + +In this case it is impossible to determine what really induced the +squint, certainly not the slight hypermetropia, for the child had +already learnt to read without squinting, and was spared any exertion at +the time when the squint arose. Neither can we look for the cause in the +inflammatory condition for which the child first came under treatment, +this was as good as removed before the squint began and no exciting +condition worth naming was present. Moreover, most cases of squint +arise without directly assignable causes. It seems to me unquestionable +that the permanent use of convex glasses made the pathological relation +between accommodation and convergence normal, before it had firmly +established itself, and before the muscular relations were definitely +changed, and that the squint was really thus cured. But if the child had +not been under treatment I should scarcely have seen the squint so soon +after its first occurrence, and most cases of squint arise at an age +which forbids the permanent wearing of spectacles. + +If permanent squint has already existed for a long time, nothing can be +hoped for from the use of convex glasses; for the conditions of the +muscles are then so much changed, that they are no longer influenced by +such weak physiological powers. I have been able to convince myself in +the case of several squinting persons, who conscientiously wore the +spectacles prescribed for them elsewhere, that the squint was concealed +by this means; that may suffice in some cases, but if it is a question +of young girls we may well ask, which is to be preferred for appearance +sake, squint or spectacles. + +Tenotomy effects essentially a cosmetic improvement--its object is to +restore the correct position of the eyes by equalising the elastic +muscular tensions. The means at our disposal are, the simple separation +of the tendon of the too-tense muscle from the sclerotic, the +distribution of the operation between both eyes, and finally, increasing +the strength of the antagonist by moving forwards its insertion. + +The method of tenotomy as I carry it out is as follows: The conjunctiva +is seized with fine forceps exactly over the insertion of the muscle to +be divided, and the fold thus raised cut into with the smallest possible +wound. Provided we operate on the right spot we enter this opening with +the forceps and immediately seize the tendon close to its insertion on +the sclerotic, which is drawn forwards, as was the conjunctiva, and +loosened with flat, curved scissors, the points of which must be rounded +off. The incision must only be large enough to allow a small hook with a +knob to be inserted through it and behind the insertion of the tendon, +which is now lifted up and divided with fine pointed scissors close to +its insertion into the sclerotic. It is important to make sure that a +few threads coming off from the tendon at the ends of the insertion do +not remain uncut; we can only consider the operation to be complete when +the hook, carried behind the edge of the insertion made clearly visible +by the foregoing proceeding, slides up to the margin of the cornea +without any interruption. + +The method of performing advancement is as follows: An incision is made +in the conjunctiva over the tendon of the muscle to be brought forward +and just at the outer bend of the latter, then loosened together with +the subconjunctival tissue to the corneal margin; it is desirable to +carry out this loosening close to the sclerotic, as the flap of the +conjunctiva thus formed must afford sufficient support to the muscle to +be brought forward. Then the capsule of Tenon is cut into at one edge of +the insertion, a flat, curved, blunt hook without a knob is carried +between muscle and sclerotic, and out again at the other edge of the +insertion. We must be careful to get the muscle as clean as possible on +the hook in the whole width of its insertion, that is without the +capsule of Tenon, for the suture put in ought only to enclose the +muscle, without at the same time dragging the capsule of Tenon. For the +suture I always use fine catgut which is provided at both ends with +curved needles; needles of slightly different form may be chosen in +order that the threads may be easily distinguished from one another. A +needle is carried behind the hook from each thread, one through the +upper, the other through the lower edge of the muscle, between it and +the sclerotic, then the thread is tied in a knot on the muscle to make +sure that it does not slip back through the loop of the thread after +its separation from the sclerotic. Then the threads are knotted on the +muscle, and the insertion is separated from the sclerotic. As the edge +of the insertion is now exposed we can see how the land lies, and can +carry the threads exactly in the direction of the muscle under the +conjunctiva to the corneal margin, where they are passed through, and +ends tied in a knot. By this means the muscle is drawn forwards +precisely in its normal direction and stretched tighter. The wound in +the conjunctiva is closed by a suture. + +It is desirable to slightly stretch the muscle that is to be brought +forward in both the above operations while the eye is rolled towards the +opposite side with forceps. Further, as I always operate under +chloroform, I dispense with the usual test of the immediate effect of +the operation; such tests have no value before the effects of the +narcotic have completely disappeared, and one must be sure in the way +above described that no single fibres are left undivided. I lay special +stress on the fact that the operation is so performed, that it is able +to bring about the desired mechanical effect. + +The immediate mechanical effects of simple tenotomy may be easily +deduced; the divided muscle retracts as far as its elasticity and its +relations with the surrounding tissues permit. With reference to the +internal and external rectus with which strabotomy specially has to do, +those relations come principally under observation which the front part +of the muscle enters into with the conjunctival tissues; the greater the +extent to which we loosen these relations, the farther the muscle can +retract. If it is a question of obtaining a greater effect, I am +accustomed to loosen the subconjunctival tissue at the front part of the +muscle behind the lachrymal caruncle to a greater extent--this offers +the additional advantage that the distorting sinking in of the caruncle +is avoided. + +By dividing one rectus its antagonist gains in proportion and rolls the +eye towards it as far as its own elastic tension and the powers still +present on the other side permit. The improvement in position which we +strive to obtain is brought about by the elastic power of the +antagonist, and not by the tenotomy itself, and it is seen by this then, +that the term strabotomy simply, does not quite express the +circumstances of the case. Tenotomy is nothing more than the means for +procuring a preponderance of the elastic power of the antagonist, +therefore the effect attainable on the position of the eye does not +depend solely on the division of the muscle, but to a great extent on +the elasticity of the antagonist, and may be nullified at once, if the +antagonist does not perform what we expect from it, and that may happen +without our being able to foresee it. For example: + +CASE 43.--Julie B--, æt. 21, is stated to have squinted inwards since +her third year, principally with the right eye, but with occasional +alternation. The deviation amounts to 5 mm., the outward movement of +both eyes is perfectly normal. Hypermetropia 2 D., visual acuteness 5/18 +on both sides. Ophthalmoscopically with atropine the same degree of +hypermetropia. Tenotomy of both interni on March 7th, 1879. On March +14th, deviation 5 mm., just as before. Then renewed division of the +internal rectus and shortening of the external rectus of the right eye; +but still the result was insufficient. Therefore, on March 21st, the +left eye was dealt with in the same way. By this means a normal position +of the eye was obtained, which was perfectly preserved when I saw the +patient again a year and a half later. Everything led me to suppose +beforehand that simple tenotomy of both internal recti would perfectly +suffice to remove the squint, yet it was of no use, but had to be +supplemented by shortening both external recti. In such cases I would +not advise repeated tenotomies, but for the correction of the +insufficient result as soon as possible by advancement of the +antagonist. + +Advancement very frequently gives us an opportunity of seeing with our +own eyes the insufficiency of the antagonist and its faulty anatomical +development. We may suppose this to be the case if the mobility towards +the side of the antagonist is faulty, however that is no proof; +considerable insufficiency may co-exist with perfectly normal mobility. +If limitation of movement is present, to which insufficiency of the +antagonist may be assigned as the cause, or if it is desirable to obtain +the greatest possible result by means of an operation on the squinting +eye, we must combine tenotomy of the deviating muscle with advancement +of the antagonist. The same is stretched tighter, and rolls the eye more +strongly to its side, and we can regulate the degree of shortening of +the muscle, by the distance behind the insertion at which we place the +threads in the muscle, also by the distance from the corneal margin at +which we place our anterior sutures, although the rapidly increasing +ductility of the conjunctiva makes it desirable that we should not go +far from the corneal margin. + +The exact rules for the application of the methods of operation differ +according to the nature of the case under consideration. If we +contemplate first the largest group, that of the ordinary permanent +convergent squint, the choice of the method is principally determined by +the average degree of deviation, the condition of error, and the visual +power, lastly by the mobility, particularly the outward movement of the +eyes. If the visual power of both eyes is nearly the same, or if the +squinting eye possesses such a visual acuteness that it can be used in +fixation, it is advisable as a rule to arrange the relations of the +muscles as equally as possible in both eyes--simple division of the +internal recti is therefore, as a rule, to be performed in both eyes. +If, on the other hand, the vision of the squinting eye is in a high +degree defective, so that only the better one is used, it is generally +advisable to confine the operation as far as possible to the squinting +eye; in that case, tenotomy of the internal rectus and advancement of +the external rectus is usually indicated in the squinting eye, and +frequently suffices. + +Deviations which are so slight, that the careful division of both +interni without loosening the conjunctiva at the front part of the +muscle makes us fear an excessive result, are seldom the subject of +operative treatment; if the deviation is slight but still a +disfigurement, if it amounts to 3 to 4 mm., distribution between both +eyes is suitable, because, when the squinting eye possesses requisite +visual acuteness it is put into fixation more frequently after the +operation than before. Under these circumstances, if the operation is +confined to the squinting eye, and a sufficient result is thereby +obtained, as soon as this eye is used for fixation a remarkable +secondary deviation of the other eye occurs, which is not the case if +the tensions of the muscles have been balanced by an operation on both +sides. + +A deviation of 5 to 6 mm. may usually be balanced by means of simple +double tenotomy if the conjunctiva is considerably loosened behind the +caruncle; not unfrequently, however, we must be careful to strengthen +the result by means of the after-treatment. Commonly, during the first +twenty-four hours, the result appears to be quite satisfactory, whilst +on the second or third day troublesome convergence again sets in. By +practice of the outward movement we then usually obtain at once a +perceptible improvement of the position. Both eyes are repeatedly turned +as far as possible to the right and left, by which means is obtained on +the one hand, exercise of the external recti, on the other, increase of +the effect of the tenotomy of the internal recti. I order these +exercises to be begun on the day after the operation. + +Besides this, however, in the relation between accommodation and +convergence of the visual axes there is a very essential cause which is +able to lessen the immediate effect of the operation. Persons who squint +inwards, even if emmetropic, have the habit of combining accommodation +for near objects with excessive convergence of the visual axes, thus +the immediate effect of the operation is diminished as soon as they +begin to use their eyes again. This happens, not by a lessening of the +effect of the tenotomy, which could, indeed, only be increased by +exertion of the internal recti, but in that sufficient time is not given +for the external rectus to regain its normal elastic tension. Nothing is +changed at first by the operation in the customary relation between +accommodation and innervation of the internal recti--it is a question, +then, of avoiding every exertion of the accommodation for some time, in +order that no inducement for strong convergence should be given. I am +accustomed, therefore, even in the case of emmetropes, to paralyse the +accommodation by means of atropine twenty-four hours after the +operation, and to remove the far-point by convex glasses to about 0·70 +m.; the spectacles must, of course, be worn constantly, for only by that +means can we be sure that they are always used for near objects. After a +few weeks the spectacles are discontinued, first for distance, then for +near objects also. This after-treatment is not necessary under all +circumstances; but I have repeatedly assured myself that an originally +sufficient result which perceptibly diminished after a few days, could +by this means be restored and permanently maintained even in emmetropes. + +In the case of hypermetropes, we more often meet with the same +experience; in permanent convergent squint it is by no means necessary +to neutralise the hypermetropia permanently after the operation, but it +happens here more often than in emmetropia, that a perfectly good +immediate effect is lost within the first week after the operation, and +can be restored again by permanently wearing the correcting convex +glasses. In such cases also, I am accustomed after a few months to +discontinue the spectacles for distance as an experiment, while they are +still used for working. + +Simple tenotomy of both internal recti does not, as a rule, suffice for +deviations of more than 7 mm.; therefore, even if both eyes possess good +visual power, we must still decide on tenotomy of both internal recti +together with advancement of the external rectus of the squinting eye, +or anticipate repeated tenotomies of the internal recti, or seek to +obtain the greatest possible effect by means of slight modification of +the method of procedure. + +Provided that the muscle was completely divided, and sufficiently +loosened from the conjunctiva during the first operation, a repetition +of the tenotomy can only aim at an increase of the effect if the elastic +tension of the antagonist has improved in the meantime. I very rarely +therefore carry out repeated tenotomies; it seems to me much more +desirable to obtain a sufficient result at one operation whenever that +is possible. + +In some cases where there is a deviation of 7 to 9 mm., the effect of +the tenotomy may be increased by inducing a strong divergence +immediately after the tenotomy of the internal recti, which is +maintained for 6 to 8 hours. For this a thread is passed through the +conjunctiva at the outer edge of the cornea about 4 mm. above the +horizontal meridian, and out again about 2 mm. below the horizontal +meridian, then from below upwards in the same way, so that the +conjunctiva is contained in a loop. The needle is then passed through +the external canthus from the conjunctival surface and fastened by tying +it over a roll of paper. This procedure is only to be recommended in +exceptional cases; a greater effect on the internal recti is thus +obtained, while with reference to the position the result depends on the +elastic tension of the external rectus just as in simple tenotomy. + +If the squinting eye has only an unavailable visual acuteness, a +combination of tenotomy of the internal rectus with shortening of the +external rectus is the best procedure. As a rule, simple tenotomy of the +internal rectus of the squinting eye is of very little use in such +cases, as the abducens, weakened by continual extension and wanting +practice, places too slight an opposing power in the balance. The chief +effect of the operation then devolves on the other solely available eye, +which is not a desirable circumstance, and is also frequently +insufficient. On the other hand, the combination of tenotomy of the +internal rectus with advancement of the external rectus enables us +successfully to change the opposing muscular tensions. As a rule, the +operation may be confined to the squinting, weak-sighted eye, as that +suffices to obtain a correction of 5 to 6 mm. + +If the result is seen to be insufficient, it may be supplemented by +tenotomy of the internal rectus of the other eye; in the case of +deviations of more than 7 mm. it is advisable to divide the operation +between the eyes in this way. + +The suture has a special use in so-called artificial strabismus; that +is, in those cases where convergent is converted into divergent squint +through unskilful treatment, or where tenotomy of the abducens, +performed on account of "insufficiency of the internal recti," is +followed by convergent strabismus. I have not found confirmation of the +fear expressed by Arlt, that the method proposed by me could be scarcely +practicable if it is a case of the advancement of a muscle too far +forward, and I have corrected a large number of such cases in other +practices. It is seldom profitable to take up things in which others +have been unsuccessful, but it bring its own reward in the case of +artificial squint. + +Periodic convergent squint offers a less certain ground for the +operation. The change between normal position and a very considerable +squint gives rise to the fear that an operation which would be able to +remove the convergence might finally induce divergent strabismus. This +fear is certainly not groundless, but at the same time it must be +remembered that, with the exception perhaps of a few cases of clearly +accommodative deviation, elastic preponderance of the internal recti or +insufficiency of the external recti is generally the cause of periodic +squint also. I have frequently, in periodic squint, performed double +tenotomy of the internal recti with the slightest possible loosening of +the conjunctiva. I have also attempted to confine the operation to the +shortening of the external rectus without loosening the internal recti +and with success, but not frequently enough to be able to deliver a +certain opinion upon it. + +In periodic squint, the first care must always be to determine the +condition of refraction, if possible with atropine, and to neutralise or +over-correct hypermetropia if present. If squint is absent during the +use of convex glasses, which happens frequently under these +circumstances, the operation offers no further advantages, as the +constant use of convex glasses afterwards can hardly be avoided. If the +periodic deviation continues to exist, the operation can be carried out +according to the above rules and so as to cause a slight effect. + +The final result is usually attained after two to three weeks in +convergent squint; it is better to allow a slight degree of convergence +to exist, as divergence, however slight, existing at this time, brings +with it the fear of a gradual increase. It happens occasionally, that +after years, convergence asserts itself again; I have observed it in +spontaneous (see Case 39) as well as in operative cure of squint; still, +this is so unusual, that I should like to give an illustration of the +latter observation on account of its rarity. + +CASE 44.--Hedw. von L--, æt 10, came under treatment in April, 1874, for +convergent squint on the left side which arose in her seventh year, with +occasional alternation. Emmetropia, determined with atropine on both +sides and good visual acuteness. Diplopia was present at the +commencement of the squint. Patient can only be rendered conscious of +double images by the help of a red glass and vertically deviating +prisms. Double tenotomy of the internal recti effected a normal +position, and at the end of December, 1874, the continuance of the same +could be proved as well as binocular fusion with prisms. At the +beginning of 1880, I was informed that from time to time periodic squint +had occurred with diplopia. In the middle of March, I had an opportunity +of seeing the young lady. Myopia 2 D. had meanwhile developed on both +sides, visual acuteness almost = 1. The position of the eyes was +perfectly good, slight convergence occurred during covering, homonymous +double images with a red glass which, at a distance of 5 m., were joined +by a prism of 8°; stereoscopic fusion was not perfectly certain. A true +squint could not be proved. On April 3rd, as patient stopped for a few +hours on her journey through, a striking convergent squint of the left +eye was seen. The deviation amounted to 4 to 5 mm. Single vision existed +at a distance of 15 to 20 cm., then homonymous double images appeared, +which did not correspond to the objective deviation; the double images +were however corrected by a prism of 6° (base outwards) for an object 5 +m. distant. + +We cannot conclude the consideration of the operative treatment of +convergent squint without once more returning to the relation between +the line of vision and the position of the cornea. The angle [Greek: a] +still deserves mention in a few thankful words--_hic mihi angulus +praeter omnes ridet_--it is a very useful guide in tenotomy. In tenotomy +we may count as gain the apparent divergence which it causes in +hypermetropes who do not squint. We obtain a perfect cosmetic result, +while a convergence, objectively determinable, but not otherwise easily +visible, continues to exist. It would be folly to exceed this; and for +cases where binocular fusion does not exist, and where diplopia is not +present, to wish to remove this covered convergence due to the angle +[Greek: a], the cosmetic result would be impaired by it. + +Those cases where it is a question of uniting homonymous double images +are very instructive when considering tenotomy. Only when squint arises +after childhood (after the fifteenth year) does it cause troublesome +diplopia, this accords naturally with the laws of normal binocular +fusion learnt meanwhile. (On the other hand those cases, which sometimes +occur after tenotomy, with the double images in a position which does +not correspond to the normal physiological laws and which cannot +therefore be united by prisms, are naturally unsuitable for the +operative removal of diplopia.) Cases in which convergent squint is +followed by troublesome double images, appear, with the exception of the +hysterical form mentioned on p. 41, chiefly in myopia, more seldom in +emmetropia, and very rarely in hypermetropia; for if the conditions +contained in the ocular muscles are coincident with hypermetropia, +squint usually arises in the course of childhood, before normal +binocular vision has become a fixed habit. + +As the cases here under consideration are not very common, I will relate +a few from which conclusions may be derived as to the effect of +tenotomy. + +CASE 45.--Miss von B--, æt. 14, came under treatment on May 1st, 1875, +for diplopia, which made its appearance about a year previously. +Emmetropia and full visual acuteness exist on both sides. The double +images are homonymous and further apart on both sides of the visual +field. At first single vision existed only to about 0·75 m.; gradually, +however, the area of single vision was extended by practice of the +outward movement, supported by the use of prismatic spectacles, so that +after a year patient could see singly to a great distance. This +improvement was not maintained. At the beginning of 1879, diplopia was +again present to a troublesome degree, particularly on looking +downwards; on looking straight forwards the left eye showed a slight +convergent deviation, amounting at most to 2 mm. During various +examinations the distance of the double images was stated to be now +less, now greater, a prism of at least 5°, at most of 9°, was requisite +for correction. Diplopia was at once removed by tenotomy of the left +internal rectus, with very slight loosening of the conjunctiva, and has +not appeared since. + +CASE 46.--Miss A--, æt. 17, suffered from diplopia for a few weeks, a +year and a half ago; for the last half year the diplopia is continuous, +and striking squint is stated to be sometimes present. Myopia 2 D. on +both sides, visual acuteness = 5/9. On fixation of an object about 4 m. +distant, the left eye deviates inwards at most 2 mm.; homonymous double +images, with a red glass and on correction of the myopia, which were +united by means of prism 14° at a distance of 5 m., without red glass +(with retinal images alike on both sides) prism 8° sufficed to unite +them. If a vertically deviating prism is held before one eye, the double +images stand just above one another when looking at an object 20 cm. +off, on nearer approach they are crossed. On May 3rd, 1879, tenotomy of +the left internal rectus with small conjunctival wound without loosening +of the conjunctiva, and union of the conjunctival wound by a suture. On +May 8th, single vision, also with correction of the myopia and with red +glass. Facultative divergence = 2°. On May 14th, with correction of the +myopia, there was still single vision for distance; however, with red +glass double images occurred again; and at the end of May the condition +of the double images was just the same as before the operation. On +vertical shifting of one visual field by a weak prism the double images +are brought into a vertical line by means of prism 16°, with the base +outwards. Therefore, on July 1st, the right internal rectus was also +divided, with small conjunctival wound without loosening of the +conjunctiva and without suture. The evening after the operation slight +divergence on covering. On July 24th, binocular single vision is +present; with red glass homonymous double images at 5 m., corrected by +prism 4°. This time the result was final; for in the middle of October, +three months after the operation, the report was exactly like the one of +July 24th above stated. + +CASE 47.--Mrs. A--, æt. 33, has suffered for six months from alternating +convergent squint with diplopia, for a short time even a parallel +position is still possible. On the right myopia 4 D., V. = 6/12. On the +left myopia 4 D., V. 6/9. Single vision occurs to 22 cm., at a greater +distance homonymous double images, whose mutual distance remains the +same when looking to one side. On correction of the myopia a prism of at +least 32° is necessary for the union of the double images for an object +at 4 m. Two days after tenotomy of the internal recti on both sides, the +facultative divergence amounted to 7° (at 4 m.) on correction of the +myopia. Single vision was also present when looking strongly to one +side, and with differentiation of one retinal image by a red glass. + +CASE 48.--Mr. B--, æt. 32, first observed the occurrence of diplopia at +the beginning of April, 1877. Myopia 6 D. is present in both eyes, +visual acuteness on the right 1/2, on the left rather more than 1/2 +(5/9). The double images are homonymous and sometimes (not always) move +farther apart at the limits of the visual field. Patient could only +decide after two years, in July, 1879, on the operative treatment then +proposed. Diplopia continued to exist; single vision was only now and +then possible for a short time. On correction of the myopia (if one eye +is provided with a red glass) prism 12° suffices for union of the double +images. If one visual field is moved in a vertical direction by a prism +of 5° during the trial of convergence, prism 38° is necessary in order +to equalize the lateral deviation of the double images, and to place +them perpendicularly above one another for an object 5 m. distant. On +July 14th, tenotomy of the internal rectus of the left eye; single +vision next day on correction of the myopia, prism 6° is overcome by +divergence; if, however, double images are produced by a vertically +deviating prism of 5° they immediately show homonymous lateral +deviation, which is corrected by prism 18° at a distance of 5 m. + +Two months after the operation the diplopia was certainly better, but by +no means removed; squint occurred periodically as before, so that +sometimes single vision was possible at 3 to 4 m., sometimes troublesome +diplopia was present. + +During the test of convergence with prisms deviating in a vertical +direction, a prism of 38° was necessary for the equalization of the +lateral deviation just as before the operation. Therefore in the middle +of October the internal rectus of the right eye was divided, and the +conjunctiva loosened as far as the caruncle. Three days afterwards +single vision, facultative divergence = prism 5°; in the trial of +convergence, equalization by means of prism 8°. In the middle of +October, two months after the operation, diplopia had not appeared +again; facultative divergence = 0; homonymous double images are produced +by a red glass before one eye, slight convergent deviation on covering +it, which in the trial of convergence is equalized by prism 20°. The +preponderance of the interni was now so far lessened for the ordinary +use of the eyes, that permanent binocular single vision was possible. + +Notwithstanding the small number of these cases we may conclude from +them, that homonymous diplopia in typical convergent squint (not +paralytic) can only be corrected occasionally by one-sided tenotomy when +the deviation is slight. As a rule it is necessary to distribute the +operation between the eyes. A result seems attainable by means of simple +tenotomy on both sides, which is expressed by prism 20° in the trial of +convergence. In future cases it would be desirable to determine during +correction of the anomalies of refraction (1) the weakest prism which is +able to unite the double images at about 5 m. distant (without red +glass); (2) the distance at which the double images stand apart from one +another during the trial of convergence with prisms deviating in a +vertical direction; and (3) the prism which brings the double images +immediately above one another in the case of objects about 5 m. off. + +Next to the cases above discussed stand those where convergent squint +remains after paralysis of the abducens; at the same time slightly +defective mobility and a distinct moving apart of the double images +towards the affected side can usually be detected. In a few such cases I +could restrict myself to tenotomy of the internal rectus of the affected +eye, but in those cases which I was able to attend to more particularly, +double tenotomy was necessary, and did not always suffice. Here also the +advancement of the external rectus is suitably applied, which I should +like to illustrate by means of a few examples. + +CASE 49.--Mr. B--, æt. 20, was seized by paralysis of the abducens of +the right eye in November, 1877. In April, 1878, convergent squint was +still present, and as it continued patient decided on an operation in +February, 1879. Both eyes are emmetropic and possess full visual +acuteness. + +Immediately before the operation the double images were united at 4 to 5 +m. in the horizontal plane by a prism of 39°; towards the right their +deviation rather increased. The measurable deviation amounted to 4 mm. +in the right eye, the secondary deviation of the left to 5 mm. In order +to proceed carefully, I confined myself at first to tenotomy of the +internal rectus of the right eye. After the space of a week single +vision was present at the distance of 1 metre in the middle line and at +the height of the eyes; at about 5 m. homonymous double images corrected +by prism 12°, together with slight difference in height (= prism 4°, +base upwards before the right eye). The area of double vision extended +from the limit of the right visual field to about 20° the other side of +the middle line. + +This result would have sufficed perfectly for a cosmetic tenotomy where +binocular fusion did not exist; the annoyance caused to patient by +diplopia, however, was only slightly relieved. I decided, therefore, on +a second operation, not without fearing an excessive result, and +performed tenotomy of the left internal rectus with a very small +conjunctival wound and by closing the wound by means of a suture. The +result was by no means excessive, for it was perfectly _nil_, apparently +even negative at first, for a few days after the operation the area of +single vision approached the eye to less than 0·5 m. and at 4 to 5 m. a +prism of 20° was requisite for correction; however, eighteen days after +the tenotomy of the left internus everything was as before. Single +vision to 1 m. while prism 12° corrected for a distance of 4 to 5 m. The +tenotomy then had no effect at all on the position of the eye; however, +the restriction of movement dependent on it, asserted itself in that the +double images were crossed on the limit of the right visual field (about +45° towards the right). On the supposition that this insufficient result +might be caused by the suture of the conjunctival wound I decided to +repeat the separation of the internal rectus. The agglutination of the +muscle with the sclerotic is so slight for two to three weeks after the +operation that the strabismus hook perfectly suffices to sever the +connection; no suture was put in, but the result again was _nil_, and on +the day after the operation single vision was only present to 0·5 m. in +the middle line, just as after the previous tenotomy of the left +internal rectus. It was now clear that the result with respect to the +position of the eye was only unsuccessful because the antagonist did not +do its duty. I shortened the abducens (without touching the internus +again). The immediate effect, during the chloroform narcosis, was a +terrible divergence, but on the same evening it was less, and +twenty-four hours after the operation with a red glass, homonymous +double images were present close together at a distance of 4 m. Ten days +afterwards binocular single vision was insured, facultative divergence += 3° at 4 m., crossed double images towards the limits of both visual +fields, but only on moving the eyes in a lateral direction; no practical +use was made of this. If one could have diagnosed beforehand the +insufficiency of the externi assuredly present here, which was probably +the reason for the development of squint on the healing of the paralysis +of the abducens, one would have been able to combine shortening of the +right abducens with tenotomy of the internus in the first operation, +whereas the necessity for the advancement was only shown by the +abnormally slight effect of the tenotomy on the left side. According to +accounts received by letter the favorable result has continued. + +We obtain a result more quickly by the immediate advancement of the +abducens. For example: + +CASE 50.--Mr. K--, æt. 29, suffered from paresis of the right abducens +in the autumn of 1877. In December, 1878, convergent squint is present, +linear deviation 5 mm. (scarcely more on the left than on the right). +The defect of movement towards the side of the right abducens amounts to +about 2 or 3 mm. Diplopia is present in the whole visual field with +increase of the deviation towards the right. Emmetropia and full visual +acuteness on both sides. Tenotomy of the internal rectus and advancement +of the abducens of the right eye at the end of December. Three weeks +later single vision is present in the middle line; on the left limit of +the visual field crossed double images, on the right side homonymous +ones, beginning about 20° from the middle line. The result was by no +means excessive. + +In convergent squint with congenital paresis of the abducens, not much +can be attained without shortening the abducens. Of course only the +squint can be removed, not the paralysis, but if once a correct position +is attained for the middle line, cosmetic demands are satisfied; the +outward movement, which is absent, must be replaced by turning the +head. + +The chief method for absolute divergent squint is the combination of +shortening with tenotomy of the externus. If the impulse for convergence +is once lost, so that an associated movement occurs in place of an +accommodative one on fixation of a point situated on the middle line, a +removal of the squint cannot be obtained by simple tenotomy of the +externi--another proof that a change of position of the eye is by no +means a necessary result of tenotomy. + +Moreover, this slight aid given by tenotomy has its ground not solely in +the condition of the opposing recti muscles. In other practices I have +seen cases enough in which tenotomy of the externi, performed on account +of relative divergence, was followed by convergent squint, just as +injudicious division of the interni may induce divergent squint. It is +probable, therefore, that the faulty effect of simple tenotomy in +permanent absolute divergent squint depends on other causes, which, in +my opinion, are to be found in the obliques. The loop formed by the +obliques round the posterior circumference of the eye is most stretched, +when the visual line falls in with the muscular plane of the obliques in +a medial direction of the eyes. On the whole, then, it is proved that +the obliques are extended on turning the eyes inwards, but shortened on +turning the eyes outwards by means of their muscular action. In +divergent squint, if the movement inwards occurs but seldom or not at +all, the obliques consequently are not extended in a normal way--it +follows then that they lose in ductility, offer greater resistance to +the inward movement, and by means of their elastic tension continually +draw the posterior pole of the eye inwards and the cornea outwards. As +in strabotomy we cannot get at the obliques, it seems all the more +desirable to offer them stronger resistance by greater tension of the +internus by means of advancement. Certainly tenotomy of the external +rectus of the fixing eye is as a rule also necessary. A sufficient +result is usually thus obtained at once; if it is much lessened in the +course of one or two months there is nothing to prevent the repetition +of the tenotomy of one or the other external rectus. + +The innervation for the movement of convergence is not always perfectly +lost; it withdraws itself from the influence of binocular fusion because +this is gradually forgotten while a convergence, even if an insufficient +one, unites itself with the effort of accommodation. If we ask such +patients to fix a large object lying near, a pencil, for example, they +cannot usually converge upon it, whilst if we ask them to read at the +same distance, a distinct convergent movement occurs; large objects are +sufficiently clearly recognised, even without distinct retinal images, +and the supposition that an effort of accommodation is present is only +justified if we employ sufficiently small objects at the examination, in +order to distinguish which, clear retinal images are necessary. Of +course we must have regard to the condition of refraction; myopes, who +use their far point for reading, want no accommodation, therefore no +convergent movement occurs, even if the impulse of innervation for it, +is not yet quite lost. However, the innervation for convergence may be +lost, without the internal recti losing in elastic tension. The +operative importance of this relation may be illustrated by an example. + +CASE 51.--Bertha K--, æt. 10, has myopia 5 D. on both sides, visual +acuteness 12/20, and divergent strabismus. At 4 mm. the crossed diplopia +is corrected by prism 23°; a convergent movement is no longer attained, +at most parallelism of the visual axes. Tenotomy of both interni on +October 2nd, 1873. The immediate result was convergent squint, with a +defect in movement outwards amounting to 4 to 5 mm. in both eyes. On +October 9th prism 37° was still necessary to unite the homonymous double +images at a distance of 4 m.; single vision existed only to about 20 cm. +The area of single vision gradually extended itself; at the end of +October it was restored for distance also, facultative divergence +_nil_; however, relative divergence was present for near objects. +Naturally this was not the result of muscular weakness of the interni, +for they had proved their capabilities by a convergent squint, +fortunately only temporary, which made one anxious, but was solely the +result of a faulty innervation. The further course was also interesting. +After three years, in October, 1876, the myopia of the left eye amounted +to 8 D., that of the right 7 D., visual acuteness 1/2 on the right, on +the left 3/4 of the normal; a posterior staphyloma measuring about 1/3 +of the diameter of the optic disc was present. The left eye was used for +near objects with relative divergence of the right and the occasional +occurrence of diplopia; there was convergence only to about 15 cm. +Facultative divergence _nil_. + +We very frequently have the opportunity of seeing, that myopia increases +even after tenotomy of the externus, and if von Graefe's assertion that +the progress of myopia would be brought to a standstill by means of +tenotomy still finds believers, I should like to cite one example which +offers proof to the contrary. + +In permanent divergent squint we shall have, as a rule, to combine +shortening of the internus of the squinting eye with tenotomy of both +externi, even if the convergent movement is still possible to a slight +degree. The result thus obtained differs somewhat; sometimes it suffices +at once, sometimes a repetition of the separation of the externi is +necessary later on. Two examples may illustrate this. + +CASE 52.--Miss Marie M--, æt. 22, has squinted on the left side since +her third year, nominally after a keratitis, which left behind in the +left eye a nebula of the cornea of small circumference. The deviation +amounts to 8 mm. The visual power is much worse than the opacity of the +cornea leads us to suppose, with visual axes deviating inwards fingers +were only counted at a distance of about 1 m. + +On the right myopia 1 D., V. = 4/5. A slight convergent movement is +still practicable. At the end of May, 1879, shortening of the left +internal rectus, tenotomy of both externi. The next day slight +convergence on viewing distant objects, correct position after four +days. In January, 1880, correct position of the eyes, convergence +possible to about 20 cm. While a correction of 8 mm. was immediately +obtained here, the same operation does not always permanently suffice +for slighter deviations. + +CASE 53.--Ernest Sp--, æt. 11-1/2; divergent squint had been observed as +early as his second year. The deviation amounts to 5 or 6 mm., is +sometimes alternating, generally the left eye deviates. No convergent +movement on fixing a pencil about 25 cm. distant; the right eye is then +used for reading, the left one makes a distinct, but not a sufficient, +movement inwards. Emmetropia on both sides, visual acuteness nearly +perfect on the right, on the left 2/3 of the normal. Even with red glass +and prisms deviating in a vertical direction, double images not +perceived. On October 2nd, 1879, shortening of the left internal rectus, +tenotomy of both externi. A week later divergence was no longer present. +When reading, the left eye makes a distinct, perhaps rather too great, +movement of convergence, and yet six weeks after the operation, distinct +divergent squint was again present, even if to a slighter degree than +before; the left eye deviates 3 to 4 mm., the right 2 to 3 mm. outwards. +The result obtained amounted then to not more than about 3 mm. In the +middle of December the tenotomy of both externi was therefore repeated. +A week after the operation convergent squint of 2 mm. is present with +homonymous diplopia. A pencil made to approach on the middle line is +seen double to about 20 cm., on approaching nearer, double images are +not perceived in spite of distinct relative divergence. Double images at +a distance of 4 m. are corrected by prism 25°; as, however, normal +binocular vision is not present, the value of this statement is very +questionable. Three weeks after the second operation the position of the +eyes was normal, and the slightest convergence was perceived only on +close investigation. Double images are no longer observed, however they +may still be brought to view. + +In periodic divergent squint, if the deviation is considerable and +frequent, if at the same time the normal near point of convergence is +only attained with difficulty or not at all, we can hardly combine +shortening of the internus with tenotomy of the externus; more often +indeed, additional tenotomy of the externus of the other eye is +necessary in order to obtain a permanent cure. In exceptional cases +(when it seemed to me as if the squint depended more on insufficiency of +the internus than on preponderance of the externus) I have confined +myself to shortening the internus without separating the externus; I +will quote just one example of this. + +CASE 54.--Ida K--, æt. 11. On the right, hypermetropia 3 D. with the +ophthalmoscope, visual acuteness 5/24. No. 0·3 is read with difficulty. +On the left, with the ophthalmoscope hypermetropia 4·5 D. with +asymmetric meridian. Single letters of 3·0 m. are recognised with convex +6·5 D. Fingers are counted at about 1-1/2 m. The choroid is slightly and +unequally pigmented, no ophthalmoscopically assignable reason exists for +the considerable visual defect. The left eye frequently deviates +outwards, convergence is attainable to 15 cm. On May 2nd, 1877, +shortening of the internus (without tenotomy of the externus). Two weeks +later slight convergent squint was present; in November, 1877, six +months after the operation, the position of the left eye was perfectly +normal. + +Tenotomy of the externi suffices when the divergent deviation is +inconsiderable and does not occur often, if the normal near point of +convergence can still be reached, and binocular fusion is possible. + +If we want to increase the effect of simple tenotomy of the externi, +this may be done just as well by practice of the associated movements of +the eyes as by practice of the convergence, of course for a short time +only after the operation. As long as the detached tendon of the external +rectus is not re-attached firmly with the sclerotic, all these movements +of the eyes help to strengthen the result of the tenotomy. In order to +practise convergence we can bring a suitable fixed point on to a mirror +and so make it possible for the patient himself to see the position of +his eyes, of course only in cases where binocular fusion is no longer +present. He who possesses a normal binocular vision is troubled in these +exercises by diplopia; but this is not the case in the suppression of +binocular fusion so frequent as a result of squint. + +Periodic divergent squint is divided by no sharply defined limits from +those cases in which only a preponderance of the externi exists without +insufficiency of the interni. We frequently find very considerable +degrees of facultative divergence as a casual symptom, without the +occurrence of manifest divergence or the presence of asthenopic +troubles. If this is accompanied by weakness of the interni, absolute +divergence occurs on looking at near objects, sometimes for distance +also and certainly if we suppress binocular fusion by covering one eye +or render it difficult by colouring one visual field with a red glass. + +In these cases the indications for the operation are given either by +asthenopia, by troublesome double images or by the disfigurement +inseparable from periodic squint; it will depend on the degree of the +facultative divergence, whether we confine the tenotomy of the externus +to one eye or whether we distribute it between both eyes. + +Finally, it may be desirable to still say a few words as to the most +favorable period for the operation. The comprehension of the defective +sight often present in squint as caused by "non-use" has resulted in +the preposterous advice that tenotomy should be carried out as early as +possible. I can vouch for the fact that even the earliest tenotomy of +the ocular muscles is of no avail against congenital amblyopia. I have +repeatedly seen children on whom tenotomy had been performed in their +first year, usually with bad cosmetic result but with continuance of +defective sight of the squinting eye. + +The final result of the operation is almost always very unsatisfactory +when performed on children before their fourth year. I can show a number +of good results in children on whom I operated between their fifth and +sixth year; however, the more I considered the subject, the more it +seemed to me advisable to raise the tests which must be imposed on the +patients. With children it is not so much a question of determining the +limit of age, but whether their intelligence is sufficiently developed +to render a reliable examination possible. A sufficient knowledge of +letters and the power of reading is necessary to an accurate trial of +vision; the entire bearing of the children must permit of the +ophthalmoscopic diagnosis of the weak condition and should raise no +scruples as to wearing spectacles which may be necessary after the +operation. Under any circumstances no harm is done by deferring the +operation until these conditions are fulfilled; the interval may be +filled up by practising the mobility of the eyes, which does more good +than the customary strabismus spectacles or even tying up the eye. If we +tie up the fixing eye, the squinting one is certainly put into fixation, +but the other squints instead, and of course it is just the same with +the plan, as childish as it is antiquated, of tying on a pierced walnut +shell before each eye. + +Strabismus spectacles, _i. e._ those with a leather band to go round the +head, provided with leaden discs which cover one eye completely and +leave only a side aperture for the other, of course only induce a +transfer of the squint to the covered eye, together with practice of +the eye in a lateral direction; but apart from their unsightly +appearance they require a constant lateral direction of the eye, which +is followed even after a short time by fatigue of the muscles employed +and soon becomes unbearable. This is not the case if we cause the +mobility to be practised alternately and towards both sides; here we +must insist that the limits of the outward movement are really reached. +These exercises are at least rational and tend to increase the strength +of the antagonist, on which we must depend so much in the operation and +to diminish an insufficiency made worse by want of practice. + + +PRINTED BY ADLARD AND SON, BARTHOLOMEW CLOSE. + + * * * * * + + +Catalogue B] _London, 11, New Burlington Street March, 1887_ + + +_SELECTION_ + +FROM + +J. & A. CHURCHILL'S GENERAL CATALOGUE + +COMPRISING + +_ALL RECENT WORKS PUBLISHED BY THEM_ + +ON THE + +ART AND SCIENCE OF MEDICINE + +[Illustration] + +N.B.--As far as possible, this List is arranged in the order in which +medical study is usually pursued. + + * * * * * + +J. & A. CHURCHILL publish for the following Institutions and Public +Bodies:-- + +ROYAL COLLEGE OF SURGEONS. + CATALOGUES OF THE MUSEUM. + Twenty-three separate Catalogues (List and Prices can be obtained of J. +& A. CHURCHILL). + +GUY'S HOSPITAL. + REPORTS BY THE MEDICAL AND SURGICAL STAFF. + Vol. XXVIII., Third Series. 7s. 6d. + FORMULÆ USED IN THE HOSPITAL IN ADDITION TO THOSE + IN THE B. P. 1s. 6d. + +LONDON HOSPITAL. + PHARMACOPOEIA OF THE HOSPITAL. 3s. + CLINICAL LECTURES AND REPORTS BY THE MEDICAL AND + SURGICAL STAFF. Vols. I. to IV. 7s. 6d. each. + +ST. BARTHOLOMEW'S HOSPITAL. + CATALOGUE OF THE ANATOMICAL AND PATHOLOGICAL + MUSEUM. Vol. I.--Pathology. 15s. Vol. II.--Teratology, Anatomy + and Physiology, Botany. 7s. 6d. + +ST. GEORGE'S HOSPITAL. + REPORTS BY THE MEDICAL AND SURGICAL STAFF. + The last Volume (X.) was issued in 1880. Price 7s. 6d. + CATALOGUE OF THE PATHOLOGICAL MUSEUM. 15s. + SUPPLEMENTARY CATALOGUE (1882). 5s. + +ST. THOMAS'S HOSPITAL. + REPORTS BY THE MEDICAL AND SURGICAL STAFF. + Annually. Vol. XV., New Series. 7s. 6d. + +MIDDLESEX HOSPITAL. + CATALOGUE OF THE PATHOLOGICAL MUSEUM. 12s. + +WESTMINSTER HOSPITAL. + REPORTS BY THE MEDICAL AND SURGICAL STAFF. + Annually. Vol. II. 6s. + +ROYAL LONDON OPHTHALMIC HOSPITAL. + REPORTS BY THE MEDICAL AND SURGICAL STAFF. + Occasionally. Vol. XI., Part III. 5s. + +OPHTHALMOLOGICAL SOCIETY OF THE UNITED KINGDOM. + TRANSACTIONS. + Vol. VI. 12s. 6d. + +MEDICO-PSYCHOLOGICAL ASSOCIATION. + JOURNAL OF MENTAL SCIENCE. + Quarterly. 3s. 6d. each, or 14s. per annum. + +PHARMACEUTICAL SOCIETY OF GREAT BRITAIN. + PHARMACEUTICAL JOURNAL AND TRANSACTIONS. + Every Saturday. 4d. each, or 20s. per annum, post free. + +BRITISH PHARMACEUTICAL CONFERENCE. + YEAR BOOK OF PHARMACY. + In December. 10s. + +BRITISH DENTAL ASSOCIATION. + JOURNAL OF THE ASSOCIATION AND MONTHLY REVIEW + OF DENTAL SURGERY. + On the 15th of each Month. 6d. each, or 7s. per annum, post free. + + * * * * * + +A SELECTION + +from + +J. & A. CHURCHILL'S GENERAL CATALOGUE, + +comprising + +ALL RECENT WORKS PUBLISHED BY THEM ON THE ART AND SCIENCE OF MEDICINE. + +N.B.--_J. & A. Churchill's Descriptive List of Works on Chemistry, +Materia Medica, Pharmacy, Botany, Photography, Zoology, the Microscope, +and other Branches of Science, can be had on application._ + +Practical Anatomy: A Manual of Dissections. By CHRISTOPHER HEATH, +Surgeon to University College Hospital. Sixth Edition. Revised by +RICKMAN J. GODLEE, M.S. Lond., F.R.C.S., Demonstrator of Anatomy in +University College, and Assistant Surgeon to the Hospital. Crown 8vo, +with 24 Coloured Plates and 274 Engravings, 15s. + +Wilson's Anatomist's Vade-Mecum. Tenth Edition. By GEORGE BUCHANAN, +Professor of Clinical Surgery in the University of Glasgow; and HENRY E. +CLARK, M.R.C.S., Lecturer on Anatomy at the Glasgow Royal Infirmary +School of Medicine. Crown 8vo, with 450 Engravings (including 26 +Coloured Plates), 18s. + +Braune's Atlas of Topographical Anatomy, after Plane Sections of Frozen +Bodies. Translated by EDWARD BELLAMY, Surgeon to, and Lecturer on +Anatomy, &c., at, Charing Cross Hospital. Large Imp. 8vo, with 34 +Photolithographic Plates and 46 Woodcuts, 40s. + +An Atlas of Human Anatomy. By RICKMAN J. GODLEE, M.S., F.R.C.S., +Assistant Surgeon and Senior Demonstrator of Anatomy, University College +Hospital. With 48 Imp. 4to Plates (112 figures), and a volume of +Explanatory Text. 8vo, £4 14s. 6d. + +Harvey's (Wm.) Manuscript Lectures. Prelectiones Anatomiæ Universalis. +Edited, with an Autotype reproduction of the Original, by a Committee of +the Royal College of Physicians of London. Crown 4to, half bound in +Persian, 52s. 6d. + +Anatomy of the Joints of Man. By HENRY MORRIS, Surgeon to, and Lecturer +on Anatomy and Practical Surgery at, the Middlesex Hospital. 8vo, with +44 Lithographic Plates (several being coloured) and 13 Wood Engravings, +16s. + +Manual of the Dissection of the Human Body. By LUTHER HOLDEN, Consulting +Surgeon to St. Bartholomew's Hospital. Edited by JOHN LANGTON, F.R.C.S., +Surgeon to, and Lecturer on Anatomy at, St. Bartholomew's Hospital. +Fifth Edition. 8vo, with 208 Engravings. 20s. + +_By the same author._ + +Human Osteology. Sixth Edition, edited by the Author and JAMES SHUTER, +F.R.C.S., M.A., M.B., Assistant Surgeon to St. Bartholomew's Hospital. +8vo, with 61 Lithographic Plates and 89 Engravings. 16s. + +_Also._ + +Landmarks, Medical and Surgical. Fourth Edition. 8vo. [_In the Press._ + +The Student's Guide to Surgical Anatomy. By EDWARD BELLAMY, F.R.C.S. and +Member of the Board of Examiners. Third Edition. Fcap. 8vo, with 81 +Engravings. 7s. 6d. + +The Student's Guide to Human Osteology. By WILLIAM WARWICK WAGSTAFFE, +late Assistant Surgeon to St. Thomas's Hospital. Fcap. 8vo, with 23 +Plates and 66 Engravings. 10s. 6d. + +The Anatomical Remembrancer; or, Complete Pocket Anatomist. Eighth +Edition. 32mo, 3s. 6d. + +Diagrams of the Nerves of the Human Body, exhibiting their Origin, +Divisions, and Connections, with their Distribution to the Various +Regions of the Cutaneous Surface, and to all the Muscles. By W. H. +FLOWER, F.R.S., F.R.C.S. Third Edition, with 6 Plates. Roya. 4to, 12s. + +General Pathology. An Introduction to. By JOHN BLAND SUTTON, F.R.C.S., +Sir E. Wilson Lecturer on Pathology, R.C.S.; Assistant Surgeon to, and +Lecturer on Anatomy at, Middlesex Hospital. 8vo, with 149 Engravings, +14s. + +Atlas of Pathological Anatomy. By Dr. LANCEREAUX. Translated by W. S. +GREENFIELD, M.D., Professor of Pathology in the University of Edinburgh. +Imp. 8vo, with 70 Coloured Plates, £5 5s. + +A Manual of Pathological Anatomy. By C. HANDFIELD JONES, M.B., F.R.S., +and E. H. SIEVEKING, M.D., F.R.C.P. Edited by J. F. Payne, M.D., +F.R.C.P., Lecturer on General Pathology at St. Thomas's Hospital. Second +Edition. Crown 8vo, with 195 Engravings, 16s. + +Post-mortem Examinations: A Description and Explanation of the Method of +Performing them, with especial reference to Medico-Legal Practice. By +Prof. VIRCHOW. Translated by Dr. T. P. SMITH. Second Edition. Fcap. 8vo, +with 4 Plates, 3s. 6d. + +The Human Brain: Histological and Coarse Methods of Research. A Manual +for Students and Asylum Medical Officers. By W. BEVAN LEWIS, L.R.C.P. +Lond., Medical Superintendent, West Riding Lunatic Asylum. 8vo, with +Wood Engravings and Photographs, 8s. + +Manual of Physiology: For the use of Junior Students of Medicine. By +GERALD F. YEO, M.D., F.R.C.S., Professor of Physiology in King's +College, London. Crown 8vo, with 300 Engravings, 14s. + +Principles of Human Physiology. By W. B. CARPENTER, C.B., M.D., F.R.S. +Ninth Edition. By HENRY POWER, M.B., F.R.C.S. 8vo, with 3 Steel Plates +and 377 Wood Engravings, 31s. 6d. + +Syllabus of a Course of Lectures on Physiology. By PHILIP H. PYE-SMITH, +B.A., M.D., F.R.C.P., Physician to Guy's Hospital. Crown 8vo, with +Diagrams, Notes, and Tables, 5s. + +A Treatise on Human Physiology. By JOHN C. DALTON, M.D. Seventh Edition. +8vo, with 252 Engravings, 20s. + +Elementary Practical Biology: Vegetable. By THOMAS W. SHORE, M.D., B.Sc. +Lond., Lecturer on Comparative Anatomy at St. Bartholomew's Hospital. +8vo. 6s. + +Histology and Histo-Chemistry of Man. By HEINRICH FREY, Professor of +Medicine in Zurich. Translated by ARTHUR E. J. BARKER, Assistant Surgeon +to University College Hospital. 8vo, with 608 Engravings, 21s. + +A Text-Book of Medical Physics, for Students and Practitioners. By J. C. +DRAPER, M.D., LL.D., Professor of Physics in the University of New York. +With 377 Engravings. 8vo, 18s. + +The Law of Sex. By G. B. STARKWEATHER, F.R.G.S. With 40 Illustrative +Portraits. 8vo, 16s. + +Influence of Sex in Disease. By W. ROGER WILLIAMS, F.R.C.S., Surgical +Registrar to the Middlesex Hospital. 8vo, 3s. 6d. + +Medical Jurisprudence: Its Principles and Practice. By ALFRED S. TAYLOR, +M.D., F.R.C.P., F.R.S. Third Edition, by THOMAS STEVENSON, M.D., +F.R.C.P., Lecturer on Medical Jurisprudence at Guy's Hospital. 2 vols. +8vo, with 188 Engravings, 31s. 6d. + +By the same Authors. + +A Manual of Medical Jurisprudence. Eleventh Edition. Crown 8vo, with 56 +Engravings, 14s. + +_Also._ + +Poisons, In Relation to Medical Jurisprudence and Medicine. Third +Edition. Crown 8vo, with 104 Engravings, 16s. + +Lectures on Medical Jurisprudence. By FRANCIS OGSTON, M.D., late +Professor in the University of Aberdeen. Edited by FRANCIS OGSTON, Jun., +M.D. 8vo, with 12 Copper Plates, 18s. + +The Student's Guide to Medical Jurisprudence. By JOHN ABERCROMBIE, M.D., +F.R.C.P., Lecturer on Forensic Medicine to Charing Cross Hospital. Fcap. +8vo, 7s. 6d. + +Microscopical Examination of Drinking Water and of Air. By J. D. +MACDONALD, M.D., F.R.S., Ex-Professor of Naval Hygiene in the Army +Medical School. Second Edition. 8vo, with 25 Plates, 7s. 6d. + +Pay Hospitals and Paying Wards throughout the World. By HENRY C. +BURDETT. 8vo, 7s. + +_By the same Author._ + +Cottage Hospitals--General, Fever, and Convalescent: Their Progress, +Management, and Work. Second Edition, with many Plans and Illustrations. +Crown 8vo, 14s. + +A Manual of Practical Hygiene. By F. A. PARKES, M.D., F.R.S. Sixth +Edition, by F. DE CHAUMONT, M.D., F.R.S., Professor of Military Hygiene +in the Army Medical School. 8vo, with numerous Plates and Engravings. +18s. + +A Handbook of Hygiene and Sanitary Science. By GEO. WILSON, M.A., M.D., +F.R.S.E., Medical Officer of Health for Mid-Warwickshire. Sixth Edition. +Crown 8vo, with Engravings. 10s. 6d. + +_By the same Author._ + +Healthy Life and Healthy Dwellings: A Guide to Personal and Domestic +Hygiene. Fcap. 8vo, 5s. + +Sanitary Examinations Of Water, Air, and Food. A Vade-Mecum for the +Medical Officer of Health. By CORNELIUS B. FOX, M.D., F.R.C.P. Second +Edition. Crown 8vo, with 110 Engravings, 12s. 6d. + +Dangers to Health: A Pictorial Guide to Domestic Sanitary Defects. By T. +PRIDGIN TEALE, M.A., Surgeon to the Leeds General Infirmary. Fourth +Edition. 8vo, with 70 Lithograph Plates (mostly coloured), 10s. + +Hospitals, Infirmaries, and Dispensaries: Their Construction, Interior +Arrangement, and Management; with Descriptions of existing Institutions, +and 74 Illustrations. By F. OPPERT, M.D., M.R.C.P.L. Second Edition. +Royal 8vo, 12s. + +Hospital Construction and Management. By F. J. MOUAT, M.D., Local +Government Board Inspector, and H. SAXON SNELL, Fell. Roy. Inst. Brit. +Architects. In 2 Parts, 4to, 15s. each; or, the whole work bound in half +calf, with large Map, 54 Lithographic Plates, and 27 Woodcuts, 35s. + +Manual of Anthropometry: A Guide to the Measurement of the Human Body, +containing an Anthropometrical Chart and Register, a Systematic Table of +Measurements, &c. By CHARLES ROBERTS, F.R.C.S. 8vo, with numerous +Illustrations and Tables, 8s. 6d. + +_By the same Author._ + +Detection of Colour-Blindness and Imperfect Eyesight. 8vo, with a Table +of Coloured Wools, and Sheet of Test-types, 5s. + +Illustrations of the Influence of the Mind upon the Body in Health and +Disease; Designed to elucidate the Action of the Imagination. By DANIEL +HACK TUKE, M.D., F.R.C.P., LL.D. Second Edition. 2 vols, crown 8vo, 15s. + +_By the same Author._ + +Sleep-Walking and Hypnotism. 8vo, 5s. + +A Manual of Psychological Medicine. With an Appendix of Cases. By JOHN +C. BUCKNILL, M.D., F.R.S., and D. HACK TUKE, M.D., F.R.C.P. Fourth +Edition. 8vo, with 12 Plates (30 Figures) and Engravings, 25s. + +Mental Diseases. Clinical Lectures. By T. S. CLOUSTON, M.D., F.R.C.P. +Edin., Lecturer on Mental Diseases in the University of Edinburgh. With +8 Plates (6 Coloured). Crown 8vo, 12s. 6d. + +Private Treatment of the Insane as Single Patients. By EDWARD EAST, +M.R.C.S., L.S.A. Crown 8vo, 2s. 6d. + +Manual of Midwifery. By ALFRED L. GALABIN, M.A., M.D., F.R.C.P., +Obstetric Physician to, and Lecturer on Midwifery, &c. at, Guy's +Hospital. Crown 8vo, with 227 Engravings, 15s. + +The Student's Guide to the Practice of Midwifery. By D. LLOYD ROBERTS, +M.D., F.R.C.P., Lecturer on Clinical Midwifery and Diseases of Women at +the Owens College; Obstetric Physician to the Manchester Royal +Infirmary. Third Edition. Fcap. 8vo, with 2 Coloured Plates and 127 Wood +Engravings, 7s. 6d. + +Lectures on Obstetric Operations: Including the Treatment of Hæmorrhage, +and forming a Guide to the Management of Difficult Labour. By ROBERT +BARNES, M.D., F.R.C.P., Consulting Obstetric Physician to St. George's +Hospital. Fourth Edition. 8vo, with 121 Engravings, 12s. 6d. + +_By the same Author._ + +A Clinical History of Medical and Surgical Diseases of Women. Second +Edition. 8vo, with 181 Engravings, 28s. + +Clinical Lectures on Diseases of Women: Delivered in St. Bartholomew's +Hospital, by J. MATTHEWS DUNCAN, M.D., LL.D., F.R.S. Third Edition. 8vo, +16s. + +_By the same Author._ + +Sterility in Woman. Being the Gulstonian Lectures, delivered in the +Royal College of Physicians, in Feb., 1883. 8vo, 6s. + +Notes on Diseases of Women: Specially designed to assist the Student in +preparing for Examination. By J. J. REYNOLDS, L.R.C.P., M.R.C.S. Third +Edition. Fcap. 8vo, 2s. 6d. + +_By the same Author._ + +Notes on Midwifery: Specially designed for Students preparing for +Examination. Second Edition. Fcap. 8vo, with 15 Engravings, 4s. + +The Student's Guide to the Diseases of Women. By ALFRED L. GALABIN, +M.D., F.R.C.P., Obstetric Physician to Guy's Hospital. Third Edition. +Fcap. 8vo, with 78 Engravings, 7s. 6d. + +West on the Diseases of Women. Fourth Edition, revised by the Author, +with numerous Additions by J. MATTHEWS DUNCAN, M.D., F.R.C.P., F.R.S.E., +Obstetric Physician to St. Bartholomew's Hospital. 8vo, 16s. + +Dysmenorrhoea, its Pathology and Treatment. By HEYWOOD SMITH, M.D. +Crown 8vo, with Engravings, 4s. 6d. + +Obstetric Aphorisms: For the Use of Students commencing Midwifery +Practice. By JOSEPH G. SWAYNE, M.D. Eighth Edition. Fcap. 8vo, with +Engravings, 3s. 6d. + +A Manual of Obstetrics. By A. F. A. KING, A.M., M.D., Professor of +Obstetrics, &c, in the Columbian University, Washington, and the +University of Vermont. Third Edition. Crown 8vo, with 102 Engravings, +8s. + +Handbook of Midwifery for Midwives: By J. E. BURTON, L.R.C.P. Lond., +Surgeon to the Hospital for Women, Liverpool. Second Edition. With +Engravings. Fcap. 8vo, 6s. + +A Handbook of Uterine Therapeutics, and of Diseases of Women. By E. J. +TILT, M.D., M.R.C.P. Fourth Edition. Post 8vo, 10s. + +_By the same Author._ + +The Change of Life In Health and Disease: A Clinical Treatise on the +Diseases of the Nervous System incidental to Women at the Decline of +Life. Fourth Edition. 8vo, 10s. 6d. + +The Principles and Practice of Gynæcology. By THOMAS ADDIS EMMET, M.D., +Surgeon to the Woman's Hospital, New York. Third Edition. Royal 8vo, +with 150 Engravings, 24s. + +Diseases of the Uterus, Ovaries, and Fallopian Tubes: A Practical +Treatise by A. COURTY, Professor of Clinical Surgery, Montpellier. +Translated from Third Edition by his Pupil, AGNES MCLAREN, M.D., +M.K.Q.C.P.I., with Preface by J. MATTHEWS DUNCAN, M.D., F.R.C.P. 8vo, +with 424 Engravings, 24s. + +The Female Pelvic Organs: Their Surgery, Surgical Pathology, and +Surgical Anatomy. In a Series of Coloured Plates taken from Nature; with +Commentaries, Notes, and Cases. By HENRY SAVAGE, M.D., F.R.C.S., +Consulting Officer of the Samaritan Free Hospital. Fifth Edition. Roy. +4to, with 17 Lithographic Plates(15 coloured) and 52 Woodcuts, £1 15s. + +Ovarian and Uterine Tumours: Their Pathology and Surgical Treatment. By +Sir T. SPENCER WELLS, Bart., F.R.C.S., Consulting Surgeon to the +Samaritan Hospital. 8vo, with Engravings, 21s. + +_By the same Author._ + +Abdominal Tumours: Their Diagnosis and Surgical Treatment. 8vo, with +Engravings, 3s. 6d. + +A Practical Treatise on the Diseases of Women. By T. GAILLARD THOMAS, +M.D., Professor of Diseases of Women in the College of Physicians and +Surgeons, New York. Fifth Edition. Roy. 8vo, with 266 Engravings, 25s. + +Backward Displacements of the Uterus and Prolapsus Uteri: Treatment by +the New Method of Shortening the Round Ligaments. By WILLIAM ALEXANDER, +M.D., M.Ch.Q.U.I., F.R.C.S., Surgeon to the Liverpool Infirmary. Crown +8vo, with Engravings, 3s. 6d. + +The Student's Guide to Diseases of Children. By JAS. F. GOODHART, M.D., +F.R.C.P., Physician to Guy's Hospital, and to the Evelina Hospital for +Sick Children. Second Edition. Fcap. 8vo, 10s. 6d. + +Diseases of Children. For Practitioners and Students. By W. H. DAY, +M.D., Physician to the Samaritan Hospital. Second Edition. Crown 8vo, +12s. 6d. + +A Practical Treatise on Disease in Children. By EUSTACE SMITH, M.D., +Physician to the King of the Belgians, Physician to the East London +Hospital for Children. 8vo, 22s. + +_By the same Author._ + +Clinical Studies of Disease in Children. Second Edition. Post 8vo, 7s. +6d. + +_Also._ + +The Wasting Diseases of Infants and Children. Fourth Edition. Post 8vo, +8s. 6d. + +A Practical Manual of the Diseases of Children. With a Formulary. By +EDWARD ELLIS, M.D. Fifth Edition. Crown 8vo, 10s. + +A Manual for Hospital Nurses and others engaged in Attending on the +Sick. By EDWARD J. DOMVILLE, Surgeon to the Exeter Lying-in Charity. +Fifth Edition. Crown 8vo, 2s. 6d. + +A Manual of Nursing, Medical and Surgical. By CHARLES J. CULLINGWORTH, +M.D., Physician to St. Mary's Hospital, Manchester. Second Edition. +Fcap. 8vo, with Engravings, 3s. 6d. + +_By the same Author._ + +A Short Manual for Monthly Nurses. Fcap. 8vo, 1s. 6d. + +Notes on Fever Nursing. By J. W. ALLAN, M.B., Physician, Superintendent +Glasgow Fever Hospital. Crown 8vo, with Engravings, 2s. 6d. + +_By the same Author._ + +Outlines of Infectious Diseases: For the use of Clinical Students. Fcap. +8vo. + +Hospital Sisters and their Duties. By EVA C. E. LÜCKES, Matron to the +London Hospital. Crown 8vo, 2s. 6d. + +Diseases and their Commencement. Lectures to Trained Nurses. By DONALD +W. C. HOOD, M.D., M.R.C.P., Physician to the West London Hospital. Crown +8vo, 2s. 6d. + +Infant Feeding and its Influence on Life; By C. H. F. ROUTH, M.D., +Physician to the Samaritan Hospital. Fourth Edition. Fcap. 8vo. +[Preparing. + +Manual of Botany: Including the Structure, Classification, Properties, +Uses, and Functions of Plants. By ROBERT BENTLEY, Professor of Botany in +King's College and to the Pharmaceutical Society. Fifth Edition. Crown +8vo, with 1,178 Engravings, 15s. + +_By the same Author._ + +The Student's Guide to Structural, Morphological, and Physiological +Botany. With 660 Engravings. Fcap. 8vo, 7s. 6d. + +_Also._ + +The Student's Guide to Systematic Botany, including the Classification +of Plants and Descriptive Botany. Fcap. 8vo, with 350 Engravings, 3s. +6d. + +Medicinal Plants: Being descriptions, with original figures, of the +Principal Plants employed in Medicine, and an account of their +Properties and Uses. By Prof. BENTLEY and Dr. H. TRIMEN. In 4 vols., +large 8vo, with 306 Coloured Plates, bound in Half Morocco, Gilt Edges, +£11 11s. + +The National Dispensatory: Containing the Natural History, Chemistry, +Pharmacy, Actions and Uses of Medicines. By ALFRED STILLÉ, M.D., LL.D., +and John M. Maisch, Ph.D. Fourth Edition. 8vo, with 311 Engravings, 36s. + +Royle's Manual of Materia Medica and Therapeutics. Sixth Edition, +including additions and alterations in the B. P. 1885. By JOHN HARLEY, +M.D., Physician to St. Thomas's Hospital. Crown 8vo, with 139 +Engravings, 15s. + +Materia Medica. A Manual for the use of Students. By ISAMBARD OWEN, +M.D., F.R.C.P., Lecturer on Materia Medica, &c., to St. George's +Hospital. Second Edition. Crown 8vo, 6s. 6d. + +Materia Medica and Therapeutics: Vegetable Kingdom--Organic +Compounds--Animal Kingdom. By CHARLES D. F. PHILLIPS, M.D., F.R.S. +Edin., late Lecturer on Materia Medica and Therapeutics at the +Westminster Hospital Medical School. 8vo, 25s. + +The Student's Guide to Materia Medica and Therapeutics. By JOHN C. +THOROWGOOD, M.D., F.R.C.P. Second Edition. Fcap. 8vo, 7s. + +The Pharmacopoeia of the London Hospital. Compiled under the direction +of a Committee appointed by the Hospital Medical Council. Fcap. 8vo, 3s. + +A Companion to the British Pharmacopoeia. By PETER SQUIRE, Revised by +his Sons, P. W. and A. H. Squire. 14th Edition. 8vo, 10s. 6d. + +_By the same Authors._ + +The Pharmacopoeias of the London Hospitals, arranged in Groups for +Easy Reference and Comparison. Fifth Edition. 18mo, 6s. + +The Prescriber's Pharmacopoeia: The Medicines arranged in Classes +according to their Action, with their Composition and Doses. By NESTOR +J. C. TIRARD, M.D., F.R.C.P., Professor of Materia Medica and +Therapeutics in King's College, London. Sixth Edition. 32mo, bound in +leather, 3s. + +Clinical Medicine: A Systematic Treatise on the Diagnosis and Treatment +of Disease. By AUSTIN FLINT, M.D., Professor of Medicine in the Bellevue +Hospital Medical College. 8vo, 20s. + +_By the same Author._ + +A Treatise on the Principles and Practice of Medicine. Sixth Edition. By +the AUTHOR, and W. H. WELCH, M.D., and AUSTIN FLINT, jun., M.D. 8vo, +with Engravings, 26s. + +Climate and Fevers of India, with a series of Cases (Croonian Lectures, +1882). By Sir JOSEPH FAYRER, K.C.S.I., M.D. 8vo, with 17 Temperature +Charts, 12s. + +Family Medicine for India. A Manual. By WILLIAM J. MOORE, M.D., C.I.E., +Honorary Surgeon to the Viceroy of India. Published under the Authority +of the Government of India. Fifth Edition. Post 8vo, with Engravings. +[_In the Press._ + +_By the same Author._ + +A Manual of the Diseases of India: With a Compendium of Diseases +generally. Second Edition. Post 8vo, 10s. + +_Also._ + +Health-Resorts for Tropical Invalids, in India, at Home, and Abroad. +Post 8vo, 5s. + +Practical Therapeutics: A Manual. By EDWARD J. WARING, C.I.E., M.D., +F.R.C.P., and DUDLEY W. BUXTON, M.D., B.S. Lond. Fourth Edition. Crown +8vo, 14s. + +_By the same Author._ + +Bazaar Medicines of India, And Common Medical Plants: With Full Index of +Diseases, indicating their Treatment by these and other Agents +procurable throughout India, &c. Fourth Edition. Fcap. 8vo, 5s. + +A Commentary on the Diseases of India. By NORMAN CHEVERS, C.I.E., M.D., +F.R.C.S., Deputy Surgeon-General H. M. Indian Army. 8vo, 24s. + +The Principles and Practice of Medicine. By C. HILTON FAGGE, M.D. Edited +by P. H. PYE-SMITH, M.D., F.R.C.P., Physician to, and Lecturer on +Medicine at, Guy's Hospital. 2 vols. 8vo, 1860 pp. Cloth, 36s.; Half +Persian, 42s. + +The Student's Guide to the Practice of Medicine. By MATTHEW CHARTERIS, +M.D., Professor of Materia Medica in the University of Glasgow. Fourth +Edition. Fcap. 8vo, with Engravings on Copper and Wood. 9s. + +Hooper's Physicians' Vade-Mecum. A Manual of the Principles and Practice +of Physic. Tenth Edition. By W. A. GUY, F.R.C.P., F.R.S., and J. HARLEY, +M.D., F.R.C.P. With 118 Engravings. Fcap. 8vo, 12s. 6d. + +The Student's Guide to Clinical Medicine and Case-Taking. By FRANCIS +WARNER, M.D., F.R.C.P., Physician to the London Hospital. Second +Edition. Fcap. 8vo, 5s. + +How to Examine the Chest: Being a Practical Guide for the use of +Students. By SAMUEL WEST, M.D., F.R.C.P., Physician to the City of +London Hospital for Diseases of the Chest; Medical Tutor and Registrar +at St. Bartholomew's Hospital. With 42 Engravings. Fcap. 8vo, 5s. + +The Contagiousness of Pulmonary Consumption, and its Antiseptic +Treatment. By J. BURNEY YEO, M.D., Physician to King's College Hospital. +Crown 8vo, 3s. 6d. + +The Operative Treatment of Intra-thoracic Effusion. Fothergillian Prize +Essay. By NORMAN PORRITT, L.R.C.P. Lond., M.R.C.S. With Engravings. +Crown 8vo, 6s. + +Diseases of the Chest: Contributions to their Clinical History, +Pathology, and Treatment. By A. T. HOUGHTON WATERS, M.D., Physician to +the Liverpool Royal Infirmary. Second Edition. 8vo, with Plates, 15s. + +The Student's Guide to Medical Diagnosis. By SAMUEL FENWICK, M.D., +F.R.C.P., Physician to the London Hospital, and BEDFORD FENWICK, M.D., +M.R.C.P. Sixth Edition. Fcap. 8vo, with 114 Engravings, 7s. + +_By the same Author._ + +The Student's Outlines of Medical Treatment. Second Edition. Fcap. 8vo, +7s. + +_Also._ + +On Chronic Atrophy of the Stomach, and on the Nervous Affections of the +Digestive Organs. 8vo, 8s. + +The Microscope in Medicine. By LIONEL S. BEALE, M.B., F.R.S., Physician +to King's College Hospital. Fourth Edition. 8vo, with 86 Plates, 21s. + +_Also._ + +On Slight Ailments: Their Nature and Treatment. Second Edition. 8vo, 5s. + +The Spectroscope in Medicine. By CHARLES A. MACMUNN, B.A., M.D. 8vo, +with 3 Chromo-lithographic Plates of Physiological and Pathological +Spectra, and 13 Engravings, 9s. + +Notes on Asthma: Its Forms and Treatment. By JOHN C. THOROWGOOD, M.D., +Physician to the Hospital for Diseases of the Chest. Third Edition. +Crown 8vo, 4s. 6d. + +What is Consumption? By G. W. HAMBLETON, L.K.Q.C.P.I. Crown 8vo, 2s. 6d. + +Winter Cough (Catarrh, Bronchitis, Emphysema, Asthma). By HORACE DOBELL, +M.D., Consulting Physician to the Royal Hospital for Diseases of the +Chest. Third Edition. 8vo, with Coloured Plates, 10s. 6d. + +_By the same Author._ + +Loss of Weight, Blood-Spitting, and Lung Disease. Second Edition. 8vo, +with Chromo-lithograph, 10s. 6d. + +_Also._ + +The Mont Doré Cure, and the Proper Way to Use it. 8vo, 7s. 6d. + +Pulmonary Consumption: A Practical Treatise on its Cure with Medicinal, +Dietetic, and Hygienic Remedies. By JAMES WEAVER, M.D., L.R.C.P. Crown +8vo, 2s. + +Croonian Lectures on Some Points in the Pathology and Treatment of +Typhoid Fever. By WILLIAM CAYLEY, M.D., F.R.C.P., Physician to the +Middlesex and the London Fever Hospitals. Crown 8vo, 4s. 6d. + +Treatment of Some of the Forms of Valvular Disease of the Heart. By A. +E. SANSOM, M.D., F.R.C.P., Physician to the London Hospital. Second +Edition. Fcap. 8vo, with 26 Engravings, 4s. 6d. + +Diseases of the Heart and Aorta: Clinical Lectures. By G. W. BALFOUR, +M.D., F.R.C.P., F.R.S. Edin., late Senior Physician and Lecturer on +Clinical Medicine, Royal Infirmary, Edinburgh. Second Edition. 8vo, with +Chromo-lithograph and Wood Engravings, 12s. 6d. + +Medical Ophthalmoscopy: A Manual and Atlas. By WILLIAM R. GOWERS, M.D., +F.R.C.P., Assistant Professor of Clinical Medicine in University +College, and Senior Assistant Physician to the Hospital. Second Edition, +with Coloured Autotype and Lithographic Plates and Woodcuts. 8vo, 18s. + +_By the same Author._ + +Pseudo-Hypertrophic Muscular Paralysis: A Clinical Lecture. 8vo, with +Engravings and Plate, 3s. 6d. + +_Also._ + +Diagnosis of Diseases of the Spinal Cord. Third Edition. 8vo, with +Engravings, 4s. 6d. + +_Also._ + +Diagnosis of Diseases of the Brain. 8vo, with Engravings, 7s. 6d. + +_Also._ + +A Manual of Diseases of the Nervous System. Vol. I. Diseases of the +Spinal Cord and Nerves. Roy. 8vo, with 171 Engravings (many figures), +12s. 6d. + +Diseases of the Nervous System. Lectures delivered at Guy's Hospital. By +SAMUEL WILKS, M.D., F.R.S. Second Edition. 8vo, 18s. + +Diseases of the Nervous System: Especially in Women. By S. WEIR +MITCHELL, M.D., Physician to the Philadelphia Infirmary for Diseases of +the Nervous System. Second Edition. 8vo, with 5 Plates, 8s. + +Nerve Vibration and Excitation, as Agents in the Treatment of Functional +Disorder and Organic Disease. By J. MORTIMER GRANVILLE, M.D. 8vo, 5s. + +_By the same Author._ + +Gout in its Clinical Aspects. Crown 8vo, 6s. + +Regimen to be adopted in Cases of Gout. By WILHELM EBSTEIN, M.D., +Professor of Clinical Medicine in Göttingen. Translated by JOHN SCOTT, +M.A., M.B. 8vo, 2s. 6d. + +Diseases of the Nervous System. Clinical Lectures. By THOMAS BUZZARD, +M.D., F.R.C.P., Physician to the National Hospital for the Paralysed and +Epileptic. With Engravings, 8vo. 15s. + +_By the same Author._ + +Some Forms of Paralysis from Peripheral Neuritis: of Gouty, Alcoholic, +Diphtheritic, and other origin. Crown 8vo, 5s. + +Diseases of the Liver: With and without Jaundice. By GEORGE HARLEY, +M.D., F.R.C.P., F.R.S. 8vo, with 2 Plates and 36 Engravings, 21s. + +_By the same Author._ + +Inflammations of the Liver, and their Sequelæ. Crown 8vo, with +Engravings, 5s. + +Gout, Rheumatism, And the Allied Affections; with Chapters on Longevity +and Sleep. By PETER HOOD, M.D. Third Edition. Crown 8vo, 7s. 6d. + +Diseases of the Stomach: The Varieties of Dyspepsia, their Diagnosis and +Treatment. By S. O. HABERSHON, M.D., F.R.C.P. Third Edition. Crown 8vo, +5s. + +_By the same Author._ + +Pathology of the Pneumogastric Nerve: Lumleian Lectures for 1876. Second +Edition. Post 8vo, 4s. + +_Also._ + +Diseases of the Abdomen, Comprising those of the Stomach and other parts +of the Alimentary Canal, (Esophagus, Cæcum, Intestines, and Peritoneum) +Third Edition. 8vo, with 5 Plates, 21s. + +_Also._ + +Diseases of the Liver, Their Pathology and Treatment. Lettsomian +Lectures. Second Edition. Post 8vo, 4s. + +Acute Intestinal Strangulation, And Chronic Intestinal Obstruction (Mode +of Death from). By THOMAS BRYANT, F.R.C.S., Senior Surgeon to Guy's +Hospital. 8vo, 3s. + +A Treatise on the Diseases of the Nervous System. By JAMES ROSS, M.D., +F.R.C.P., Assistant Physician to the Manchester Royal Infirmary. Second +Edition. 2 vols. 8vo, with Lithographs, Photographs, and 332 Woodcuts, +52s. 6d. + +_By the same Author._ + +Handbook of the Diseases of the Nervous System. Roy. 8vo, with 184 +Engravings, 18s. + +_Also._ + +Aphasia: Being a Contribution to the Subject of the Dissolution of +Speech from Cerebral Disease. 8vo, with Engravings, 4s. 6d. + +Spasm in Chronic Nerve Disease. (Gulstonian Lectures.) By SEYMOUR J. +SHARKEY, M.A., M.B., F.R.C.P., Assistant Physician to, and Joint +Lecturer on Pathology at, St. Thomas's Hospital. 8vo, with Engravings, +5s. + +On Megrim, Sick Headache, and some Allied Disorders: A Contribution to +the Pathology of Nerve Storms. By E. LIVEING, M.D., F.R.C.P. 8vo, 15s. + +Food and Dietetics, Physiologically and Therapeutically Considered. By +F. W. PAVY, M.D., F.R.S., Physician to Guy's Hospital. Second Edition. +8vo, 15s. + +_By the same Author._ + +Croonian Lectures on Certain Points connected with Diabetes. 8vo, 4s. +6d. + +Headaches: Their Nature, Causes, and Treatment. By W. H. DAY, M.D., +Physician to the Samaritan Hospital. Fourth Edition. Crown 8vo, with +Engravings. [In the Press. + +Health Resorts at Home and Abroad. By MATTHEW CHARTERIS, M.D., Physician +to the Glasgow Royal Infirmary. Crown 8vo, with Map, 4s. 6d. + +The Principal Southern and Swiss Health-Resorts: their Climate and +Medical Aspect. By WILLIAM MARCET, M.D., F.R.C.P., F.R.S. With +Illustrations. Crown 8vo, 7s. 6d. + +Winter and Spring On the Shores of the Mediterranean. By HENRY BENNET, +M.D. Fifth Edition. Post 8vo, with numerous Plates, Maps, and +Engravings, 12s. 6d. + +_By the same Author._ + +Treatment of Pulmonary Consumption by Hygiene, Climate, and Medicine. +Third Edition. 8vo, 7s. 6d. + +The Riviera: Sketches of the Health-Resorts of the Coast of France and +Italy, from Hyères to Spezia: its Medical Aspect and Value, &c. By +EDWARD I. SPARKS, M.B., F.R.C.P. Crown 8vo, 8s. 6d. + +Medical Guide to the Mineral Waters of France and its Wintering +Stations. With a Special Map. By A. VINTRAS, M.D., Physician to the +French Embassy, and to the French Hospital, London. Crown 8vo, 8s. + +The Ocean as a Health-Resort: A Practical Handbook of the Sea, for the +use of Tourists and Health-Seekers. By WILLIAM S. WILSON, L.R.C.P. +Second Edition, with Chart of Ocean Routes, &c. Crown 8vo, 7s. 6d. + +Ambulance Handbook for Volunteers and Others. By J. ARDAVON RAYE, L.K. & +Q.C.P.I., L.R.C.S.I., late Surgeon to H.B.M. Transport No. 14, Zulu +Campaign, and Surgeon E.I.R. Rifles. 8vo, with 16 Plates (50 figures), +3s. 6d. + +Ambulance Lectures: To which is added a NURSING LECTURE. By JOHN M. H. +MARTIN, Honorary Surgeon to the Blackburn Infirmary. Crown 8vo, with 53 +Engravings, 2s. + +Handbook of Medical and Surgical Electricity. By HERBERT TIBBITS, M.D., +F.R.C.P.E., Senior Physician to the West London Hospital for Paralysis +and Epilepsy. Second Edition. 8vo, with 95 Engravings, 9s. + +_By the same Author._ + +How to Use a Galvanic Battery in Medicine and Surgery. Third Edition. +8vo, with Engravings, 4s. + +_Also._ + +A Map of Ziemssen's Motor Points of the Human Body: A Guide to Localised +Electrisation. Mounted on Rollers, 35 × 21. With 20 Illustrations, 5s. + +_Also._ + +Electrical and Anatomical Demonstrations Delivered at the School of +Massage and Electricity. Crown 8vo, with Illustrations, 5s. + +Surgical Emergencies: Together with the Emergencies attendant on +Parturition and the Treatment of Poisoning. By PAUL SWAIN, F.R.C.S., +Surgeon to the South Devon and East Cornwall Hospital. Third Edition. +Crown 8vo, with 117 Engravings, 5s. + +Operative Surgery in the Calcutta Medical College Hospital. Statistics, +Cases, and Comments. By KENNETH MCLEOD, A.M., M.D., F.R.C.S.E., +Surgeon-Major, Indian Medical Service, Professor of Surgery in Calcutta +Medical College. 8vo, with Illustrations, 12s. 6d. + +A Course of Operative Surgery. By Christopher Heath, Surgeon to +University College Hospital. Second Edition. With 20 coloured Plates +(180 figures) from Nature, by M. LÉVEILLÉ, and several Woodcuts. Large +8vo, 30s. + +_By the same Author._ + +The Student's Guide to Surgical Diagnosis. Second Edition. Fcap. 8vo, +6s. 6d. + +_Also._ + +Manual of Minor Surgery and Bandaging. For the use of House-Surgeons, +Dressers, and Junior Practitioners. Eighth Edition. Fcap. 8vo, with 142 +Engravings, 6s. + +_Also._ + +Injuries and Diseases of the Jaws. Third Edition. 8vo, with Plate and +206 Wood Engravings, 14s. + +Injuries and Diseases of the Neck and Head, the Genito-Urinary Organs, +and the Rectum. Hunterian Lectures, 1885. By EDWARD LUND, F.R.C.S., +Professor of Surgery in the Owens College, Manchester. 8vo, with Plates +and Engravings, 4s. 6d. + +The Practice of Surgery: A Manual. By Thomas Bryant, Surgeon to Guy's +Hospital. Fourth Edition. 2 vols, crown 8vo, with 750 Engravings (many +being coloured), and including 6 chromo plates, 32s. + +The Surgeon's Vade-Mecum: A Manual of Modern Surgery. By R. DRUITT, +F.R.C.S. Twelfth Edition. By STANLEY BOYD, M.B., F.R.C.S. Assistant +Surgeon and Pathologist to Charing Cross Hospital. Crown 8vo, with 373 +Engravings 16s. + +Regional Surgery: Including Surgical Diagnosis. A Manual for the use of +Students. By F. A. SOUTHAM, M.A., M.B., F.R.C.S., Assistant Surgeon to +the Manchester Royal Infirmary. Part I. The Head and Neck. Crown 8vo, +6s. 6d.--Part II. The Upper Extremity and Thorax. Crown 8vo, 7s. 6d. +Part III. The Abdomen and Lower Extremity. Crown 8vo, 7s. + +Surgical Enquiries: Including the Hastings Essay on Shock, the Treatment +of Inflammations, and numerous Clinical Lectures. By FURNEAUX JORDAN, +F.R.C.S., Professor of Surgery, Queen's College, Birmingham. Second +Edition, with numerous Plates. Royal 8vo, 12s. 6d. + +Illustrations of Clinical Surgery. By JONATHAN HUTCHINSON, F.R.S., +Senior Surgeon to the London Hospital. In occasional fasciculi. I. to +XVIII., 6s. 6d. each. Fasciculi I. to X. bound, with Appendix and Index, +£3 10s. + +_By the same Author._ + +Pedigree of Disease: Being Six Lectures on Temperament, Idiosyncrasy, +and Diathesis. 8vo, 5s. + +Treatment of Wounds and Fractures. Clinical Lectures. By SAMPSON GAMGEE, +F.R.S.E., Surgeon to the Queen's Hospital, Birmingham. Second Edition. +8vo, with 40 Engravings, 10s. + +Electricity and its Manner of Working in the Treatment of Disease. By +WM. E. STEAVENSON, M.D., Physician and Electrician to St. Bartholomew's +Hospital. 8vo, 4s. 6d. + +Lectures on Orthopædic Surgery. By BERNARD E. BRODHURST, F.R.C.S., +Surgeon to the Royal Orthopædic Hospital. Second Edition. 8vo, with +Engravings, 12s. 6d. + +_By the same Author._ + +On Anchylosis, and the Treatment for the Removal of Deformity and the +Restoration of Mobility in Various Joints. Fourth Edition. 8vo, with +Engravings, 5s. + +_Also._ + +Curvatures and Diseases of the Spine. Third Edition. 8vo, with +Engravings, 6s. + +Diseases of Bones and Joints. By CHARLES MACNAMARA, F.R.C.S., Surgeon +to, and Lecturer on Surgery at, the Westminster Hospital. 8vo, with +Plates and Engravings, 12s. + +Injuries of the Spine and Spinal Cord, and NERVOUS SHOCK, in their +Surgical and Medico-Legal Aspects. By HERBERT W. PAGE, M.C. Cantab., +F.R.C.S., Surgeon to St. Mary's Hospital. Second Edition, post 8vo, 10s. + +Face and Foot Deformities. By FREDERICK CHURCHILL, C.M., Surgeon to the +Victoria Hospital for Children. 8vo, with Plates and Illustrations, 10s. +6d. + +Clubfoot: Its Causes, Pathology, and Treatment. By WM. ADAMS, F.R.C.S., +Surgeon to the Great Northern Hospital. Second Edition. 8vo, with 106 +Engravings and 6 Lithographic Plates, 15s. + +_By the same Author._ + +On Contraction of the Fingers, and its Treatment by Subcutaneous +Operation; and on Obliteration of Depressed Cicatrices, by the same +Method. 8vo, with 30 Engravings, 4s. 6d. + +_Also._ + +Lateral and other Forms of Curvature of the Spine: Their Pathology and +Treatment. Second Edition. 8vo, with 5 Lithographic Plates and 72 Wood +Engravings, 10s. 6d. + +Spinal Curvatures: Treatment by Extension and Jacket; with Remarks on +some Affections of the Hip, Knee, and Ankle-joints. By H. MACNAUGHTON +JONES, M.D., F.R.C.S. I. and Edin. Post 8vo, with 63 Engravings, 4s. 6d. + +On Diseases and Injuries of the Eye: A Course of Systematic and Clinical +Lectures to Students and Medical Practitioners. By J. R. WOLFe, M.D., +F.R.C.S.E., Lecturer on Ophthalmic Medicine and Surgery in Anderson's +College, Glasgow. With 10 Coloured Plates and 157 Wood Engravings. 8vo, +£1 1s. + +Hints on Ophthalmic Out-Patient Practice. By CHARLES HIGGENS, Ophthalmic +Surgeon to Guy's Hospital. Third Edition. Fcap. 8vo, 3s. + +Short Sight, Long Sight, and Astigmatism. By GEORGE F. HELM, M.A., M.D., +F.R.C.S., formerly Demonstrator of Anatomy in the Cambridge Medical +School. Crown 8vo, with 35 Engravings, 3s. 6d. + +Manual of the Diseases of the Eye. By CHARLES MACNAMARA, F.R.C.S., +Surgeon to Westminster Hospital. Fourth Edition. Crown 8vo, with 4 +Coloured Plates and 66 Engravings, 10s. 6d. + +The Student's Guide to Diseases of the Eye. By EDWARD NETTLESHIP, +F.R.C.S., Ophthalmic Surgeon to St. Thomas's Hospital. Fourth Edition. +Fcap. 8vo, with Engravings and a Set of Coloured Papers illustrating +Colour-Blindness, [_Nearly Ready._ + +Normal and Pathological Histology of the Human Eye and Eyelids. By C. +FRED. POLLOCK, M.D., F.R.C.S. and F.R.S.E., Surgeon for Diseases of the +Eye to Anderson's College Dispensary, Glasgow. Crown 8vo, with 100 +Plates (230 drawings), 15s. + +Atlas of Ophthalmoscopy. Composed of 12 Chromo-lithographic Plates (59 +Figures drawn from nature) and Explanatory Text. By RICHARD LIEBREICH, +M.R.C.S. Translated by H. ROSBOROUGH SWANZY, M.B. Third edition, 4to, +40s. + +Glaucoma: Its Causes, Symptoms, Pathology, and Treatment. By PRIESTLEY +SMITH, M.R.C.S., Ophthalmic Surgeon to the Queen's Hospital, Birmingham. +8vo, with Lithographic Plates, 10s. 6d. + +Refraction of the Eye: A Manual for Students. By GUSTAVUS HARTRIDGE, +F.R.C.S., Assistant Physician to the Royal Westminster Ophthalmic +Hospital. Second Edition. Crown 8vo, with Lithographic Plate and 94 +Woodcuts, 5s. 6d. + +The Electro-Magnet, And its Employment in Ophthalmic Surgery. By SIMEON +SNELL, Ophthalmic Surgeon to the Sheffield General Infirmary, &c. Crown +8vo, 3s. 6d. + +Hare-Lip and Cleft Palate. By FRANCIS MASON, F.R.C.S., Surgeon to St. +Thomas's Hospital. 8vo, with 66 Engravings, 6s. + +_By the same Author._ + +The Surgery of the Face. 8vo, with 100 Engravings, 7s. 6d. + +A Practical Treatise on Aural Surgery. By H. MACNAUGHTON JONES, M.D., +Professor of the Queen's University in Ireland, late Surgeon to the Cork +Ophthalmic and Aural Hospital. Second Edition. Crown 8vo, with 63 +Engravings, 8s. 6d. + +_By the same Author._ + +Atlas of Diseases of the Membrana Tympani. In Coloured Plates, +containing 62 Figures, with Text. Crown 4to, 21s. + +Endemic Goitre or Thyreocele: Its Etiology, Clinical Characters, +Pathology, Distribution, Relations to Cretinism, Myxoedema, &c., and +Treatment. By WILLIAM ROBINSON, M.D. 8vo, 5s. + +Diseases and Injuries of the Ear. By Sir WILLIAM B. DALBY, Aural Surgeon +to St. George's Hospital. Third Edition. Crown 8vo, with Engravings, 7s. +6d. + +_By the Same Author._ + +Short Contributions to Aural Surgery, between 1875 and 1886. 8vo, with +Engravings, 3s. 6d. + +Diseases of the Throat and Nose: A Manual. By MORELL MACKENZIE, M.D. +Lond., Senior Physician to the Hospital for Diseases of the Throat. + +Vol. II. Diseases of the Nose and Naso-Pharynx; with a Section on +Diseases of the Oesophagus. Post 8vo, with 93 Engravings, 12s. 6d. + +_By the same Author._ + +Diphtheria: Its Nature and Treatment, Varieties, and Local Expressions. +8vo, 5s. + +Lectures on Syphilis of the Larynx (Lesions of the Secondary and +Intermediate Stages). By W. M. WHISTLER, M.D., Physician to the Hospital +for Diseases of the Throat. Post 8vo, 4s. + +Sore Throat: Its Nature, Varieties, and Treatment. By PROSSER JAMES, +M.D., Physician to the Hospital for Diseases of the Throat. Fifth +Edition. Post 8vo, with Coloured Plates and Engravings, 6s. 6d. + +A Treatise on Vocal Physiology and Hygiene. By GORDON HOLMES, M.D., +Physician to the Municipal Throat and Ear Infirmary. Second Edition, +with Engravings. Crown 8vo, 6s. 6d. + +_By the same Author._ + +A Guide to the Use of the Laryngoscope in General Practice. Crown 8vo, +with Engravings, 2s. 6d. + +A System of Dental Surgery. By Sir JOHN TOMES, F.R.S., and C. S. Tomes, +M.A., F.R.S. Third Edition. Fcap. 8vo, with many Engravings. [_Nearly +Ready._ + +Dental Anatomy, Human and Comparative: A Manual. By CHARLES S. TOMES, +M.A., F.R.S. Second Edition. Crown 8vo, with 191 Engravings, 12s. 6d. + +The Student's Guide to Dental Anatomy and Surgery. By HENRY SEWILL, +M.R.C.S., L.D.S. Second Edition. Fcap. 8vo, with 78 Engravings, 5s. 6d. + +Notes on Dental Practice. By HENRY C. QUINBY, L.D.S. R.C.S.I. 8vo, with +87 Engravings, 9s. + +Mechanical Dentistry in Gold and Vulcanite. By F. H. BALKWILL, L.D.S. +R.C.S. 8vo, with 2 Lithographic Plates and 57 Engravings, 10s. + +A Practical Treatise on Mechanical Dentistry. By JOSEPH RICHARDSON, +M.D., D.D.S., late Emeritus Professor of Prosthetic Dentistry in the +Indiana Medical College. Fourth Edition. Roy. 8vo, with 458 Engravings, +21s. + +Principles and Practice of Dentistry: including Anatomy, Physiology, +Pathology, Therapeutics, Dental Surgery, and Mechanism. By C. A. HARRIS, +M.D., D.D.S. Edited by F. J. S. GORGAS, A.M., M.D., D.D.S., Professor in +the Dental Department of Maryland University. Eleventh Edition. 8vo, +with 750 Illustrations, 31s. 6d. + +A Manual of Dental Mechanics. By OAKLEY COLES, L.D.S. R.C.S. Second +Edition. Crown 8vo, with 140 Engravings, 7s. 6d. + +Elements of Dental Materia Medica and Therapeutics, with +Pharmacopoeia. By JAMES STOCKEN, L.D.S. R.C.S., Pereira Prizeman for +Materia Medica, and THOMAS GADDES, L.D.S. Eng. and Edin. Third Edition. +Fcap. 8vo, 7s. 6d. + +Dental Medicine: A Manual of Dental Materia Medica and Therapeutics. By +F. J. S. GORGAS, A.M., M.D., D.D.S., Editor of "Harris's Principles and +Practice of Dentistry," Professor in the Dental Department of Maryland +University. 8vo, 14s. + +Atlas of Skin Diseases. By TILBURY FOX, M.D., F.R.C.P. With 72 Coloured +Plates. Royal 4to, half morocco, £6 6s. + +Diseases of the Skin: With an Analysis of 8,000 Consecutive Cases and a +Formulary. By L. D. BULKLEY, M.D., Physician for Skin Diseases at the +New York Hospital. Crown 8vo, 6s. 6d. + +_By the same Author._ + +Acne: its Etiology, Pathology, and Treatment: Based upon a Study of +1,500 Cases. 8vo, with Engravings, 10s. + +On Certain Rare Diseases of the Skin. By JONATHAN HUTCHINSON, F.R.S., +Senior Surgeon to the London Hospital, and to the Hospital for Diseases +of the Skin. 8vo, 10s. 6d. + +Diseases of the Skin: A Practical Treatise for the Use of Students and +Practitioners. By J. N. HYDE, A.M., M.D., Professor of Skin and Venereal +Diseases, Rush Medical College, Chicago. 8vo, with 66 Engravings, 17s. + +Parasites: A Treatise on the Entozoa of Man and Animals, including some +Account of the Ectozoa. By T. SPENCER COBBOLD, M.D., F.R.S. 8vo, with 85 +Engravings, 15s. + +Manual of Animal Vaccination, preceded by Considerations on Vaccination +in general. By E. WARLOMONT, M.D., Founder of the State Vaccine +Institute of Belgium. Translated and edited by ARTHUR J. HARRIES, M.D. +Crown 8vo, 4s. 6d. + +Leprosy in British Guiana. By JOHN D. HILLIS, F.R.C.S., M.R.I.A., +Medical Superintendent of the Leper Asylum, British Guiana. Imp. 8vo, +with 22 Lithographic Coloured Plates and Wood Engravings, £1 11s. 6d. + +Cancer of the Breast. By THOMAS W. NUNN, F.R.C.S., Consulting Surgeon to +the Middlesex Hospital. 4to, with 21 Coloured Plates, £2 2s. + +On Cancer: Its Allies, and other Tumours; their Medical and Surgical +Treatment. By F. A. PURCELL, M.D., M.C., Surgeon to the Cancer Hospital, +Brompton. 8vo, with 21 Engravings, 10s. 6d. + +Sarcoma and Carcinoma: Their Pathology, Diagnosis, and Treatment. By +HENRY T. BUTLIN, F.R.C.S., Assistant Surgeon to St. Bartholomew's +Hospital. 8vo, with 4 Plates, 8s. + +_By the same Author._ + +Malignant Disease of the Larynx (Sarcoma and Carcinoma). 8vo, with 5 +Engravings, 5s. + +Cancerous Affections of the Skin. (Epithelioma and Rodent Ulcer.) By +GEORGE THIN, M.D. Post 8vo, with 8 Engravings, 5s. + +Cancer of the Mouth, Tongue, and Alimentary Tract: their Pathology, +Symptoms, Diagnosis, and Treatment. By FREDERIC B. JESSETT, F.R.C.S., +Surgeon to the Cancer Hospital, Brompton. 8vo, 10s. + +Clinical Notes on Cancer, Its Etiology and Treatment; with special +reference to the Heredity-Fallacy, and to the Neurotic Origin of most +Cases of Alveolar Carcinoma. By HERBERT L. SNOW, M.D. Lond., Surgeon to +the Cancer Hospital, Brompton. Crown 8vo, 3s. 6d. + +Lectures on the Surgical Disorders of the Urinary Organs. By REGINALD +HARRISON, F.R.C.S., Surgeon to the Liverpool Royal Infirmary. Second +Edition, with 48 Engravings. 8vo, 12s. 6d. + +Hydrocele: Its several Varieties and their Treatment. By SAMUEL OSBORN, +late Surgical Registrar to St. Thomas's Hospital. Fcap. 8vo, with +Engravings, 3s. + +_By the same Author._ + +Diseases of the Testis. Fcap. 8vo, with Engravings, 3s. 6d. + +Diseases of the Urinary Organs. Clinical Lectures. By Sir HENRY +THOMPSON, F.R.C.S., Emeritus Professor of Clinical Surgery in University +College. Seventh (Students') Edition. 8vo, with 84 Engravings, 2s. 6d. + +_By the same Author._ + +Diseases of the Prostate: Their Pathology and Treatment. Sixth Edition. +8vo, with 39 Engravings, 6s. + +_Also._ + +Surgery of the Urinary Organs. Some Important Points connected +therewith. Lectures delivered in the R.C.S. 8vo, with 44 Engravings. +Students' Edition, 2s. 6d. + +_Also._ + +Practical Lithotomy and Lithotrity; or, An Inquiry into the Best Modes +of Removing Stone from the Bladder. Third Edition. 8vo, with 87 +Engravings, 10s. + +_Also._ + +The Preventive Treatment of Calculous Disease, and the Use of Solvent +Remedies. Second Edition. Fcap. 8vo, 2s. 6d. + +_Also._ + +Tumours of the Bladder: Their Nature, Symptoms, and Surgical Treatment. +8vo, with numerous Illustrations, 5s. + +_Also._ + +Stricture of the Urethra, and Urinary Fistulaæ: their Pathology and +Treatment. Fourth Edition. With 74 Engravings. 8vo, 6s. + +_Also._ + +The Suprapubic Operation of Opening the Bladder for the Stone and for +Tumours. 8vo, with 14 Engravings, 3s. 6d. + +The Surgery of the Rectum. By HENRY SMITH, Professor of Surgery in +King's College, Surgeon to the Hospital. Fifth Edition. 8vo, 6s. + +Modern Treatment of Stone in the Bladder by Litholopaxy. By P. J. +FREYER, M.A., M.D., M.Ch., Bengal Medical Service. 8vo, with Engravings, +5s. + +Diseases of the Testis, Spermatic Cord, and Scrotum. By THOMAS B. +CURLING, F.R.S., Consulting Surgeon to the London Hospital. Fourth +Edition. 8vo, with Engravings, 16s. + +Diseases of the Rectum and Anus. By W. HARRISON CRIPPS, F.R.C.S., +Assistant Surgeon to St. Bartholomew's Hospital, &c. 8vo, with 13 +Lithographic Plates and numerous Wood Engravings, 12s. 6d. + +Urinary and Renal Derangements and Calculous Disorders. By LIONEL S. +BEALE, F.R.C.P., F.R.S., Physician to King's College Hospital. 8vo, 5s. + +Fistula, Hæmorrhoids, Painful Ulcer, Stricture, Prolapsus, and other +Diseases of the Rectum: Their Diagnosis and Treatment. By WILLIAM +ALLINGHAM, Surgeon to St. Mark's Hospital for Fistula. Fourth Edition. +8vo, with Engravings, 10s. 6d. + +Pathology of the Urine. Including a Complete Guide to its Analysis. By +J. L. W. THUDICHUM, M.D., F.R.C.P. Second Edition, rewritten and +enlarged. 8vo, with Engravings, 15s. + +Student's Primer on the Urine. By J. TRAVIS WHITTAKER, M.D., Clinical +Demonstrator at the Royal Infirmary, Glasgow. With 16 Plates etched on +Copper. Post 8vo, 4s. 6d. + +Syphilis and Pseudo-Syphilis. By ALFRED COOPER, F.R.C.S., Surgeon to the +Lock Hospital, to St. Mark's and the West London Hospitals. 8vo, 10s. +6d. + +Genito-Urinary Organs, including Syphilis: A Practical Treatise on their +Surgical Diseases, for Students and Practitioners. By W. H. VAN BUREN, +M.D., and E. L. KEYES, M.D. Royal 8vo, with 140 Engravings, 21s. + +Lectures on Syphilis. By HENRY LEE, Consulting Surgeon to St. George's +Hospital. 8vo, 10s. + +Diagnosis and Treatment of Syphilis. By TOM ROBINSON, M.D., Physician to +St. John's Hospital for Diseases of the Skin. Crown 8vo, 3s. 6d. + +Coulson on Diseases of the Bladder and Prostate Gland. Sixth Edition. By +WALTER J. COULSON, Surgeon to the Lock Hospital and to St. Peter's +Hospital for Stone. 8vo, 16s. + +The Medical Adviser in Life Assurance. By Sir E. H. SIEVEKING, M.D., +F.R.C.P. Second Edition. Crown 8vo, 6s. + +A Medical Vocabulary: An Explanation of all Terms and Phrases used in +the various Departments of Medical Science and Practice, their +Derivation, Meaning, Application, and Pronunciation. By R. G. MAYNE, +M.D., LL.D. Fifth Edition. Fcap. 8vo, 10s. 6d. + +A Dictionary of Medical Science: Containing a concise Explanation of the +various Subjects and Terms of Medicine, &c. By ROBLEY DUNGLISON, M.D., +LL.D. Royal 8vo, 28s. + +Medical Education And Practice in all parts of the World. By H. J. +HARDWICKE, M.D., M.R.C.P. 8vo, 10s. + + + + +INDEX. + + +Abercrombie's Medical Jurisprudence, 4 + +Adams (W.) on Clubfoot, 11; + on Contraction of the Fingers, 11; + on Curvature of the Spine, 11 + +Alexander's Displacements of the Uterus, 6 + +Allan on Fever Nursing, 7; + Outlines of Infectious Diseases, 7 + +Allingham on Diseases of the Rectum, 14 + +Anatomical Remembrancer, 3 + + +Balfour's Diseases of the Heart and Aorta, 9 + +Balkwill's Mechanical Dentistry, 12 + +Barnes (R.) on Obstetric Operations, 5; + on Diseases of Women, 5 + +Beale's Microscope in Medicine, 8; + Slight Ailments, 8; + Urinary and Renal Derangements, 14 + +Bellamy's Surgical Anatomy, 3 + +Bennet (J. H.) on the Mediterranean, 10; + on Pulmonary Consumption, 10 + +Bentley and Trimen's Medicinal Plants, 7 + +Bentley's Manual of Botany, 7; + Structural Botany, 7; + Systematic Botany, 7 + +Braune's Topographical Anatomy, 3 + +Brodhurst's Anchylosis, 11; + Curvatures, &c., of the Spine, 11; + Orthopædic Surgery, 11 + +Bryant's Acute Intestinal Strangulation, 9; + Practice of Surgery, 11 + +Bucknill and Tuke's Psychological Medicine, 5 + +Bulkley's Acne, 13; + Diseases of the Skin, 13 + +Burdett's Cottage Hospitals, 4; + Pay Hospitals, 4 + +Burton's Midwifery for Midwives, 6 + +Butlin's Malignant Disease of the Larynx, 13; + Sarcoma and Carcinoma, 13 + +Buzzard's Diseases of the Nervous System, 9; + Peripheral Neuritis, 9 + + +Carpenter's Human Physiology, 4 + +Cayley's Typhoid Fever, 8 + +Charteris on Health Resorts, 10; + Practice of Medicine, 8 + +Chavers' Diseases of India, 8 + +Churchill's Face and Foot Deformities, 11 + +Clouston's Lectures on Mental Diseases, 5 + +Cobbold on Parasites, 13 + +Coles' Dental Mechanics, 13 + +Cooper's Syphilis and Pseudo-Syphilis, 14 + +Coulson on Diseases of the Bladder, 14 + +Courty's Diseases of the Uterus, Ovaries, &c., 6 + +Cripps' Diseases of the Rectum and Anus, 14 + +Cullingworth's Manual of Nursing, 6; + Short Manual for Monthly Nurses, 6 + +Curling's Diseases of the Testis, 14 + + +Dalby's Diseases and Injuries of the Ear, 12 + +Dalton's Human Physiology, 4 + +Day on Diseases of Children, 6; + on Headaches, 10 + +Dobell's Lectures on Winter Cough, 8; + Loss of Weight, &c., 8; + Mont Doré Cure, 8 + +Domville's Manual for Nurses, 6 + +Draper's Text Book of Medical Physics, 4 + +Druitt's Surgeon's Vade-Mecum, 11 + +Duncan on Diseases of Women, 5; + on Sterility in Woman, 5 + +Dunglison's Medical Dictionary, 14 + + +East's Private Treatment of the Insane, 5 + +Ebstein on Regimen in Gout, 9 + +Ellis's Diseases of Children, 6 + +Emmet's Gynæcology, 6 + + +Fagge's Principles and Practice of Medicine, 8 + +Fayrer's Climate and Fevers of India, 7 + +Fenwick's Chronic Atrophy of the Stomach, 8; + Medical Diagnosis, 8; + Outlines of Medical Treatment, 8 + +Flint on Clinical Medicine, 7; + on Principles and Practice of Medicine, 7 + +Flower's Diagrams of the Nerves, 4 + +Fox's (C. B.) Examinations of Water, Air, and Food, 5 + +Fox's (T.) Atlas of Skin Diseases, 13 + +Freyer's Litholopaxy, 14 + +Frey's Histology and Histo-Chemistry, 4 + + +Galabin's Diseases of Women, 6; + Manual of Midwifery, 5 + +Gamgee's Treatment of Wounds and Fractures, 11 + +Godlee's Atlas of Human Anatomy, 3 + +Goodhart's Diseases of Children, 6 + +Gorgas' Dental Medicine, 13 + +Gowers' Diseases of the Brain, 9; + Diseases of the Spinal Cord, 9; + Manual of Diseases of Nervous System, 9; + Medical Ophthalmoscopy, 9; + Pseudo-Hypertrophic Muscular Paralysis, 9 + +Granville on Gout, 9; + on Nerve Vibration and Excitation, 9 + +Guy's Hospital Formulæ, 2; + Reports, 2 + + +Habershon's Diseases of the Abdomen, 9; + Liver, 9; + Stomach, 9; + Pneumogastric Nerve, 9 + +Hambleton's What is Consumption?, 8 + +Hardwicke's Medical Education, 14 + +Harley on Diseases of the Liver, 9; + Inflammations of the Liver, 9 + +Harris's Dentistry, 13 + +Harrison's Surgical Disorders of the Urinary Organs, 13 + +Hartridge's Refraction of the Eye, 12 + +Harvey's Manuscript Lectures, 3 + +Heath's Injuries and Diseases of the Jaws, 10; + Minor Surgery and Bandaging, 10; + Operative Surgery, 10; + Practical Anatomy, 3; + Surgical Diagnosis, 10 + +Helm on Short and Long Sight, &c., 11 + +Higgens' Ophthalmic Out-patient Practice, 11 + +Hills' Leprosy in British Guiana, 13 + +Holden's Dissections, 3; + Human Osteology, 3; + Landmarks, 3 + +Holmes' (G.) Guide to Use of Laryngoscope, 12; + Vocal Physiology and Hygiene, 12 + +Hood's (D. C.) Diseases and their Commencement, 7 + +Hood (P.) on Gout, Rheumatism, &c., 9 + +Hooper's Physician's Vade-Mecum, 8 + +Hutchinson's Clinical Surgery, 11; + Pedigree of Disease, 11; + Rare Diseases of the Skin, 13 + +Hyde's Diseases of the Skin, 13 + + +James (P.) on Sore Throat, 12 + +Jessett's Cancer of the Mouth, &c., 13 + +Jones (C. H.) and Sieveking's Pathological Anatomy, 4 + +Jones' (H. McN.) Aural Surgery, 12; + Atlas of Diseases of Membrana Tympani, 12; + Spinal Curvatures, 11 + +Jordan's Surgical Enquiries, 11 + +Journal of British Dental Association, 2; + Mental Science, 2 + + +King's Manual of Obstetrics, 6 + + +Lancereaux's Atlas of Pathological Anatomy, 4 + +Lee (H.) on Syphilis, 14 + +Lewis (Bevan) on the Human Brain, 4 + +Liebreich's Atlas of Ophthalmoscopy, 12 + +Liveing's Megrim, Sick Headache, &c., 9 + +London Hospital Reports, 2 + +Lückes' Hospital Sisters and their Duties, 7 + +Lund's Hunterian Lectures, 10 + + +Macdonald's (J. D.) Examination of Water and Air, 4 + +Mackenzie on Diphtheria, 12; + on Diseases of the Throat and Nose, 12 + +McLeod's Operative Surgery, 10 + +MacMunn's Spectroscope in Medicine, 8 + +Macnamara's Diseases of the Eye, 11; + Bones and Joints, 11 + +Marcet's Southern and Swiss Health-Resorts, 10 + +Martin's Ambulance Lectures, 10 + +Mason on Hare-Lip and Cleft Palate, 12; + on Surgery of the Face, 12 + +Mayne's Medical Vocabulary, 14 + +Middlesex Hospital Reports, 2 + +Mitchell's Diseases of the Nervous System, 9 + +Moore's Family Medicine for India, 7; + Health-Resorts for Tropical Invalids, 7; + Manual of the Diseases of India, 7 + +Morris' (H.) Anatomy of the Joints, 3 + +Mouat and Snell on Hospitals, 5 + + +Nettleship's Diseases of the Eye, 12 + +Nunn's Cancer of the Breast, 13 + + +Ogston's Medical Jurisprudence, 4 + +Ophthalmic (Royal London) Hospital Reports, 2 + +Ophthalmological Society's Transactions, 2 + +Oppert's Hospitals, Infirmaries, Dispensaries, &c., 5 + +Osborn on Diseases of the Testis, 13; + on Hydrocele, 13 + +Owen's Materia Medica, 7 + + +Page's Injuries of the Spine, 11 + +Parkes' Practical Hygiene, 5 + +Pavy on Diabetes, 10 + +Pavy on Food and Dietetics, 10 + +Pharmaceutical Journal, 2 + +Pharmacopoeia of the London Hospital, 7 + +Phillips' Materia Medica and Therapeutics, 7 + +Pollock's Histology of the Eye and Eyelids, 12 + +Porritt's Intra-Thoracic Effusion, 8 + +Purcell on Cancer, 13 + +Pye-Smith's Syllabus of Physiology, 4 + + +Quinby's Notes on Dental Practice, 12 + + +Raye's Ambulance Handbook, 10 + +Reynolds' (J. J.) Diseases of Women, 5; + Notes on Midwifery, 5 + +Richardson's Mechanical Dentistry, 13 + +Roberts' (C.) Manual of Anthropometry, 5; + Detection of Colour-Blindness, 5 + +Roberts' (D. Lloyd) Practice of Midwifery, 5 + +Robinson (Tom) on Syphilis, 14 + +Robinson (W.) on Endemic Goitre or Thyreocele, 12 + +Ross's Aphasia, 9; + Diseases of the Nervous System, 9; + Handbook of ditto, 9 + +Routh's Infant Feeding, 7 + +Royal College of Surgeons Museum Catalogues, 2 + +Royle and Harley's Materia Medica, 7 + + +St. Bartholomew's Hospital Catalogue, 2 + +St. George's Hospital Reports, 2 + +St. Thomas's Hospital Reports, 2 + +Sansom's Valvular Disease of the Heart, 8 + +Savage on the Female Pelvic Organs, 6 + +Sewill's Dental Anatomy, 12 + +Sharkey's Spasm in Chronic Nerve Disease, 9 + +Shore's Elementary Practical Biology, 4 + +Sieveking's Life Assurance, 14 + +Smith's (E.) Clinical Studies, 6; + Diseases in Children, 6; + Wasting Diseases of Infants and Children, 6 + +Smith's (Henry) Surgery of the Rectum, 14 + +Smith's (Heywood) Dysmenorrhoea, 6 + +Smith (Priestley) on Glaucoma, 12 + +Snell's Electro-Magnet in Ophthalmic Surgery, 12 + +Snow's Clinical Notes on Cancer, 13 + +Southam's Regional Surgery, 11 + +Sparks on the Riviera, 10 + +Squire's Companion to the Pharmacopoeia, 7; + Pharmacopoeias of London Hospitals + +Starkweather on the Law of Sex, 4 + +Steavenson's Electricity, 11 + +Stillé and Maisch's National Dispensatory, 7 + +Stocken's Dental Materia Medica and Therapeutics, 13 + +Sutton's General Pathology, 4 + +Swain's Surgical Emergencies, 10 + +Swayne's Obstetric Aphorisms, 6 + + +Taylor's Medical Jurisprudence, 4 + +Taylor's Poisons in relation to Medical Jurisprudence, 4 + +Teale's Dangers to Health, 5 + +Thin's Cancerous Affections of the Skin, 13 + +Thomas's Diseases of Women, 6 + +Thompson's (Sir H.) Calculous Disease, 14; + Diseases of the Prostate, 14; + Diseases of the Urinary Organs, 14; + Lithotomy and Lithotrity, 14; + Stricture of the Urethra, 14; + Suprapubic Operation, 14; + Surgery of the Urinary Organs, 14; + Tumours of the Bladder, 14 + +Thorowgood on Asthma, 8; + on Materia Medica and Therapeutics, 7 + +Thudichum's Pathology of the Urine, 14 + +Tibbits' Medical and Surgical Electricity, 10; + Map of Motor Points, 10; + How to use a Galvanic Battery, 10; + Electrical and Anatomical Demonstrations, 10 + +Tilt's Change of Life, 6; + Uterine Therapeutics, 6 + +Tirard's Prescriber's Pharmacopoeia, 7 + +Tomes' (C. S.) Dental Anatomy, 12 + +Tomes' (J. and C. S.) Dental Surgery, 12 + +Tuke's Influence of the Mind upon the Body, 5; + Sleep-Walking and Hypnotism, 5 + + +Van Buren on the Genito-Urinary Organs, 14 + +Vintras on the Mineral Waters, &c., of France, 10 + +Virchow's Post-mortem Examinations, 4 + + +Wagstaffe's Human Osteology, 3 + +Waring's Indian Bazaar Medicines, 8; + Practical Therapeutics, 8 + +Warlomont's Animal Vaccination, 13 + +Warner's Guide to Medical Case-Taking, 8 + +Waters' (A. T. H.) Diseases of the Chest, 8 + +Weaver's Pulmonary Consumption, 8 + +Wells' (Spencer) Abdominal Tumours, 6; + Ovarian and Uterine Tumours, 6 + +West and Duncan's Diseases of Women, 6 + +West's (S.) How to Examine the Chest, 8 + +Whistler's Syphilis of the Larynx, 12 + +Whittaker's Primer on the Urine, 14 + +Wilks' Diseases of the Nervous System, 8 + +Williams' (Roger) Influence of Sex, 4 + +Wilson's (Sir E.) Anatomists' Vade-Mecum, 3 + +Wilson's (G.) Handbook of Hygiene, 5; + Healthy Life and Dwellings, 5 + +Wilson's (W. S.) Ocean as a Health-Resort, 10 + +Wolfe's Diseases and Injuries of the Eye, 11 + + +Year Book of Pharmacy, 2 + +Yeo's (G. F.) Manual of Physiology, 4 + +Yeo's (J. B.) Contagiousness of Pulmonary Consumption, 8 + + * * * * * + +The following CATALOGUES issued by J. & A. CHURCHILL will be forwarded +post free on application:-- + +A. _J. & A. Churchill's General List of about 650 works on Anatomy, +Physiology, Hygiene, Midwifery, Materia Medica, Medicine, Surgery, +Chemistry, Botany, &c., &c., with a complete Index to their Subjects, +for easy reference._ N.B.--_This List includes_ B, C, & D. + +B. _Selection from J. & A. Churchill's General List, comprising all +recent Works published by them on the Art and Science of Medicine._ + +C. _J. & A. Churchill's Catalogue of Text Books specially arranged for +Students._ + +D. _A selected and descriptive List of J. & A. Churchill's Works on +Chemistry, Materia Medica, Pharmacy, Botany, Photography, Zoology, the +Microscope, and other branches of Science._ + +E. _The Half-yearly List of New Works and New Editions published by J. & +A. Churchill during the previous six months, together with particulars +of the Periodicals issued from their House._ + + [Sent in January and July of each year to every Medical + Practitioner in the United Kingdom whose name and address + can be ascertained. A large number are also sent to the + United States of America, Continental Europe, India, and the + Colonies.] + +AMERICA.--_J. & A. Churchill being in constant communication with +various publishing houses in Boston, New York, and Philadelphia, are +able, notwithstanding the absence of international copyright, to conduct +negotiations favourable to English Authors._ + + +LONDON: 11, NEW BURLINGTON STREET. +_Pardon & Sons, Printers,] [Wine Office Court, Fleet Street, E.C._ + + + + + +End of the Project Gutenberg EBook of Schweigger on Squint, by C. Schweigger + +*** END OF THIS PROJECT GUTENBERG EBOOK SCHWEIGGER ON SQUINT *** + +***** This file should be named 35639-8.txt or 35639-8.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/3/5/6/3/35639/ + +Produced by Ian Deane, Josephine Paolucci and the Online +Distributed Proofreading Team at https://www.pgdp.net. + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. If you +do not charge anything for copies of this eBook, complying with the +rules is very easy. You may use this eBook for nearly any purpose +such as creation of derivative works, reports, performances and +research. They may be modified and printed and given away--you may do +practically ANYTHING with public domain eBooks. Redistribution is +subject to the trademark license, especially commercial +redistribution. + + + +*** START: FULL LICENSE *** + +THE FULL PROJECT GUTENBERG LICENSE +PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK + +To protect the Project Gutenberg-tm mission of promoting the free +distribution of electronic works, by using or distributing this work +(or any other work associated in any way with the phrase "Project +Gutenberg"), you agree to comply with all the terms of the Full Project +Gutenberg-tm License (available with this file or online at +https://gutenberg.org/license). + + +Section 1. General Terms of Use and Redistributing Project Gutenberg-tm +electronic works + +1.A. By reading or using any part of this Project Gutenberg-tm +electronic work, you indicate that you have read, understand, agree to +and accept all the terms of this license and intellectual property +(trademark/copyright) agreement. If you do not agree to abide by all +the terms of this agreement, you must cease using and return or destroy +all copies of Project Gutenberg-tm electronic works in your possession. +If you paid a fee for obtaining a copy of or access to a Project +Gutenberg-tm electronic work and you do not agree to be bound by the +terms of this agreement, you may obtain a refund from the person or +entity to whom you paid the fee as set forth in paragraph 1.E.8. + +1.B. "Project Gutenberg" is a registered trademark. It may only be +used on or associated in any way with an electronic work by people who +agree to be bound by the terms of this agreement. There are a few +things that you can do with most Project Gutenberg-tm electronic works +even without complying with the full terms of this agreement. See +paragraph 1.C below. There are a lot of things you can do with Project +Gutenberg-tm electronic works if you follow the terms of this agreement +and help preserve free future access to Project Gutenberg-tm electronic +works. See paragraph 1.E below. + +1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" +or PGLAF), owns a compilation copyright in the collection of Project +Gutenberg-tm electronic works. Nearly all the individual works in the +collection are in the public domain in the United States. If an +individual work is in the public domain in the United States and you are +located in the United States, we do not claim a right to prevent you from +copying, distributing, performing, displaying or creating derivative +works based on the work as long as all references to Project Gutenberg +are removed. Of course, we hope that you will support the Project +Gutenberg-tm mission of promoting free access to electronic works by +freely sharing Project Gutenberg-tm works in compliance with the terms of +this agreement for keeping the Project Gutenberg-tm name associated with +the work. You can easily comply with the terms of this agreement by +keeping this work in the same format with its attached full Project +Gutenberg-tm License when you share it without charge with others. + +1.D. The copyright laws of the place where you are located also govern +what you can do with this work. Copyright laws in most countries are in +a constant state of change. If you are outside the United States, check +the laws of your country in addition to the terms of this agreement +before downloading, copying, displaying, performing, distributing or +creating derivative works based on this work or any other Project +Gutenberg-tm work. The Foundation makes no representations concerning +the copyright status of any work in any country outside the United +States. + +1.E. Unless you have removed all references to Project Gutenberg: + +1.E.1. The following sentence, with active links to, or other immediate +access to, the full Project Gutenberg-tm License must appear prominently +whenever any copy of a Project Gutenberg-tm work (any work on which the +phrase "Project Gutenberg" appears, or with which the phrase "Project +Gutenberg" is associated) is accessed, displayed, performed, viewed, +copied or distributed: + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + +1.E.2. If an individual Project Gutenberg-tm electronic work is derived +from the public domain (does not contain a notice indicating that it is +posted with permission of the copyright holder), the work can be copied +and distributed to anyone in the United States without paying any fees +or charges. If you are redistributing or providing access to a work +with the phrase "Project Gutenberg" associated with or appearing on the +work, you must comply either with the requirements of paragraphs 1.E.1 +through 1.E.7 or obtain permission for the use of the work and the +Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or +1.E.9. + +1.E.3. If an individual Project Gutenberg-tm electronic work is posted +with the permission of the copyright holder, your use and distribution +must comply with both paragraphs 1.E.1 through 1.E.7 and any additional +terms imposed by the copyright holder. Additional terms will be linked +to the Project Gutenberg-tm License for all works posted with the +permission of the copyright holder found at the beginning of this work. + +1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm +License terms from this work, or any files containing a part of this +work or any other work associated with Project Gutenberg-tm. + +1.E.5. Do not copy, display, perform, distribute or redistribute this +electronic work, or any part of this electronic work, without +prominently displaying the sentence set forth in paragraph 1.E.1 with +active links or immediate access to the full terms of the Project +Gutenberg-tm License. + +1.E.6. You may convert to and distribute this work in any binary, +compressed, marked up, nonproprietary or proprietary form, including any +word processing or hypertext form. However, if you provide access to or +distribute copies of a Project Gutenberg-tm work in a format other than +"Plain Vanilla ASCII" or other format used in the official version +posted on the official Project Gutenberg-tm web site (www.gutenberg.org), +you must, at no additional cost, fee or expense to the user, provide a +copy, a means of exporting a copy, or a means of obtaining a copy upon +request, of the work in its original "Plain Vanilla ASCII" or other +form. Any alternate format must include the full Project Gutenberg-tm +License as specified in paragraph 1.E.1. + +1.E.7. Do not charge a fee for access to, viewing, displaying, +performing, copying or distributing any Project Gutenberg-tm works +unless you comply with paragraph 1.E.8 or 1.E.9. + +1.E.8. You may charge a reasonable fee for copies of or providing +access to or distributing Project Gutenberg-tm electronic works provided +that + +- You pay a royalty fee of 20% of the gross profits you derive from + the use of Project Gutenberg-tm works calculated using the method + you already use to calculate your applicable taxes. The fee is + owed to the owner of the Project Gutenberg-tm trademark, but he + has agreed to donate royalties under this paragraph to the + Project Gutenberg Literary Archive Foundation. Royalty payments + must be paid within 60 days following each date on which you + prepare (or are legally required to prepare) your periodic tax + returns. Royalty payments should be clearly marked as such and + sent to the Project Gutenberg Literary Archive Foundation at the + address specified in Section 4, "Information about donations to + the Project Gutenberg Literary Archive Foundation." + +- You provide a full refund of any money paid by a user who notifies + you in writing (or by e-mail) within 30 days of receipt that s/he + does not agree to the terms of the full Project Gutenberg-tm + License. You must require such a user to return or + destroy all copies of the works possessed in a physical medium + and discontinue all use of and all access to other copies of + Project Gutenberg-tm works. + +- You provide, in accordance with paragraph 1.F.3, a full refund of any + money paid for a work or a replacement copy, if a defect in the + electronic work is discovered and reported to you within 90 days + of receipt of the work. + +- You comply with all other terms of this agreement for free + distribution of Project Gutenberg-tm works. + +1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm +electronic work or group of works on different terms than are set +forth in this agreement, you must obtain permission in writing from +both the Project Gutenberg Literary Archive Foundation and Michael +Hart, the owner of the Project Gutenberg-tm trademark. Contact the +Foundation as set forth in Section 3 below. + +1.F. + +1.F.1. Project Gutenberg volunteers and employees expend considerable +effort to identify, do copyright research on, transcribe and proofread +public domain works in creating the Project Gutenberg-tm +collection. Despite these efforts, Project Gutenberg-tm electronic +works, and the medium on which they may be stored, may contain +"Defects," such as, but not limited to, incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other intellectual +property infringement, a defective or damaged disk or other medium, a +computer virus, or computer codes that damage or cannot be read by +your equipment. + +1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right +of Replacement or Refund" described in paragraph 1.F.3, the Project +Gutenberg Literary Archive Foundation, the owner of the Project +Gutenberg-tm trademark, and any other party distributing a Project +Gutenberg-tm electronic work under this agreement, disclaim all +liability to you for damages, costs and expenses, including legal +fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT +LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE +PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE +TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE +LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR +INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH +DAMAGE. + +1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a +defect in this electronic work within 90 days of receiving it, you can +receive a refund of the money (if any) you paid for it by sending a +written explanation to the person you received the work from. If you +received the work on a physical medium, you must return the medium with +your written explanation. The person or entity that provided you with +the defective work may elect to provide a replacement copy in lieu of a +refund. If you received the work electronically, the person or entity +providing it to you may choose to give you a second opportunity to +receive the work electronically in lieu of a refund. If the second copy +is also defective, you may demand a refund in writing without further +opportunities to fix the problem. + +1.F.4. Except for the limited right of replacement or refund set forth +in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO +WARRANTIES OF MERCHANTIBILITY OR FITNESS FOR ANY PURPOSE. + +1.F.5. Some states do not allow disclaimers of certain implied +warranties or the exclusion or limitation of certain types of damages. +If any disclaimer or limitation set forth in this agreement violates the +law of the state applicable to this agreement, the agreement shall be +interpreted to make the maximum disclaimer or limitation permitted by +the applicable state law. The invalidity or unenforceability of any +provision of this agreement shall not void the remaining provisions. + +1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the +trademark owner, any agent or employee of the Foundation, anyone +providing copies of Project Gutenberg-tm electronic works in accordance +with this agreement, and any volunteers associated with the production, +promotion and distribution of Project Gutenberg-tm electronic works, +harmless from all liability, costs and expenses, including legal fees, +that arise directly or indirectly from any of the following which you do +or cause to occur: (a) distribution of this or any Project Gutenberg-tm +work, (b) alteration, modification, or additions or deletions to any +Project Gutenberg-tm work, and (c) any Defect you cause. + + +Section 2. Information about the Mission of Project Gutenberg-tm + +Project Gutenberg-tm is synonymous with the free distribution of +electronic works in formats readable by the widest variety of computers +including obsolete, old, middle-aged and new computers. It exists +because of the efforts of hundreds of volunteers and donations from +people in all walks of life. + +Volunteers and financial support to provide volunteers with the +assistance they need are critical to reaching Project Gutenberg-tm's +goals and ensuring that the Project Gutenberg-tm collection will +remain freely available for generations to come. In 2001, the Project +Gutenberg Literary Archive Foundation was created to provide a secure +and permanent future for Project Gutenberg-tm and future generations. +To learn more about the Project Gutenberg Literary Archive Foundation +and how your efforts and donations can help, see Sections 3 and 4 +and the Foundation web page at https://www.pglaf.org. + + +Section 3. Information about the Project Gutenberg Literary Archive +Foundation + +The Project Gutenberg Literary Archive Foundation is a non profit +501(c)(3) educational corporation organized under the laws of the +state of Mississippi and granted tax exempt status by the Internal +Revenue Service. The Foundation's EIN or federal tax identification +number is 64-6221541. Its 501(c)(3) letter is posted at +https://pglaf.org/fundraising. Contributions to the Project Gutenberg +Literary Archive Foundation are tax deductible to the full extent +permitted by U.S. federal laws and your state's laws. + +The Foundation's principal office is located at 4557 Melan Dr. S. +Fairbanks, AK, 99712., but its volunteers and employees are scattered +throughout numerous locations. Its business office is located at +809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email +business@pglaf.org. Email contact links and up to date contact +information can be found at the Foundation's web site and official +page at https://pglaf.org + +For additional contact information: + Dr. Gregory B. Newby + Chief Executive and Director + gbnewby@pglaf.org + + +Section 4. Information about Donations to the Project Gutenberg +Literary Archive Foundation + +Project Gutenberg-tm depends upon and cannot survive without wide +spread public support and donations to carry out its mission of +increasing the number of public domain and licensed works that can be +freely distributed in machine readable form accessible by the widest +array of equipment including outdated equipment. Many small donations +($1 to $5,000) are particularly important to maintaining tax exempt +status with the IRS. + +The Foundation is committed to complying with the laws regulating +charities and charitable donations in all 50 states of the United +States. Compliance requirements are not uniform and it takes a +considerable effort, much paperwork and many fees to meet and keep up +with these requirements. We do not solicit donations in locations +where we have not received written confirmation of compliance. To +SEND DONATIONS or determine the status of compliance for any +particular state visit https://pglaf.org + +While we cannot and do not solicit contributions from states where we +have not met the solicitation requirements, we know of no prohibition +against accepting unsolicited donations from donors in such states who +approach us with offers to donate. + +International donations are gratefully accepted, but we cannot make +any statements concerning tax treatment of donations received from +outside the United States. U.S. laws alone swamp our small staff. + +Please check the Project Gutenberg Web pages for current donation +methods and addresses. Donations are accepted in a number of other +ways including including checks, online payments and credit card +donations. To donate, please visit: https://pglaf.org/donate + + +Section 5. General Information About Project Gutenberg-tm electronic +works. + +Professor Michael S. Hart was the originator of the Project Gutenberg-tm +concept of a library of electronic works that could be freely shared +with anyone. For thirty years, he produced and distributed Project +Gutenberg-tm eBooks with only a loose network of volunteer support. + + +Project Gutenberg-tm eBooks are often created from several printed +editions, all of which are confirmed as Public Domain in the U.S. +unless a copyright notice is included. Thus, we do not necessarily +keep eBooks in compliance with any particular paper edition. + + +Most people start at our Web site which has the main PG search facility: + + https://www.gutenberg.org + +This Web site includes information about Project Gutenberg-tm, +including how to make donations to the Project Gutenberg Literary +Archive Foundation, how to help produce our new eBooks, and how to +subscribe to our email newsletter to hear about new eBooks. |