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diff --git a/31691.txt b/31691.txt new file mode 100644 index 0000000..09c7860 --- /dev/null +++ b/31691.txt @@ -0,0 +1,5661 @@ +The Project Gutenberg EBook of The Bacillus of Long Life, by Loudon Douglas + +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: The Bacillus of Long Life + a manual of the preparation and souring of milk for dietary + purposes, together with and historical account of the use + of fermente + +Author: Loudon Douglas + +Release Date: March 18, 2010 [EBook #31691] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK THE BACILLUS OF LONG LIFE *** + + + + +Produced by Peter Vachuska, Turgut Dincer, Chuck Greif and +the Online Distributed Proofreading Team at +https://www.pgdp.net + + + + + + + + +---------------------------------------------------------+ + | Transcriber's note: | + | | + | Words in bold characters are enclosed within "+" signs. | + | The list of Putnam Science Series has been moved to the | + | advertisement section at the end of the book. The UTF-8 | + | version of the text file will require a Unicode capable | + | text reader to display a few Greek characters and "oe" | + | ligatures which occur in the book. | + +---------------------------------------------------------+ + + + + + [Illustration: THE OLDEST WOMAN IN THE WORLD AND HER SON + + Baba Vasilka is 126 years old, and her son Tudor is 101. + They are peasants, and have lived all their lives in a + little village in Bulgaria. They are typical examples of + people who live to a great age by the use of soured milk, + as it has been their principal food all their lives.] + + + The + Bacillus of Long Life + + A Manual of the Preparation and Souring of Milk for + Dietary Purposes, Together with an Historical + Account of the Use of Fermented Milks, from + the Earliest Times to the Present Day, + and Their Wonderful Effect in the + Prolonging of Human Existence + + By + Loudon M. Douglas, F.R.S.E. + + _With 62 Illustrations_ + + + G. P. Putnam's Sons + New York and London + The Knickerbocker Press + 1911 + + + _Revised Edition_ + + + COPYRIGHT, 1911 + BY + G. P. PUTNAM'S SONS + + + The Knickerbocker Press, New York + + + + +PREFACE + + +This book has been designed with a view to meet an extensive demand for +definite data on the subject of Soured Milks. The author has had this +matter brought before him, times without number, by those inquiring for +authentic information on the subject, and he has therefore considered it +desirable to gather together such information as is available in +connection with ancient and modern practice. He has endeavoured to +present this to the reader in concise form. + +The author is indebted to many friends for their assistance in getting +the book together, and would specially mention Dr. H. B. Hutchinson, +Bacteriologist, Rothamsted Experimental Station, for assistance in +connection with the bacteriology of fermented milks; Mr. Thomas Douglas, +of Wimbledon, who has assisted with the chemistry of the subject; Mr. S. +Javrilovitch, of Belgrade, Servia, for local information and +illustrations; Dr. Otokar Laxa, Bacteriologist, of Prague, Bohemia, for +general assistance; the editor of _Bacteriotherapy_, New York, U.S.A., +for the use of the group of illustrations 30-44; the publishers of the +_Centralblatt fuer Bakteriologie_, Jena, for the group of illustrations +14-29; and many others, some of whom are referred to in the text. + + + CONTENTS + + + CHAPTER PAGE + + I.--INTRODUCTORY--HISTORICAL 1 + + II.--FERMENTED MILKS 15 + + III.--THE CHEMISTRY OF MILK 47 + + IV.--HANDLING OF MILK 68 + + V.--THE BACTERIOLOGY OF FERMENTED OR SOURED MILK 84 + + VI.--THE PREPARATION OF SOURED MILK IN THE HOUSE 125 + + VII.--THE PREPARATION OF SOURED MILK IN THE DAIRY 139 + + VIII.--SOURED MILK IN HEALTH AND DISEASE 151 + + INDEX 165 + + + + +ILLUSTRATIONS + + + FIG. PAGE + + THE OLDEST WOMAN IN THE WORLD AND HER SON _Frontispiece_ + + THE PASS OF BUKOVA 2 + + KABYLES SOURING MILK 4 + + THE HANDLING OF MILK IN THE PYRENEES 8 + + THE CONSTITUENTS OF MILK 48 + + 1.--MICRO-PHOTOGRAPH OF A DROP OF WHOLE MILK 58 + + 2.--MICRO-PHOTOGRAPH OF SEPARATED MILK 58 + + 3.--MICRO-PHOTOGRAPH OF CREAM 58 + + 4.--PHOTOGRAPH OF TWO PETRI DISHES, WHICH HAVE BEEN + INOCULATED WITH ORDINARY MILK 60 + + 5.--THE CREAMOMETER 62 + + 6.--TESTING-GLASS FOR EXTRANEOUS MATTER IN MILK 62 + + 7.--LACTOMETER AND TEST-GLASS 64 + + 8.--PASTEURISER 78 + + 9.--CONTINUOUS APPARATUS FOR THE PRODUCTION OF LARGE + QUANTITIES OF SOURED MILK 82 + + 10.--A MILK-FILLING APPARATUS 90 + + 11.--SECTION THROUGH A KEPHIR GRAIN 94 + + 12.--_Streptococcus lacticus_ (GROTENFELDT) GROWING ON + LACTOSE-AGAR, STAINED BY GRAM'S METHOD 96 + + 13.--PHOTO-MICROGRAPH OF PREPARATION FROM ARMENIAN SOURED + MILK (MATZOON) 106 + + 14.--GRANULE BACILLUS FROM YOGHOURT. SHREDDED PREPARATION + OF A FRESH SKIM-MILK CULTURE 110 + + 15.--GRANULE BACILLUS FROM YOGHOURT, CULTIVATED AFTER + THE USUAL AGAR METHOD 110 + + 16.--GRANULE BACILLUS FROM YOGHOURT. AGAR MILK SUGAR + CULTURE 110 + + 17.--_Bacteria W._ FROM MILK, CULTIVATED TWENTY-FOUR + HOURS 110 + + 18.--AGAR MILK SUGAR CULTURE. FROM THE ORIGINAL BULGARIAN + YOGHOURT 112 + + 19.--AGAR MILK SUGAR CULTURE. SURFACE COLONY OF GRANULE + BACILLUS FROM CALF'S STOMACH 112 + + 20.--AGAR MILK SUGAR CULTURE. DEEP-LYING COLONY + OF GRANULE BACILLUS FROM CALF'S STOMACH 112 + + 21.--AGAR MILK SUGAR. COLONY OF _Bacterium W._ FROM + YOGHOURT 112 + + 22.--TWO COLONIES OF _Bacillus Acidophilus_ FROM CALVES' + MANURE 114 + + 23.--BEER-WORT GELATINE 114 + + 24.--SHREDDED PREPARATION OF BULGARIAN ORIGINAL YOGHOURT 114 + + 25.--GRANULE BACILLUS FROM YOGHOURT. CULTIVATED IN SKIM + MILK IN TWENTY-FOUR HOURS 114 + + 26.--_Bacteria W._, AGAR MILK SUGAR CULTURE 116 + + 27.--_Bacteria acidophilus_ FROM CALVES' MANURE 116 + + 28.--MUCUS FROM CALF'S STOMACH INOCULATED INTO MILK AFTER + EIGHT TRANSFERRINGS 116 + + 29.--DIPLOSTREPTOCOCCUS FROM YOGHOURT. PURE CULTURE IN + SKIM MILK 116 + + 30.--PHOTO-MICROGRAPH OF PREPARATION MADE FROM YOGHOURT, + SHOWING YEAST CELLS 118 + + 31.--PHOTO-MICROGRAPH OF SMEAR FROM GREEK CURDLED MILK + CALLED "GIAOURTI" 118 + + 32.--PHOTO-MICROGRAPH OF SOURED MILK INOCULATED WITH + A TABLET CONTAINING VIABLE AND PURE CULTURES OF + _Bacillus bulgaricus_ 120 + + 33.--PHOTO-MICROGRAPH OF MILK INOCULATED WITH A FERMENT + TABLE IN WHICH _Bacillus bulgaricus_ IS NO LONGER + VIABLE 120 + + 34.--PHOTO-MICROGRAPH OF SMEAR OF CULTURE OF _Bacillus + bulgaricus_ 122 + + 35.--_Bacillus bulgaricus_, SHOWING THE CULTURES + IN ENGLISH COW'S MILK 124 + + 36.--PHOTO-MICROGRAPH OF PURE CULTURE OF _Bacillus + bulgaricus_ 124 + + 37.--PHOTO-MICROGRAPH OF SMEAR OF COMBINED CULTURE + OF _Bacillus bulgaricus_ AND _Bacteria + paralacticus_ 124 + + 38.--PHOTO-MICROGRAPH OF SMEAR OF ONE-MONTH CULTURE + OF _Bacillus bulgaricus_ 126 + + 39.--PHOTO-MICROGRAPH OF CULTURE OF _Bacillus bulgaricus_ + IN MALT 126 + + 40.--PHOTO-MICROGRAPH OF SMEAR FROM MILK THAT HAD BEEN + ALLOWED TO SOUR SPONTANEOUSLY 126 + + 41.--PHOTOGRAPH OF AGAR CULTURE, INOCULATED WITH A LACTIC + POWDER 128 + + 42.--PHOTOGRAPH OF TEST-TUBES OF STERILE MILK, INOCULATED + WITH A TABLET PREPARATION SAID TO CONTAIN PURE + CULTURES 128 + + 43.--PHOTOGRAPH OF TEST-TUBES OF STERILE MILK, EACH TUBE + HAVING BEEN INOCULATED WITH A TABLET OF A + PREPARATION SAID TO CONTAIN PURE CULTURES 128 + + 44.--PHOTOGRAPH OF TEST-TUBES OF STERILE MILK INOCULATED + WITH A TABLET OF "LACTOBACILLINE" 130 + + 45.--APPARATUS OF "LE FERMENT" CO. 129 + + 46.--SOURED MILK APPARATUS OF THE MAYA BULGARE COMPANY, + LIMITED 130 + + 47.--LACTIC FERMENTS, LIMITED, APPARATUS 131 + + 48.--MESSRS. ALLEN & HANBURY'S SOURED MILK APPARATUS 132 + + 49.--VIRONELLE APPARATUS FOR SOURING MILK, MADE BY + MESSRS. CLAY, PAGET & COMPANY, LIMITED 132 + + 50.--"LACTOBATOR" MADE BY MESSRS. CHARLES HEARSON & CO., + LIMITED 140 + + 51.--MESSRS. HEARSON & COMPANY'S "LACTOBATOR" 142 + + 52.--EDGAR'S "LACTOGENERATOR," SOLD BY THE DAIRY SUPPLY + CO., LIMITED 143 + + 53.--APPARATUS OF THE WILLOWS REFRIGERATING CO., LIMITED 144 + + 54.--"LACTO" APPARATUS OF THE DAIRY OUTFIT CO., LIMITED 145 + + 55.--STERILISING APPARATUS FOR STERILISING MILK ON + THE LARGE SCALE 146 + + 56.--ANOTHER METHOD OF STERILISING (DAIRY SUPPLY + CO., LTD.). AN AMERICAN APPARATUS FOR PREPARING + SOURED MILK 148 + + 57.--AN AMERICAN APPARATUS FOR PREPARING SOURED MILK 149 + + + + +THE BACILLUS OF LONG LIFE + + + + +CHAPTER I + +INTRODUCTORY--HISTORICAL + + +The milk industry is one of the oldest known to mankind, and it is +difficult to imagine a time when milk in one way or another did not form +a part of the diet of the human race. There is a good deal of evidence +to show that in Paleolithic and Neolithic times, cattle were part of the +possessions of the nomadic races; and, according to the Vedas, the +manufacture of butter was known in India 1500 years B.C. + +In the eastern part of Europe, milk has always been looked upon as one +of the principal kinds of food, but not necessarily the milk of cows, +as, from ancient times to the present day, the milk from camels, +buffaloes, sheep, and goats has been used indiscriminately throughout +the East. + +According to Layard,[1] "the Bedouins do not make cheese. The milk of +their sheep and goats is shaken into butter or turned into curds; it is +rarely or never drunk fresh, new milk being thought very unwholesome, as +soon by experience I found it to be, in the desert. I have frequently +had occasion to describe the process of making butter by shaking the +milk in skins. This is also an employment confined to women, and one of +a very laborious nature. The curds are formed by boiling the milk, and +then putting some curds made on the previous day into it and allowing it +to stand. When the sheep no longer give milk, some curds are dried, to +be used as a leaven on a future occasion. This preparation, called +_leben_, is thick and acid, but very agreeable and grateful to the taste +in a hot climate. The sour milk, or _sheneena_, a universal beverage +amongst the Arabs, is either buttermilk pure and diluted, or curds mixed +with water. + + [Illustration: THE PASS OF BUKOVA.--During the revolution + of 1904, a number of Turkish soldiers, just before + traversing this pass, were given coffee containing "cafe" + by a Bulgarian coffee-seller, or keeper of a small khan. + Whilst in the pass the poison began to take effect, and + they realized that they had been poisoned. Fortunately for + them, a peasant with three horses loaded with Yoghourt + (soured milk) had taken advantage of their escort. The + soldiers ate freely of the Yoghourt, which counteracted + the effects of the poison.] + +"The camel's milk is drunk fresh. It is pleasant to the taste, rich, and +exceedingly nourishing. It is given in large quantities to the horses. +The Shammar and Aneyza Bedouins have no cows or oxen, those animals +being looked upon as the peculiar property of tribes who have forgotten +their independence, and degraded themselves by the cultivation of land. +The sheep are milked at dawn, or even before daybreak, and again in the +evening on their return from the pastures. The milk is immediately +turned into leben, or boiled to be shaken into butter. Amongst the +Bedouins and Jebours it is considered derogatory to the character of a +man to milk a cow or sheep, but not to milk the camel. The Sheikhs +occasionally obtain dates from the cities. They are eaten dry with bread +and leben, or fried in butter, a very favourite dish of the Bedouin...." + +The practice is now the same as it was in scriptural times, when milk +was looked upon as the principal article of diet, and throughout the +Scriptures there are copious references to milk in different forms, some +of which are of peculiar interest at the present day. + +It may be noticed, for example, that milk is absent from the sacred +offerings amongst the Hebrews, and this was ascribed by the late +Professor Robertson Smith to the fact that all ferments were excluded +from presentation at the altar,[2] it being recognised that, owing to +the hot climate, milk of all kinds became rapidly sour, and in this way +came to be looked upon as only fit for consumption when in that +condition. It has been suggested that the prohibition referred to is on +the same level as the prohibition of the use of blood, "as milk has +sometimes been regarded as a kind of equivalent for blood, and +containing the sacred life."[3] To this day the wandering tribes of +Arabia consider the milk of their camels and flocks more refreshing when +it has been slightly fermented or soured by being poured into a +milk-skin on the inside of which are still sticking sour clots from the +previous milking, and there shaken for a brief period; but this slightly +soured milk (the _Oxygala_ of Pliny) is known widely in the East simply +as leben (milk). The name is also applied to what we term buttermilk.[4] + + [Illustration: KABYLES SOURING MILK + + In the north of Africa the use of soured milk is common, + and the illustration shows Kabyles shaking a skin full of + milk so as to sour it. The skin has previously been used + for the same operation, and, as a consequence, clots of + milk are left from the previous day's use, and thus + fermentation is set up.] + +The use of milk-skins for the carrying of milk is not confined to one +country, as, while it is common all over the north of Africa, it is also +known in the Pyrenees and in some parts of the Balkan Peninsula, the +object being identical in each case; and when it is intended to make +butter from the milk, the skin is simply rocked between the knees until +the butter separates, a process of butter-making which was also used +after the introduction of earthenware churns.[5] Dried soured milk is +also used by the Arabs, and it is reconstituted when required by rubbing +it up with a little water, and it is known as _Meeresy_.[6] The ordinary +soured milk is the common article of diet, and is looked upon as being +necessary at every meal, and travellers frequently refer to the use of +this product, as a few references will show. + +Charles G. Addison states: "A supper was brought in on a round tray. In +the centre was a huge pilaff of rice, and around it several small dishes +of stewed meats, grilled bones, sour clotted milk called _yaoort_,[7] +bits of meat roasted, etc.... + +"We retired into a tent to breakfast, where we found an immense bowl of +delicious fresh camels' milk, with thin hot cakes of unleavened bread, +baked upon the ashes, ready prepared for us. The principal food of the +Bedouins consists of flour and some camels' milk made into a paste, +boiled, and eaten swimming in melted grease and butter; boiled wheat +and beans dried in the sun and prepared with butter are a favourite +dish. They are all remarkably fond of butter and grease; the butter is +made in a goat-skin, suspended to the tent pole, and constantly shaken +about by the women."[8] + +Burckhardt[9] says: "The provisions of my companion consisted only of +flour; besides flour, I carried some butter and dried leben (sour milk), +which would dissolve in water. It forms not only a refreshing beverage, +but is much to be recommended as a preservative of health when +travelling in summer. These are our only provisions." With regard to the +inhabitants of the Houran, Burckhardt relates that the most common +dishes of these people are _bourgoul_ and _keshk_. "In summer they +supply the place of the latter by milk, leben, and fresh butter. Of the +bourgoul I have spoken on other occasions; there are two kinds of +keshk--_keshk-hammer_ and _keshk-leben_. The first is prepared by +putting leaven into the bourgoul and pouring water over it. It is then +left until almost putrid, and afterwards spread out in the sun and +dried, after which it is pounded, and, when called for, served up mixed +with oil or butter. The keshk-leben is prepared by putting leben into +the bourgoul instead of leaven; in other respects the process is the +same. Keshk and bread are the common breakfasts. Towards sunset a plate +of bourgoul, or some Arab dish, forms the dinner." + +Again, Taylor[10] says: "I received a small jug of thick buttermilk, not +remarkably clean, but very refreshing." + +These references particularly refer to the East, from which it would +appear that soured milk was universally known in ancient times as it is +at the present day, and this remark applies not only to Egypt, +Palestine, and Arabia, but throughout Turkey and the Balkan States, +where the consumption of soured milk is equally common. It seems curious +that the use of this commodity should have been confined for centuries +to the East, as we shall see later on that its dietetic value is so +great that it is really a wonderful thing that no one has taken the +trouble to introduce its use to the Western nations until quite +recently. + + [Illustration: THE HANDLING OF MILK IN THE PYRENEES + + The handling of milk in the Pyrenees is, more especially + in the villages, conducted in goat or sheep skins, in a + similar way to the methods which prevail in Eastern + Europe, and the picture shows a skin of milk on a small + farm in the Pyrenees. The churning is very often performed + by simply rocking the skin between the knees, acidity + being induced by remnants of the previous day's milk; + souring of milk is induced by the same method.] + +A curious example of how the virtues of such an article may be +independently discovered by another nation is to be found in Lapland, +where reindeer's milk is the article used. "The reindeer's milk," says +Acerbi,[11] "constitutes a principal part of the Laplander's food, and +he has two methods of preparing it, according to the season. In summer +he boils the milk with sorrel till it arrives to a consistence; in this +manner he preserves it for use during that short season. In winter the +following is his method of preparation: The milk, which he collects in +autumn till the beginning of November, from the reindeer, is put into +casks, or whatever vessels he has, in which it soon turns sour, and, as +the cold weather comes on, freezes, and in this state it is kept. The +milk collected after this time is mixed with cranberries and put into +the paunch of the reindeer, well cleaned from filth; thus the milk soon +congeals, and it is cut out in slices, together with the paunch, to +effect which a hatchet is used, for no smaller instrument would perform +the office of dividing that lump of ice. It is then separated into small +pieces and eaten throughout the winter every day at noon, which is the +Laplander's dinner-hour. It must be presumed, as it is served up without +being brought to the fire, that this is ice-cream in the greatest +perfection: here are flesh and fruit blended with the richest +butyraceous milk that can be drawn from any animal; but, notwithstanding +the extraordinary fatness, which may be supposed to resist in a great +degree the effect of cold, this preparation, as our good missionary +remarks with a degree of feeling, as if his teeth still chattered whilst +he delivered the account, chills and freezes the mouth in a violent +manner whenever it is taken. The milk which is drawn late in the winter +freezes immediately after being drawn. This is put into small vessels +made of birchwood, and is considered by the Laplander as such an +extraordinary delicacy, that he reserves it as the most acceptable +present he can offer even a missionary. It is placed before the fire and +eaten with a spoon as it is thawed. When put by, it is carefully covered +up, because if the cold air gets to it afterwards, it turns of a yellow +colour and becomes rancid." + +Amongst the peasants at the present day, soured milk is known as +_yoghourt_, a word which is spelt differently according to the locality +in which it is used. The method of preparation is practically the same +everywhere, and a short description of the process as now carried out +in one place would, with slight modifications, apply to the general +method adopted all over the East. + +"The culture," says a correspondent at Varna, "which is used for the +preparation of yogourt, is known as 'Maya' or as 'Bulgarian Maya.' The +milk which is to be converted into yogourt must first be freed from all +bacteria by boiling and allowed to cool to the temperature of 45 deg. C.; +it is then inoculated with maya and maintained at an even temperature of +45 deg. C. during several hours. There are two kinds of maya, or ferment, +one known as sour, and the other as sweet maya. + +"In Europe small stoves, made expressly for the purpose, are used to +maintain the milk at the proper temperature. In this country, however, +after the milk has been boiled, it is merely poured into a bowl and +allowed to cool to approximately 45 deg. C., then a tablespoonful of this +tepid milk is well mixed (in a small bowl apart) with a similar quantity +of maya, and the mixture, when it has become quite homogeneous, is added +to the bowl of tepid milk and stirred slightly. (One tablespoonful of +maya is sufficient to ferment one litre of milk.) A cover is then placed +on the bowl and the whole is enveloped in flannel and left in a warm +place for three hours in summer, and somewhat longer in winter. + +"The process of preparation is complete when the mixture assumes the +appearance of a soft mass somewhat resembling cream cheese, but less +solid. The flannel is then removed, the bowl uncovered and placed in a +cool spot until needed for consumption. Of the yogourt thus prepared, a +tablespoonful is kept to serve as maya for the following day. + +"The best yogourt is prepared from sheep's milk, the second quality from +buffaloes' milk, and the third quality from cows' milk. Yogourt forms an +almost daily article of diet with the natives in this country."[12] + +With regard to the time stated for the fermenting process, it must be +noted that since the subject has been investigated so thoroughly, the +time required for fermentation has been found to be nearer ten than +three hours, but this will be dealt with in a subsequent chapter. + +Historically it may be gleaned from the fragmentary references which we +have given, that soured milk has, from time immemorial, formed the +principal article of diet of a great many peoples, and the notable +feature in connection with it is, that in some countries where it is in +daily use, the age limit for human beings seems to be very much +extended, and it would appear that there is a direct connection between +the use of soured milk and longevity. In Bulgaria, for example, it is +stated that the majority of the natives live to an age considerably in +excess of what is recognised as the term of life amongst Western +nations, and inquiry has shown that in the eastern part of Southern +Europe, amongst a population of about three millions, there were more +than three thousand centenarians found performing duties which would not +be assigned to a man of sixty-five years of age elsewhere. It is quite +common to find amongst the peasants who live to such a large extent upon +soured milk, individuals of 110 and 120 years of age.[13] + +In the ancient dairy practice, as we have seen, soured milk was the +principal product, and the extraordinary ages which are recorded of the +patriarchs, if translated into the modern denomination, would not appear +to be so imaginary after all, when it is considered that we have +thousands of examples at the present day of men and women enjoying quite +as long a term of existence. It has been noticed also, that while these +very old people are able to perform a certain amount of manual labour, +there is not the same tendency to the mental decay which is so prominent +and sad a feature amongst Western nations, at a period of about seventy +or eighty years of age. It would seem, indeed, as if the habit of living +long was well known in ancient times, and that, like many other of the +valuable arts and sciences, it fell under a cloud during the Middle +Ages, or, perhaps, the significance of the use of soured milk fell into +neglect, and, even after the revival of letters in the sixteenth +century, still remained obscure. + +The discovery of micro-organisms in perishable products, which is +attributable to Anthony Van Leeuwenhoek, a Dutchman, whose vocation was +the polishing of lenses, and who lived between 1632 and 1723, altered +our point of view, not only of disease, but of all the functions carried +on by the lower organisms. Since Van Leeuwenhoek's time, the germ theory +has grown to vast proportions and has more especially been applied with +splendid results to the study of milk. As we shall see later, the +researches of modern investigators have led them to the conclusion that +micro-organisms play such an important part in the milk supply, that it +is impossible to carry it on safely without a knowledge of the +bacteriology of the subject. This view began to prevail about 1890, some +twenty years after Pasteur had shown what fermentation really meant. +Since that time, the progress in dairying has been continuous, and, +during recent years, attention has been directed to soured milk to such +an extent that it has become necessary for all who are interested in the +handling of milk and milk products to have a knowledge of the subject, +as it seems clearly demonstrated that, under proper direction, there is +every possibility of its forming an important element in the +prolongation of life. + + + + +CHAPTER II + +FERMENTED MILKS + + +There is considerable variety in the number of soured or fermented +milks, and they are known by various names, such as Koumiss or Koomiss, +which is prepared from mares' milk; Keffir, which was originally +discovered in the mountains of the Caucasus, and which is prepared with +Keffir grains; Leben, an Egyptian product prepared from the milk of the +buffalo, cow, or goat; Matzoon, a soured milk which is prepared in +Armenia from ordinary cows' milk; Dadhi, an Indian preparation from +cows' milk. All of these owe their special characteristics to the fact +of their having undergone lactic and alcoholic fermentation. + +"Milk left to itself," says Blyth,[14] "at all temperatures above 90 deg. +F. begins to evolve carbon dioxide, and this is simply a sign and result +of fermentation. If this fermentation is arrested or prevented, the fluid +remains perfectly sweet and good for an indefinite time. Besides the +production of carbon dioxide during decomposition, a certain portion of +milk sugar is converted into lactic acid, some of the casein and albumen +are broken up into simpler constituents, and a small proportion of +alcohol produced, which by oxidation appears as acetic acid, while the +fat is in part separated into free fatty acids, which ultimately unite +with the ammonia produced by the breaking up of the albuminoids. The +main fermentation of milk is a special kind which of late years has been +much studied, and is known as _lactic fermentation_. Accompanying lactic +fermentation there is nearly always a weak butyric and a weak alcoholic +fermentation." + +One of the organisms causing _Butyric Acid Fermentation_ is a bacillus 3 +to 10 mu in length, and about 1 mu in breadth. It has power of movement, and +when cultivated in gelatine, liquefies the gelatine, forming a scum on +the surface. When the bacillus is sown into sterile milk, the following, +according to Hueppe, are the changes: + +"If the milk thus infected is incubated, on the second day a clear, +slightly yellow fluid is seen under the layer of cream; this fluid +increases from day to day, so that gradually a column of fluid is +formed which is quite clear above, but below is turbid; the casein, at +first thrown down in a firm coagulum, in the course of eight days begins +to be attacked, and by the end of two or three weeks most of it is +dissolved. The filtered fluid gives the biuret reaction; it contains +leucin, tyrosin, and ammonia; hence it is clear that the ferment acts to +some extent as a digestive of albumen. In advanced butyric acid +fermentation, the fluid is most offensive, and may have an alkaline +reaction." + +Lactic acid was first isolated by Scheele in 1780 from soured milk, but +its exact constitution was not determined until later by Liebig, +Mitscherlich, Gay-Lussac, and Pelouze: "It is widely distributed in +nature, occurring in the sap of the vine and in most fermented liquids, +especially in soured milk; it is not, however, present in fresh +milk."[15] + +In all the Eastern preparations referred to, the lactic fermentation is +produced, followed by alcoholic fermentation, which is due to the slow +decomposition of the milk sugar, the vinous fermentation being most +readily set up in milks which contain a larger relative proportion of +milk sugar and water, such as the milk derived from the mare, the sheep, +and the camel. As these fermented milks have different characteristics, +it is necessary to the thorough understanding of the process of +manufacture at the present day, to examine them in some detail. + +_Koumiss._--The greatest of all the fermented milks is koumiss, and it +has been celebrated from the most ancient times until the present day, +as being the principal food of the wandering tribes of Khirgiz, +Bashkirs, Kalmucks, and Tartars, who inhabit the steppes of European +Russia and the plains of South, Western, and Central Asia. According to +Carrick, who has written an interesting volume on the subject,[16] the +nomads who inhabit these vast territories are shut up under the most +miserable circumstances during the winter time and at the advent of +spring they roam over the steppes from morning to night, usually in the +saddle. The milk yielded at such time by the mares is carefully +collected, and these nomads consume enormous quantities of it in the +fermented state, this habit having been in existence amongst them from +time immemorial. It is said that the Scythians, long before the +Christian era, used fermented mares' milk; and there are ornaments in +existence in Russia, of Scythian origin, which exhibit in detail the +preparation of koumiss from mares' milk. In historical times, the first +mention of koumiss was in the twelfth century, when it is referred to in +the Ipatof Chronicles. During the thirteenth century William de +Rubruquis, a French missionary, wrote about his travels in Tartary, and +he described how he had first become acquainted with koumiss, and how he +found it savoury to the palate. Subsequent to this, however, there is +very little mention of koumiss in Russian history, or, for that matter, +in any other, and the first really scientific contribution on the +subject was by Dr. John Grieve, who was a surgeon in the Russian army, +and who in the year 1784 sent a description of koumiss to the Royal +Society of Edinburgh,[17] of which he was a member, and the title of it +was, "An Account of the Method of Making Wine called by the Tartars +Koumiss, with Observations on its Use as a Medicine." Dr. Grieve +strongly advocated the use of koumiss as beneficial in cases of wasting +diseases, and subsequently it was adopted by the medical profession, +with the result that sanatoria for the treatment of pulmonary +consumption were established at Samara and other places in Russia, and +met with very great success; and at the present day such sanatoria are +carried on, but the bacteriology of the subject now being thoroughly +understood, the methods of preparation have been somewhat modified. + +An interesting account of koumiss is given by Clarke,[18] who says: + +"Everybody has heard of koumiss, and the brandy which the Kalmucks are +said to distil from the milk of mares. The manner of preparing these +liquids has been differently related, and perhaps is not always the +same. They assured us that the brandy was merely distilled from +buttermilk. The milk which they collect overnight is churned in the +morning into butter; and the buttermilk is distilled over a fire made +with the dung of their cattle, particularly the dromedary, which makes a +steady and clear fire like peat. But other accounts have been given both +of the koumiss and the brandy. It has been usual to confound them, and +to consider the koumiss as their appellation for the brandy so obtained. +By other information I could gain, not only here, but in many other +camps which we afterwards visited, they are different modifications of +the same thing although different liquors; the koumiss being a kind of +sour milk, like that so much used by the Laplanders called _pina_, and +which has undergone, in a certain degree, the vinous fermentation; and +the brandy an ardent spirit obtained from koumiss by distillation. In +making koumiss they sometimes employ the milk of cows, but never if +mares' milk can be had, as the koumiss from the latter yields three +times as much brandy as that made from cows' milk. + +"The manner of preparing the koumiss is, by combining one sixth part of +warm water with any given quantity of warm mares' milk. To these they +add, as a leaven, a little old koumiss, and agitate the mass till +fermentation ensues. To produce the vinous fermentation, artificial heat +and more agitation is sometimes necessary. This affords what is called +koumiss. The subsequent process of distillation afterwards obtains an +ardent spirit from the koumiss. They call it _vina_. In their own +language it bears the very remarkable appellation of _rack_ and _racky_, +doubtless nearly allied to the names of our East India spirit _rack_ +and _arrack_. We brought away a quart bottle of it, and considered it +very weak bad brandy, not unlike the common spirit distilled by the +Swedes and other northern nations. Some of their women were busy making +it in an adjoining tent. The simplicity of the operation and their +machinery was very characteristic of the antiquity of this chemical +process. Their still was constructed of mud, or very coarse clay; and +for the neck of the retort they employed a cane. The receiver of the +still was entirely covered by a coating of wet clay. The brandy had +already passed over. The woman who had the management of the distillery, +wishing to give us a taste of the spirit, thrust a stick, with a small +tuft of camel's hair at its end, through the external covering of clay, +and thus collecting a small quantity of the brandy, she drew out the +stick, dropped a portion on the retort, and, waving the instrument above +her head, scattered the remaining liquor in the air. I asked the meaning +of this ceremony, and was answered that it is a religious custom to give +always the first drop of the brandy which they draw from the receiver to +their God. The stick having been plunged into the receiver again, she +squeezed it into the palm of her dirty and greasy hand, and after +tasting the liquor, presented it to our lips." + +Another interesting account of the preparation of koumiss is given by +John M. Wilson in the _Rural Encyclopaedia_,[19] and it shows that the +methods in use about the middle of last century did not differ +materially from those which existed centuries before. + +Wilson says: "Khoumese is vinously fermented mares' milk. Any quantity +of fresh mares' milk is put into wooden vessels; a sixth part of water +just off the boil is mixed with it; an eighth part of old khoumese or of +the sourest possible cows' milk is added; the mixture is kept from +fifteen to twenty-four hours, covered up with several folds of coarse +linen cloth and with a very thick board, and without being stirred or in +any degree disturbed, in a moderately warm place till it becomes +thoroughly sour, and sends up a thick mass to its surface; it is then +beaten and pounded and stirred till the curd is not only broken, but so +thoroughly mixed with the serum as to form a thick liquid; it next +remains covered and at rest during twenty-four hours more, and it is +finally put into a common butter churn and beaten and blended into a +state of perfect homogeneity. It is now fit for use; yet it acquires an +increase of given properties if it be allowed to stand for a few days, +and either then or now it would, if distilled, yield nearly one third of +its own bulk of a weak spirit which will bear to be rectified. Whenever +it is used it must be previously so agitated that its component parts +may be well mixed together, and it may be kept either in pans for +immediate use or in casks for more remote use; and if placed in a cool +cellar it will remain good during three or four months." + +Mares' milk owes its peculiar fitness for making koumiss to its +containing a large proportion of sugar of milk, and readily undergoing +the vinous fermentation, and it possesses a general medicinal reputation +among the Tartars similar to that which asses' milk has partially +acquired in Britain. "That mares' milk will undergo vinous fermentation +and yield a certain quantity of spirit," says a writer in the _Magazine +of Domestic Economy_, "is not generally known, and it was reserved for a +nation of demi-savages to render this circumstance available as an agent +of health, as well as an agreeable and nourishing beverage. Every +educated person, however, has heard that the Tartars drink mares' milk, +though few know that this milk is taken on account of its specific +virtues alone, and not as a substitute for cows' milk, of which they +have abundance, and with which they adulterate mares' milk when scarce." +But the koumiss is reputed to be much more medicinal than the mares' +milk itself; and on account of its being free from all tendency to +curdle in the stomach, and of its possessing most of the nutritive power +of the milk in combination with native fermented spirit, it has been +strongly recommended by some persons as a remedy for most or all cases +of general debility, of nervous languor, and even pulmonary disease. + +"Khoumese is called sometimes _koumiss_ and sometimes milk wine." + +From these references it will be seen that koumiss is an alcoholic drink +made by the fermentation of mares' milk, but it is also frequently +prepared from the milk of the camel and cows' milk. It is stated that a +similar preparation to Russian koumiss is made in Switzerland from cows' +milk simply by the addition of a little sugar and yeast to skim milk; +"it contains more sugar and less lactic acid than Russian koumiss, and +on account of the much greater proportion of casein contained in cows' +milk, differs considerably from that prepared from mares' milk." +Suter-Naef gives the composition of a Swiss koumiss[20] manufactured at +Davos as follows: + + In Grams. Per Litre + Per cent. (by weight). + Water 90.346 1019.64 grams. + Alcohol 3.210 36.23 " + Lactic acid 0.190 2.14 " + Sugar 2.105 23.75 " + Albuminates 1.860 20.99 " + Butter 1.780 20.09 " + Inorganic salts 0.509 5.74 " + Free carbonic acid 0.177 2.00 " + +The ferments used in the preparation of koumiss are stated by Carrick to +be of two different kinds, artificial and natural. + +"Of the natural ferments two have been resorted to. One is mentioned by +Grieve, which he borrowed from the Bashkirs of Orenbourg, and which +simply consists in the addition of one sixth part of water and one +eighth of the sourest cows' milk to fresh mares' milk; the other has +been employed, and was, if I mistake not, first recommended by +Bogoyavlensky. It is a very simple if rather a tedious method. New +mares' milk, diluted with one third its bulk of water, is placed in the +_saba_,[21] and while allowed to sour spontaneously, is continually +beaten up. This milk gradually undergoes the vinous fermentation, and in +twenty-four hours is converted into weak koumiss. The disadvantage of +this mode of commencing fermentation is obvious--viz., the great waste +of time in agitation. Hence it is only employed when no artificial +ferment is obtainable. + +"In starting the process of fermentation in mares' or any other kind of +milk, therefore, an artificial ferment is more frequently employed than +a natural one. The former is used only for converting the first portion +of milk into koumiss; the latter is always resorted to afterwards. + +"Of artificial ferments the variety is great, for besides all putrefying +animal matters which contain nitrogen--such as blood, white of egg, +glue, and flesh--certain mineral substances which act by souring the +milk are also capable of exciting fermentation. + +"Now, many of the nomads, whose mares either give no milk or are not +milked in winter, commence the preparation of their koumiss in spring by +borrowing a ferment from the animal, mineral, or vegetable kingdom. Thus +a mixture of honey and flour is the favourite ferment with some races of +nomads; a piece of fresh horse-skin or tendon is preferred by others, +while a few resort to old copper coins, covered with verdigris, for +starting fermentation. In the choice of a ferment they are guided solely +by habit and tradition. As it would be useless, almost impossible, to +give a list of all the foreign substances that have been employed with +the view of converting mares' milk into koumiss, it will be best to +consider the simplest artificial ferments, and those most generally in +use. + +"The simplest way is that recommended by Bogoyavlensky, and adopted and +modified by Tchembulatof.[22] It is prepared thus: 'Take a quarter of a +pound of millet-flour, add water to it, and boil it down to the +consistence of thick oatmeal porridge. Then heat separately, in another +vessel, eleven pints of milk to boiling-point, and allow it to cool +down. When its temperature has fallen to 95 deg. F., pour it into a wooden +bowl or tub, and add the boiled flour to it. The upper and open part of +the vessel is then covered with a piece of coarse linen, and left at +rest--at a temperature of about 99 deg. F.--from twenty-four to forty-eight +hours. The appearance of small bubbles, which keep bursting on the +surface of this liquid, combined with a vinous or acid odour, prove that +the ferment is ready. To this fermenting fluid twenty-two quarts of new +milk are gradually (_i.e._, every ten minutes) added, and the whole mass +is continuously beaten up for twelve hours. The temperature during +stirring should never be higher than 94 deg. F. The whole fluid soon begins +to ferment, and after twelve hours a not unpleasant koumiss is ready. +This should be filtered through a horse-hair or muslin sieve, after +which it is fit for drinking. This liquid is called weak koumiss; but a +limited portion of the lactine has undergone the lactuous and vinous +fermentations, and thus the percentage of alcohol is small. Koumiss at +an ordinary temperature remains weak for twelve hours after it has been +beaten up, and then gradually passes into medium.'" + +Curiously enough, the richness of cows' milk in fat militates against +its being a good raw material for the making of koumiss, owing to the +production of small quantities of butyric acid, which follows upon the +fermentation, so that it is desirable, if koumiss is to be prepared from +cows' milk, that the fat should be first of all eliminated, so that the +separated milk will then approximate to the composition of mares' milk. + +"The chemical changes," says Hutchison,[23] "which take place in the +milk under the double fermentation are not difficult to follow; the +lactic ferment simply changes part of the sugar into lactic acid, the +vinous ferment eats up a very small part of the proteid of the milk, +and, at the same time, produces from the sugar a little alcohol and a +good deal of carbon dioxide; the milk thus becomes sour, it effervesces +and is weakly alcoholic, but the lactic acid causes the casein to be +precipitated just as it does in the ordinary souring of milk, and the +casein falls down in flocculi." + +As will have been noticed, it is an essential part of the process of +koumiss-making to keep the milk in a state of agitation during the +period of fermentation, a process which is intended to permit of oxygen +being taken up by the fermenting fluid, while, at the same time, the +casein is broken up into a state of fine division. The casein also, or +at least a portion of it, becomes very soluble, and after twelve hours +of fermentation the taste of the product is only slightly sour, and the +milk taste still remains. This taste, however, disappears in +twenty-four hours, owing to the rapid development of the lactic acid +organisms. After this lapse of time the sugar is entirely destroyed, and +the strong koumiss which results is a thin sour fluid which effervesces +briskly, and in this condition will keep for an indefinite period. "The +net change which has taken place in the original milk may be summed up +by saying that the sugar of the milk has been replaced by lactic acid, +alcohol, and carbon dioxide, the casein has been partly precipitated in +a state of very fine division, and partly pre-digested and dissolved, +while the fat and salts have been left much as they were."[24] + +Violent stirring or agitation of the cultures does not seem to work so +much by supplying oxygen to the fermenting liquid, as by ensuring a +thorough distribution of the micro-organisms throughout the liquid, and +thus dividing the casein. + +The greater number of the organisms are facultative anaerobes and oxygen +is not necessary. Again, koumiss put up in bottles on the first day is +regularly shaken although air is excluded. + +_Keffir._--Keffir is a kind of fermented milk which has been in use in +the Caucasus for quite a long time, as koumiss has been in the steppes. +It differs from koumiss, however, in this respect, that it is prepared +from either sheep's, goats', or cows' milk. The process is started by +the addition of keffir grains to the milk, which is contained in +leathern bottles. These keffir grains are small solid kernels which are +kept in families and handed on from one generation to another.[25] The +grains are the origin of the ferment, as they disseminate in the milk +micro-organisms of a lactic yeast (_Saccharomyces kefir_ Beyerinck and +Freudenreich) and also the bacillus _Bacterium caucasicum_, which +develop rapidly and split up the milk sugar into carbon dioxide, +alcohol, and lactic acid. Small quantities of glycerine, acetic, +succinic, and butyric acids are also formed, the casein and albumen +being partly peptonised.[26] Keffir becomes slightly effervescent in +twenty-four hours, and in that time develops a small quantity of +alcohol, but after three days the amount of alcohol and lactic acid +is much increased.[27] It has been determined that the fermentation of +the milk is due to _Saccharomyces kefir_, and that the _Lactobacillus +Caucasicus_ does not take any part in the fermentation, a fact which +seems to be supported by the capacity of ordinary keffir for starting +the fermentation in fresh milk in the same manner as the keffir grains. +The use of this beverage seems to be universal throughout the Caucasus, +and travellers in these regions have frequently referred to it. Thus +Freshfield[28] states in one part of his book of travels as follows: + +"The pig-faced peasant against whom we had at first sight conceived such +an unjust prejudice turned out a capital fellow. He brought us not only +fresh milk, but a peculiar species of liquor, something between +public-house beer and sour cider, for which we expressed the greatest +admiration, taking care at the same time privately to empty out the +vessel containing it, on the first opportunity." And again: + +"The hospitable shepherds regaled us, not only with the inevitable and +universal airam or sour milk--if a man cannot reconcile himself to sour +milk, he is not fit for the Caucasus--but with a local delicacy that +has lately been brought to the knowledge of Europe--kefir. This may best +be described as 'effervescing milk.' It is obtained by putting into the +liquid some yellow grains, parts of a mushroom which contains a bacillus +known to science as _Dispora caucasia_. The action of the grains is to +decompose the sugar in the milk, and to produce carbonic acid and +alcohol. The grains multiply indefinitely in the milk; when dried they +can be preserved and kept for future use; its results on the digestion +are frequently unsatisfactory, as one of my companions learnt to his +cost." + +"It has been supposed," says Metchnikoff, "that the chief merit of +kephir was that it was more easy to digest than milk, as some of its +casein is dissolved in the process of fermentation. Kephir, in fact, was +supposed to be partly digested milk. This view has not been confirmed. +Professor Hayem thinks that the good effects of kephir are due to the +presence of alcoholic acid, which replaces the acid of the stomach and +has an antiseptic effect. The experiments of M. Rovigh, which I speak of +in _The Nature of Man_, have confirmed the latter fact, which now may be +taken as certain. The action of kephir in preventing intestinal +putrefaction depends on the lactic acid bacillus which it contains. +Kephir, although in some cases certainly beneficial, cannot be +recommended for the prolonged use necessary, if intestinal putrefaction +is to be overcome.... Professor Hayem prohibits its use in the case of +persons in whom food is retained for long in the stomach. When it is +retained in the stomach, kephir goes on fermenting, and there are +developed in the contents butyric and acetic acids, which aggravate the +digestive disturbances. Kephir is produced by combined lactic and +alcoholic fermentations ... and it is the lactic and not the alcoholic +fermentation on which the valuable properties of kephir depend; it is +correct to replace it by sour milk, that contains either no alcohol or +merely the smallest traces of it. The fact that so many races make sour +milk and use it copiously is an excellent testimony of its usefulness." + +There are two methods given by Fluegge[29] for the preparation of keffir: + +"In the first, the dry brown kefir grains of commerce are allowed to lie +in water for five or six hours until they swell; they are then carefully +washed and placed in fresh milk, which should be changed once or twice +a day until the grains become pure white in colour and when placed in +fresh milk, quickly mount to the surface--twenty to thirty minutes. One +litre of milk is then poured into a flask, and a full tablespoonful of +the prepared _koerner_ added to it. This is allowed to stand open for +five to eight hours; the flask is then closed and kept at 18 deg. C. It +should be shaken every two hours. At the end of twenty-four hours the +milk is poured through a fine sieve into another flask, which must not +be more than four fifths full. This is corked and allowed to stand, +being shaken from time to time. At the end of twenty-four hours a drink +is obtained which contains but little carbon-dioxide or alcohol. Usually +it is not drunk until the second day, when, upon standing, two layers +are formed, the lower milky, translucent; and the upper containing fine +flakes of casein. When shaken it has a cream-like consistence. On the +third day it again becomes thin and very acid. The second method is used +when one has a good kefir and two or three days to start with. Three or +four parts of fresh cows' milk are added to one part of this and poured +into flasks which are allowed to stand for forty-eight hours with +occasional shaking. When the drink is ready for use, a portion (one +fifth to one third) is left in the flask as ferment for a fresh quantity +of milk. The temperature should be maintained at about 18 deg. C., but at +the commencement a higher temperature is desirable. The grains should be +carefully cleaned from time to time and broken up to the size of peas. +The clean grains may be dried upon blotting-paper, in the sun, or in the +vicinity of a stove; when dried in the air they retain their power to +germinate for a long time." + +_Leben._--In our earlier references to fermented milks in scriptural +times, we observed that alcoholic fermented milks were not permitted to +be presented at the altar. Such offerings, however, were quite allowable +amongst the ancient Egyptians, the Arabs and Carthaginians,[30] and from +remote antiquity these nations placed great value on this product. +Leben, which is peculiarly associated with Egypt, is a soured milk +prepared from the milk of buffaloes, cows, or goats. It is usually +prepared by the boiling of the fresh milk over a slow fire, after which +some fermented milk from a previous preparation is added to the warm +article, and the fermentation takes place rapidly and is considered to +be complete in about six hours.[31] The Egyptian leben is valued so +highly that it is offered in hospitality to the passing stranger, and it +is regarded as so much of a duty to present this milk, that in some +parts of Arabia it would be looked upon as scandalous if any payment +were received in return.[32] + +_Matzoon._--Matzoon is prepared in Armenia in somewhat the same manner +as keffir is prepared in the Caucasus, and indeed it differs very +slightly from keffir in composition. Its use is universal in Armenia. + +_Dadhi._--In India large quantities of fermented milk are used, under +the name of Dadhi, and its characteristics are not unlike the similar +products in Europe. The specific bacillus has been investigated by +Chatterjee,[33] who concludes that it is somewhat akin to the _Bacillus +bulgaricus_ and the bacillus of leben (_B. lebenis_). Dr. Chatterjee +gives a resume of his investigations which sums up the whole matter +thus: + +"1. The fermented milk of India called Dadhi resembles in all essential +points the Bulgarian fermented milk as well as the leben and other forms +of fermented milk in use in the East. + +"2. The causative element of the curdling process of Dadhi is a +streptothrix having characters similar to the _Bacillus bulgaricus_ and +_Streptobacilli lebeni_, and _Bacillus caucasina_ and the Long Bacilli +of Mazun, in (1) not growing in ordinary media; (2) producing a large +amount of lactic acid in milk; (3) producing, besides coagulation of +casein and splitting up the sugar of milk into lactic acid, no other +change in milk; (4) not producing any indol, nor peptone, nor +saponification of fat, nor formation of any gas. + +"3. It differs from the above by showing peculiar pink-stained granules, +when stained with methylene blue and showing peculiarly convoluted +chains in glucose agar. + +"4. The importance of the organism lies in the fact that, as in the case +of _Bacillus bulgaricus_, it kills all pathogenic non-sporing germs and +also destroys all proteolytic gas-forming bacilli in milk." + +In the account of these investigations the following table is given, +showing the amount of lactic acid produced by different lactic acid +bacilli in one litre of milk, in terms of lactic acid--the culture +being kept at 37 deg. C. + + +--------------+-------+-------+-------+-------+-------+-------------------+ + | Name of the | After | After | After | After | After | | + | Bacillus. | 24 | 48 | 72 | 96 | a | Remarks | + | | Hours.| Hours.| Hours.| Hours.| Week. | | + +--------------+-------+-------+-------+-------+-------+-------------------+ + | B. lactis | 1.8 | ... | 10.08 | ... | ... | Observed by | + | aerogenes | | | | | | Hall and Smith | + | | | | | | | | + | B. coli | 1.8 | ... | 4.77 | ... | ... | Observed by | + | communis | | | | | | Hall and Smith | + | | | | | | | | + | B. | 12.8 | 16.5 | 20.2 | ... | 22 | Observed by | + | bulgaricus | -.4 | -.4 | -.4 | ... | -.4 | Gabriel Bertrand | + | | | | | | | and Weisweller; | + | | | | | | | the initial | + | | | | | | | acidity of the | + | | | | | | | milk was 4 | + | | | | | | | | + | Matzoon Long | 10.8 | 12. | ... | ... | ... | Observed by | + | staebschen B.| | | | | | Dueggeli | + | | | | | | | | + | Strepto- |2.61[34] ... | ... | ... | ... | Observed by | + | bacillus | | | | | | Rist and Khoury | + | lebenis | | | | | | | + | | | | | | | | + | Streptothrix | 10.8 | 1.08 | 11.25 | 11.70 | 18.5 | Med. Coll., | + | dadhi | | | | | | Calcutta | + +--------------+-------+-------+-------+-------+-------+-------------------+ + +In different parts of the world sour milk is consumed in great +quantities, and it is stated by Metchnikoff[35] that the chief food of +the natives of tropical Africa consists of soured milk, and in Western +Africa in the region south of Angola, the natives live almost entirely +on this product, there being a difference in the curdled milks produced +according to the nature of the microbial flora which is introduced. + +It is stated[36] that in Servia, Bulgaria,[37] and Roumania there were +5000 centenarians living in 1896, and while many reasons are advanced +for such an abnormal condition of affairs, it seems fairly certain that +the sole reason why people in these districts live to such great ages is +because of their mode of living and the fact that they live very largely +on soured milk. The hygienic conditions throughout these countries are +not such as would give the population in the towns and villages any +special advantages in the prolongation of life, and while it may be +stated that a pastoral and agricultural life are likely to contribute to +longevity, these conditions would not account for a general tendency to +live long in the countries referred to, more than in any other +agricultural area. There are many countries throughout the world in +which the pastoral and agricultural existence is general, but it has +not been shown that in these countries life is prolonged. Hence the +conclusion has been forced upon investigators that the reason is to be +found not in the pastoral conditions, but in the habit which has existed +from time immemorial of consuming sour milk as a principal article of +diet. + +There is no curtailment of the use of fermented milks in Eastern Europe, +and the methods of preparation at the present day are those which have +been carried out from time immemorial. A local observer states that in +Bulgaria yoghourt is made in nearly every household, especially in the +spring and summer. The method of preparation is very simple: The milk is +boiled until a quarter of its volume has evaporated, it is then cooled +to 45 deg. C. and the ferment added. This ferment is a portion of the +yoghourt of good flavour and is called "Maya" or "Zakvaska." The vases, +a kind of earthenware pot, are enveloped in woollen stuff or sheepskin +and placed in a warm place near the chimney. In ten hours the yoghourt +is made, and it is preserved in a cold place. The great reputation that +the yoghourt has acquired in Western Europe has caused this "Maya" to +become an article of commerce. It is sent out by rail hermetically +sealed in tinplate boxes. According to a Sophia chemist, the "Maya" is +employed in the following manner: For a litre of milk it is necessary to +take about 10 gr. of the ferment. This ferment is diluted with three +times the amount of water and put into a bowl previously heated with hot +water and dried. Into this bowl the milk, previously boiled and cooled +to a temperature of 75 deg. to 50 deg. C., is poured; it is then covered +over and put in a temperature of about 30 deg. C., and, in default of a +stove of constant temperature, the bowl is wrapped round with flannel or +a plaid, and left to curdle for eight to ten hours. It is then ready for +consumption. During winter, curdled milk keeps for several days, and in +summer it becomes sour in from twelve to twenty-four hours. + +A similar food to the yoghourt is prepared in the Balkan mountains from +sheep's milk under the name of "Urgoutnik."[38] The milk is poured into +a goat-skin or sheepskin bag, and a little of the fermented milk added, +and is then left for some hours in a warm place. The milk consumed is +replaced by a fresh supply. In some of the Balkan countries, they are +not content with the fermentation of the milk, they add a little alum, +which, under the name of "typsa," is well known for this purpose. The +milk attains such a solid consistency that it can be put into a cloth +and carried to market.[39] + +The various forms of sour milk which have been described in the +foregoing pages may be said to be of the traditional kind, and with the +light of modern knowledge, it has been possible to determine exactly +what constitutes the active principle in use in the milk consumed in +these countries, and, as we shall see, this principle has been applied +so that, at the present day, a pure fermented milk may be obtained in +any country, and there is every reason to believe that should such be +adopted as a general article of food, it would contribute to the +prolongation of human existence. + +It is due to Metchnikoff, of the Pasteur Institute, that so much +prominence has been given to the use of fermented milks. He gave it as +his opinion[40] that senility was caused partly by auto-intoxication or +by the poison derived from putrefactive micro-organisms which inhabit +the digestive track. These organisms increase with age, and under +certain unhealthy conditions multiply enormously, particularly in the +large intestine. Having arrived at this knowledge, Metchnikoff set to +work to devise some means of combating the influence of these harmful +microbes, and set up the hypothesis that the tendency to longevity which +is exhibited in Eastern countries is due to the consumption of lactic +acid organisms in the shape of soured milk. These organisms are more +powerful than those of a putrefactive character and inhibit their +growth. + +"In the presence of such facts," says Metchnikoff, "it becomes +exceedingly important to find some means of combating the intestinal +putrefaction which constitutes so incontestable a source of danger. Such +putrefaction is not only capable of producing diseases of the digestive +tube--_enteritis_ and _colitis_--but even of becoming a source of +intoxication of the organism in its most varied manifestations. + +"It is some years since I proposed to combat intestinal putrefaction and +its injurious consequences by means of lactic ferments. I thought the +acidity produced by such microbes would be much more effective in +preventing the germination of putrefying microbes than the small +quantity of acids produced by _Bacillus coli_. On the other hand, I had +no illusion as to the difficulty sure to be encountered in any effort to +introduce lactic microbes into the intestinal flora which has been +preoccupied by a multitude of other microbes. To make surer of the +result, I chose the lactic microbe, which is the strongest as an acid +producer. It is found in the _yahourt_ (yoghourt), which originates in +Bulgaria. The same bacillus has also been isolated from the _leben_ of +Egypt; and it is now proved that it is found in the curdled milk of the +whole Balkan peninsula, and even in the Don region of Russia."[41] + +It is a short step from considerations like these to the adoption of the +_Bacillus bulgaricus_ as the most potent of the various lactic organisms +which have been examined, and which is likely to play such an important +role in the destiny of the human race. The _Bacillus bulgaricus_ may +claim to be the Bacillus of Long Life. + + + + +CHAPTER III + +THE CHEMISTRY OF MILK + + +_The Composition of Milk._--Like all other organic substances, or those +built up in connection with the life processes of plants and animals, +milk is of complex composition. It is also very liable to change--every +one is acquainted with its tendency to "go bad." This instability is +more or less inherent in all highly organised chemical compounds, and, +indeed, it seems to be necessary that the materials used in growth and +nutrition should be very plastic in a chemical sense, in order, _e.g._, +that the constituents, say of a plant, may easily be transformed into +the substances of the body of the animal which feeds on it. + +The perishable nature of milk--the food of young and growing animals--is +therefore essential, so that it may be changed easily into the blood, +bone, muscle, etc., so abundantly required in the early stages of +existence. + +Milk is a complete food, and, therefore, naturally it is not a simple +chemical compound, but a mechanical mixture of a number of substances. +The present state of chemical knowledge on the subject does not permit +of its composition being given in detail, but for practical purposes, +such as those of measuring its purity and food value, this is not +necessary. + +A proximate analysis, in which, at least, some of the ingredients are +lumped together, is sufficient, and has been adopted everywhere by +analysts. On this basis the average composition of cows' milk may be +stated as follows: + + Per cent. + Water 87.50 + Fat 3.50 + Casein and albumen 3.65 + Milk sugar 4.60 + Ash 0.75 + ---- + 100.00 + ------ + +The constituents other than water added together form the "total +solids," and they amount to 12.5 per cent. + + Per cent. + Water 87.5 + Total solids 12.5 + ---- + 100.0 + ----- + + [Illustration: THE CONSTITUENTS OF MILK + In the illustration, a pint of milk is shown in a glass + jar, and the various percentages of water, casein, sugar, + ash, albumen, and fat, which make up its constituent + parts, are shown in separate bottles, the percentage of + each being stated beneath.] + +Milk varies a good deal in composition; the different breeds of cows +give varying qualities. The Short-horn gives large quantities of milk of +rather poor analysis, while the Jersey yields smaller proportions of +very rich milk. During the period of lactation (the time which has +elapsed since the cow gave birth to a calf), care in milking, food, +health, etc., all have an effect on the quality of the milk. + +The limits of variation may be stated as follows: + + Per cent. Per cent. + Water 87.5 to 82.5 + Fat 2.5 " 6.0 + Casein and albumen 3.0 " 4.5 + Milk sugar 3.5 " 6.0 + Ash 0.6 " 0.8 + +These figures are extreme, and it is very seldom indeed that either the +minimum or maximum is reached. Indeed, by the regulation laid down under +Clause 4 of the British Sale of Food and Drugs Act of 1899, when the +percentage of solids not fat falls below 8.5 per cent., and fat under 3 +per cent., it is assumed that the milk has been adulterated. This +regulation is a perfectly just one. While genuine milk may, in rare +instances, show figures as low as 7.1 per cent. of solids not fat, or +2.5 per cent. of fat, the right can hardly be claimed of supplying such +an abnormal article to the public as milk of proper quality, and the +dairyman who understands his business, and wishes to deal fairly with +his customers, can, by attention to the conditions enumerated above +which influence the composition of milk, entirely avoid the production +of such a low-grade article. + +In the nutrition of both plants and animals large quantities of water +are needed. The solids must be supplied in solution or dissolved in the +assimilative processes, and this cannot take place without water, which +also conveys the dissolved solids to the various parts of the economy, +and in the case of animals removes waste materials. For the most part, +water passes through the body unchanged, but a certain proportion unites +chemically with the food materials and assists in their digestion. It is +therefore not surprising that seven eighths of milk is composed of +water. Blood contains a similar proportion, and this agreement +emphasises the fact that milk is a perfectly balanced food. + +The fat of milk, which yields cream and butter, differs in some +important respects from other fats. Like these, it is made up chiefly +of stearin, palmitin, and olein, but, in addition, it contains an +abnormally large proportion of compounds of certain of the volatile +fatty acids. It is these which give to butter its agreeable flavour. By +the methods of Duclaux, the following is the approximate composition of +butter fat: + + Per cent. + Stearin, palmitin, olein, and traces of + myristin and butin 91.50 + Butyrin 4.20 + Capronin 2.50 + Caprylin, caprinin, and traces of laurin 1.80 + ----- + 100.00 + ------ + +Myristin occurs in nutmegs; butyrin in another combination flavours +pineapples and rum; caprinin is found in cocoanut fat, mutton fat, and +in the offensive odour given off by the goat (from which the name is +derived); caprylin is a by-product of alcoholic fermentation, and also +occurs in cocoa fat; laurin is found in sweet bay; from which it is +evident that there are some curious relationships in flavouring +materials. + +Fats are very concentrated foods, furnishing a large amount of energy to +the body. At one time they were classed together with starch, sugar, +and other carbohydrates as heat-producers, but the distinction which +was drawn between the kinds of food which were thought solely to keep up +the temperature of the organism, and those which produced force in work +and other forms of bodily energy, has broken down, and by direct +experiment has been found not to exist. It is usually calculated that +one part of fat is equal in food value to about two and a quarter parts +of any of the other carbohydrates. Milk fat or butter is more digestible +than almost any other fat, and its importance therefore can readily be +realised. All the above constituents of milk fat are composed of +different proportions of carbon, hydrogen, and oxygen, but milk also +contains minute quantities of lecithin, a fat containing phosphorus in +addition. Lecithin is also found in the brain and nerve material of +animals, in the yolk of egg, and in several plants. + +The nitrogenous constituents of milk--casein and albumen--are usually +estimated together, and they are reckoned as of equivalent food value. +The name protein is very commonly applied to the total of these bodies +in milk, or other animal and vegetable foods. They are composed of +different proportions of carbon, hydrogen, oxygen, and nitrogen, with +small quantities of sulphur, while casein contains phosphorus in +addition. Albumen exists to the extent of about 0.6 per cent. in milk. +It is very similar in properties to egg albumen. The coagulum which +forms on the surface of milk when boiled is largely composed of albumen. +Casein is combined with, and kept in solution by, lime, soda, and +calcium phosphate, and its amount averages a little over 3 per cent. + +The remarkable property possessed by rennet, of curdling or coagulating +casein, is well known; rennet is an extract from the stomach of the +calf, and similar principles are present in the stomachs of man and +other animals, so that the coagulation of milk is the first process in +its digestion. If milk is gulped down in large quantities it is apt to +coagulate in lumps, and digestion is much interfered with, but if it is +taken hot and slowly, it coagulates in small pieces which are readily +attacked by the gastric juice, and milk is then one of the most +assimilable of foods. + +Nature provides that the milk for young animals is supplied in finely +divided streams, so that coagulation takes place in the best possible +way. + +The proteids are the most important constituents of food; they are +abundant in the blood, and build up the muscles, brain, nerves, and +other bodily structures. + +Besides these mentioned, milk contains traces of another proteid of +similar composition called globulin. + +The sugar of milk is not found anywhere else. It is a carbohydrate like +cane and grape sugar--that is to say, the hydrogen and oxygen they +contain are in the same relative proportions as in water. Milk sugar is +not so soluble or so sweet as the other sugars. It does not ferment with +ordinary yeast, but certain special yeasts which are made use of in the +preparation of keffir, koumiss, etc., have the power of transforming it +into alcohol. Its most remarkable property, however, is the facility +with which, under the influence of certain bacteria, it is changed into +lactic acid. + +Every one is familiar with the souring of milk, but perhaps it is not so +generally known that there are great differences in the results obtained +in accordance with the conditions under which the souring takes place. +The skilled butter-maker, by keeping the milk in a cool and cleanly +dairy, obtains a sour milk of a characteristic and agreeable aroma and +taste, which beneficially affect the flavour of the butter produced. On +the other hand, if milk is kept in hot and dirty surroundings, the +development of acidity is accompanied by different bad tastes and +odours, and it becomes unfit for use as a food. In the first case, the +conditions are favourable to the maximum production of the lactic acid +bacteria, and these occupy the field, and largely prevent the +development of the other bacteria which are present--the survival of the +fittest in the struggle for existence. In the second case, the impure +surroundings swarm with the germs of many kinds of putrefactive +bacteria, and the high temperature assists these to gain the upper hand. +Again, the survival of the fittest, in the particular conditions. Even +in cool and cleanly surroundings injurious taints may develop, +especially if the milk has previously been subjected to a journey by +road or rail, as is the case in the modern creamery system, where the +farmers deliver their milk to a central creamery, where it is made into +butter. In such establishments it is the regular practice to kill the +germs, lactic and others, existing in the milk, by heating it to a high +temperature. This process is called pasteurising, after the great French +chemist and bacteriologist who invented it. Pure lactic cultures are +added to the pasteurised milk, and the souring process is under exact +control, with the result that butter of uniform flavour and quality is +produced. The same method is made use of in making the special sour milk +described in this book, with, of course, modifications in the apparatus +employed, to suit the smaller scale in which the manufacture is +conducted. + +The ash is the mineral matter which is left when milk, previously dried, +is burnt in a crucible. It is a complex mixture, and, as we have seen, +it amounts to about 0.7 per cent. of the milk. The process of burning +destroys all the organic matter, and, at the same time, alters somewhat +the state of combination of the inorganic or mineral elements. Attempts +have been made from the analysis of the ash to reconstitute the +composition of the mineral matter as it exists in the milk. The best +known is that of Soldner, and the following is his calculation: + + Per cent. + Sodium chloride 10.62 + Potassium chloride 9.16 + Monopotassium phosphate 12.77 + Dipotassium phosphates 9.22 + Potassium citrate 5.47 + Dimagnesium citrate 3.71 + Magnesium citrate 4.05 + Dicalcium phosphate 7.42 + Tricalcium phosphates 8.90 + Calcium citrate 23.55 + Calcium oxide, in combination with casein 5.13 + ------ + 100.00 + ------ + +The presence of citrates will be noted in this analysis. Citric acid, +which gives to lemons their acidity, and is also found in other fruits, +has been proved to exist in milk to the extent of about 0.2 per cent. +When alkaline or earthy citrates are burnt or oxidised in the blood, the +citric acid is destroyed, and corresponding carbonates remain. No doubt +the function of citrates in milk is to furnish to the body the earthy +and alkaline carbonates which are required in certain of its parts. + +The mineral constituents of milk have many important functions to +perform in the building up and nutrition of the bodily organism. +Phosphate of lime is the principal constituent of the skeleton, and the +blood must be richly supplied with the alkalies, earths, and acids which +are comprehended in the ash. + +Milk contains traces of many other substances, the most important of +which are several enzymes which assist in its digestion. + +_General Properties of Milk._--The appearance of milk is known to every +one; it ought to be a pure white opaque liquid, but very generally it is +tinted a cream colour with anatto to give it an added appearance of +richness. The average specific gravity is about 1.031; or, to put it +another way, while a gallon of pure water weighs exactly 10 lbs., a +gallon of milk weighs 10 lbs. 5 oz. It freezes at 31 deg. F. and boils at +about one third of a degree higher than water. + +When milk is examined under the microscope, the fat is found to be +distributed through it in a multitude of minute globules varying in size +from 1/16,000th to 1/25,000th part of an inch, and occasionally they are +much smaller and also much larger. + +Fig. 1 is a micro-photograph showing the fat globules in whole milk. +Fig. 2 is a micro-photograph of separated milk, and Fig. 3 a +micro-photograph of cream, all under high magnification (450 diams.); +from these figures the comparative number of fat globules present may be +seen. + + [Illustration: FIG. 1.--Micro-photograph of a Drop of + Whole Milk, showing distribution of fat globules. + (Magnified 450 diams.)] + + [Illustration: FIG. 2.--Micro-photograph of Separated + Milk, showing the almost complete absence of fat globules + as compared with whole milk. (Magnified 450 diams.)] + + [Illustration: FIG. 3.--Micro-photograph of Cream, showing + agglomeration of fat globules. (Magnified 450 diams.)] + +Fats distributed through a watery liquid in this finely divided +condition form together what is called an emulsion, in which the +particles of fat are kept apart by surface tension. The specific gravity +of milk fat averages 0.93, and compared with water weighing 10 lbs., a +gallon of fat would weigh 9 lbs. 5 oz. It is thus considerably +lighter than the other constituents, and when milk is left at rest, the +fat globules gradually rise to the top and float there, forming cream. +The difference in specific gravity between cream and milk is taken +advantage of in the mechanical separator, now so much used, and which +makes such a thorough separation between the two. Cream is an article of +the most varied composition, according to the ideas of the person who +produces it, but it ought to contain at least 20 per cent. of butter +fat, and may be made with a much larger percentage if necessary. When +cream is agitated in a particular way, as by churning, the surface +tension of the particles is overcome, and they run together into a mass +which forms butter. + +The casein of milk is not held in solution in the ordinary sense, but in +a peculiar state of suspension called the colloidal condition, +practically the whole of it remaining behind when milk is filtered +through clay filters. + +It is this state of suspension of the casein which makes milk opaque, +but the opacity is considerably increased by the emulsified fat. + +The coagulation of the casein in milk by the addition of rennet has +already been referred to. Acids, either mineral or organic, also +precipitate it in the form of flakes. Skimmed milk is now largely used +for the preparation of casein by this method, and the washed and dried +precipitate is used very extensively in the arts for such varied +purposes as the manufacture of billiard balls, paints, cements, etc. + +The clear liquid which separates when milk is curdled with rennet is +called whey, and contains the milk sugar and mineral salts. The sugar is +manufactured from it on a limited scale, and is used as an ingredient in +infant foods, and as a convenient medium in certain medical +preparations. In Sweden a kind of cheese is made from whey, but the +great bulk of it everywhere is used for feeding pigs. + +The comparative composition of different varieties of milk is given in +the following table: + + ------------------------------------------------------------------------- + Human Cow Buffalo Goat Sheep Mare Ass Reindeer Whale + ------------------------------------------------------------------------- + Water 88.32 87.75 82.57 86.34 81.08 90.38 90.30 67.7 60.47 + Fat 3.43 3.40 7.63 4.25 7.67 1.00 1.30 17.1 20.00 + Protein 1.55 3.50 4.69 4.40 6.08 1.98 1.80 10.9 12.42 + Milk Sugar 6.44 4.60 4.30 4.26 4.26 6.28 6.20 2.8 5.63 + Salts 0.26 0.75 0.81 0.75 0.91 0.36 0.40 1.5 1.48 + ------------------------------------------------------------------------- + Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 + ------------------------------------------------------------------------- + Specific 1.032 1.0315 1.033 1.033 1.038 1.034 1.033 ... ... + Gravity + ------------------------------------------------------------------------- + + [Illustration: FIG. 4 is a photograph of two Petri dishes, + which have been inoculated with ordinary milk (A), and + milk that has been subjected to sterilisation (B). The + whitish bacterial colonies on A are due to enormous + numbers of organisms, while B is quite free from such + growth. + + For the production of a reliable lactic food, it is + essential that certain precautions as to the treatment of + the milk, and the maintenance of a suitable temperature + during the growth of the lactic bacteria, should be + observed. + + In the first place, milk immediately after extraction from + the cow contains only a few organisms, but these multiply + so rapidly that in a few hours the bacterial content may + amount to many millions per ounce. In preparing a pure + culture of any specific organism, then, care must be taken + to destroy all the bacteria that have accidentally found + their way into the milk, inoculating with the organisms it + is desired to cultivate. This is best accomplished by + heating the milk to the boiling-point of water for about + thirty minutes, by which time almost all the undesirable + bacteria have been killed.] + +The milk of the cow differs a good deal from human milk, and where the +former is used for the feeding of children it is usual to add milk sugar +to it, and otherwise alter it to bring its composition more in harmony +with the human article. The high concentration of the milk of the +reindeer and the whale is noteworthy. Perhaps this may be due to the low +temperature conditions in which these animals live, necessitating strong +nutriment to enable their young to make proper progress in growth and +development. On the other hand, the milk of the ass is poor in quality, +and probably on this account it is more readily assimilated by those of +weak digestion, to whom it is sometimes recommended. Goats' milk is +richer than either cow or human milk, and its nourishing properties are +well known. The goat is usually free from tuberculosis and other +diseases which affect the cow, and its milk is therefore a very safe +article to use. + +_The Analysis of Milk._--While the analysis of milk can only be made by +a competent chemist, there are a number of simple tests and observations +by which any intelligent person can obtain a fair idea of its quality. +The taste and smell afford some guide, as also the general appearance. +To judge of the latter, place some of the milk in a tumbler or other +clear glass vessel. If the milk is of good quality it will be quite +homogeneous and opaque. Any flocculent matter indicates either disease +in the cow or that the milk is old and bacteria have multiplied in it +and altered its composition. When the milk has stood long enough for the +cream to rise freely, the latter should form a perfectly homogeneous and +strongly defined layer on the top. The quantity of cream may be measured +in a creamometer, which consists of a small glass cylinder graduated at +the top (Fig. 5). It is filled with milk to the top graduation line, and +when the cream has risen, the percentage quantity of the latter which +has separated can be taken off. + + [Illustration: FIG. 5. The Creamometer] + +The colour should be like that of porcelain, but, as already stated, it +is a common thing for the dairyman to add a small quantity of anatto or +an aniline dye of a similar shade, to give the milk a rich creamy tint. +If the milk is of a reddish colour this may be caused by blood from the +udder, although certain foods, such as beets, mangels, and carrots +sometimes give a similar tint. The milk given by cows immediately after +calving is called "colostrum" or "biestings," and is of a yellow or +yellow-brown colour. It is much thicker than ordinary milk, and +coagulates in boiling. + +In dirty byres in which care is not taken in milking, quite considerable +quantities of hairs, pieces of manure, and other filth may get into the +milk. Usually the milk is strained by the dairyman, but sometimes this +is omitted or carelessly done. To test for dirt, a ribbed glass funnel +is useful. Get a piece of the finest muslin about twice the diameter of +the funnel, fold over twice, so that it becomes one quarter of its +original size; open one of the sections and place in the funnel; pass +the milk into this. It will run through quickly and some water may be +run into the funnel to clear away the last traces of milk. The filter +cloth can then be opened out and any dirt retained will become visible. +The apparatus is shown in Fig. 6. + + [Illustration: TESTING-GLASS FOR EXTRANEOUS MATTER IN + MILK. + + FIG. 6.--A piece of muslin is folded as shown and a + measured quantity of milk is passed through the funnel; + from the sediment left in the muslin, the percentage of + extraneous matter may be arrived at.] + +If a glass funnel is not available, a very small jelly bag can be made +of fine gauze and used in the same way. The washing water should be used +in small quantities and directed to concentrating the dirt in the apex +of the bag. After washing, the latter can be turned outside in, to +permit of readier examination of the dirt. The bag should be well +washed in cold water, then boiled and dried, and is then ready for +future use. + +The acidity of milk is a very useful guide to its age. Milk has the +curious property of being "amphoteric," _i.e._, it is both slightly acid +and slightly alkaline when fresh. As its age increases, however, so does +its acidity, and at a rate varying with the temperature and moisture +contents of the atmosphere in which it is placed. Old and acid milk is +heavily contaminated with bacteria, a proportion of which are likely to +be injurious to health. + + [Illustration: FIG. 7. Lactometer and Test Tube] + +The simplest method of testing the acidity is to procure a few little +books of blue and red litmus test papers, and these can be had from any +philosophical instrument maker or laboratory furnisher. The strips of +test paper are torn out and dipped in the milk. When the milk is quite +fresh it will, owing to its amphoteric condition, change the red litmus +paper slightly blue, and the blue litmus paper slightly red. Old milk +changes blue litmus paper to a bright red because of its decided +acidity. + +The above tests do not indicate if the milk is poor or rich, but this +can be determined by the lactometer, an instrument for ascertaining in a +simple way the specific gravity. The lactometer is shown in Fig. 7. + +It is graduated usually from 25 deg. to 36 deg., corresponding to specific +gravities 1.029 to 1.038. It is graduated to degrees and half degrees. +Sometimes a thermometer is combined with the instrument. The specific +gravity rises as the temperature is lowered and decreases with increase +of temperature, so that it is important to make the test at the figure +at which the lactometer was graduated, which is usually 60 deg. F. Failing +this, an allowance has to be made for higher or lower temperatures. The +milk to be tested is well mixed, and placed in a deep vessel, and the +lactometer placed in it, holding it at first at an angle. It stands +upright and remains deeper or higher according to the specific gravity. +The reading is taken on the stem at the level of the milk. As the latter +is drawn up a little round the stem, about a half degree should be added +on to get the true figure. Thus, if the apparent reading is 31, the true +reading may be taken as 31.5. This is the average figure for good milk, +corresponding to a specific gravity of 1.0315; anything above this is +all to the good. Lower readings mean inferior quality, the latter being +proportionate to the lowness of the readings. The tests are most +conveniently made in a glass cylinder (Fig. 7), which may be purchased +with the lactometer. As there are many inaccurate instruments in the +market, it is necessary to go to a reputable maker, because an +unreliable lactometer is worse than useless. + +The following table gives, in a condensed form, the allowances to be +made when the temperature is above or below the standard (60 deg. F.): + + ------------+---------------------------------------------------------- + Temperature.| Reading of Lactometer. + ------------+------------------------------------------------------------ + Degs. F. | + 40 | 23.5 24.5 25.5 26.4 27.3 28.2 29.1 30.0 31.0 31.9 32.8 33.7 + 45 | 23.8 24.8 25.9 26.8 27.8 28.6 29.3 30.4 31.3 32.3 33.2 34.2 + 50 | 24.1 25.1 26.1 27.0 28.0 29.0 29.9 30.9 31.8 32.8 33.7 34.7 + 55 | 24.5 25.5 26.5 27.5 28.5 29.5 30.4 31.4 32.4 33.4 34.3 35.3 + ------------+------------------------------------------------------------ + 60 | 25.0 26.0 27.0 28.0 29.0 30.0 31.0 32.0 33.0 34.0 35.0 36.0 + ------------+------------------------------------------------------------ + 65 | 25.5 26.6 27.6 28.7 29.6 30.7 31.7 32.8 33.8 34.8 35.8 ... + 70 | 26.1 27.2 28.2 29.3 30.2 31.3 32.4 33.4 34.5 35.5 36.5 ... + 75 | 26.8 27.8 28.8 29.9 30.8 32.1 33.1 34.2 35.2 36.3 ... ... + 80 | 27.4 28.4 29.5 30.7 31.6 32.8 33.9 35.9 36.1 ... ... ... + ------------+------------------------------------------------------------ + +Thus if the thermometer indicates 40 deg. F., and the lactometer 29.1 deg., +the true reading at the standard temperature of 60 deg. F. is 31 deg., +corresponding to a specific gravity of 1.031. Intermediate figures can +readily be averaged. Care should be taken to wash the lactometer with cold +water under the tap, as otherwise the milk will dry on it and render it +inaccurate. + + + + +CHAPTER IV + +HANDLING OF MILK + + +MODERN DAIRY PRACTICE + +As we have seen, the dairy industry is a very ancient one, and has been +intimately associated with the development of civilisation. + +Within historical times dairying has always formed a prominent feature +in connection with agriculture, and the use of milk in one form or +another has been common to every civilised nation.[42] + +The greatest progress, however, in the study of milk has taken place +since about the year 1890, at which time the dairy industry seems to +have attracted the general attention of food specialists and scientific +investigators throughout the world. Since then it has been considered +worth while to enact laws in different countries with regard to the +regulation and control of the milk supply. + +Since 1903 there has been an International Dairy Federation formed, and +it has held conferences at Brussels, Paris, The Hague, and Buda-Pest, +and in 1911 it will hold a conference in Stockholm. The Federation was +started in a very humble way in Brussels, and owes its origin, to a +large extent, to a distinguished Belgian agriculturist, Baron Peers of +Oostcamp, Bruges; but at the present day a general committee composed of +representatives of nearly every civilised nation has been formed, and +delegates from such countries attend the Congresses, which are held +every two years. The literature which has arisen out of these +International Congresses has been disseminated in different countries, +and has been instrumental in placing the dairy industry on a thoroughly +scientific basis. + +_Milk Supply of the United Kingdom._--The milk supply of the United +Kingdom has steadily grown from year to year, and in relation to the +population works out at fifteen gallons per head. The manner in which +these figures are arrived at is shown in the following estimate: + + The population of the United Kingdom is now about + 45,500,000. The number of cows or heifers in calf or in + milk in June, 1909, was 3,360,600; the number in 1910 was + probably about 4,400,000. + + Of these about 300,000 were heifers that had not yet + produced any milk. The actual milking class, therefore, + comprised about 4,100,000 cows and heifers; of these, + about 600,000 were heifers that calved in the winter and + spring of 1909-10, and 300,000 were heifers that calved in + the summer and autumn of 1910. The number of cows that + produced two or more calves may be taken to be about + 3,200,000; of these about 600,000 should have produced + their second calf in the winter and spring 1909-10, and + would be milked as heifers in the summer and autumn of + 1910; the number of mature cows from which a full season's + supply of milk was obtained during the twelve months from + June 5, 1909, to June 4, 1910, was apparently about + 2,600,000. A large quantity of milk is yielded during the + year by cows sold or lost during the twelve months before + the census. Possibly ten per cent. of the milk produced in + the twelve months from June, 1909, to June, 1910, was + yielded by cows that were sold or lost before the census + of June, 1910. + + It is estimated that the 3,200,000 cows (including the + 600,000 that up to the winter of 1909-10 were heifers) + produced, on the average, 44 cwts. (480 gallons) of milk + per head in the twelve months from June 5, 1909, to June + 4, 1910; the 300,000 heifers that calved in the summer and + autumn, 30 cwts. (330 gallons) per head; the 600,000 + heifers that calved in the winter and spring of 1909-10, + 15 cwts. (165 gallons), making the total quantity of milk + produced in the twelve months by cows and heifers on the + farms, and that produced calves during the twelve months + (June, 1909-1910), 158,800,000 cwts. (1,746,800,000 + gallons), or about 426 gallons per head, and about 400 + gallons per head for all the cows and heifers in milk or + in calf in 1910. There remains to add the milk yielded by + the cows that were sold during the twelve months, and of + cows and heifers in feeding pastures that were milked + during the twelve months, June to June, 1909-10, and which + probably formed one tenth of the whole supply, making the + total supply for the twelve months 176,444,000 cwts., or + 1,940,884,000 gallons. This equals 2 tons, or 440 gallons + per head, crediting the whole supply to the 4,400,000 cows + and heifers in milk or in calf in June, 1910. At 7-1/4d. + per gallon the value of milk produced in the United + Kingdom in the twelve months was L58,600,000. Including + the value at birth of the calves, the total value of the + produce of the milk-giving class would be about + L62,000,000. The value of the milk, butter, cheese, and + cream sold or consumed in farmhouses would be about + L48,000,000, or equal to about 24 per cent. of the gross + annual income of farmers. + + The average consumption of new milk is about 15 gallons + per head of the population. During the twelve months of + 1911, the quantity required for this purpose will be about + 682,500,000 gallons, or about 35 per cent. of the total + supply; calves will require about 10 per cent. of the + supply; the quantity available for butter and cheese will + equal about 55 per cent. of the supply.[43] + +_The Milk Industry in the United States._--In the United States of +America, where the habits of the people are somewhat analogous to those +in the United Kingdom, it is estimated that the milk from five million +cows is annually consumed, which averages twenty-five and one half +gallons per year for each person, or equal to an ordinary sized +tumblerful each day.[44] + +Such a vast industry, so intimately associated with the food of the bulk +of the people, naturally invites the closest study, and, as a +consequence, the literature on the subject, which has arisen during the +last twenty years, has been of a voluminous character, not only from the +point of view of practice, but from that of bacteriology, chemistry, and +hygiene. + +A pure milk supply is essential to health, and it seems unfortunate that +the ordinary milk producer should, in a great many cases, take up an +antagonistic attitude to the scientific methods of handling milk. There +is a body of opinion being created, however, which is likely to alter +this attitude in the next generation, and this is attributable to the +fact that so much excellent work has been done at numerous dairy +colleges and institutes in all civilised countries that the dairy +industry is emerging from a period of rule-of-thumb procedure to its +proper place as one of the technical arts. + +_Transmission of Disease in Milk._--It is not to be wondered at that the +handling of milk should now be regarded as a technical business, seeing +that milk-borne disease is one of the commonest with which we have to +deal. + +The commoner diseases which have been transmitted by milk are scarlet +fever, typhoid, diphtheria, tuberculosis, sore throat epidemics. Others +of a more complex character have been traced to the same source of +infection, and the clearest possible evidence has been furnished of the +transmission of diseases by means of micro-organisms, which have +contaminated the milk supply. + +It is therefore necessary to watch over the milk from the source of +supply to its consumption. It is primarily on the farm and in the +cow-house that methods of handling in a hygienic way should be insisted +on, as microbial contamination increases at a prodigious rate, and it is +the early microbe therefore which does the most damage. + +The milk in the udder, for all practical purposes, may be assumed to be +sterile, and the contamination which takes place originates, therefore, +from external sources. + +One of the principal means of infection is from hairs which fall from +the cow into the milk, and many of which are carriers of dangerous +micro-organisms. + +There is also a certain amount of offensive dirty matter which may fall +into the milk-pail, and carry with it undesirable germs. + +These impurities may, to a certain extent, be eliminated by good +straining, but a surer prevention is to have the cow-house perfectly +clean and free from dust, as dust specks are in many cases the vehicles +of disease germs. Cleanliness is, in fact, the essential feature in +modern dairying, not only in the cow-house, but in the milking utensils, +the drainage, etc., and, above all, the milker should be of cleanly +habits. + +The flavours of milk sometimes arise from the absorption of +evil-smelling gases in the cow-house, or from a peculiar taint from +certain roots and feeding stuffs, and in such a case it is desirable +that aeration should take place in a fresh clear atmosphere, so that +oxygenation may have the effect of eliminating and destroying the +foreign odours and flavours which may be present. If this process of +aeration is carried out at blood heat, the result is generally highly +satisfactory. + +_Milk Management._--There have been many excellent tables of rules +published for the management of dairies in different countries, but they +are necessarily framed within certain limitations which apply to all. +The following is an excellent set, which put concisely the conditions +necessary to be observed in the modern cow-house: + + 1. The cow should be sound--no disease should exist in + the animal. + + 2. The feed should be good and free from aromatic + substances. If these aromatic foods are used, they should + be employed according to those methods which will not + cause odours or flavours to appear in the milk. + + 3. The cow should be groomed, and hair about the udder + preferably clipped. + + 4. The udder should be moistened during milking. + + 5. The milker should be a neat, tidy person. + + 6. The milker should be free from disease, and should not + come in contact with any communicable disease. + + 7. The milker's clothes and hands should be clean while + milking. + + 8. The pail should be sterilised. + + 9. The stall should be such as to reduce the amount of + disturbance of dust and dirt. + + 10. There should be good light, good ventilation, and + good drainage in the cow-house. + + 11. The cow-house should always be kept clean. + + 12. Feeding and bedding, unless moist, should be done + after milking. + + 13. A dustless milking-room is desirable. + + 14. Milk should not stand in the cow-house. + + 15. If milk is aerated, it should be done before cooling + and in pure air. + + 16. The sooner the milk is cooled after milking the + better. + + 17. Keep the milk as cold as possible when once + cooled.[45] + +The supply of milk is conducted, to a large extent, by towns' dairies, +which depend for their supplies upon the dairy farm in the country, and +it is obvious that a certain period of time must elapse, in the +generality of cases, before a town's dairy receives its supply in the +ordinary course, and this constitutes the greatest difficulty in modern +dairy practice, owing to the liability of the milk to absorb bacteria, +which during transit may multiply enormously. + +The multiplying of bacteria in milk at different temperatures is easily +demonstrated, and the result of this has been stated in various forms +many times over. As a graphic means, however, of showing the increase +that takes place in the numbers of germs present, and the consequent +product of acidity, the table below by Conn may be given. + +The consequent result of the increase in bacteria is the production of +lactic acid, which produces the souring so familiar in milk which has +been kept in the household at a high temperature. + + _Numbers of Bacteria per c.cm. in Milk kept at + Different Temperatures._ + + -------------------------------------------------------------------------- + Number In 12 In 12 In 50 In 50 hrs. or at No. hrs. No. hrs. + at hrs. at hrs. at hrs. at time of curdling to curdle to curdle + Outset 50deg.F. 70deg.F. 50deg.F. at 70deg.F. at 50deg.F. at 70deg.F. + -------------------------------------------------------------------------- + 46,000 39,000 249,500 1,500,000 542,000,000 190 56 + 47,000 44,800 360,000 127,500 792,000,000.36 hrs. 289 36 + 50,000 35,000 800,000 160,000 2,560,000,000.42 hrs. 172 42 + -------------------------------------------------------------------------- + +What actually happens is that the lactic acid is produced by the +breaking up of the milk sugar, and the appearance of this sourness is an +indication that a period has been reached in the age of the milk which +may be described as being--unwholesome.[46] + +It is necessary, therefore, for the town's milk dairy to be equipped in +such a way as to deal promptly with the milk supply. + +We have seen that the milk should first of all be aerated at blood heat, +so as to liberate objectionable odours, after which it should be cooled +to as low a temperature as possible, by means of well water. When these +operations have been performed on the farm, milk should be sent as +rapidly as possible to the distributing towns' dairies, and should be +transported in refrigerated waggons, cooled preferably with ice, during +the journey. On arrival at the town dairy, it will be necessary to +pasteurise the milk--that is to say, the milk should be heated to such a +temperature as will destroy any pathogenic organisms which may be +present, and the pasteurising temperature should therefore be in excess +of the thermal death-point of all such organisms. + +Pasteurisation owes its origin to Pasteur, and has become an adopted +method throughout the dairy industry, and there are many mechanical +devices termed "pasteurisers" (see Fig. 8) which are used for the +carrying out of this particular operation. The form of one of these is +that of a vertical jacketed cylinder with paraboloidal surface, around +which steam is made to pass, so as to maintain the temperature at about +176 deg. F. Milk is allowed to flow in at the bottom of the paraboloidal +surface, and is caught by mechanical agitating arms, which revolve at a +given speed, and by this action milk is distributed centrifugally over +the paraboloidal surface, and is forced out by the same action, at the +top of the apparatus, after being heated. + + [Illustration: PASTEURISER + + FIG. 8.--The milk enters from the bottom and circulates to + the top of the inside cylinder, which is paraboloidal in + construction. It is heated as it passes through the + apparatus, and is discharged at the top at a temperature + of 176 deg. F.] + +The centrifugal action is sufficient to raise the milk some three to +four feet, through a tube, and this is taken advantage of so as to cause +the milk to flow over a conical cooler, described as a primary cooler, +and in which water is made to circulate. As the hot milk descends over +the conical cooler it gives up most of its acquired heat to the water, +and, in practice, is reduced in temperature to within 4 deg. of the +temperature of the water. + +Below this primary cooler is fixed a cooler of the same size and shape, +which is termed a secondary cooler. In it, brine at a temperature of +about 35 deg. F. is circulated from a refrigerating machine, and, as the +milk falls over the secondary cooler, it is cooled to a temperature of +about 40 deg. F., when it may be looked upon as being pasteurised and free +from all pathogenic organisms, in which state it will keep for a +considerable length of time. + +It is desirable that the milk should, as soon as possible after the +cooling takes place, be delivered to the consumers, and be kept under +cool conditions, either in bottles or in a closed vessel covered over +with muslin, so as to keep out specks of germ-laden dust. + +Briefly speaking, the foregoing is an outline of what is carried on in +the ordinary dairy practice. + +There are many modifications of this practice, such as the introduction +of regenerative heaters, so as to utilise a portion of the heat of +pasteurisation, which would otherwise be wasted. + +In some cases, again, it is considered necessary to conduct the primary +and secondary cooling over coolers furnished with mantles, so that the +atmospheric bacteria which are everywhere present should be shut off +from the falling milk. + +Ordinarily, however, the equipment for a town's dairy consists of: + +1. Steam-boiler to generate steam for pasteurising, scalding, etc. + +2. Motive power, which may be either a steam-engine, gas-engine, or +electric motor. + +3. Refrigerating machine, which is used for supplying cold brine to the +secondary cooler. In many cases it is also used for cooling a room in +which the milk and cream are stored. + +4. Milk-receiving tank. + +5. Milk-strainer. + +6. Pasteurising apparatus, and primary and secondary coolers. + +Such a plant is necessary in order to conduct an ordinary town dairy +business in anything like a hygienic way, and is designed only for the +handling of milk intended for domestic consumption. + +There are times when another plant might be necessary, such as a plant +for the separation of milk, or for utilising it for the production of +butter or cheese, such operations being subject to the fluctuations in +the milk supply. + +It is sometimes desirable also to use up an excess of milk for cheese or +butter-making; hence it is necessary to provide such apparatus as has +been indicated. + +_Preparation of Soured Milk._--The foregoing description has been given +in some detail, as showing the ordinary practice, and we now come to +consider how it can be modified so as to provide for the production of +soured milk. It may first of all be premised that within the next few +years the preparation of soured milk as an ordinary production of the +dairy will be universal, and will form a part of the ordinary dairy +practice. The apparatus, therefore, which is necessary is one of +considerable interest to all who are engaged in the dairy industry. + +As will be seen from the chapter describing the preparation of soured +milk in the dairy, this process can be conveniently carried on, so as to +utilise the plant which is at present in general use. The milk can be +received in the same way, pasteurised and cooled to about blood-heat, +after which its preparation as soured milk is a very simple matter, and +only requires a certain amount of careful attention. + +For the keeping of soured milk, a cold room cooled by a refrigerating +machine would be desirable, so as to maintain the fermented milk at a +low temperature and prevent over-fermentation. + +Apparatus has been designed so as to handle soured milk on a large +scale, and one of the machines is shown on the illustration (see Fig. +9). It is simply a jacketed cylinder with a cover and an agitating gear. +The inside of the machine is nickel-plated, and there is an arrangement +whereby the cooling may be done rapidly, through a coil inside the +jacket, this coil being connected to the brine circulation of the +refrigerating machine. + + [Illustration: CONTINUOUS APPARATUS FOR THE PRODUCTION OF + LARGE QUANTITIES OF SOURED MILK + + FIG. 9--This apparatus is made by the Dairy Machinery and + Construction Company of Shelton, Conn., U S A. The milk is + agitated inside a jacketed cylinder, where it is allowed + to incubate at about blood heat. The milk can be rapidly + heated and also rapidly cooled by means of this + apparatus.] + +The machine is filled with milk containing three per cent. of fat, which +has been previously pasteurised to about 190 deg. F., and cooled down to +about 90 deg. F.; at this point the pure culture of _Bacillus bulgaricus_ +is introduced, and the agitator is kept working, so as to mingle it +thoroughly with the milk. The agitator is then stopped until the acidity +shows a test of 0.9 to 1.0 per cent., when the agitator is again +started, and cold brine from the refrigerating machine is turned on to +the cooling pipes, so that the product is thoroughly broken up, and +cooled down to 40 deg. F. + +The milk is then transferred to a bottle-filling machine (Fig. 10), +poured into bottles and hermetically sealed, after which it is ready for +consumption. When it has to be kept for any time it should be placed +in a cold room where there is a temperature not higher than 40 deg. F. + +The process, therefore, is a simple one, and lends itself to the +ordinary dairy business, without involving any great expenditure on +account of a new plant. + + + + +CHAPTER V + +THE BACTERIOLOGY OF FERMENTED OR SOURED MILK + + +A CHAPTER FOR STUDENTS + +During the last few years much work has been done in investigating the +action of various classes of organisms--bacteria, yeasts, and +moulds--upon milk and its products. While, however, the attention of the +dairyman has been chiefly directed to the propagation of acid-producing +organisms and the use of pure cultures of lactic acid bacteria in their +relation to butter and cheese making, a new sphere in micro-biology has +been disclosed by the study of the effects caused by the combined growth +of two or more different classes of organisms in milk and the consequent +production of lactic, alcoholic, and gaseous fermentations. The +simultaneous occurrence of these fermentative changes is responsible for +the formation of such beverages as keffir, koumiss, milk-wine, etc. It +has therefore become essential, in connection with the study of new +developments in the milk industry, that we should make a more intimate +acquaintance with the bacteriology of the ferments involved. + +_Keffir_ (_kephir_, _kifyr_, _kiafyr_, _kephor_, _kyppe_) is the name +given to an acid, slightly alcoholic drink, which for many centuries has +been prepared by the nomadic tribes in the Caucasus. The characteristic +fermentation is induced by the addition of so-called keffir grains. +These are yellow or golden-yellow, warty, and furrowed flakes or +nodules, the former varying in size from that of a rice grain to that of +a bean, while the latter are often about an inch across and one eighth +of an inch thick. Bearing in mind the fact that the preparation of +keffir has been carried on for many centuries, it is not surprising that +the origin of these grains should be surrounded by myths. + +The belief is prevalent among the Mohammedan tribes of the Caucasus that +keffir grains were, in the first instance, presented by Allah, as a sign +of immortality, to one preferred tribe. Others hold that, in past ages, +they were found by shepherds growing on a shrub in the Caucasian +highlands; while, according to Skolotowski,[47] they were originally +found adhering to the walls of an oaken vessel used for the preparation +of airam. This is a soured milk beverage similar to keffir, but +possessing a weaker alcoholic fermentation, and prepared from goats' +milk by the addition of pieces of calf's stomach. This would undoubtedly +serve to introduce various species of lactic acid bacteria, and will be +referred to in the portion dealing with soured milks. Keffir is prepared +by the Caucasians from cows', sheep's, or goats' milk, and the operation +is carried on in large leathern tubes or bottles. After the addition of +the grains or seeds to the milk the vessel is placed in a cool chamber, +and the fermentation is allowed to proceed for one or two days, by the +end of which time the normal fermentation is at an end. During this +period the keffir grains have increased enormously in size, assume a +bright yellow colour, and lose their sour buttery smell. + +Previous to the removal of the fermented liquid, a portion of the bottle +is firmly bound from the rest by a stout cord, and the greater portion +of the remaining keffir is quickly removed for use, thus avoiding, as +far as practicable, any outside infection. After the addition of fresh +warm milk the cord round the end of the bottle is removed, and the old +and new milk thoroughly mixed for a time in order to ensure uniform +inoculation of the new milk for the next fermentation. During the winter +months the leathern vessels are often placed in the sunshine, so that +the temperature remains at 61 deg. to 65 deg. F. + +The necessary agitation of the vessel is said to be supplied in the form +of kicks by passers-by or by the children during their play. + +The beverage prepared in this way is so gaseous in character that it is +often blown forcibly from the vessel during removal, and possesses, +according to Podowyssozki,[48] a very acid taste. + +During any interruption in the preparation of keffir in the above +manner, the grains are taken out, and after having been well washed in +clean water, are spread out on a clean cloth to dry in the sunshine. +They thereby assume a characteristic cheesy or buttery odour and become +rather darker in colour. Thorough desiccation is essential in order to +prevent subsequent mouldiness or disease of the grain. + +In European countries the grains are subjected to a preliminary soaking +in water for five to six hours and then placed in four to five changes +of milk, each change having a duration of two to three hours. As soon as +the grains commence to rise to the surface of the milk, they may be used +for the actual preparation. To this end, a small quantity of the grain +is added to freshly boiled milk and allowed to stand for eight to twelve +hours at a temperature of 55 deg.-62 deg. F. with agitation of the flask +every two hours. By this time the milk, now known as Sakwaska, has become +abundantly inoculated with the organisms essential to the fermentation, +and after the removal of the grains, may be poured into well-corked +flasks for the secondary brew. The flasks should be kept at a lower +temperature for twenty-four to forty-eight hours, by which time the +product is ready for consumption. + +According to the temperature and length of period to which this +subsequent fermentation is allowed to proceed, the resultant keffir is +more or less acid and gaseous. The grains may again be used for starting +a fresh portion of milk, and a regular supply obtained in this manner. +Well-fermented forty-eight-hours-old keffir should be an effervescent +beverage with prickling and acid taste and a consistency and smell +similar to sour cream. Large, persistent bubbles should form on the +surface of the liquid and the casein be present as an extremely fine +flocculent precipitate which remains suspended for a considerable time. + +From the third day there ensues a gradual peptonisation of the casein. +If the temperature at which the secondary fermentation has occurred +should be higher than 72 deg. F., or if the milk has not been sufficiently +agitated, then the casein will be present in the form of porous small +flakes, which on shaking form a fine emulsion. + +The chemical changes undergone by the milk during the preparation of +keffir are confined almost exclusively to the milk sugar. As already +stated, a slight peptonisation occurs in old samples, but this depends +very largely upon the method of preparation and purity of the culture. +Hammersten[49] and Essaulow[50] show, however, that this is not a +concomitant of normal fermentation. According to Hammersten, normal +keffir contains-- + + Per cent. + Water 88.26 + Fat 3.35 + Casein 2.98 + Lactalbumen 0.28 + Peptones 0.05 + Milk sugar 2.78 + Lactic acid 0.81 + Alcohol 0.70 + Ash 0.79 + +In no case should the acid be higher than 1.0 per cent., and the alcohol +more than 0.75 per cent. + +_Biology of the Keffir Grain._--The first communication on the biology +of the keffir grain seems to have been made by Kern.[51] He regarded the +grain as a zoogloea composed of bacilli and yeasts, the latter being +regarded as the ordinary beer yeast (_Saccharomyces cerevisseae_), while +to the former he gave the name of _Dispora caucasica_. As the name +indicates, this bacillus possesses two polar spores, and germination of +these proceeded in the same manner as with _Bac. subtilis_. As, however, +pure cultures of the organisms were not made, and the descriptions and +illustrations made by Kern fail to show any distinctive characteristics, +it seems probable that accidental confusion with other organisms must +have occurred. + + [Illustration: A MILK FILLING APPARATUS + + FIG. 10--Where soured milk is handled on the large scale, + a special filling apparatus for bottles is desirable, and + the soured milk supply should be under cover as shown. + This apparatus is made by the Dairy Machinery and + Construction Company.] + +Krannhals[52] succeeded in isolating ten different keffir bacteria among +which were several sporulating bacteria. Here too it is impossible to +attach any importance to the results, as the artificial preparation of +keffir, by means of these bacteria, was not attempted. Beijerinck[53] +studied the organisms constituting keffir grains and attached prime +importance to the occurrence of two organisms, viz., (_a_) a yeast, +_Saccharomyces kefir_, which was capable of inverting milk sugar by +means of an enzyme (lactase) and afterwards fermented the products with +the formation of alcohol and carbon dioxide, and also (_b_) a non-motile +non-sporulating bacterium, afterwards _Lactobac. caucasicus_. The +latter, when cultivated on gelatine, gave rise to tough warty colonies +about 1/40 in. diameter, and was regarded as one of the lactic acid +bacteria found in milk which has been incubated at 77 deg. to 90 deg. F. +and afterwards incubated at a higher temperature, 100 deg. to 104 deg. F. +Scholl[54] isolated three different organisms, of which a yeast inverted +milk sugar for the lactic acid bacteria, while _Dispora_ peptonised the +albuminoid matters. + +Adametz[55] failed to isolate _Dispora_, and came to the conclusion +that ordinary lactic bacteria and yeasts played the most important part +in the fermentation. + +Essaulow found in keffir grains six different organisms--yeast cells, +cocci, short thick bacilli, bent bacilli, long threads, and motile +bacteria. The two latter would seem to be _Bacillus subtilis_, while the +others may be regarded as _Bacterium acidi lactici_ (Hueppe), _Bacterium +aerogenes_, and _Streptococcus lacticus_ (Grotenfeldt). Pure cultures +were insufficient to produce keffir, while mixed cultures of _Bacterium +acidi lactici_ and yeasts were effective. + +Freudenreich,[56] to whom we owe a record of very carefully executed +experiments, could not arrive at a satisfactory explanation of the role +of _Bacillus caucasicus_. This organism is described as being 5-6 mu long +and 1 mu thick, slightly motile, and possessing bright refractive spots +at the poles of the bacilli. It is extremely difficult to cultivate, and +forms flat, small greyish colonies of irregular outline. The bright +refractive spots above referred to are, however, granules taking the +usual stains quite readily, and not spores as supposed by Kern. + +Freudenreich also found three other organisms--a yeast and two +streptococci. The yeast, to which he gave the name _Saccharomyces_ +(Torula) _keffir_, forms small oval or roundish cells 2-3 mu wide and 3-5 + mu long. The optimum temperature would seem to be about 72 deg. F.; the +maximum 82 deg. F. This organism is unable to ferment milk directly, but is +able to decompose maltose and glucose with gas production. It does not +coagulate milk, but imparts to it a characteristic taste and is unable +to withstand desiccation for more than a few days. + +Of the two streptococci isolated, _Streptococcus a_ resembles organisms +of the group _Streptococcus lacticus_ in appearance, but is able to +ferment milk, with weak acid and gas production, and is capable of +inducing coagulation. + + [Illustration: FIG. 11.--Section through a Kephir + Grain--highly magnified.] + +Contrary to what one would expect in an organism existing in keffir +grains, this streptococcus is as little able to withstand desiccation as +the above-mentioned yeast. _Streptococcus b_ forms smaller cells as well +as smaller colonies than _Streptococcus a_, but produces more lactic +acid and more gas, and retains its vitality after desiccation. The +relation of these four organisms is, according to E. von Freudenreich, +as follows: _Sacch. keffir_ is unable to ferment directly milk or +lactose, so that its growth must be preceded by that of _Streptococcus +b_. _Streptococcus a_ does not seem to play this part, but, unlike +_Streptococcus b_, is able to coagulate milk on its own account. By the +combined action of the yeast and the two streptococci, then, milk can be +coagulated, milk sugar inverted, acid and gas produced by the +streptococci, while gas and alcohol are formed by the activity of the +yeast. The role of _Bacillus caucasicus_ is unknown, but it would seem +to play a part in the formation of the keffir grain itself. By means of +mixed cultures of the above organisms Freudenreich was successful in +obtaining a fermented product possessing in all respects the +characteristic properties of normal keffir. On the other hand, +experiments to induce the formation of keffir grains gave negative +results, but in this respect the cultural characteristics of +_Lactobacillus keffir_ would seem to give promise of success in the +synthesis of the keffir grain. Fig. 11 is a photo-micrograph of an +extremely thin section through a keffir grain, after a preceding +treatment with saffranin. The matrix is composed entirely of long thin +bacilli (_Bacillus caucasicus_), while the peripheral portions, which +are more deeply stained, consist to a large extent of dense masses of +yeast cells with occasional streptococci. In a normal grain the latter +organisms are present on the surface or in the cavities and grooves of +the grain, and only to a less extent in the matrix. Nikolaiewa[57] +claimed to have isolated a hitherto unknown bacillus capable of +coagulating milk by acid production, _Bacterium caucasicum_, not +identical with, but related to Freudenreich's _Bacillus caucasicus_, and +also a torula. Although no experiments were carried out, Nikolaiewa +asserts that this organism forms the matrix of the grains. He was able +to produce a beverage resembling keffir, just as Freudenreich and +Essaulow did with entirely different organisms, but his product would +appear to have been slightly too acid and to have lacked the +characteristic aroma of the normal product. In the course of an +extensive series of experiments Kuntze[58] found the following +organisms: + + (_a_) True lactic acid forming bacteria, _Streptococcus + acidi lactici_ (Grotenfeldt). + + (_b_) Bacteria of the group _Bacterium acidi lactici_ + (Hueppe) and _Bacterium lactis aerogenes_. + + (_c_) Various torula and yeast species. + + (_d_) Two species of butyric acid bacteria, _Bacillus + esterificans_ and _Bacillus keffir_ (Kuntze). + +His conclusions are: 1. In any case the presence of a yeast capable of +directly fermenting milk sugar is not essential. 2. The significance of +the presence of yeast lies in the fact that stimulation of the lactic +bacteria occurs; further, the yeast exerts a regulating influence upon +the rapidity of the fermentation proper. The variety is of minor +importance, provided always that the yeast does not produce an +unpleasant flavour. By the use of mixed cultures of _Bacillus +esterificans_, _Bacillus keffir_, and _Streptococcus acidi lactici_, and +a keffir yeast, Kuntze obtained a product that possessed to the fullest +degree all the characteristic properties of a normal keffir. In such +cultures he was successful in obtaining the formation of keffir-like +grains. Keffir fermentation is, according to Kuntze, the result of the +action of various organisms. During the initial stage butyric acid +fermentation takes place, but is prevented from becoming predominant by +the action of the keffir yeast. Simultaneously a true lactic acid +fermentation proceeds and eventually gives place to a subsequent +secondary production of butyric acid. Finally, then, we have a certain +amount of unison in the results obtained by Freudenreich, Essaulow, +Nikolaiewa, and Kuntze. These show that, for the production of a +characteristic keffir, specific organisms are not essential, provided +always that those used possess, either individually or collectively, the +essential capacity of acidifying, coagulating, and fermenting the milk. +For the growth of normal grains the presence of a matrix-forming +organism, such as _Bacillus keffir_, is indispensable. + + [Illustration: FIG. 12--_Streptococcus lacticus_ + (Grotenfeldt) growing on lactose-agar, stained by Gram's + method. ( X 900 diams.)] + +_Diseases of Keffir Grains._--According to the age and the previous +treatment to which keffir grains have been subjected, the vitality of +one or more of the organisms constituting the grain may have been +impaired. The results of Freudenreich have shown that _Saccharomyces +keffir_ and _Streptococcus a_ are unable to withstand desiccation for +more than a few days, and this is sufficient to account for the frequent +failures to obtain normal keffir from the grain. Further, grains succumb +to a mucilaginous disease; the cavities become filled with a slimy +fluid, and the grains are covered with mucilaginous matter. They lose +their elasticity and become brittle or mealy, but large grains appear to +be more subject to this fault than do the small ones. Such grains +should be disinfected by immersion for a short time in two per cent. +salicylic acid solution, followed by drying in the sun, whereby they are +completely regenerated. + +Another disease consists in the predominance of certain butyric acid +bacteria which impart an unpleasant rancid taste to the keffir +(Podowyssozki). This is generally attributed to the use of rich milk, or +too high a temperature during preparation. + +_Koumiss._--Another product of the combined action of lactic acid and +alcohol-producing organisms is called koumiss, kumys, milk-wine, lac +fermentation, or vinum lactis. In the steppes of Southern Russia and +Asia, as we have seen,[59] it is prepared chiefly from mares' milk, but +occasionally from that of camels and jennets. The name is said to be +derived from that of a tribe mentioned by Xenophon and Pliny, viz., the +Kumanen, by whom its preparation was practised. After the war with the +Tartars in 1215 its use was adopted by the latter people, and eventually +spread to the Turkomanen, Kalmucks, Khirgiz, Mongolians, etc. + +Rubruck, in 1253, records the use of a fermented drink--kosmos--prepared +from mares' milk, and about the same time Marco Polo mentions the +occurrence of a milk-wine, chumis or chemius, among the Tartars. The +fact that the Tartars were seldom ill, and were almost invariably free +from lung troubles, led to an influx of visitors from surrounding +countries, until finally its use spread to Russia, Austria, and Germany. +At the present time the best koumiss is that produced in the province of +Orenburg; but specially equipped koumiss establishments, under the +control of physicians, exist in Odessa, Samara, Ufa in the Urals, and +other districts. The curative properties of koumiss have long been +recognised and its use is indicated in cases of indigestion, chlorosis, +scurvy, tuberculosis, etc. + +Rubinsky states that, among the nomadic tribe, of Khirgiz and Kalmucks, +a special leathern bottle (Turssuk, Orroth, or Soaba) is used for the +preparation of koumiss, while wooden tubs (Tschiljak) similar in shape +to the old-fashioned churn are used by the Bashkirs, and in koumiss +establishments. + +The fermentation is induced by the addition of koumiss to fresh mares' +milk, in proportions which vary according to the cleanliness observed in +the actual preparation. Where the process is carefully controlled, one +part of koumiss to ten parts of milk is often used, but where gross +infection from outside sources takes place one part of koumiss to three +parts of milk is taken. The mixture is stirred at frequent intervals, +and stored at a temperature of 73 deg.-90 deg. F. Weak koumiss is obtained +after twenty to twenty-four hours in winter and twelve to fourteen hours in +summer, but is scarcely ever consumed immediately, as it possesses a +strong purgative action. + +It is generally poured into bottles (bottled koumiss); or allowed to +remain in the tubs (tschiljak koumiss); in the former case the +fermentation is anaerobic, in the second it is aerobic. + +Storage of the koumiss upon ice or in a cellar is necessary since medium +koumiss is converted to strong koumiss in twelve to sixteen hours at +ordinary temperatures, while at the lower temperature this occurs only +in two to four days.[60] + +According to Biel,[61] either old koumiss or the dried sediment from old +koumiss may be used for the initial inoculation. It may also be prepared +by the repeated inoculation of mares' milk with soured cows' milk until +a fermenting product is obtained. Koumiss may be prepared by a method +stated by Allik[62] to be in general use in the Caucasian +health-resorts. One part of beer-yeast is added to four to ten parts of +fresh mares' milk (according to the strength of product required), and +after thorough mixture of the two liquids the whole is allowed to +ferment at a temperature of 70 deg. to 72 deg. F. for two days. One part of +this first product is then added to five parts of fresh cold milk, and +allowed to stand three to four hours at 75 deg. to 77 deg. F. It is then +poured into bottles, and after the expiration of another three to four +hours is stored away in a cellar at about 45 deg. F. This koumiss may be +used at any time from one to five days (generally two to three) after +bottling according to the strength desired or prescribed in each +individual case. + +The changes undergone during fermentation consist in a vigorous gas and +acid production accompanied by alcohol formation and coagulation of the +milk. The coagulum exists in an extremely fine state of division, and +the liquid froths violently on the bottle being opened. It has a full +pleasant acid taste, but should not contain more than one per cent. acid +and two per cent. alcohol. The specific gravity of koumiss is 1.008 to +1.020 at 60 deg. F. Appended is an analysis of two different samples of +koumiss: + + --------------------------------------------------- + Prepared from + --------------------------------------------------- + Mares' Milk. Separated + Cows' Milk. + --------------------------------------------------- + Per Cent. Per Cent. + Water 91.535 88.933 + Fat 1.274 0.854 + Nitrogenous bodies 1.913 2.025 + Sugar 1.253 3.108 + Ash 0.293 0.444 + Carbon dioxide 0.876 1.027 + Alcohol 1.850 2.647 + Lactic acid 1.006 0.796 + Glycerine .... 0.166 + --------------------------------------------------- + +Fleischmann[63] gives a formula for preparing an artificial koumiss from +separated cows' milk, water, cane sugar, and milk sugar, with the +addition of distillery yeast. Needless to say, this product must possess +some of the characteristic by-flavour of the yeast employed, and is less +suitable than koumiss prepared by the aid of a lactic yeast. Schipin +investigated the fermentation of koumiss and found three distinct +organisms. + +Rubinsky in a recent article threw much light on the phenomena of +koumiss fermentation. According to him, koumiss contains almost +invariably four different organisms, viz., koumiss yeast, koumiss +bacterium (_Lactobacillus_), _Streptococcus lactis_ (Lister), _Bacterium +aerogenes_, and occasionally _Bact. caucasicum_ (Nikolajewa). For the +preparation of normal koumiss only the two former organisms are +required; they exceed in number any of the other organisms whose +presence in the dairy is unavoidable. The presence of the two latter +organisms is favourable to the production of good koumiss, as, by +inducing a preliminary lactic fermentation, they tend to inhibit the +growth of undesirable extraneous bacteria, etc. In medium and strong +koumiss they die out on account of the amount of lactic acid formed +(1%). + +Koumiss yeast possesses strongly differentiated protoplasm, but lacks +any cultural characteristics. Abundant growth occurs in milk, and lactic +acid (0.3%), alcohol, carbon dioxide, albumens and peptones, volatile +acids, and aromatic substances are formed. + +Koumiss bacterium is related to the _Lactobacillus_ of various other +fermented milks, and is similar to _Bac. acidophilus_, and possesses +like these a distinct polymorphism (branched cells, long and short +bacilli, etc.). It is non-sporogenous, has an optimum temperature of 90 +deg. to 97 deg. F., and possesses cultural characteristics similar to +those of the rest of the _Lactobacilli_. + +The by-products of koumiss yeast appear to favour the growth of the +koumiss bacterium, as this organism, like the other _Lactobacilli_, is +favourably influenced by the presence of small quantities of peptone, +alcohol, and acid. + +The organisms found by Schipin consisted of a species of _Saccharomyces_ +and two bacilli, _Bacillus acidi lactici_ and a non-sporulating +bacillus. The latter organisms coagulate milk at 98 deg. F., but not at +room temperature, and although a minute description of cultural +characteristics is not given it would seem to be related to _Bacillus_ +or _Lactobacillus caucasicus_. + +_Leben Raib_ or _Leben_ (_Laban._)--This is a beverage prepared largely +by the Egyptians, and differs from keffir, as does matzoon, in +possessing a characteristic aroma and taste. It differs also from the +former by having only a very weak alcoholic fermentation, and by the +coagulum being coarse and lumpy instead of being extremely fine. It is +made from buffaloes', goats', or cows' milk by the addition of roba (or +old leben) to the previously boiled and cooled fresh milk. The use of +leben is many centuries old, and it is used in Egypt as in Arabia for +medicinal purposes, although that of the Syrians and Arabians is said to +differ from that of the Egyptians and Algerians. The fermentative +changes occurring in the formation of the Egyptian leben have been +investigated by Rist and Khoury,[64] and also by Guerbet,[65] who found +that five organisms were normally present. These comprised a +chain-forming bacillus (_Streptobacillus_), a second smaller bacillus +(_Bacillus lebenis_), a diplococcus, a saccharomyces, and a mycoderma. +Of these five organisms, it would appear that four live in metabiosis, +the streptobacilli and bacilli hydrolyse the milk sugar, the components +of which are split up by the yeast to alcohol and carbon-dioxide. The +alcohol thus formed, together with the glucose formed by hydrolysis, are +eventually converted to acid or combusted by the mycoderma species. The +leben thereby assumes the sharp, unpleasant flavour met with in old +samples. The diplococcus merely produces acidification and coagulation +of the milk. Rist and Khoury were able, by the use of these organisms, +to produce normal leben, especially when the true yeast was allowed to +grow in the milk for some time before inoculation with the other +organisms was made. + +Some of the half-civilised tribes of Siberia, the Tartars and the +Burgaten, prepare a strong alcoholic beverage, araka or ojran, from +fermented milk. This is really a product of distillation, and contains +seven to eight per cent. of alcohol and volatile fatty acids. + + [Illustration: FIG. 13--Photo-micrograph of preparation + from Armenian soured milk (Matzoon). This is related to + Yoghourt, and contains, as will be seen from the above + photo, yeasts, streptococci, diplococci, and a bacillus + with the morphology of _Bacillus bulgaricus._ This, and + similar foods, owe their peculiar properties primarily to + the presence of _Bacillus bulgaricus_ (type A, White and + Avery), and only in a lesser degree to the yeasts and + lactic streptococci.] + +_Matzoon._--This is a drink used largely in Western Asia, and is similar +in character to keffir, but has a peculiar taste which distinguishes it +from all other fermented milks. According to Weigmann,[66] it is +prepared from buffaloes', goats', or cows' milk, and is used partly as a +means of souring milk for butter-making and also as a lactic food, eaten +with spoons. In the same way buttermilk produced from milk which has +been previously ripened by matzoon is used as a beverage. Finally, the +coagulum (_than_) of such buttermilk is strained off, and, after being +pressed, is mixed with meal and dried by exposure to the sun's rays. The +preparation of matzoon is in many respects very similar to that of +keffir and koumiss, but differs by inducing a comparatively weak alcohol +fermentation. In common, too, with yoghourt, the prevailing temperature +is much higher than is required for keffir and koumiss. + +In regard to the biology of matzoon, the occurrence of various organisms +has been recorded. Emmerling[67] isolated, in addition to a yellow +pigment-forming organism, _Bacillus subtilis_, _Bacillus lactis acidi_, +and several fungi, a small micrococcus capable of hydrolysing milk- and +cane-sugar. The organism produces and without gas formation, or +peptonisation of the medium. Of the nine yeasts isolated from matzoon by +Lindner[68] and Kalantharianz,[69] three were able to ferment milk sugar +without previous hydrolysis, while two others, by the simultaneous +production of lactic acid and fruit esters, gave to the matzoon its +characteristic taste and aroma. + +_Yoghourt and Soured Milk._--Yoghourt is another fermented milk, and is +related to the matzoon of Armenia, the gioddu of Sardinia, and the leben +of Egypt. After a preceding boiling and reduction of the volume of the +milk, inoculation of the mass is made by the addition of a small +quantity of old culture, and it is then allowed to sour at a +comparatively high temperature. A moderately compact, jelly-like +coagulum is thus formed, while keffir and koumiss possess a liquid +consistency. The fermentation necessary for the two latter products only +proceeds, too, at a much lower temperature, at which yeasts play an +important part. According to Guerbet, yoghourt incubated for ten hours +at 113 deg. F. contained 0.34 per cent. lactic acid and 0.012 per cent. +alcohol. Luerssen and Kuehn[70] came to the conclusion that yoghourt +contained chiefly a mixture of _Bacillus bulgaricus_, diplostreptococci, +and a "granule" bacillus, so called on account of its granulated +appearance after treatment with methylene blue. According to these +authors, the first two organisms were found in each of eight samples of +maya (young yoghourt) and of yoghourt itself, but the occurrence of the +"granule" bacillus in plate cultures was by no means regular. In +addition, yeasts were found in almost every sample examined, but were +regarded more as accidental infections rather than as essential to the +formation of a typical product. The combined action of the three +organisms already mentioned gave rise to a product closely resembling +normal yoghourt. Piorkowski[71] subjected Bulgarian maya to examination +and associated himself with Metchnikoff[72] in finding three species, a +streptococcus, a diplococcus, and a specific organism to which he gave +the name _Yoghourt bacillus_. Similar results were also obtained by +Grigoroff.[73] Piorkowski's _Yoghourt bacillus_ is similar in form to +_Bacillus subtilis_, but does not sporulate, nor does it liquefy +gelatine. Young individuals are stained by Gram's method; older +individuals are, however, Gram negative. The optimum temperature is 112 +deg. F. Kuntze attempted to isolate the organisms mentioned by Luerssen and +Kuehn, and by plate culture procured growth of a spore-forming bacillus +similar to Weigmann's _Bacillus matzoon_. To this organism is attributed +the power to impart a specific taste to the matzoon, but as growth is +comparatively slow, it can only be of significance in determining the +quality of the curd and cheese prepared from this product. Cultures were +also obtained which resembled in general character those of the organism +described by Luerssen and Kuehn as _Bacillus bulgaricus_ and named by +Kuntze _Bacterium W_. Granule formation was transient in this culture, +and the organisms eventually became inactive. Further analysis of maya +gave cultures of the "granule" bacillus, but these passed over from the +type forming irregular colonies (see Figs. 14, 15, 16) to that producing +smooth colonies. Further, although the granule formation persists +largely in milk, the organisms soon revert to the non-granular type if +cultivated on agar. By the use of the Gram-Weigert stain organisms from +a several-days-old culture on beer-wort-agar gave an interesting +reaction. The bacillar threads are in places Gram-negative, in others +Gram-positive, and bear small club-like swellings (see Fig. 14). Results +similar to these were also obtained with cultures of _Bacillus matzoon_ +(Weigmann and Gruebner) and also with _Bacillus acidophilus_. + +Neisser's method of staining failed to give such good effects by the +examination of fresh maya, as did an alcoholic aqueous solution of +methylene blue in showing up the granules of the organisms. Again, +Grixoni[74] found, but did not isolate, a similar granule-forming +organism (_Bacterium sardous_) in Sardinian gioddu. As already +mentioned in the description of leben, Rist and Khoury found a long +bacillar lactic ferment (_Streptobacillus lebenis_) which also exhibited +the irregular greyish white hairy colonies and high optimum temperature +characteristic of this group. On account of the similarity in form, +staining reactions, temperature requirements, and cultural growth of the +organisms described by Emmerling, Dueggeli, Weigmann, Grixoni, and Rist +and Khoury, Kuntze is inclined to regard them as belonging to one single +group of lactic ferments. According to him the granule formation is +rather variable, and may be induced or suppressed by cultural methods. +Not only do organisms of this group produce far more acid than the +normal lactic bacteria; they are also more resistant to acid, and are +able to develop in milk to which 0.5 per cent. hydrochloric acid has +been added. A comparatively high percentage of alcohol seems to +encourage growth, and this was obtained in milk containing 4 per cent. +alcohol. This would no doubt tend to explain the phenomenon observed by +Kuntze that milk is not so rapidly fermented by organisms of this group +as when cultures of diplococci and yeasts are added. Since organisms of +this group would seem to be widely distributed, the question of their +natural habitat arises. Luerssen and Kuehn were unsuccessful in their +search for such organisms in Koenigsberg milk, but Leichmann records the +occurrence of a long bacillus (_Bacillus lactis acidi_) in milk that had +spontaneously soured at 112 deg. to 120 deg. F. This organism, too, showed +characteristic growth on agar media, and produces laevo-rotatory lactic +acid. The examination of calves' stomachs showed, according to Kuntze, +only occasional long bacilli, but inoculation of sterile milk and +incubation at 100 deg. F. with repeated over-inoculation gave a culture +showing the characteristic granule reaction (see Figs. 18 and 20). +Although plate cultures made direct from calves' stomachs do not exhibit +the regular contours generally shown by the granule bacillus, yet this +growth may be induced by preceding cultivation in lactose bouillon to +which 0.5 per cent. acetic acid has been added. A similar organism, +_Bacillus acidophilus_, was isolated from calves' manure by means of +this acetic bouillon, as was also a diplostreptococcus which resembled +very closely the typical lactic acid streptococcus. This resemblance was +made all the more striking by the fact that they were capable of +coagulating milk at a temperature of 99 deg. to 104 deg. F. Since these +organisms are present in large numbers in manure and also in the +digestive tract of ruminants, it would seem probable that their +occurrence is not without significance for the operations of cheese +manufacture. According to Jensen, the practice of applying farmyard +manure to Swiss meadows has been regarded as absolutely essential to the +production of cheese of the best quality; while, on the other hand, the +application of artificial manures would seem to have been responsible +for an increase in abnormal cheese. Kuntze found further that by the +combined inoculation of sterile milk with the diplostreptococcus and the +"granule" bacillus from calves' stomachs, together with a yoghourt +yeast, he was able to obtain a product possessing a taste and aroma +little different from normal yoghourt. During their investigations upon +the ripening of Swiss hard cheese, Freudenreich and Jensen[75] isolated +five varieties of lactic acid bacilli, and were able to show that one of +these, especially _Bacillus casei [Greek: e]_, was of the greatest +importance for the production of good cheese. This organism has been +found by Thoeni to be present in rennet tablets, while a related +variety, _Bacillus casei [Greek: d]_, was found in fresh calves' +stomachs. Unfortunately, staining tests with these organisms were not +carried out, so that no data are available in regard to the presence of +granules. The photo-micrographs of these organisms show the small clubs +and true-branched forms. The presence of these diplococci and bacillar +lactic ferments in the intestinal tract of ruminants and horses might +possess some importance for the preparation of yoghourt in bags or tubes +made from the stomachs of these animals. Finally, Moro[76] has isolated +an acidophilic organism from the dejecta of infants which resembles +closely, both in manner of growth, resistance to acids, true branching, +and temperature optimum, the granule bacillus and related forms. + +[This group of sixteen illustrations (Figs. 14 to 29), showing various +aspects of the Yoghourt bacillus and others of a cognate nature, is +taken from the _Centralblatt fuer Bakteriologie_ of Jena.--L. M. D.] + + [Illustration: FIG. 14.--Granule Bacillus from Yoghourt. + Shredded preparation of a fresh skim-milk culture at 37 deg. + C. for six hours. Stain: aqueous methylene blue. (Enlarged + 1:500.) In Figs. 15 and 17 will be noticed the chain + arrangement of the bacillus, which, in spite of the + supposed data of Luerssen and Kuhn, will be generally + noticed in the granule bacillus.] + + [Illustration: FIG. 15.--Granule Bacillus from Yoghourt, + cultivated after the usual Agar method, for twenty-four + hours at 37 deg. C. Stain: aqueous methylene blue. (Enlarged + 1:500.)] + + [Illustration: FIG. 16.--Granule Bacillus from Yoghourt. + Agar Milk Sugar Culture cultivated for forty-eight hours + at 37 deg. C. Below is the true branching, above, the + distorted involution form. This production of involution + forms occurs chiefly in old cultures, and is an indication + of degeneration. Stain: aqueous methylene blue. (Enlarged + 1:700.)] + + [Illustration: FIG. 17.--_Bacteria W._ from Milk, + cultivated twenty-four hours at 37 deg. C. Methylene blue. + (Enlarged 1:500.) The similarity in the pictures ought to + serve as a proof of the near relation of the granule form + and non-granule varieties.] + + [Illustration: FIG. 18.--Agar Milk Sugar Culture. From the + original Bulgarian Yoghourt. In the centre, and beneath, + the characteristic hairy irregular colonies of the granule + bacillus (_Bacillus bulgaricus_ group), to the left, the + smooth contoured yeast colonies. The colonies of the + former organism always remain microscopic in size. + (Incubated several days at 20 deg. to 25 deg. C. Magnified X 10.)] + + [Illustration: FIG. 19.--Agar Milk Sugar Culture. Surface + colony of granule bacillus from calf's stomach. The great + resemblance this colony bears to those formed by the + granule bacillus from Yoghourt will be apparent. This + fact, as well as close agreement in other cultured + features, induced Kuntze to place these organisms in one + group. (Incubated two days at 37 deg. C. Magnified X 100.)] + + [Illustration: FIG. 20.--Agar Milk Sugar Culture. + Deep-lying colony of granule bacillus from calf's stomach. + The form of the colony is often determined by the relative + presence or absence of air. (Two days at 37 deg. C. Enlarged + about 1:50.)] + + [Illustration: FIG. 21.--Agar Milk Sugar. Colony of + _Bacterium W._ from Yoghourt (non-granular variety of the + granule bacteria, as far as possible identical with + Luersen and Kuehn's _Bacillus bulgaricus_), of a cubical + branching-out form. + + According to Kuntze, the granule formation of this and + related organisms is variable, while White and Avery + regard it as a constant characteristic. (Incubated two + days at 37 deg. C. Magnified x 50.)] + + [Illustration: FIG. 22.--Two colonies of _Bacillus + acidophilus_ from calf's manure. Agar Milk Sugar Culture. + With this organism, also, we have conformation to one type + of colony, while, in other respects, temperature + requirements and production, etc., we have close agreement + with the granule bacillus (_Bacillus bulgaricus_). (Two + days at 37 deg. C. Enlarged about 1:50.)] + + [Illustration: FIG. 23.--Beer-wort Gelatine. + Fourteen-days-old colony of Yoghourt yeast. (Enlarged + about 1:50.)] + + [Illustration: FIG. 24.--Shredded preparation of the + Bulgarian original Yoghourt. Stain: aqueous methylene + blue. Granule bacillus, diplostreptococci, and yeast. (See + also other photo-micrographs of Yoghourt. Enlarged + 1:70.)] + + [Illustration: FIG. 25.--Granule Bacillus from Yoghourt. + Cultivated in skim milk in twenty-four hours at 37 deg. C. + Stain: aqueous methylene blue. (Enlarged 1:50.) + + By means of this staining treatment the presence of + granules (not spores) can be easily detected. Treatment + with fuchsine fails to bring out these formations.] + + [Illustration: FIG. 26.--_Bacteria W._, Agar Milk Sugar + Culture. Cultivated twenty-four hours (knobs, clubs). + Stain: Gram's method coloured with aqueous fuchsine + afterwards. (Enlarged 1:600.)] + + [Illustration: FIG. 27.--_Bacteria acidophilus_ from + calves' manure, isolated by means of bouillon as acid as + vinegar. Shredded out of the usual Agar culture. + Twenty-four hours at 37 deg. C. Stain: aqueous methylene blue. + (Enlarged 1:700.)] + + [Illustration: FIG. 28.--Mucus from calf's stomach + inoculated into milk after eight transferrings. Shredded + preparation cultivated in milk for twenty-four hours at + 37 deg. C. Diplostreptococci and granule bacillus. Stain: + aqueous methylene blue. (Enlarged 1:500.)] + + [Illustration: FIG. 29.--Diplostreptococcus from Yoghourt. + Pure culture in skim milk. A comparison of the + illustrations will show how close a resemblance exists + between bacteria found in the mucous membrane of calf's + stomach and those occurring in Yoghourt. In fact, by the + combined action of granule bacilli, and of + diplostreptococci from calf's stomach, together with a + Yoghourt yeast, it is possible to prepare normal + Yoghourt.] + +In a review of the literature of the subject of soured milks, Makrinoff +suggests the adoption of the two names, _Streptobac. lebenis viscosus_ +and _Streptobac. lebenis non-viscosus_, for the organisms of the +so-called Bulgaricus group, and known at present as +_Bacillus-bulgaricus_, _Streptobac. lebenis_, _Bacillus of Massol_, +_Granule bacillus_, _Bact. Mazun_, _Bac. lactis acidi_, etc.[77] + +White and Avery[78] have made a comparative study of a large number of +varieties and species of lactic acid bacteria of the above type obtained +from various fermented milks and milk tabloids. Their descriptions are +so detailed and their conclusions are so important that we give them at +length. According to this work, the whole of the thermophilic lactic +acid bacilli of the so-called Bulgaricus type may be divided into two +sub-types, A and B. + + +_The Cultural Characteristics of the Bacillus Bulgaricus Group_ + +The cultural characteristics of all the strains of _Bacillus bulgaricus_ +(granule bacillus) are as follows: + +_In Whey Agar._--All strains exhibit wide variation in size, 2 mu to 50 mu +long and about 1 mu broad. + +Almost all individuals are intensely Gram-positive, and show regularity +of outline. All strains show involution form, exhibiting vacuoles, and +often show empty cell membranes. The latter are Gram-negative, and vary +greatly in both dimensions as well as in form. All strains show tendency +to chain formation, some being arranged in chains of six to twenty-five +segments, which may contain both Gram-positive and Gram-negative +individuals. Type B exhibits Gram-negative spherical bodies varying from +0.25 mu to 1 mu in size, adhering to the sides of some of the +Gram-negative individuals. + +_In Whey._--In this medium there is a marked tendency toward +degeneration and involution. In the early stages of incubation, at 100 deg. +to 112 deg. F., the bacilli are uniform in size and intensely Gram-positive; +in succeeding stages the irregular, vacuolated, inflated, and ruptured +forms predominate. Between the eighteenth and twenty-fourth hours of +incubation at 112 deg. F. the strains of type A develop oval to +kidney-shaped nodules attached to a stem extending from the cell +substance. As the incubation is prolonged these nodules increase in +size, often measuring 1 mu to 2 mu in length; this nodule formation occurs +at the expense of the cell protoplasm, and appears to be a marked +characteristic of growth in whey. Cultures of type B do not form nodules +or clubs, but small spherical bodies more or less securely attached to +the cell wall are seen. Again, type A assumes the form of small bacilli +in chains, while type B strains develop to a greater length and exist +almost exclusively as single isolated forms. True branching has been +observed in strains of type B. + +_In Milk._--In milk there is a tendency to thread-formation consisting +of four to ten segments in the case of type A, while type B shows longer +and more curved forms. With increasing age of the culture there also +appears to be increase in the length of the organisms. All strains are +non-motile, non-sporogenous, and non-capsule-forming. + +_Staining Reactions._--All strains are readily stained by the usual +aniline dyes. + +_A. Gram's Method._--Young individuals give an intense reaction with +this stain; old bacilli are easily decolourised, and degenerate forms +are always Gram-negative, while single individuals have been observed +which showed gradation from one pole of the cell to the other. + +_B. Loeffler's Methylene Blue._--According to the behaviour of the +organisms studied, a separation into two types appears possible, type A +being uniformly impregnated, while type B shows distinct +differentiation. The cell body is seen to contain a varying number of +round to oval bodies or granules. This is the appearance already +mentioned by Dueggeli, Luerssen and Kuehn, and Kuntze, and from which the +granule bacillus derives its name. In opposition to the observations of +Kuntze, the occurrence of granules was not found to be variable; it was, +indeed, so constant as to constitute a distinguishing characteristic +between the two types. The organisms of this group are difficult to +cultivate, and freshly isolated growth is obtainable only on media +containing whey, malt, or in milk. They grow equally well under aerobic +or anaerobic conditions. The optimum temperature for growth is 113 deg. to +115 deg. F.; growth is fair at 85 deg. F., slight at 75 deg. F., and does +not take place at 68 deg. F. + +Colonies on whey agar are round to irregular, greyish white, curled and +filamentous, often streaming, and in a few cases smooth and even in +structure. Gelatine is not liquefied. There is no surface growth on +gelatine stab-cultures. Along the stab the growth is filiform, beaded, +with subsequent horizontally projecting ramifications. Milk is +coagulated in eight to eighteen hours at 112 deg. F., and is the most +favourable medium for growth. + +[I am indebted for this group of illustrations (seventeen in number) to +the editor of _Bacteriotherapy,_ New York, U.S.A.--L.M.D.] + + [Illustration: FIG. 30--Photo micrograph of preparation + made from Yoghourt, showing yeast cells, large lactic + diplococci, small slender bacilli and many large bacilli + possessing the morphology of _Bacillus bulgaricus_. Yeast + cells are almost invariably found in native Yoghourt, but + do not appear to be essential to the production of a + tropical beverage. Indeed, they would seem to be + responsible for the unpleasant astringent taste often met + with in old samples of this product.] + + [Illustration: FIG. 31--Photo micrograph of smear from + Greek Curdled Milk called "Giaourti," and showing yeast + cells, long bacilli and a mould (_Oidium lactis_), + possessing very large elongate cells. The presence of the + latter is very undesirable, as it rapidly combusts the + lactic acid, digests the casein, and imparts a strong + unpleasant cheesy flavour to the beverage.] + +Type A produces 2.7 per cent. to 3.7 per cent. inactive lactic acid in +milk, while type B produces only 1.2 per cent. to 1.6 per cent. +laevo-rotatory lactic acid in milk. There is a small quantity of acetic, +formic, and succinic acids formed. The conclusions of White and Avery +are: + +I. A review of the morphological culture and biochemical features of the +lactic acid producing bacilli from yoghourt, matzoon, and leben, appears +to justify their classification as a single group. + +II. This group would seem to be identical with _Bacterium caucasicum_ +(Kern). + +III. The significant variations exhibited by these bacilli in regard to +the presence or absence of granules demonstrable by differential stains, +the degree of lactic acid production, and the nature of the acid +produced, suggest a division into two different types--the true type A, +and the paratype B. + +Quite recently Hastings and Hammer[79] recorded the isolation from milk +of an organism producing more acid than either _Bacterium coli commune_ +or _Bacillus lactis acidi_. It is characterised by possessing a high +optimum temperature, and by the limited conditions under which it grows +on nutrient media. On this account these investigators suppose it to be +related to those described in the paragraphs on fermented milks, leben, +matzoon, etc., and which are regarded by Kuntze as being identical. + +Similarly Boutroux[80] found 1.5 per cent. acidity produced in a +solution containing albuminous matter and glucose; while Richet[81] +states that with the addition of gastric juice to milk as much as four +per cent. acidity may be formed. After storing samples of milk for eight +days at 100 deg. F., Koning[82] found 2.35 per cent. and 2.5 acid; while +similar samples stored at 60 deg. to 62 deg. F. for the same period only +developed 0.9 per cent. Heinemann[83] records the production of 3.0 per +cent. acid in milk incubated at 100 deg. F.; and Jensen states that +_Bacillus casei [Greek: e]_ is capable of developing 2.7 per cent. +lactic acid. + +Dr. H. B. Hutchinson, bacteriologist at Rothamsted Experimental Station, +has also been successful in isolating a bacillus from English market +milk resembling in every particular those classified by White and Avery +as type A. + + [Illustration: FIG. 32 is a photo-micrograph of soured + milk inoculated with a tablet containing viable and pure + cultures of _Bacillus bulgaricus_, and incubated for + seventy-two hours. These tablets constitute a valuable + means of preparing soured milk for therapeutic purposes.] + + [Illustration: FIG. 33 is a photo-micrograph of milk + inoculated with a ferment tablet in which _Bacillus + bulgaricus_ is no longer viable, and the only growth + obtained is that of an organism allied to the _Bacillus + subtilis_ (Hay bacillus) group. Such milk would be + absolutely without value.] + +It will thus be seen that organisms related to those of Oriental and +Occidental milk beverages are present in conditions where it is +impossible for them to attain to any active growth. The same class of +organism has also been found in many cases in butter and cheese +throughout the United States. + +Of recent years the consumption of milk fermented by these organisms has +been introduced more or less successfully into all European countries. +This custom is due, as we have seen,[84] to a very great extent to the +announcement of Metchnikoff[85] that the action of such organisms in the +alimentary tract conduce to a prolongation of life. Moro found that the +dejecta of children contain large numbers of _Bac. lacidophilus_ and +_Bac. bifidus_, but, as age advances, the bacterial flora of the +intestines tends to change. The number of acid-producing organisms +gradually becomes less, and other bacteria capable of producing +far-reaching decomposition of albuminoid matter tend to increase. + +Working on the assumption that senility is partially due to the +absorption of by-products formed from albuminoid food by the +decomposing or putrefactive bacteria mentioned, Metchnikoff instituted a +search for organisms capable of suppressing the growth of the +putrefactive bacteria. + +It has long been known that milk allowed to become sour will keep for a +considerably longer period in hot weather than if lactic bacteria had +not grown. This preservative action of lactic acid also comes into play +in the manufacture of sauerkraut and in the preservation of meat by +immersion in sour milk. + + [Illustration: FIG. 34.--Photo-micrograph of smear of + culture of _Bacillus bulgaricus_, recommended by + Metchnikoff for use in cases of intestinal + auto-intoxication. Unlike the ferments of normally soured + milk, which are sometimes indifferent, or even injurious, + in their action, this bacillus is capable of growth at + blood heat, and, by producing much larger quantities of + lactic acid than such organisms as _Streptococcus + lacticus_, _Bacillus coli commune_, or _Bacteria lacticus + aerogenes_, inhibits the multiplication of bacteria + responsible for the putrefaction of albuminoid food in the + intestines.] + +Bienstock has shown that the growth of _Bac. putrificus_ is inhibited by +the action of _Bact. coli commune_, which is capable of setting up a +slight lactic acid fermentation. _Bact. coli commune_, however, gives +rise to substances of an injurious character, and, although present very +abundantly in the intestinal tract, it may by reduced almost entirely by +the active growth of lactic acid bacteria. This fact is of great value +to the cheese-maker, since by the addition of a lactic acid culture +(starter) to milk before renneting, gas-producing bacteria such as +_Bact. coli_ may be checked in growth. Since the ordinary lactic acid +bacteria such as _Streptococcus lacticus_, _Bac. lactis acidi_, and +others, are incapable of growth at blood temperature, it appeared +necessary to procure cultures of lactic bacteria able to grow at +temperatures of 100 deg. F. to 112 deg. F. Such an organism was found in +Bulgarian soured milk (yoghourt), and was considered pre-eminently +adapted to this purpose. As has been shown in the preceding paragraphs, +this organism is merely one of a large group of bacteria found +distributed in the intestinal canal of many domestic animals, in manure, +and in ordinary market milk. It is then not surprising that the +introduction into the intestinal tract of bacteria of the type +_Bulgaricus_ in the form of tabloids has not met with any decided +success. Although it was considered to be merely necessary to introduce +the desired type of organism into the body, and the amount of lactic +acid taken into the system by the administration of soured milks was +looked upon as of secondary importance, yet, it would seem, in the light +of recent investigations, that benefits derived from a soured milk +regimen are attributable in part to a chemical as well as a purely +bacterial action. This receives support from the fact that soured milk +beverages prepared by the use of ordinary lactic bacteria, distinct from +those of the _Bulgaricus_ type, often exert a beneficial influence upon +human beings even although the organisms responsible for the +fermentation are incapable of growth at blood temperature. + +It may be mentioned in conclusion that cultures prepared by the use of +organisms of the type _Streptococcus lacticus_ combined with _Bac. +bulgaricus_ possess a more agreeable flavour and aroma than those +prepared from a pure culture of _Bulgaricus_ alone. + + [Illustration: FIG. 35--_Bacillus bulgaricus_, showing the + cultures in English cow's milk. (Magnified 450 diams.)] + + [Illustration: FIG. 36--Photo-micrograph of pure culture + of _Bacillus bulgaricus_. The administration of cultures + of this organism is indicated in all cases of intestinal + ailments, caused by the excessive growth of proteolytic + bacteria, and consequent putrefaction of foods in the + alimentary tract. By the formation of large quantities of + lactic acid, a state of asepsis is ensured, which is + particularly valuable in cases of operations on the + abdomen and intestines.] + + [Illustration: FIG. 37.--Photo-micrograph of smear of + combined culture of _Bacillus bulgaricus_ and _Bacteria + paralacticus_. This double culture possesses an advantage + over single cultures in that, while the characteristic + disinfecting action of the former is retained, any + secondary action of the growth of this organism upon the + milk-fat is checked by the growth of _Bacillus + paralacticus_, thus ensuring the production of a more + palatable product.] + + + + +CHAPTER VI + +THE PREPARATION OF SOURED MILK IN THE HOUSE + + +There is no great difficulty in making soured milk at home: the +necessary operations are quite simple, but at the same time they must be +conducted with precision and care, otherwise the results may be +unsatisfactory and disagreeable; there may even sometimes be danger in +badly prepared sour milk. It is always an advantage in such matters to +understand the reason of things, and a few notes on the surrounding +conditions, and what has to be accomplished, may be of assistance to the +would-be experimenter. + +The majority of intelligent people are now acquainted with the fact that +the germs of bacteria are to be found everywhere on the surface of the +earth, in air, and in water, and that they are the sole cause of the +decay of all manner of perishable articles. + +The distribution is unequal--bacteria are much more plentiful where +there is decaying matter--in dirty houses, sewage, or other contaminated +water, etc. Milk is a splendid food for bacteria, and numerous varieties +multiply in it exceedingly, and many of these are injurious, producing +putrefactive changes which render the milk unwholesome, even poisonous +in some cases. Others are beneficial, and are absolutely necessary for +the souring of milk for making butter or cheese and for the ripening of +the latter. The soured milk which is the subject of this book is the +work of certain lactic-acid-producing bacteria, and the problem we have +before us is to encourage the growth of the latter to the uttermost and +to exclude the others. + +As bacterial germs are present in the air and readily sow themselves +into any medium with which they come in contact, the first consideration +is to get good fresh milk which has been as little exposed to the air as +possible. The second is to conduct the experiment where the germs are +fewest, and in cleanly surroundings, far removed from decaying matter +and free from taints and smells. + + [Illustration: FIG. 38.--Photo-micrograph of smear of + one-month culture of _Bacillus bulgaricus_. In spite of + its age, the culture is perfectly free from any foreign + organisms, which would otherwise lower its value for the + preparation of soured milk, and might, indeed, make it + directly injurious.] + + [Illustration: FIG. 39.--Photo-micrograph of culture of + _Bacillus bulgaricus_ in malt. In cases of acute + enteritis, where milk cannot be supported, the lactic + bacilli may be cultivated in malt, and administered to the + patient in this form, with occasional doses of syrup of + malt, in order to induce a vigorous growth of the lactic + ferments in the body.] + + [Illustration: FIG. 40.--Photo-micrograph of smear from + milk that had been allowed to sour spontaneously. Ordinary + market milk is always subject to infection from the air, + milking vessels, manure, etc., and from these sources a + mixed bacterial flora arises, with the result that the + milk exhibits curdling, acidity, gaseous fermentation, or + mould growth, after being stored for a short time. This is + due to the action of sush bacilli, diplococci, yeasts, and + moulds as are shown in this illustration.] + +However fresh the milk may be, it will contain useless or injurious +bacteria, and we must get rid of these before attempting to introduce +those whose growth we wish to encourage. This is effected by heat. All +the living bacteria and most of the germs are killed at temperatures +somewhat under the boiling point. Having sterilised the milk in this +way, it is necessary, as far as possible, to prevent the entrance of +fresh germs from the atmosphere, and we therefore let the milk cool down +in covered dishes. When the temperature descends to about 100 deg. F. the +culture of the special bacteria is introduced, the covers are replaced, +and the milk vessels maintained at or near this temperature for twelve +hours, when the soured milk is ready for use. It is not necessary to use +fresh culture every time--a little of the soured milk will take its +place, and this may be repeated as many as fourteen times before it is +necessary to start off again with a fresh culture. A great deal depends +on the care exercised and the freedom of the surroundings from bacterial +germs. Under the best conditions wild germs will gradually accumulate in +the soured milk, but their increase may be greatly delayed by attention +to the precautions mentioned. The ordinary souring of milk for butter +and cheese making is conducted in cool surroundings, as already stated, +because in such conditions the lactic-acid-producing germs increase +relatively faster than the wild germs, and so gain the upper hand, but +in the case of our special soured milk we kill out, practically, all +wild bacteria and germs, and the pure culture having the field to +itself, we can conduct the operation at a higher temperature where the +action of the bacteria is at its maximum, and so obtain the necessary +lactification in the minimum of time. + +The appliances for the souring of milk on the domestic scale require +some consideration. We propose to describe the principal forms of +apparatus which have been put on the market for the purpose, and then to +give such suggestions as may assist the ingenious in making apparatus +for themselves. Those who wish for information on the subject of larger +apparatus will find it in the following chapter. + + [Illustration: FIG. 41--Photograph of Agar Culture, + inoculated with a lactic powder offered to consumers under + a fancy name. Working on the assumption that the presence + of lactic bacteria is inimical to the growth of septic + organisms, this preparation has been placed on the market. + + The plate shows, however an abundance of colonies of + foreign organisms--sporogenous bacilli, _Staphylococcus + pyogenes albus_, and _Staphylococcus pyogenes aureus_. + These organisms are shown in the appended + photo-micrographs, and constitute impurities in the + preparation.] + + [Illustration: Spore forming bacillus] + + [Illustration: _Staphylococcus pyogenes albus_] + + [Illustration: FIG. 42--Photograph of Test Tubes of Sterile + Milk, inoculated with a tablet preparation said to contain + pure cultures. The darker liquefied portion of the + tube-contents is due to digestion of the curd by + proteolytic bacteria, thus indicating impure culture. Pure + cultures of lactic acid bacteria coagulate the milk + uniformly, but do not produce any subsequent change in the + appearance of the culture, even after several months.] + + [Illustration: FIG. 43--Photograph of Test Tubes of + Sterile Milk, each tube having been inoculated with a + tablet of a preparation said to contain pure cultures. + Here, again, there is evident peptonisation of the curd, + thus indicating infection by proteolytic ferments. + Cultures from these tubes demonstrated the presence of a + foreign organism. Microscopical examination failed to + disclose the presence of _Bacillus Bulgaricus_.] + + [Illustration: FIG. 44--Photograph of Test Tubes of + Sterile Milk, inoculated with a tablet of + "Lactobacilline." In contra-distinction to those shown in + Figs. 42 and 43, these tubes exhibit homogeneous curdling + of the milk without any subsequent digestion or + peptonisation of the coagulum. This is indicative of the + purity of the culture.] + +The Society "Le Ferment" of Paris, which has been authorised by +Professor Metchnikoff to prepare and supply to the public his sour milk +culture, provides an apparatus for the treatment of the milk. It is +shown in Fig. 45, which consists of a double box having the intervening +space packed with a non-conducting material. It is provided with a +tight lid. Inside, there is accommodation for two milk vessels, each +with a capacity of about two thirds of a pint. The most difficult thing +in the souring of milk is to maintain the temperature as nearly at 100 deg. +F. as possible while the culture is in action. This result is attained +by filling the vessel in the middle with boiling water. The insulated +walls hinder the escape of heat, and the quantity of boiling water used +is calculated to maintain the temperature steady for the twelve hours of +cultivation; but in cold, frosty weather it is necessary to refill the +central vessel with boiling water in the middle of the period. + + [Illustration: FIG. 45] + +The milk jars are washed with hot boiled water and turned upside down to +dry. They should not be wiped with a cloth. Boil the milk to be treated +for ten minutes, stirring it to promote evaporation, as it is +advantageous to have it in concentrated form. Cool rapidly to 100 deg. F. +by placing the boiling vessel in cold water, add to each bowl one third of +a tube of the culture in powder form, fill up with the boiled and cooled +milk, stir well and cover. Place the jars in the box and fill the +central vessel with boiling water, shut the lid tight, and do not open +it (unless a fresh charge of boiling water is needed) for ten or twelve +hours, when it will be ready for use. If the liquid culture is used (one +small phial for each bowl) the milk should be cooled to 86 deg. F. instead +of 100 deg. F., as with the powder. The culture is also supplied in tabloid +form. The powder and tabloids keep well, but the liquid can only be +relied on for about two months. The milk prepared as above should be +stored in a cool place, the lids being kept on the bowls. It is good for +about two days, after which it becomes too sour. It can be eaten with +sugar, which not only sweetens it but is beneficial in affording +additional suitable food for the acid-producing bacilli. If fresh milk +cannot be had, condensed, sterilised, or pasteurised milk may be used, +but, of course, fresh milk is best. Condensed milk should be diluted +with two parts of boiling water and then treated like ordinary milk. + +An apparatus on similar principles is sold by the Maya Bulgare Company, +Ltd., and is illustrated in Fig. 46. + + [Illustration: FIG. 46--Soured Milk Apparatus of the Maya + Bulgare Company, Limited, consisting of an insulated box, + hot-water vessel, and covered vessels containing the milk + and culture. The apparatus consists of cabinet in deal, + Maya Bulgare ferment in 20-dose bottles, Maya Bulgare + ferment in 100-dose bottles, compressed Maya Bulgare + tablets in boxes of 8 tubes, Maya Bulgare caramels in + boxes of 40, reduced milk, china funnels, and + thermometers.] + +The box is insulated, but the door is on the side, the hot water vessel +is underneath, and the covered vessels containing the milk and culture +are placed on a shelf above. In the front of the illustration are shown +the various packages in which the liquid and powder cultures are put up. +The procedure is exactly the same as with "Le Ferment" apparatus. + +Lactic Ferments, Limited, make use of a different principle to maintain +the temperature steady during the lactifying period. Their apparatus +(Fig. 47) consists of a water vessel mounted on a stand. The milk +vessels (tumblers) are placed in the water, and the temperature +maintained at the proper figure by a small night light burning +underneath. It is recommended that the milk should be placed in an +earthenware jar or jug, which is stood in a pot of water kept boiling +for an hour. After cooling add from three to six previously crushed +tabloids of culture, and stir well with a glass rod which has been +sterilised in boiling water. The milk is then transferred to three +tumblers, which it should fill, and these are put into the water vessel, +the water in which should be at about 100 deg. F., and the night light +started. + + [Illustration: FIG. 47] + +Messrs. Allen & Hanbury, Limited, also make use of the night light to +maintain the proper temperature during incubation in their "Sauerin" +apparatus (Fig. 48). + +No water, however, is placed in the metal container. The procedure is +the same as that already described, and both tablet and liquid pure +cultures are supplied. For children it is recommended that the +incubation should occupy from three to four hours only, in other cases +eight to ten hours. Grated nutmeg, ground cinnamon, or other flavouring, +and cream may be used with the soured milk. + +The night light is also employed in the "Veronelle" apparatus of Messrs. +Clay, Paget and Company, Limited (Fig. 49). + + [Illustration: FIG. 48.--Messrs. Allen & Hanbury's Soured + Milk Apparatus. They maintain the temperature by means of + a night light, and the culture they use they call + "Sauerin."] + + [Illustration: FIG. 49.--Vironelle Apparatus for souring + milk, made by Messrs. Clay, Paget & Company, Limited. The + milk in this case is placed in an earthenware jar, and is + sterilised by placing in a saucepan of water and boiling + it. The culture is added after cooling, the period of + incubation being about six hours.] + +The containing vessel is of tin or aluminium, and has two stands, the +high one for hot and the low one for cold weather, as in the latter +case greater heat is needed to maintain the incubating temperature. The +milk is placed in an earthenware jar and is sterilised by placing it in +a saucepan of water and boiling it; continuing the boiling for half an +hour. It is allowed to cool to about 98 deg. F., and placed in the +incubator, culture added, and the lamp lighted, the cover of the +incubator being kept on. The period of incubation is given as six hours. +To prepare the next day's supply a tablespoonful of the soured milk is +retained and used instead of the culture. This may be continued for +fourteen days, when a fresh start with culture is necessary. The soured +milk will keep for thirty-six hours. Capacity, one and one half and two +pints; also a large size for family use. + +For the preparation of soured milk on a small scale, one of the various +forms of vacuum flasks now on the market may be used with satisfactory +results. A little cold water must be poured into the flasks, and warm +water added, until, by means of three to four changes, boiling water can +be safely poured in without cracking the flask. + +This boiling water must be allowed to remain in for about twenty +minutes, and then replaced by freshly boiled milk that has been cooled, +so that its temperature in the flask is about 105 deg. F. The culture of +lactic organisms should then be added, the opening of the flask plugged +with clean cotton-wool, and the cap screwed on. + +In an actual test, the temperature of the milk placed in such a flask +was 105 deg. F., at 7.30 P.M., and had dropped to 93 deg. F. by 9 A.M., the +following day. The milk was curdled, and possessed the normal acid taste +of such cultures. + +The different types of apparatus are all quite simple, and it would be +easy to make something at home. Get two round tins, the one less in +diameter by from two to three inches than the other, put one or two +pieces of wood across the bottom inside the larger tin, and fill up the +space between with cotton-wool, which is an excellent non-conductor of +heat. Place the smaller tin centrally inside the larger one. Fix three +or four distance pieces of wood in the space between them, fill up with +cotton-wool, leaving a little space at the top to permit the lid of the +smaller tin to be fixed on. The boiling-water vessel may be a tin +saucepan with a lid, but no handle, and its proper place would be on the +bottom of the inner tin. A tripod stand made of three pieces of wire +bound together, and with legs reaching past the hot-water vessel to the +bottom of the tin, would support a false bottom of tin forming the shelf +on which the vessels of milk to be treated would rest. These might be +tumblers covered with tin lids. To prevent radiation through the lid of +the inner tin, a thick pad or hood of cotton-wool packed between cloth +would be placed over the top. A little experimenting would be necessary +to determine the quantity of boiling water required to maintain the +proper temperature. + +The soured milk obtained in the above manner is of the consistency of +ordinary buttermilk; a separation of whey frequently takes place, and +this may be poured off if desired. The taste and flavour should be +pleasantly acid and agreeable, and both are distinctive enough to give a +good idea of the purity of the product. In many places a more +concentrated article is made by boiling down the milk to one half or one +third of its bulk, and then fermenting it in the ordinary way. A kind of +thick pudding is thus obtained, which is highly recommended both as an +agreeable article of food and as a stronger medium for the support of +the germs it is the purpose of the sour milk treatment to introduce +into the digestive system. + +The cultures for making soured milk can now be had from all the leading +wholesale and retail chemists, with directions as to the quantities to +be used. + +It is very necessary that the milk used should be not only fresh and +good, but also free from chemical preservatives. The effect of these is +to inhibit the growth and development of bacteria, and they have +therefore an injurious influence on the special lactifying germs it is +our object to cultivate. Preservatives are now not nearly so much used +as they were, a few years ago, and there should be no difficulty in +obtaining milk free from them. + +For keeping both fresh and soured milk good a small ice-chest is an +excellent device. The germs which are continually dropping into milk +kept in open vessels in the air, even in cleanly surroundings, are +mostly kept out in the close ice-chest, and the low temperature prevents +in a natural way the development of the bacterial germs already in the +milk. For the preservation of all kinds of foods the ice-chest is a +capital investment, not to mention the benefit of having cooled drinks, +etc., as required. They manage things well in this respect in the United +States, where ice is regarded as a necessity in the summer time by even +the poorest people, and is delivered with the same regularity as the +milk. + +It is necessary to utter a word of warning as to certain forms in which +the sour milk bacillus is being offered to the public. It is being +compounded with sugar, chocolate, and other articles, and sold in the +form of sweets, etc. There is no reliable proof that these preparations +are valuable. Certainly, sugar is a medium in which the lactifying germs +can live, but the quantity so introduced into the system must be very +small compared with what is obtained from properly fermented milk. It +takes some time, even with strong cultures, to fix the acid-producing +germs in the large bowel where they are wanted, and until proper +evidence is forthcoming that confectionery preparations are efficacious +we would recommend that only the regularly fermented milk be used. It +would save trouble, no doubt, to treat oneself with a few chocolate +creams containing the necessary germs daily, but if the matter is taken +up seriously it will be better to take some pains and stick to methods +the efficacy of which has been demonstrated, leaving the others until +their _bona fides_ has been proved. There are always enterprising firms +who are prepared to simplify things for us, but we must make sure that +their simplifications are warranted. + + + + +CHAPTER VII + +THE PREPARATION OF SOURED MILK IN THE DAIRY + + +There is a tendency in certain medical quarters to discourage the use of +soured milk "made for profit." This view leaves out of account the fact +that besides being of value in medicine, the article in question is also +an excellent food, which, as we have seen, has been consumed by +multitudes of people for ages in many parts of the world. There seems +also to be satisfactory evidence that a larger percentage than usual of +the people who make soured milk a staple of diet attain to a ripe old +age. How does it become such a dangerous thing the moment the doctors +get it into their hands? Of course if a man has an acute disease he +places himself entirely in the hands of his medical man, and eats what +is prescribed for him, or at least he ought to do so, and if he makes +such a submission he is entitled at least to the comfort of being able +to feel that his doctor is free from unreasonable prejudices. For the +implication that an article "made for profit" is naturally suspect casts +an unwarranted stigma on a large number of honourable people. There are +dishonest tradesmen just as there are dishonest and careless doctors, +but to saddle a whole class with the offences of a few would not be a +justifiable proceeding in either case. Besides, it is not to the +interest of the manufacturing chemist or the dairyman to turn out +spurious cultures or bad soured milk, and on the whole we see no reason +why they should not engage in the business. + +The widespread use of soured milk in other countries as a regular +article of diet seems to indicate that all manner of people, except +those suffering from diseases which necessitate medical regulation of +diet, might with probable benefit to themselves add this article to +their food list; and it looks as if a good many of them intend doing so, +even if scandalised doctors threaten "to abandon the cure." + +The dairyman who knows his business does not need to be told of the care +which is necessary to keep milk in good condition. The merely commercial +consideration of avoiding loss has made him ready to inquire into the +best means of prolonging the life of milk as a merchantable article. +For a time he relied on chemical preservatives, but their day is now +almost over, and filtration, pasteurisation, and cold storage have taken +their place. Any one conversant with the trade knows how widely these +methods have been adopted of late years; we may, therefore, assume that +the average dairyman has at his command milk suitable for the incubation +process. + +The demand for soured milk is not as yet a very large one, and the +apparatus so far developed for its production is meant for the treatment +of small quantities. After describing the principal appliances at +present in the market we propose to make some suggestions as to the +construction of larger apparatus. + +A firm which has given great attention to the question of maintaining +fixed temperatures is that of Messrs. Charles Hearson & Co., Ltd. Their +incubators for chicken hatching are known all over the world; and their +appliances for biological incubation are very generally used in +bacteriological laboratories. With such experience it was natural that +they should turn their attention to soured milk apparatus, and the +result is the "Lactobator" (Figs. 50 and 51). + + [Illustration: FIG. 50.--"Lactobator" made by Messrs. + Charles Hearson & Co., Limited, which is used for the + incubation of pure culture in milk in a fairly large way. + The illustration shows the "Lactobator" closed.] + + [Illustration: FIG. 51.--Messrs. Hearson & Company's + "Lactobator," showing the internal arrangements.] + +A copper vessel made to contain water has placed in it a stoneware jar +which holds two gallons of milk; on the top is a lid which carries a +thermometer for indicating the temperature of the milk. Heat is supplied +by a gas ring under the copper vessel; and in the gas supply is the +patent thermostat made use of by Messrs. Hearson also in their +biological and poultry incubators, in which a capsule containing a +liquid arranged to boil at a certain predetermined temperature is the +regulating factor. When the liquid boils, the capsule expands, and by +certain mechanical devices regulates the gas supply so as to produce +exactly the temperature required. + +The procedure is as follows: The jar is filled with milk, and water is +run into the copper vessel by the funnel until it runs over at the +overflow pipe. The thermostat is lifted off and the full gas supply +allowed to pass to the burner, the temperature of the milk brought up to +180 deg. F. and maintained for half an hour at this figure. The gas is then +turned off, and cold water run through the funnel until the temperature +of the milk registers 95 deg. F. The culture is added, the lid replaced, +and the thermostat put into the pocket at the side of the vessel; the gas +relighted, and when the temperature reaches 100 deg. to 106 deg. F. the +capsule of the thermostat will expand and close the gas to a peep, which +is just sufficient to maintain the temperature within the above limits. +After eight hours the incubation is completed. + +Edgar's patent apparatus, the "Lactogenerator," as provided by the Dairy +Supply Co., Ltd., is shown in Fig. 52. + + [Illustration: FIG. 52. Edgar's "Lactogenerator"] + +The milk is placed in a tinned copper-jacketed vessel and water run in +through a vertical pipe until it runs off at the overflow. Two gas +connections are required with cocks on each, the one to heat up the milk +to the boiling point and maintain it at this for thirty minutes. A +skimmer which has been placed in the milk lifts out the coagulated +protein and albumen which rise to the top. The cock is then shut and +cold water run through the jacket till the thermometer shows 90 deg. F., +when the culture is added, and the other gas supply with the regulator +turned on, and the temperature is automatically maintained at about 90 deg. +F. Time of incubation eight to nine hours. It is recommended to turn +cold water into the jacket at the end of the period to prevent +overincubation. + +A somewhat similar apparatus is that of the Willows Refrigerating Co., +Ltd. (Fig. 53), with the exception that it has no automatic heat +regulator. It is made of tinned steel, and the operations are the same, +but the sterilising temperature (obtained by a gas ring or hot plate) is +given as 180 deg., and the incubating temperature 100 deg. to 104 deg. F. +for a period of twelve hours. Presumably this temperature is maintained +by a small gas jet or other similar source of heat. The capacity is two +gallons. + + [Illustration: FIG. 53 + + Apparatus of the Willows Refrigerating Co., Ltd.] + +In the apparatus hitherto described the milk is sterilised in bulk, and +is filled into bottles or jars after incubation, which is not a +desirable thing to do, unless the soured milk is for immediate +consumption, as there is likely to be contamination with injurious germs +from the atmosphere. In the domestic apparatus the milk is usually +incubated in covered jars in which it can be kept until required for +use, and the practice on the larger scale should be the same. + +The Dairy Outfit Co., Ltd., have recognised this in their "Lacto" +apparatus (Fig. 54). + + [Illustration: FIG. 54 + + "Lacto" Apparatus of the Dairy + Outfit Co., Ltd.] + +A cylindrical vessel is set loosely on a stand, beneath which is a lamp +calculated to maintain the incubating temperature. The milk is placed in +bottles with metal screw tops, and these are put into the cylindrical +vessel; water is run in round them through the side funnel, the vessel +lifted off the stand, and heated to sterilising point on a stove. Cold +water is then run in through the funnel until the temperature is low +enough for incubation. Culture is added to each bottle and the lids +screwed on, the vessel lifted on to its stand, and the lamp lighted. The +cover of the apparatus has a thermometer fixed on it. + +On the large scale the treatment of the milk would take place entirely +in the jars in which it would be sent out, and the sterilisation and +incubation would be conducted in different pieces of apparatus. The +sterilisation would be effected either (1) by direct steaming, or (2) by +hot water heated by steam. Fig. 55 shows the first type of +sterilisation. The tank is of wrought iron or steel with strengthening +pieces of angle iron. The door, with pulleys and counterweight for easy +handling, is fastened steam-tight by hinged bolts. The apparatus is +mounted on a stand at a convenient height for handling the bottles; and +in front is another stand with channel iron rails to take the waggon in +which the bottles or jars to be sterilised are packed. When the door is +fast, steam is turned on, and regulated to produce the proper +temperature by the thermometer fixed in the shell, in which a pressure +gauge is also secured. After sterilising, the door is opened and the +waggon drawn forward to the outside, allowed to cool, or removed +elsewhere to cool, and allow space for a new charge. + + [Illustration: FIG. 55.--Sterilising Apparatus for + sterilising milk on the large scale. The bottles of milk + are sterilised, and the culture can then be added, and the + incubation allowed to proceed in an insulated chamber.] + +The second method of sterilising is by hot water, as in Fig. 56. The +bottles or jars are placed on a perforated false bottom in the +rectangular tank, water run in up to the necks, and steam turned on; the +lid is fastened with hinged and hooked bolts; a thermometer fastened in +the lid, and with a long stem enclosed in metal, indicates the +temperature. At the end of the sterilising process cold water is turned +on, and at the same time the overflow water cock is opened; the cold +water gradually reduces the temperature, and the incubating point is +quickly reached. + + [Illustration: FIG. 56 Another Method of Sterilising + (Dairy Supply Co., Ltd.).] + +Incubation in bottles or jars, sterilised in these ways, can best be +conducted in an insulated room, with say, six inches of silicate cotton, +granulated cork, or washed cow hair packed between two-inch by six-inch +battens, covered with matching on either side, and lined with sheet +zinc. It would be an advantage to have an air-lock or anteroom into +which the waggons or trays of sterilised jars could be run, and the door +of the anteroom closed before the door of the insulated room is opened. +This would tend to prevent variations of temperature in the room, and +also, by checking free communication with the outside air, decrease +contamination. The waggons of jars would be run in, and culture added to +each jar by a sterilised pipette. The atmosphere of the room would be +kept pure by running in air frequently through a filter of moist +cotton-wool by means of an electric fan, and at intervals the interior +would be sterilised by the use of formalin vapour. + + + [Illustration: _Details of an American Apparatus for + Preparing Soured Milk_ + + FIG. 57 + + The figures give diagrams A, B, C, and D of an apparatus + useful for the preparation of lactic foods. The incubating + can A, is made of block tin, and is intended to contain + the milk. B, the warm water container, should be a stout + walled vessel with a circular aperture in the lid, through + which the incubating can may be passed, and clamped down + as in C. + + B is fitted with three stout iron legs, which should be + sufficiently long to allow of a small lamp or gas-jet + being placed beneath the container to maintain a uniform + temperature. + + D gives an external view of the apparatus. + + For the preparation of soured milk, separated milk is + placed in the incubating can, and heated up to 100 deg. C. + (212 deg. F.) for thirty minutes. It is then allowed to cool + to room temperature, and the culture, or tablet containing + the lactic acid bacteria, is then added, and thoroughly + stirred for a minute or so. The can is then immersed in + the warm water container and kept at a temperature of 86 deg. + F. to 104 deg. F., according to the organisms used, for ten to + twelve hours. By the end of this time the milk ought to be + converted to a jelly-like mass, and after being stirred + vigorously for a short time, may be cooled on ice, and is + then ready for consumption.] + +The incubating temperature could very conveniently be maintained by an +electric radiator, and as the insulation would largely prevent leakage, +the amount of electric current used would not be large. The regulating +apparatus might consist of a thermometer with platinum wires fused +through the stem at the proper temperature, say 100 deg. F. When the +mercury rises to this figure it will complete the circuit of a battery +which will actuate certain well-known devices for turning off the current +which actuates the radiator. In this way a very fine automatic +arrangement would be achieved. Steam pipes might be used instead of the +radiator, and the thermometer above described could be used in this case +also, with appliances to cut off the steam. + +On the large scale, labour-saving appliances, such as the mechanical +brush jar and bottle washer, and the automatic filler for jars or +bottles, would be employed, and an overhead trackway for carrying the +trays of jars from the steriliser to the incubator would be a great +convenience. A further adjunct of considerable importance would be a +cold room, worked either by ice or a refrigerating machine, in which the +jars could be stored after incubation, so as to arrest the process of +lactification, and maintain the soured milk in good condition until +required for use. + + + + +CHAPTER VIII + +SOURED MILK IN HEALTH AND DISEASE + + +When people are ill the best thing they can do is to place themselves in +the hands of the doctor, who will try to regulate their lives, including +their diet, in accordance with the conditions which science suggests as +the most likely to lead to their recovery. + +It is not the aim of this book to teach persons who should be under +medical treatment to doctor themselves; soured milk may or may not be +beneficial in their case--that is for the medical man to say; and +further, if it should be beneficial the doctor ought to have its +preparation under his control. Slight differences in quality and purity +may count for much in cases of acute disease, differences which might +not matter to the person who requires no medical attention, and who +consumes the article as a health-giving food. A considerable body of +evidence is already on record as to the potency in certain cases of +soured milk as a curative agent, and it seems to have taken its place in +medicine as a recognised remedy. + +There is a wide field of usefulness, however, outside of the strictly +medical one. Professor Metchnikoff has collected many striking examples +of individuals and peoples inhabiting different parts of the world, who +thrive, and in many cases attain to a great age, and whose diet consists +largely of soured milk. He has made a wide and general inquiry into the +causes which tend to shorten life, and makes out a strong case in +support of the view that in many cases this is the result of what is +called auto-intoxication or self-poisoning. In man and in the mammalia +generally, the colon or large intestine is very largely developed; this +organ is not of much value in the digestion of food, and seems to be +chiefly a receptacle for waste material; it is, as a rule, extremely +rich in bacterial flora, which produce putrefactive changes in the waste +material. As a result various poisonous principles are evolved, and +these find their way into the blood, accompanied frequently, there is +every reason to believe, by the injurious bacteria themselves. In this +way many diseases and ailments are produced which shorten life. The +inquiry then naturally turns to what is the best way of dealing with +this state of matters. It is known that the bacteria referred to +flourish best in alkaline or at least non-acid surroundings, and it is +known that these conditions very frequently exist in the large +intestine. Acids are the best antiseptics; they have been used from time +immemorial as preservatives; pickles are preserved in vinegar or acetic +acid, and when milk is allowed to sour under proper conditions, the +germs of putrefaction are destroyed or their activity inhibited, and it +keeps a considerable time. Doubtless, in hot countries, it was this +property of lactic acid which first led to milk being artificially +soured with a view to its preservation as an article of food. So +powerful is lactic acid in this respect that it is a custom in some +countries to preserve meat by placing it in soured milk. + +How can acids be applied so as to control the bacterial flora of the +large intestine? Not in the ordinary way, because, when administered +through the mouth, they are used up long before they can penetrate to +the colon. The brilliant idea occurred to Professor Metchnikoff, of +administering acid-producing germs which might work their way through +the digestive system, and, reaching the large intestine, produce the +acid required. After much experimenting the bacillus of Massol, +_Bacillus bulgaricus_, was adopted as the most suitable. The Bulgarian +bacillus is an extremely vigorous one, multiplying with great rapidity, +and persisting in conditions that would be inimical to other microbes. +The growth and development of bacteria is interfered with by the +products of their own activity; thus, ordinary lactic-acid-producing +organisms die when a certain amount of lactic acid has been developed; +the same fate overtakes the Bulgarian bacillus, but it survives longer +and is able to produce as much as two and one half per cent. of lactic +acid in milk before it ceases operations. It seemed therefore the most +likely to be able to survive the journey through the digestive system. +Experiments fully bore out this supposition, as no great difficulty was +encountered in naturalising the Bulgarian bacillus in the large +intestine, not only in milk cultures, but grown in solution of malt, +bouillon, etc. It thrives in all kinds of sugar, and therefore can be +administered in a variety of media, very beneficial results following in +many cases. Direct tests showed a large reduction of the injurious +intestinal flora when the Bulgarian bacillus had been naturalised in +the colon, and the bacillus persisted long after it had ceased to be +administered. Specialists who have taken up the subject report the cure +of many ailments through the agency of soured milk, and it seems to have +entered upon a lengthening career of medical usefulness. + +The fact of so many old people being found in countries where soured +milk is a staple of diet naturally raises the question as to whether its +general use in other countries might not have a beneficial effect on +health and longevity. Its usefulness as a remedial agent in certain +diseases is already demonstrated; is there not a strong probability, +amounting almost to a certainty, that its consumption by people in +health would tend to ward off many ailments and prolong life? Of course +there will be some for whom it is not suitable; there are people who +cannot eat strawberries without discomfort, but no one thinks of +prohibiting the general use of the fruit on that account. In the matter +of diet the person in health, if he exercises ordinary care, may be left +to find out for himself what suits him. The soured milk remedy is not a +disagreeable one, as, when properly prepared, the article forms both a +pleasant and refreshing article of diet. The question of getting the +right article, however, is a very important one. Milk is a splendid +rearing ground for many bacteria, some of which are very injurious; +among these may be pathological germs, the seeds of tuberculosis, +enteritis, etc. The danger with soured milk is, that in the process of +culture we develop the best condition for the increase of these when +they preponderate, or when, through the use of bad cultures, the +lactic-acid-producing bacteria are absent, or present only in small +numbers. By the thorough boiling of the milk, we get rid of all living +bacteria and nearly all spores or germs, and by scrupulous cleanliness +in the vessels used--scalding or even boiling them, and allowing them to +dry naturally in an inverted position--we greatly diminish the +probability of infection with fresh injurious germs from the atmosphere. +All depends on the purity of the culture employed; this can now be +obtained, prepared in the most careful manner, from wholesale chemists +making a speciality of its manufacture. + +As we have seen, even the Bulgarian bacillus is ultimately killed by the +products of its own activity, and the natural corollary is, that the +life of cultures cannot be a long one. Only those cultures should be +bought which are labelled with the date to which they are guaranteed to +maintain their efficiency. With fresh good milk, careful boiling, +scalding, and cleanliness with regard to the containing vessels, and the +means of maintaining the incubating temperature for ten or twelve hours, +there is not the slightest difficulty in preparing perfectly reliable +soured milk. There are simple tests which will sufficiently guide the +experimenter; the soured milk should not be too acid to the taste, and +it has a flavour of its own by which its quality can be recognised. The +litmus test-papers mentioned in the chapter on the chemistry of milk are +very useful; both the red and the blue papers should be obtained and +used first of all in testing the quality of the fresh milk. After +incubation the soured milk should turn the blue paper decidedly red; if +this does not occur, test it with the red paper; if the latter turns +blue it is proof that the wrong fermentation has taken place--that +putrefactive germs have gained the upper hand. The most probable +explanation is, that the culture is bad, the Bulgarian bacillus is not +present, or if so, only in small numbers. With these simple tests, +combined with proper care, one cannot go far wrong. The Eastern nations +who prepare soured milk in various forms do not exercise the care we +have predicated, but they seem to make the article of fairly constant +and good quality. It has been suggested in explanation that, as the +ordinary flora differs in different countries, the bacterial flora +varies in a similar manner, and that in these Eastern countries +injurious bacteria are not so prevalent in the atmosphere as they are +with us. + +It is also said that the flavour of the soured milk prepared in Bulgaria +is quite different from that prepared in Paris, London, or New York; one +reason probably is that the "maya" or ferment used in Bulgaria contains +several other organisms besides the Bulgarian bacillus, which raises the +question whether a pure culture of one bacillus is the best to use. + +Professor Metchnikoff found that this bacillus alone had certain +defects; it attacks fat and is apt to give a tallowy taste when cream is +present in the milk. He therefore associated with it another +lactic-acid-producing organism, and this combination is the basis of his +culture called "lactobacilline." The presence of yeasts, which occur in +the Eastern ferments, has been advocated by some; the yeast in +association with the lactic organisms produces a small amount of +alcohol. The question of the composition of the culture will have to be +fought out by the experts, but meantime, if we go to the right source, +we have good enough cultures to go on with. + +A good deal can be said for the use of skimmed or separated milk instead +of whole milk. Cream as a rule contains far more bacteria than the rest +of the milk, and we therefore start from a surer foundation when it is +removed; besides, the mechanical separator, now so largely used, removes +slime and other impurities from the milk, and these also are hotbeds of +bacteria. + +Soured milk may be taken at any time, the first thing in the morning, +before or after meals, or the last thing at night. The quantity will +vary with the individual, but from half a pint to a pint is a fair +amount for daily use. If one wishes to have the maximum effect it is +necessary for the time being to curtail the use of butcher's meat and +substitute fish, yolk of eggs, and other similar foods; not much alcohol +should be taken, and smoking might be reduced to a minimum. Those who +cannot take even skimmed milk may use whey in which to cultivate the +bacillus; it is not desirable to employ the whey which has been +separated by the use of rennet, as in cheese- or junket-making. A better +article is obtained by adding a very small quantity of pure hydrochloric +acid to milk which has been boiled, and then filtering through a sieve, +which retains the curd while the liquid whey passes through; a pinch of +soda is added to neutralise the excess of acid, and, after boiling, the +liquid should turn red litmus paper blue; it is then ready for the +addition of the culture and incubation in the same manner as with milk. +A solution of malt--the extract dissolved in hot water is +convenient--may also be used instead of milk, and strongly malted bread +or biscuits are excellent to take with the soured milk or cultures in +other mediums, to supply food for the bacillus in the form of malt +sugar. Other sugars, cane or grape, are also very useful, and may be +taken in the form of fruit juices, syrups, confections, jams, sweet +puddings, etc. + +We lay stress on the use of soured milk or other cultures of the +Bulgarian bacillus by people in health as a probable preventive of +disease and a possible agent in the lengthening of life, but it may be +of interest to give a short account of its use by medical men in the +treatment of various ailments. An English authority on the subject, Dr. +Herschell, states that the symptoms of the poisoning of the system by +the toxic substances produced by injurious bacteria in the large +intestine may include headaches, misery and depression of spirits, +drowsiness and stupor, giddiness, dimness of sight and dizziness, +fatigue without obvious cause, both of the muscles and brain, fear, +panic, and nervousness, disagreeable sensations in the limbs or face, +such as numbness, tingling, or prickling, crawling sensation of weight +or of heat or cold, dyspepsia of the sort where there is a deficiency of +hydrochloric acid and pepsin in the gastric juice, accompanied by +flabbiness and loss of power in the muscles of the stomach, and +characterised by flatulence, nausea, loss of appetite, with discomfort +and weight after food, furred tongue, emaciation, earthy colour of the +skin, offensive perspiration and the other signs of biliousness, +enlargement of the liver, and anaemia. These symptoms may have other +causes, and when one or several of them are present a chemical and +physical examination of the urine and faeces is necessary to prove that +they have resulted from auto-intoxication. When this is shown the +soured milk treatment is indicated, and many striking cures are detailed +as witnesses to its efficacy. The liver and kidneys are the natural +guardians of the body against the toxines we are speaking of, and +frequently they are over-strained; the soured milk treatment greatly +lightens their load. In malignant disease of the stomach, soured milk +will frequently be retained when all other foods are rejected. In cases +of neurasthenia and gout it has also proved of value, and in the +"run-down" condition which is so common in middle life. Chronic +diarrhoea and certain forms of constipation have in numerous instances +yielded to the treatment, the whey culture being usually found the most +suitable. Then, in some forms of anaemia, the lactic acid cultures have +proved most successful, and, as a means of rendering the +gastro-intestinal track aseptic previous to operations, they have proved +of considerable value. + +If all this has been accomplished in a year or two, what may not we look +forward to in the future when more extended use and experiment shall +have more fully exhausted the possibilities of the cure? But if we +follow the example of the different nations who have so long used +soured milk as a regular article of diet, does it not seem probable that +we may eliminate some, at least, of the causes of ill-health that call +for the intervention of the doctor? + +The human organism is by no means perfect; we have within us many +defective parts, and some organs whose working seems to be against the +welfare of the economy. It has now been clearly shown that one of the +chief of these is the large intestine, as to the use of which only vague +and unsatisfactory theories have been formed. There can be no doubt as +to the damage which it frequently inflicts on the system, and, thanks to +the researches of Professor Metchnikoff and other investigators, we seem +to be in possession of a natural remedy which is sufficient to deal with +the evils it produces. + + + FOOTNOTES: + + [1] _Discoveries in Nineveh and Babylon_, by Layard, chap. + xiii. + + [2] Ex. xviii. and xxiii.; Lev. ii. and xi. + + [3] _Encyclo. Biblica._ + + [4] Burckhardt and Doughty. + + [5] _Annals of Dairying in Europe_, by Loudon M. Douglas. + + [6] Burckhardt, _Bedouins_. + + [7] This word is spelt in a great many ways by different + writers: _Yoghourt_ would seem to be the one most + favoured.--AUTHOR. + + [8] _Damascus and Palmyra_, by Chas. G. Addison, 1838. + + [9] _Travels in Syria and the Holy Land_, by Burckhardt, + 1822. + + [10] _Lands of the Saracens_, by B. Taylor. + + [11] _Travels through Sweden, Finland, and Lapland and to + the North Cape in the years 1798 and 1799_, by Joseph + Acerbi, 1802. + + [12] Letter to the author, from Mr. H. Cavendish Venables, + British Vice-Consul at Varna. + + [13] _One Hundred and Twenty Years of Life_, by Reinhardt; + _The Secret of Longevity_, by an F.R.M.S. + + [14] _Foods, their Composition and Analysis_, by A. W. + Blyth. + + [15] _Dictionary of Applied Chemistry_, by T. E. Thorpe, + C.B. + + [16] _Koumiss or Fermented Mares' Milk and its Uses, and + the Treatment and Cure of Pulmonary Consumption and Other + Diseases_, by L. Carrick, M.D., 1881. + + [17] _Transactions of the Royal Society of Edinburgh_, + vol. i. + + [18] Clarke's _Travels_, 1810. + + [19] 1845. + + [20] _Dictionary of Applied Chemistry_, by Thorpe. + + [21] A leathern bottle. + + [22] "I have brought forward Tchembulatof's receipt, which + differs from Bogoyavlensky's in the use of a larger + quantity of millet-flour, and in the boiling of the latter + apart from the milk. Dr. Postnikof's plan is the + following: Half a pound of millet-flour and a quarter of a + pound of malt are mixed with a sufficient quantity of + honey to form a paste, which is put into a clean jar, + covered with a linen cloth, and placed on a warm stove. + The mass soon begins to rise, and is then taken out, + wrapped in a piece of muslin, and dropped into a clean + earthenware vessel, containing about a quart of new mares' + milk, which is placed in the same temperature that the + paste was kept in. As soon as signs of fermentation begin + to show themselves in the fluid, the paste must be + removed, while the milk, after being stirred, should be + left in the same temperature till bubbles appear (only in + very small quantities) on its surface. The ferment is then + ready." + + [23] _Food and the Principles of Dietetics._ + + [24] _Food and the Principles of Dietetics_, by Robert + Hutchison, M.D. + + [25] _Bacteria in Milk and its Products_, by Conn. + + [26] _Dict. App. Chem._, Thorpe. + + [27] _Nature_, July 23, 1884. + + [28] _The Exploration of the Caucasus_, by Duncan W. + Freshfield, 1896. + + [29] Quoted by George M. Sternberg, M.D., LL.D., + _Text-Book of Bacteriology_, 1898. + + [30] _Encyclo. Biblica._ + + [31] Conn. + + [32] _Cyclo. of Biblical Lit._, M'Clintock and Strong, and + Burckhardt's _Arabia_. + + [33] _The Indian Medical Gazette_, Sept., 1909, "A New + Lactic Acid producing Streptothrix," by Gopal Ch. + Chatterjee, M.B. + + [34] In their studies on Leben in the _Annales de + l'Institut Pasteur_ of 1899, Rist and Khoury, in speaking + of the amount of lactic acid produced by _Streptobacillus + lebenis_ in milk, say "Nous avons mesure cette acidite + dans une culture sur petit lait de vingt-quatre heures; + elle etait .261 grms. per cent. exprimee en acide + lactique," which will make the amount of lactic acid + produced in one litre of milk 2.61 grms. The production of + this small amount of lactic acid does not tally with the + ordinary view of the vigorous lactic-acid-producing power + of the bacillus. + + [35] _Prolongation of Life._ + + [36] _Prolongation of Life._ + + [37] An accurate census of Bulgaria is being prepared and + will exhibit the cases of long life in that country. + + [38] See A. Rosam, _Oesterreichische Molkerei Zeitung_, 15, + p. 31. + + [39] _Revue generale du Lait_, vii., pp. 8 and 9 (letter + from Dr. Otakar Laxa of Prague, Bohemia, to the author). + + [40] _On the Prolongation of Human Life_, by Elie + Metchnikoff; also _The Century Magazine_, Nov., 1909, "The + Utility of Lactic Microbes," by the same author. + + [41] _Century Magazine_, Nov., 1909. + + [42] See _Annals of Dairying in Europe_, by Loudon M. + Douglas. + + [43] Adapted from a report by Robert E. Turnbull, in _Live + Stock Journal_. + + [44] _Facts about Milk_, by R. A. Pearson, B.S., + Washington. + + [45] _Care and Handling of Milk_, Marshall and Wright, + Bulletin 221, Michigan, 1904. + + [46] _Journal of the Royal Society of Arts_, March 6, + 1908--"Modern Dairy Practice," by Loudon M. Douglas. + + [47] Skolotowski, _Wratsch_, 1883 (Russian), from + Codwyssozki. + + [48] Podowyssozki, _Zeitschr. f. diat. u. physik. + Therapie_ vol. v., 1901, p. 570. + + [49] Hammersten, _Jahresb. u. d. Fortsch. d. Tierchem_, + 1886, Bd. 16, p. 163. + + [50] Essaulow, _Dissert. Moscow_, 1895, _Abstr., Koch's + Jahresb._, 1895, Bd. 6, p. 222. + + [51] Kern, _Bulletin Soc. des Naturalistes de Moscow_, + 1881, 3, p. 141. + + [52] Krannhals, _Deutsch. Arch. f. Klin. Med._, 1884, Bd. + 35, p. 18. + + [53] Beijerinck, _Centralbl. Bakt. Par._, 1889, Bd. 6, p. + 44. + + [54] Scholl, _Die Milch_, Wiesbaden, 1891, p. 38. + + [55] Adametz, _Centralbl. Bakt. Par._, 1889, Bd. 5, p. + 116. + + [56] Freudenreich, _Landw. Jahrb. d. Schweiz._, 1896, vol. + x., p. 1. + + [57] Nikolaiewa, _Annals of the Botan. Lab. of the Med. + Inst. for Women_, No. 10. St. Petersburg, 1907. + + [58] Kuntze, _Centralbl. Bakt. Par._, 1909, 24, p. 101. + + [59] See Chap. II. + + [60] Rubinsky, _Centralbl. Bakt. Par. II._, 1910, vol. + xxviii., p. 161. + + [61] Biel, _Jahresb. ue. d. Fortschr. d. Tierchem_, 1886, + 16, p. 159. + + [62] Allik, _Dissertat. Dorpat._, 1896, 19, p. 303. + + [63] Fleischmann, _Lehrb. d. Milchwirtschaft_, 2d edition. + Bremen, 1898. + + [64] Rist and Khoury, _Annal. Pasteur_, 1902, 16, p. 65. + + [65] Guerbet, _Comptes Rendus_, 1906. + + [66] Weigmann, _Lafar's Handb. d. Techn. Mykol._, 2d + edit., 1905, vol. ii., p. 134. + + [67] Emmerling, _Cent. Bakt. Par._ 1898, vol. iv., p. 418. + + [68] Lindner, _Mikroscop. Betriebscontrolle, i. d. + Gaerungsgew_, 3d edit., Berlin, 1901. + + [69] Kalantharianz, _Dissert. Berlin_, Abs. in _Koch's + Jahresb._, 1898, Bd. 9. + + [70] Luerssen and Kuehn, _Centralbl. Bakt._ + + [71] Piorkowski, _Sitzungsber. der Berl. med. Ges._, Nov., + 1907. + + [72] Metchnikoff, _The Prolongation of Life._ + + [73] Grigoroff, _Revue Medicale de la Suisse Romande_, + 1905, p. 10. + + [74] Grixoni, _Abstr. Cent. Bakt. Par._ 11, 15, p. 750. + + [75] Freudenreich and Jensen, _Cent. Bakt. Par._ 11, 1897, + 3, 545. + + [76] Moro, _Wien. klin. Wochenschr._, 5, 1900. + + [77] Makrinoff, _Cent. Bakt. Par._ 11, 1910, vol. xxvi., + p. 374. + + [78] White and Avery, _Cent. Bakt. Par._ II, 1909, vol. + xxv., p. 161. + + [79] Hastings and Hammer, _Research Bull., Wisconsin + Experimental Station_, 6, 1909. + + [80] Boutroux, _Comp. Rend._, 86, 1905, 605. + + [81] Richet, _Comp. Rend._, 86, 1905, 550. + + [82] Koning, _Milchw. Zentralbl._, 1905, 1, 280. + + [83] Heinemann, _Centralbl. Bakt. Par._ 1908, 21, 57. + + [84] Chap. I. + + [85] Metchnikoff, _The Prolongation of Life_, 1908, p. + 161. + + + INDEX + + + A + + Acerbi, 8 + + Acidity of milk, 64 + + Adametz on keffir, 92 + + Albumen, 52 + + Alcoholic fermentation, 17, 84 + + Allen & Hanbury's apparatus, 132 + + American incubating apparatus, 149 + + Analysis of milk, 48, 61 + + Aneyza Bedouins, 2 + + Arabs, 2 + + Araka, 106 + + Ash of milk, 56 + + + B + + _Bacillus acidi lactici_, 107, 112 + + _Bacillus acidophilus_, 110, 112 + + _Bacillus bulgaricus_, 39, 46, 82, 108, 110, 123, 154 + + _Bacillus casei_, 113 + + _Bacillus caucasicus_, 92, 94, 95, 119 + + _Bacillus caucasina_, 39 + + _Bacillus coli_, 45 + + _Bacillus esterificans_, 96 + + _Bacillus keffir_, 96, 97 + + _Bacillus lebenis_, 105 + + _Bacillus matzoon_, 109, 110 + + Bacillus of long life, 46 + + _Bacillus putrificus_, 122 + + _Bacillus subtilis_, 90, 92, 107 + + Bacteria in milk, 76 + + Bacteriology of fermented milks, 84 + + _Bacterium acidi lactici_, 92, 96 + + _Bacterium aerogenes_, 92, 96 + + _Bacterium coli commune_, 119, 122 + + _Bacterium sardous_, 110, 111 + + Balkan Peninsula, 4 + + Bedouins, 2 + + Beijerinck on keffir, 91 + + Biestings, 63 + + Biology of the keffir grain, 90 + + Blood, water contents of, 50 + + Bourgoul, 6 + + Bulgarian maya, 10, 109 + + Bulgaricus group, cultural characteristics of, 115 + + Burckhardt, 6 + + Butin, 51 + + Butyric acid fermentation, 16 + + Butyrin, 51 + + + C + + Camels' milk, 2 + + Caprinin, 51 + + Capronin, 51 + + Caprylin, 51 + + Carrick on koumiss, 18 + + Casein, 52, 53 + + Centenarians in Servia, Bulgaria, and Roumania, 41 + + Chatterjee on Dadhi, 38 + + Chemistry of milk, 47 + + Chocolate preparations and the soured-milk bacillus, 137 + + Citrates in milk, 57 + + Clay, Paget & Company's apparatus, 132 + + Coagulation of casein, 59 + + _Colitis_, 45 + + Colostrum, 63 + + Constituents of milk, 48 + + Continuous apparatus for producing soured milk, 81 + + Creamometer, 62 + + + D + + Dadhi, 15, 38 + + Dairy Machinery & Construction Company's apparatus, 80, 82 + + Dairy Outfit Company's apparatus, 145 + + Dairy Supply Company's apparatus, 143; + steriliser, 148 + + Dirt in milk, 63 + + Diseases of keffir grains, 97 + + _Dispora caucasia_, 34, 90 + + Dried sour milk, 5 + + Duclaux, 51 + + + E + + Edgar's "Lactogenerator," 143 + + Eggs, yolk of, 52 + + _Enteritis_, 45 + + Enzymes in milk, 57 + + Equipment for town's dairy, 80 + + Essaulow on keffir, 89, 92 + + + F + + Fat of milk, 50 + + Ferments at the altar, 3 + + Fluegge, 35 + + Freshfield on keffir, 33 + + Freudenreich, 92 + + + G + + Gaseous fermentation, 84 + + Gay-Lussac, 17 + + Gioddu, 107 + + Globulin, 54 + + Grieve, Dr. John, on koumiss, 19 + + + H + + Hammerstein on keffir, 89 + + Handling of milk, 68 + + Health and disease, 151 + + Hearson & Company's "Lactobator," 141 + + Hebrews, 3 + + Houran, inhabitants of, 6 + + Hueppe, 16 + + Hutchinson, Dr. H. B., bacillus from English market milk, 120 + + Hutchison on koumiss, 30 + + + I + + Ice chest, 136 + + Impure cultures, 158 + + Incubators, 141 + + India, 1 + + International Dairy Federation, 68 + + + J + + Jebours, 3 + + + K + + Kalmucks, 20 + + Keffir, 15, 32, 85; + old, 88 + + Keffir grain, biology of, 90 + + Kephir, 34, 85. + _See also_ Keffir. + + Keshk, 6 + + Keshk-leben, 6 + + Koumiss, 15, 18; + Bogoyavlensky's method of preparation, 28, 98; + analysis, 102; + artificial, 102 + + Krannhals on keffir, 91 + + Kuntze, 95 + + + L + + Lactic acid, bacillus, 16; + cultures, 55; + fermentation, 16, 84; + Ferments apparatus, 131 + + "Lacto" apparatus, 145 + + "Lactobacilline," 158 + + _Lactobac. caucasicus_, 91 + + _Lactobacillus keffir_, 94 + + Lactometer, 64 + + Lapland, 8 + + Laurin, 51 + + Layard, 2 + + Leben, 15, 37, 104 + + Leben Raib, 104 + + Lecithin, 52 + + "Le Ferment" apparatus, 128 + + Liebig, 17 + + Longevity, 155 + + + M + + Mares' milk, 24 + + Matzoon, 15, 38, 106 + + Maya, 42; + Bulgarian, 10 + + Maya Bulgare Company's apparatus, 131 + + Meeresy, 5 + + Metchnikoff, 34, 40, 44, 121, 158, 163 + + Micro-organisms, discovery of, 13 + + Middle Ages, 13 + + Milk-filling apparatus for bottles, 82 + + Milk, general properties of, 57; + of different animals, 60; + supply of the United Kingdom, 69; + industry in the United States, 71; + management, 74 + + Mitscherlich, 17 + + Myristin, 51 + + + N + + Neolithic times, 1 + + Nikolaiewa, 95 + + Nitrogenous constituents of milk, 52 + + + O + + Ojran, 106 + + Olein, 51 + + Oxygala of Pliny, 4 + + + P + + Paleolithic times, 1 + + Palmitin, 51 + + Pasteur, 14, 78 + + Pasteurisation, 78 + + Pelouze, 17 + + Pilaff of rice, 5 + + Pina, 21 + + Podowyssowski on keffir, 87 + + Preparation, of soured milk, 81; + in the house, 125; + in the dairy, 139 + + Primary cooler, 78 + + Proteids, 53 + + Pyrenees, 4 + + + R + + Reindeer's milk as soured milk, 8 + + Rubruquis, William de, 19 + + + S + + _Saccharomyces cerevisseae_, 90 + + _Saccharomyces keffir_, 32, 33, 91, 93, 94 + + Sakwaska, 88 + + Sale of Food and Drugs Act, 1899, 49 + + Scheele, 17 + + Scholl on keffir, 91 + + Scythians, 18 + + Secondary cooler, 79 + + Shammar Bedouins, 2 + + Sheneena, 2 + + Skolotowski on keffir, 86 + + Smith, Professor Robertson, 3 + + Soured milk, in the house, 125; + in the dairy, 139; + in health and disease, 151; + from impure cultures, 158; + use of, 159 + + Souring of milk, 47, 54 + + Specific gravity of milk, 65 + + Stearin, 51 + + Steriliser, 148 + + _Streptobacilli lebeni_, 39 + + _Streptobacillus lebenis_, 111 + + _Streptococcus a_, 93, 94 + + _Streptococcus acidi lactici_, 95, 96 + + _Streptococcus b_, 93, 94 + + _Streptococcus lacticus_, 92, 93, 122, 124 + + Sugar of milk, 54 + + Sugar preparations and the soured-milk bacillus, 137 + + Suter-Naef on Swiss koumiss, 26 + + Swedish whey cheese, 60 + + Swiss hard cheese, 113 + + Symptoms of disease, 161 + + + T + + Temperature allowances when testing milk, tables of, 66 + + Town's dairy equipment, 80 + + Transmission of disease by milk, 72 + + + U + + United Kingdom, milk supply of, 69 + + United States, milk industry of, 71 + + Urgoutnik, 43 + + + V + + Van Leeuwenhoek, 13 + + Variation limits of milk, 49 + + Vedas, 1 + + "Veronelle" apparatus, 132 + + Vina, 21 + + Vinous fermentation, 17 + + + W + + Willows Refrigerating Company's apparatus, 144, 145 + + Wilson on koumiss, 23 + + + Y + + Yoghourt, 9, 42, 46, 107 + + Yoghourt bacillus, 109 + + + Z + + Zakvaska, 42 + + * * * * * + + Putnam's + Science Series + + + 1. +The Study of Man.+ By A. 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ARTHUR THOMPSON, M.A. + + 20. +Climate.+ By ROBERT DECOURCY WARD. + + 21. +Age, Growth, and Death.+ By CHARLES S. MINOT. + + 22. +The Interpretation of Nature.+ By C. LLOYD MORGAN. + + 23. +Mosquito Life.+ By EVELYN GROESBEECK MITCHELL. + + 24. +Thinking, Feeling, Doing.+ By E. W. SCRIPTURE. + + 25. +The World's Gold.+ By L. DE LAUNAY. + + 26. +The Interpretation of Radium.+ By F. SODDY. + + 27. +Criminal Man.+ By CESARE LOMBROSO. + + 28. +The Origin of Life.+ By H. CHARLTON BASTIAN. + + 29. +The Bacillus of Long Life.+ By LOUDON M. DOUGLAS. + + _For list of works in preparation see end of this volume_ + + * * * * * + + _A Selection from the + Catalogue of_ + + G. P. PUTNAM'S SONS + + Complete Catalogue sent + on application + + Putnam's + Science Series + + + +1.--The Study of Man.+ By Professor A. C. HADDON, M.A., D.Sc., + M.R.I.A. Fully illustrated. 8o., net $2.00. + + "A timely and useful volume.... 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Net, $1.25. + + Dr Morgan seeks to prove that a belief in purpose as the causal + reality of which nature is an expression is not inconsistent with a + full and whole-hearted acceptance of the explanations of naturalism. + + + +23.--Mosquito Life.+ The Habits and Life Cycles of the Known + Mosquitoes of the United States; Methods for their Control; + and Keys for Easy Identification of the Species in their Various + Stages. An account based on the investigation of the late James + William Dupree, Surgeon-General of Louisiana, and upon the + original observations by the Writer. By EVELYN GROESBEECK + MITCHELL, A.B., M.S. With 64 Illustrations. Crown 8vo. + Net, $2.00. + + This volume has been designed to meet the demand of the constantly + increasing number of students for a work presenting in compact form + the essential facts so far made known by scientific investigation in + regard to the different phases of this, as is now conceded, important + and highly interesting subject. While aiming to keep within reasonable + bounds, that it may be used for work in the field and in the + laboratory, no portion of the work has been slighted, or fundamental + information omitted, in the endeavor to carry this plan into effect. + + + +24.--Thinking, Feeling, Doing.+ An Introduction to Mental Science. + By E. W. SCRIPTURE, Ph.D., M.D., Assistant Neurologist Columbia + University, formerly Director of the Psychological Laboratory at + Yale University. 189 Illustrations. 2d Edition, Revised and + Enlarged. Crown 8vo. Net, $1.75. + + "The chapters on Time and Action, Reaction Time, Thinking Time, + Rhythmic Action, and Power and Will are most interesting. This book + should be carefully read by every one who desires to be familiar with + the advances made in the study of the mind, which advances, in the + last twenty-five years, have been quite as striking and epoch-making + as the strides made in the more material lines of knowledge."--_Jour. + Amer. Med. Ass'n._, Feb. 22, 1908. + + + +25.--The World's Gold.+ By L. DE LAUNAY, Professor at the Ecole + Superieure des Mines. Translated by Orlando Cyprian Williams. + With an Introduction by Charles A. Conant, author of "History of + Modern Banks of Issue," etc. Crown 8vo. Net, $1.75. + + M. de Launay is a professor of considerable repute not only in France, + but among scientists throughout the world. In this work he traces the + various uses and phases of gold; first, its geology; secondly, its + extraction; thirdly, its economic value. + + + +26.--The Interpretation of Radium.+ By FREDERICK SODDY, Lecturer + in Physical Chemistry in the University of Glasgow. Crown 8vo. + With Diagrams. Net, $1.75. + + As the application of the present day interpretation of Radium (that + it is an element undergoing spontaneous disintegration) is not + confined to the physical sciences, but has a wide and general bearing + upon our whole outlook on Nature, Mr. Soddy has presented the subject + in non-technical language, so that the ideas involved are within reach + of the lay reader. No effort has been spared to get to the root of the + matter and to secure accuracy, so that the book should prove + serviceable to other fields of science and investigation, as well as + to the general public. + + + +27.--Criminal Man.+ According to the Classification of CESARE + LOMBROSO. Briefly Summarized by his Daughter, Gina Lombroso + Ferrero. With 36 Illustrations and a Bibliography of Lombroso's + Publications on the Subject. Crown 8vo. Net, $2.00. + + Signora Guglielmo Ferrero's resume of her father's work on criminal + anthropology is specially dedicated to all those whose office it is to + correct, reform, and punish the criminal, with a view to diminishing + the injury caused to society by his anti-social acts; also to + superintendents, teachers, and those engaged in rescuing orphans and + children of vicious habits, as a guide in checking the development of + evil germs and eliminating incorrigible subjects whose example is a + source of corruption to others. + + * * * * * + + The most valuable production since Darwin's "Origin of Species." + + The Nature of Man + + _Studies in Optimistic Philosophy_ + + By Elie Metchnikoff + + Sub-Director of the Pasteur Institute, Paris + + Translated with an Introduction by + + P. Chambers Mitchell + + Secretary of the Zoological Society + + Octavo. Illustrated. Popular Edition. $1.50 net. By mail, $1.65 + + It is not often that a scientific book may be read with ease, profit, + and pleasure by the general reader, so that M. Metchnikoff's book + comes in the nature of an agreeable surprise. It is marked by a + refreshing _naivete_ and a large simplicity which are + characteristically Russian. The scientific importance of this work is + so great that it is spoken of in England as the most valuable + production since Darwin's _Origin of Species_. + + Opinions of the Press + + "An extremely interesting and typical book.... With a distinguished + frankness, M. Metchnikoff defines his attitude to our universal + prepossessions. It is his theory that the infirmities of age are to be + overcome. If there be ground for this conception, humanity is to be + profoundly changed and what we call life now, will be the childhood + and youth of that longer and larger life."--H. G. WELLS, in _London + Speaker_. + + "Undoubtedly a great book (in some quarters it has been hailed as the + greatest since Darwin's famous message to the world) and should be + read by all intelligent men and women."--_The Nation._ + + "A book to be set side by side with Huxley's Essays, whose spirit it + carries a step further on the long road towards its goal."--_Mail and + Express._ + + New York--G. P. Putnam's Sons--London + + * * * * * + + "_Remarkable for its simple language and clear + style.... Bears the stamp of a production of + an erudite scientist and a deep thinker._"--Science. + + + The Prolongation of Life + + Optimistic Essays + + _By_ Elie Metchnikoff + + _Author of "The Nature of Man," etc._ + + _8vo. Illustrated Popular Edition. $1.75 net By mail, $1.90_ + + M. Elie Metchnikoff is one of those rare scientists who have found a + way to lay hold of and present to the world in untechnical + phraseology, intelligible to the lay mind, such results of his + researches as are of universal interest and go straight home to the + bosoms and business of intelligent men. _The Nature of Man_, by the + same author, was one of the most fascinating books, at once popular, + and scientific, which have appeared for decades. The book here in + question will stand beside it as a worthy companion volume. It is + satisfactory to report that, absorbed as Metchnikoff is in "material" + problems, and deep as he is in the mysteries of the physical universe, + these essays show him to be an optimist who speaks with no uncertain + voice. + + A great deal of attention is given in _The Prolongation of Human Life_ + to the subject of old age and its causes, with scientific observations + of special cases among human beings and the lower animals. The author + suggests means of prolonging life and health, while contemplating + natural death with serenity, and finding that agreeable sensations + accompany its approach. Beyond a certain point it seems to him a + disadvantage to prolong life. Passing on from these mortuary + lucubrations, the essays concern themselves with psychological + matters, with optimism and pessimism and in general with questions of + science and morals. The temperaments of certain great men are analyzed + in studies that have for their subjects respectively Byron, Leopardi, + Schopenhauer, and Goethe. In the preface the author says that he has + avoided, as far as possible, repeating points which have been + sufficiently treated in _The Nature of Man_. + + + G. P. PUTNAM'S SONS + + NEW YORK LONDON + + + + + +End of Project Gutenberg's The Bacillus of Long Life, by Loudon Douglas + +*** END OF THIS PROJECT GUTENBERG EBOOK THE BACILLUS OF LONG LIFE *** + +***** This file should be named 31691.txt or 31691.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/3/1/6/9/31691/ + +Produced by Peter Vachuska, Turgut Dincer, Chuck Greif 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. 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