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diff --git a/41812-8.txt b/41812-8.txt deleted file mode 100644 index ff0bb41..0000000 --- a/41812-8.txt +++ /dev/null @@ -1,6233 +0,0 @@ -The Project Gutenberg EBook of Variation in the Muscles and Nerves of the -Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes), by E. Bruce Holmes - -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/license - - -Title: Variation in the Muscles and Nerves of the Leg in - Two Genera of Grouse (Tympanuchus and Pedioecetes) - -Author: E. Bruce Holmes - -Release Date: January 10, 2013 [EBook #41812] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK VARIATION IN THE MUSCLES AND *** - - - - -Produced by Chris Curnow, Matthias Grammel, Joseph Cooper, -some pages courtesy of The Internet Archive and the Online -Distributed Proofreading Team at http://www.pgdp.net - - - - - - - - - - UNIVERSITY OF KANSAS PUBLICATIONS - MUSEUM OF NATURAL HISTORY - - Vol. 12, No. 9, pp. 363-474, 20 figs. - - October 25, 1963 - - - Variation in the Muscles and Nerves - of the Leg in Two Genera of Grouse - (Tympanuchus and Pedioecetes) - - BY - E. BRUCE HOLMES - - - - UNIVERSITY OF KANSAS - LAWRENCE - 1963 - - - - -UNIVERSITY OF KANSAS PUBLICATIONS -MUSEUM OF NATURAL HISTORY - - -Institutional libraries interested in publications exchange may obtain -this series by addressing the Exchange Librarian, University of Kansas -Library, Lawrence, Kansas. Copies for individuals, persons working in a -particular field of study, may be obtained by addressing instead the -Museum of Natural History, University of Kansas, Lawrence, Kansas. There -is no provision for sale of this series by the University Library, which -meets institutional requests, or by the Museum of Natural History, which -meets the requests of individuals. Nevertheless, when individuals -request copies from the Museum, 25 cents should be included, for each -separate number that is 100 pages or more in length, for the purpose of -defraying the costs of wrapping and mailing. - - * An asterisk designates those numbers of which the Museum's supply (not - the Library's supply) is exhausted. Numbers published to date, in this - series, are as follows: - - Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950. - - *Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. - 1-444, 140 figures in text. April 9, 1948. - - Vol. 3. *1. The avifauna of Micronesia, its origin, evolution, and - distribution. By Rollin H. Baker. Pp. 1-359, 16 figures - in text. June 12, 1951. - - *2. A quantitative study of the nocturnal migration of birds. - By George H. Lowery, Jr. Pp. 361-472, 47 figures in text. - June 29, 1951. - - 3. Phylogeny of the waxwings and allied birds. By M. Dale - Arvey. Pp. 473-530, 49 figures in text, 13 tables. - October 10, 1951. - - *4. Birds from the state of Veracruz, Mexico. By George H. - Lowery, Jr., and Walter W. Dalquest. Pp. 531-649, 7 - figures in text, 2 tables. October 10, 1951. - - Index. Pp. 651-681. - - *Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, - 41 plates, 31 figures in text. December 27, 1951. - - Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953. - - *Vol. 6. (Complete) Mammals of Utah, _taxonomy and distribution_. By - Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables. - August 10, 1952. - - Vol. 7. Nos. 1-15 and index. Pp. 1-651, 1952-1955. - - Vol. 8. Nos. 1-10 and index. Pp. 1-675, 1954-1956. - - Vol. 9. *1. Speciation of the wandering shrew. By James S. Findley. - Pp. 1-68, 18 figures in text. December 10, 1955. - - 2. Additional records and extension of ranges of mammals - from Utah. By Stephen D. Durrant, M. Raymond Lee, and - Richard M. Hansen, Pp. 69-80. December 10, 1955. - - 3. A new long-eared myotis (Myotis evotis) from - northeastern Mexico. By Rollin H. Baker and Howard J. - Stains. Pp. 81-84. December 10, 1955. - - 4. Subspeciation in the meadow mouse, Microtus - pennsylvanicus, in Wyoming. By Sydney Anderson. Pp. - 85-104, 2 figures in text. May 10, 1956. - - 5. The condylarth genus Ellipsodon. By Robert W. Wilson. - Pp. 105-116, 6 figures in text. May 19, 1956. - - 6. Additional remains of the multituberculate genus - Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10 figures - in text. May 19, 1956. - - 7. Mammals of Coahulia, Mexico. By Rollin H. Baker. Pp. - 125-335, 75 figures in text. June 15, 1956. - - 8. Comments on the taxonomic status of Apodemus peninsulae, - with description of a new subspecies from North China. - By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text, 1 - table. August 15, 1956. - - 9. Extensions of known ranges of Mexican bats. By Sydney - Anderson. Pp. 347-351. August 15, 1956. - - 10. A new bat (Genus Leptonycteris) from Coahulia. By Howard - J. Stains. Pp. 353-356. January 21, 1957. - - 11. A new species of pocket gopher (Genus Pappogeomys) from - Jalisco, Mexico. By Robert J. Russell. Pp. 357-361. - January 21, 1957. - - 12. Geographic variation in the pocket gopher, Thomomys - bottae, in Colorado. By Phillip M. Youngman. Pp. 363-384, - 7 figures in text. February 21, 1958. - - 13. New bog lemming (genus Synaptomys) from Nebraska. By J. - Knox Jones, Jr. Pp. 385-388. May 12, 1958. - - 14. Pleistocene bats from San Josecito Cave, Nuevo León, - México. By J. Knox Jones, Jr. Pp. 389-396. December 19, - 1958. - - 15. New subspecies of the rodent Baiomys from Central - America. By Robert L. Packard. Pp. 397-404. December 19, - 1958. - - 16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson. - Pp. 405-414, 1 figure in text. May 20, 1959. - - 17. Distribution, variation, and relationships of the montane - vole, Microtus montanus. By Sydney Anderson. Pp. 415-511, - 12 figures in text, 2 tables. August 1, 1959. - - (Continued on inside of back cover) - - - - - UNIVERSITY OF KANSAS PUBLICATIONS - MUSEUM OF NATURAL HISTORY - - Vol. 12, No. 9, pp. 363-474, 20 figs. - - October 25, 1963 - - Variation in the Muscles and Nerves - of the Leg in Two Genera of Grouse - (Tympanuchus and Pedioecetes) - - BY - E. BRUCE HOLMES - - UNIVERSITY OF KANSAS - LAWRENCE - 1963 - - - - -UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY - - Editors: E. Raymond Hall, Chairman, Henry S. Fitch, - Theodore H. Eaton, Jr. - - - Volume 12, No. 9, pp. 363-474, 20 figs. - Published October 25, 1963 - - - UNIVERSITY OF KANSAS - Lawrence, Kansas - - - PRINTED BY - JEAN M. NEIBARGER, STATE PRINTER - TOPEKA, KANSAS - 1963 - - [Illustration] - - 29-5835 - - - - - Variation in the Muscles and Nerves - of the Leg in Two Genera of Grouse - (Tympanuchus and Pedioecetes) - - BY - - E. BRUCE HOLMES - - - - -CONTENTS - - - PAGE - - Introduction 367 - - Materials and Methods 368 - - Terminology 369 - - Acknowledgments 375 - - Skeleton 375 - - Nerves 376 - Lumbosacral Plexus 376 - Femoral Nerve 377 - Obturator Nerve 379 - Sciatic Nerve 379 - Peroneal Nerve 382 - Tibial Nerve 384 - - Muscles 396 - M. Extensor Iliotibialis Lateralis 398 - M. Extensor Iliotibialis Anticus 405 - M. Ambiens 408 - M. Vastus Lateralis 408 - M. Vastus Medialis 410 - M. Femoritibialis Internus 410 - M. Extensor Iliofibularis 411 - M. Piriformis 412 - M. Gluteus Profundus 413 - M. Iliacus 414 - M. Iliotrochantericus Medius 415 - M. Psoas 416 - M. Flexor Cruris Lateralis 416 - M. Flexor Cruris Medialis 417 - M. Caudofemoralis 418 - M. Flexor Ischiofemoralis 420 - M. Adductor Superficialis 420 - M. Adductor Profundus 421 - M. Obturator 422 - M. Femorocruralis 425 - M. Gastrocnemius 426 - M. Flexor Perforans et Perforatus Digiti II 427 - M. Flexor Perforans et Perforatus Digiti III 429 - M. Flexor Perforatus Digiti IV 430 - M. Flexor Perforatus Digiti III 432 - M. Flexor Perforatus Digiti II 433 - M. Flexor Hallucis Longus 435 - M. Plantaris 435 - M. Flexor Digitorum Longus 436 - M. Popliteus 438 - M. Peroneus Longus 438 - M. Tibialis Anticus 439 - M. Extensor Digitorum Longus 440 - M. Peroneus Brevis 441 - M. Extensor Hallucis Longus 442 - M. Abductor Digiti II 443 - M. Extensor Brevis Digiti III 444 - M. Extensor Proprius Digiti III 444 - M. Extensor Brevis Digiti IV 445 - M. Lumbricalis 445 - M. Abductor Digiti IV 446 - M. Flexor Hallucis Brevis 446 - - Discussion and Conclusions 446 - Analysis of Individual Variation 446 - Muscles 447 - Nerves 449 - Analysis of Variation Between Species 451 - Comparison with Other Studies of Innervation 452 - - Summary 457 - - Literature Cited 473 - - - - -LIST OF ILLUSTRATIONS - - - PAGE - - - FIG. 1. Pelvis of _Tympanuchus pallidicinctus_. - A. Lateral view. × 1. B. Ventral view. × 1-1/8. 370 - - FIG. 2. Ventral views of the lumbosacral plexus of - _Tympanuchus pallidicinctus_. - Sympathetic ganglionated chain removed. Numbers indicate - synsacral spinal nerves. × 2. A. T.p. 1L. B. T.p. 2L. 386 - - FIG. 3. Ventral views of the lumbosacral plexus. - Sympathetic ganglionated chain removed. Numbers indicate - synsacral spinal nerves. × 2. A. _Tympanuchus cupido pinnatus_ - 3L. B. _Pedioecetes phasianellus jamesi_ 4L. 387 - - FIG. 4. Semidiagrammatic ventral views of the femoral - nerve, showing the distribution of the branches. × 3. 1,2, - M. extensor iliotibialis anticus; 3, cutaneous; 4-6, M. extensor - iliotibialis lateralis; 7,8, M. iliacus; 9, M. gluteus - profundus; 10-12, fused Mm. vastus lateralis and vastus - medialis; 13,14, M. vastus medialis; 15, M. ambiens; - 16, M. femoritibialis internus; 17, nonmuscular; 18, M. - psoas; 19, M. iliotrochantericus medius. A. _Tympanuchus - cupido pinnatus_ 3L. B. _Pedioecetes phasianellus - jamesi_ 3L. 388 - - FIG. 5. Semidiagrammatic ventral views of the femoral - nerve, showing the distribution of the branches. × 3. 1,2, M. - extensor iliotibialis anticus; 3, cutaneous; 5,6, M. extensor - iliotibialis lateralis; 7,8, M. iliacus; 9, M. gluteus - profundus; 10,11, fused Mm. vastus lateralis and vastus - medialis; 13, M. vastus medialis; 15, M. ambiens; 16, - M. femoritibialis internus; 17, nonmuscular; 18, M. psoas; - 19, M. iliotrochantericus medius. A. _Tympanuchus - pallidicinctus_ 2L. B. _Tympanuchus cupido attwateri_ 1R. 389 - - FIG. 6. Semidiagrammatic dorsolateral view of the sciatic - nerve of _Pedioecetes phasianellus jamesi_ 3R, showing - the distribution of the branches. × 2-1/2. 1, M. gluteus - profundus; 2, M. piriformis; 3, M. extensor iliotibialis - lateralis; 4-7, M. extensor iliofibularis; 8, M. flexor cruris - medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. flexor - cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; - 13-15, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor - ischiofemoralis; 18,19, M. femorocruralis (branch of tibial - nerve); 20, cutaneous; 21, M. gastrocnemius pars media (branch - of tibial nerve); 22, cutaneous. 390 - - FIG. 7. Semidiagrammatic dorsolateral view of the sciatic - nerve of _Tympanuchus pallidicinctus_ 2L, showing the - distribution of the branches. × 2-1/2. 1, M. gluteus profundus; - 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4, 7, - M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, - cutaneous; 10, to pudendal plexus; 11, M. flexor cruris - lateralis; 12, M. caudofemoralis pars caudifemoralis; 13-15, - M. caudofemoralis pars iliofemoralis; 17, M. flexor - ischiofemoralis; 18, M. femorocruralis (branch of tibial nerve); - 22, cutaneous; 23, nonmuscular (branch of peroneal nerve). 391 - - FIG. 8. Semidiagrammatic dorsolateral view of the - sciatic nerve of _Tympanuchus cupido pinnatus_ 3L, - showing the distribution of the branches. × 2-1/2. 1, - M. gluteus profundus; 2, M. piriformis; 3, M. extensor - iliotibialis lateralis; 4,7, M. extensor iliofibularis; - 8, M. flexor cruris medialis; 9, cutaneous; 11, M. flexor - cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; - 13, M. caudofemoralis pars iliofemoralis; 17, M. flexor - ischiofemoralis; 18, M. femorocruralis (branch of tibial - nerve); 20, cutaneous; 22, cutaneous. 392 - - FIG. 9. Semidiagrammatic dorsolateral view of the - sciatic nerve of _Pedioecetes phasianellus jamesi_ 3L, - showing the distribution of the branches. × 2-1/2. 1, - M. gluteus profundus; 2, M. piriformis; 3, M. extensor - iliotibialis lateralis; 4,5,7, M. extensor iliofibularis; - 8, M. flexor cruris medialis; 9, cutaneous; 11, M. flexor - cruris lateralis; 13,14, M. caudofemoralis pars iliofemoralis; - 16,17, M. flexor ischiofemoralis; 18,19, M. femorocruralis - (branch of tibial nerve); 20, cutaneous; 22, cutaneous. 393 - - FIG. 10. A,B. Semidiagrammatic drawings of the peroneal - nerve of _Tympanuchus pallidicinctus_ 1L, showing the - distribution of the branches. × 2. C. Semidiagrammatic drawing - of the distal part of the peroneal nerve of _Tympanuchus - cupido attwateri_ 1R, showing the distribution of the - branches. × 2. 1,2, M. tibialis anticus (tibial head); 3,4, - M. tibialis anticus (femoral head); 5, M. extensor digitorum - longus; 6, nonmuscular; 7,8, M. peroneus longus; 9, M. peroneus - brevis; 10,11, M. extensor hallucis longus (proximal head); - 12, M. extensor hallucis longus (distal head); 13-15, nonmuscular - (to toes); 16, M. abductor digiti II; 17, M. extensor brevis - digiti III; 18, M. extensor brevis digiti IV. 394 - - FIG. 11. A,B. Semidiagrammatic drawings of the tibial - nerve (excluding the paraperoneal branch) of _Tympanuchus - pallidicinctus_, showing the distribution of the branches. - × 2. A. T.p. 1L. B. T.p. 3R. C. Semidiagrammatic drawing - of the distal part of the paraperoneal branch of the tibial - nerve of _Pedioecetes phasianellus jamesi_ 2L, showing - the distribution of the branches. × 2. 1, M. femorocruralis; - 2, M. gastrocnemius pars media; 3, M. popliteus; 4, M. plantaris; - 5, M. flexor digitorum longus; 6-8, nonmuscular; 9-11, M. - gastrocnemius pars interna; 12,13, M. flexor hallucis longus; - 14-16, M. flexor perforatus digiti IV (medial head); 17, M. - flexor perforatus digiti III (medial head); 18-20, M. flexor - perforatus digiti II; 21, M. flexor perforatus digiti IV - (lateral head); 22-24, M. flexor perforatus digiti IV - (anterolateral head); 25, M. flexor perforatus digiti III - (anterolateral head); 26, M. flexor perforans et perforatus - digiti III; 27,28, M. flexor perforans et perforatus digiti II; - 29, M. gastrocnemius pars externa; 30,31, M. abductor digiti IV; - 32,33, M. flexor hallucis brevis; 34,35, nonmuscular (to toes). 395 - - FIG. 12. _Tympanuchus pallidicinctus_ 2L. Lateral - view of the superficial muscles of the left leg. × 1. 397 - - FIG. 13. _Tympanuchus pallidicinctus_ 2L. Medial - view of the superficial muscles of the left leg. × 1. Articular - capsule shown by concentrically arranged dashes. 398 - - FIG. 14. _Tympanuchus pallidicinctus_ 2L. Lateral - view of the muscles of the left leg. The following muscles have - been removed: extensor iliotibialis lateralis, extensor - iliotibialis anticus, gastrocnemius pars externa and pars - interna, and peroneus longus. × 1. 399 - - FIG. 15. _Tympanuchus pallidicinctus_ 2L. Medial - view of the muscles of the left leg. The following muscles have - been removed: extensor iliotibialis lateralis, extensor - iliotibialis anticus, ambiens, flexor cruris lateralis (in part), - flexor cruris medialis (in part), gastrocnemius pars externa - and pars interna, and peroneus longus. × 1. 400 - - FIG. 16. _Tympanuchus pallidicinctus_ 2L. Lateral - view of the muscles of the left leg. The following muscles, - in addition to those listed for Fig. 14, have been removed: - ambiens, vastus lateralis pars lateralis, vastus medialis (except - for part of patellar tendon), extensor iliofibularis, flexor - cruris lateralis (in part), flexor perforans et perforatus - digiti II, and flexor perforans et perforatus digiti III. × 1. 401 - - FIG. 17. _Tympanuchus pallidicinctus_ 2L. Lateral - view of the muscles of the left leg. The following muscles, in - addition to those listed for Fig. 16, have been removed: vastus - lateralis pars postica, gluteus profundus, flexor cruris medialis - (in part), caudofemoralis, flexor perforatus digiti IV, and - tibialis anticus. × 1. 402 - - FIG. 18. _Tympanuchus pallidicinctus_ 2L. Lateral - view of the muscles of the left leg. The following muscles, in - addition to those listed for Fig. 17, have been removed: patellar - tendon, iliacus, iliotrochantericus medius, flexor cruris - lateralis, flexor cruris medialis, flexor ischiofemoralis, - adductor superficialis, femorocruralis, gastrocnemius pars media, - flexor perforatus digiti III, flexor perforatus digiti II, flexor - hallucis longus, plantaris, flexor digitorum longus, popliteus, - and extensor digitorum longus. × 1. 403 - - FIG. 19. _Tympanuchus pallidicinctus_ 2L. A. - Posterior view of the muscles of the left shank. The following - shank muscles, in addition to those listed for Fig. 17, have - been removed: gastrocnemius pars media, flexor perforatus - digiti III, and flexor perforatus digiti II. × 1. B. Posterior - view of the proximal end of the shank, showing the most deeply - situated muscle. × 1. C. Lateral view of the head of the left - femur and the middle part of the pelvis, showing the deepest - part of M. obturator. × 1. D. Medial view of the posteroventral - part of the left side of the pelvis, showing the intrapelvic part - of M. obturator. × 1. E. Anterior view of the left - tarsometatarsus, showing the dorsal intrinsic muscles of the - foot. × 1-1/2. F. Posterior view of the left tarsometatarsus, - showing the ventral intrinsic muscles of the foot. × 1-1/2. 404 - - FIG. 20. A-D. Dorsal views of M. iliotrochantericus - medius, showing its relationship to femoral notch. × 1. In D, - note absence of femoral notch and location of branch of femoral - nerve. A. _Tympanuchus pallidicinctus_ 2L. B. _T. cupido - pinnatus_ 4L. C. _Pedioecetes phasianellus jamesi_ 1L. - D. _T. pallidicinctus_ 3L. - E. Medial view of distal end of M. flexor cruris medialis of - _P. p. jamesi_ 4L. × 1. Part of insertion is covered by - medial collateral ligament. - F,G. Lateral views of posteroproximal corner of M. extensor - iliotibialis lateralis (removed from specimen). × 1. F. - _T. pallidicinctus_ 2L. G. _P. p. jamesi_ 3L. - H,I. Dorsolateral views of M. piriformis. × 1. H. _P. - p. jamesi_ 1L. I. _T. cupido attwateri_ 1L. - J. Lateral view of M. caudofemoralis pars caudifemoralis - (removed from specimen) of _T. c. pinnatus_ 4L. × 1. - K. Lateral view of extrapelvic part of M. obturator of - _T. pallidicinctus_ 3L (bones not shown). × 2. - L,M. Region surrounding obturator foramen of _T. - pallidicinctus_ 3L, showing points of attachment of three - parts of M. obturator (muscles removed). × 3. L. Lateral - view. M. Medial view. - N. Anterior view of left tarsometatarsus of _P. p. - jamesi_ 4L, showing dorsal intrinsic muscles of foot. - × 1-1/2. Tendon of M. extensor digitorum longus has been - removed. 406 - - - - -INTRODUCTION - - -The purposes of this study were: (1) to obtain information on individual -variation in the anatomy of the muscles and nerves of the leg of -_Tympanuchus cupido pinnatus_ (Greater Prairie Chicken), _T. c. -attwateri_ (Attwater's Prairie Chicken), _T. pallidicinctus_ (Lesser -Prairie Chicken), and _Pedioecetes phasianellus jamesi_ (Sharp-tailed -Grouse); (2) to determine whether or not the two species of the genus -_Tympanuchus_ differ constantly in the myology of the leg; and (3) to -determine what constant differences in the myology of the leg exist -between the two closely related genera _Tympanuchus_ and _Pedioecetes_. - -These particular birds were chosen because they are closely related, and -closely resemble one another in habitats occupied and in patterns of -behavior. It was desired to study examples that showed as few adaptive -differences as possible among the grouse. Series of each of the three -species of grouse were readily obtainable, making it possible to draw -comparisons at the level of individuals, subspecies, species, and -genera. - -The study here reported on was begun in the spring of 1957 and was -completed in the autumn of 1961. - -Prior work on the muscles of the leg of birds has been reviewed by -Hudson (1937) and Hudson, _et al._ (1959). Only papers dealing with the -innervation of the leg in birds are reviewed below. - - DeMan (1873) treated the nerves of _Paradisea papuana_, _Corvus - monedula_, and the chicken; he also commented briefly on a few - other species. Jhering (Ihering, 1873) briefly described the - lumbosacral plexus in approximately a dozen birds, but illustrated - only two. Gadow (1880) described the nerves in _Struthio_, _Rhea_, - and _Casuarius_; his paper contains some excellent illustrations of - nerves. Unfortunately, the text is marred by numerous confusing - typographical errors. Carlsson (1884) described the nerves of - _Eudyptes chrysolopha_, _Alca torda_, _Mergulus alle_, and _Mormon - arcticus_. Gadow (1891) described the nerves in a study that - included a large variety of birds, but published few illustrations. - DuToit (1913) described the lumbosacral plexus of the chicken. - Romer (1927) gave the innervation of the hip and thigh muscles in - the chicken, but did not cover the lumbosacral plexus. Appleton - (1928) gave the innervation, in various birds, only of those - muscles of the hip and thigh that are supplied by the tibial and - peroneal nerves; he did not include the lumbosacral plexus. - Sudilovskaya (1931) described the nerves of _Struthio_, _Rhea_, and - _Dromaeus_ (_Dromiceius_). Unfortunately, his illustrations are - almost useless as far as the nerves are concerned. Boas (1933) - described the lumbosacral plexus in a large number of birds. His - extensive account includes numerous good illustrations. Howell - (1938) listed the innervation of the hip and thigh muscles in the - chicken; he did not include the lumbosacral plexus. Fisher (1946) - listed the innervation of the muscles of vultures, but did not - include the lumbosacral plexus. Wilcox (1948) gave the innervation - of the muscles of _Gavia immer_, but did not include the lumbosacral - plexus. Fisher and Goodman (1955) described the nerves in the Whooping - Crane. Papers by Chomiak (1950) and Yasuda, _et al._ (1959), both - dealing with the chicken, were not examined. - - - - -MATERIALS AND METHODS - - -Complete dissections of the muscles and nerves were made in eight legs -(of five specimens) of the Lesser Prairie Chicken (_Tympanuchus -pallidicinctus_), six legs (of four specimens) of the Greater Prairie -Chicken (_T. cupido pinnatus_), three legs (of two specimens) of -Attwater's Prairie Chicken (_T. cupido attwateri_), and six legs (of -four specimens) of the Sharp-tailed Grouse (_Pedioecetes phasianellus -jamesi_). - -For convenience and simplicity of reference, each specimen has been -designated by a symbol consisting of the first letter of the genus and -of the species (and also of the subspecies in _T. cupido_) plus a -number. The letter "L" or "R" is added to indicate the left or right -leg. Thus the symbol T.p. 1L refers to the left leg of specimen number -one of _T. pallidicinctus_. - -All specimens are in the University of Kansas Museum of Natural History. -The catalogue number of each specimen, and the legs of it that were -dissected, are listed below. - - T.p. 1L,R KU38520 T.c.p. 4L KU38518 - T.p. 2L,R KU38521 T.c.a. 1L,R KU36617 - T.p. 3L,R KU38522 T.c.a. 2L KU36618 - T.p. 4L KU38523 P.p. 1L,R KU38526 - T.p. 5R KU38524 P.p. 2L KU38527 - T.c.p. 1L,R KU38515 P.p. 3L,R KU38528 - T.c.p. 2L,R KU38516 P.p. 4L KU38529 - T.c.p. 3L KU38517 - -The specimens were injected in the field either with formalin (10%) or -embalming fluid, except for those of _T. c. attwateri_, which were -frozen; the latter were later injected with embalming fluid. Injection -in all the birds was by hypodermic syringe into all major muscle masses, -into the body cavities, and subcutaneously in the neck, wings, and feet. -In those specimens injected with embalming fluid, the body cavities were -injected with formalin. The embalming fluid consisted of 70 per cent -alcohol, glycerin (or propylene glycol), and formalin (full strength) in -the approximate ratio of 78:20:2, respectively. This fluid gave good -preservation; these specimens had the advantages of lacking almost -entirely the irritating odor of formalin and of having pliable tissues. -The skin of those specimens originally injected with formalin was slit -in several places and they were transferred to crocks containing -embalming fluid (without the formalin). After a period of many weeks, -with two changes of fluid, most of the formalin odor was eliminated and -the muscles were sufficiently pliable to be easily dissected. All -specimens were kept in containers filled with embalming fluid. No mold -ever appeared, even though no phenol or other chemical was added. - -To facilitate comparison, two or three specimens were frequently -dissected simultaneously. The nerves and smaller muscles were dissected -with the aid of a stereoscopic microscope mounted on a long movable arm. -In order satisfactorily to expose the lumbosacral plexus the posterior -half of the sternum and pectoral muscles, as well as the abdominal -viscera, were removed. - -To insure more nearly accurate proportions, drawings of the pelvis and -of some of the muscles were made with the aid of photographs of the -several specimens listed above. - - - - -TERMINOLOGY - - -_Skeleton_ - -The majority of the osteological terms used in the present paper are -those used by Howard (1929); however, many skeletal features are not -named by Howard. Since names for most of these parts were not found in -the other literature examined, it was necessary for me to propose terms -for them. Most of this new terminology pertains to the pelvis. All of -the osteological terms used in the present paper, whether used by Howard -or not, are briefly defined below. Those of the pelvis are illustrated -in fig. 1. Most of the remaining terms are illustrated by Howard (1929). - - -PELVIS - -The _median dorsal ridge_ is the blunt ridge in the midline of the -anterior part of the synsacrum formed by the neural spines of the -vertebrae. The _antitrochanter_, on the posterodorsal rim of the -acetabulum, is a pyramid-shaped projection that articulates with the -proximal end of the femur. The _anterior iliac crest_ is a ridge along -the dorsomedial border of the ilium, beginning almost at the anterior -end of that bone; the crest curves laterally as it extends posteriorly -and (for purposes of the present definition) ends at the level of the -posterior edge of the antitrochanter, where the crest is continuous with -the lateral iliac process. The _lateral iliac process_ is a pronounced, -laterally or ventrolaterally, projecting ridge on the ventrolateral -surface of the ilium posterior to the level of the antitrochanter; the -process does not extend as far as the posterior end of the ilium. The -_lateral ischiatic ridge_ is a relatively slight ridge continuous with -the posterior end of the lateral iliac process and curves -posteroventrally across the lateral surface of the posterior part of the -ischium; the ridge extends to the ventral edge of the ischium in some -individuals and not in others. The _dorsolateral iliac ridge_ begins at -the lateral edge of the ilium near the posterior end of the lateral -iliac process and curves posteromedially and somewhat dorsally, -extending to the posterior edge of the ilium. The _lateral iliac fossa_ -is the concavity below the overhanging lateral iliac process. The -_ilio-ischiatic fenestra_ is a large oblong opening behind the -acetabulum between the ilium and the ischium. The _obturator foramen_ is -a small oval opening posteroventral to the acetabulum between the -ischium and the pubis. The _ventral ischiatic tubercle_ is the angle -formed by the ventrally projecting ischium at the point (near its -midlength) where the ischium overlaps and lies lateral to (and fused to) -the pubis. The _pectineal process_ is an anterolaterally directed -projection of the ventrolateral edge of the ilium anteroventral to the -acetabulum. The _femoral notch_ of the ilium is a shallow notch in the -ventrolateral edge of the ilium approximately halfway between the last -rib and the pectineal process. The _oblique iliac crest_ is a pronounced -blunt ridge on the ventral surface of the ilium and extends from the -posterolateral corner of the last synsacro-thoraco-lumbar vertebra to -near the anteroventral border of the ilio-ischiatic fenestra. The -_internal ilio-ischiatic crest_ is more or less continuous with the -oblique iliac crest and extends posteriorly along the dorsal border of -the ischium (forming the ventral border of the ilio-ischiatic fenestra), -and then curves sharply dorsomedially onto the ventral surface of the -ilium. The _iliac recess_ is a concavity dorsolateral to the sharply -curving posterior end of the internal ilio-ischiatic crest. - -[Illustration: FIG. 1. Pelvis of _Tympanuchus pallidicinctus_. A. -Lateral view. × 1. B. Ventral view. × 1-1/8.] - -The terminology applied to the synsacral vertebrae by different authors -varies. The terminology proposed by DuToit (1913) is employed in the -present account. See my fig. 1B. This terminology differs considerably -from that used by Howard (1929). DuToit divides the fused synsacral -vertebrae into the following five groups, listed in anteroposterior -sequence: (1) _synsacro-thoracic_, which bear movable ribs; (2) -_synsacro-thoraco-lumbar_, which lack movable ribs but possess well -developed laterally directed parapophyses, in addition to the more -dorsally directed diapophyses; (3) _synsacro-lumbar_, which lack -parapophyses, although possessing inconspicuous diapophyses; these -vertebrae are shortened anteroposteriorly and are so firmly fused -together that often the number present can be determined only by -counting the intervertebral foramina; (4) _synsacro-sacral_, which have -much more pronounced transverse processes than do the synsacro-lumbar -vertebrae; these transverse processes are expanded distally where they -fuse with the ilium and represent both parapophyses and diapophyses -partly or completely fused together plus sacral ribs (detectable only in -the embryo); there are considered to be two of these vertebrae; they are -situated at approximately the level of the acetabulum; (5) -_synsacro-caudal_, which include the remainder of the fused vertebrae; -no marked gross morphological features differentiate the synsacro-sacral -and the synsacro-caudal groups of vertebrae. The boundaries between all -but the last two groups of vertebrae are usually, but not always, easily -determined. It may be difficult to determine whether a vertebra with -rudimentary parapophyses belongs to the synsacro-thoraco-lumbar or the -synsacro-lumbar group. Sometimes a parapophysis will be better developed -on one side of a vertebra than on the other. - - -FEMUR - -The _trochanter_ is a large squarish tuberosity on the lateral surface -of the proximal end of the femur. The _trochanteric ridge_ is a sharp, -longitudinal (relative to the femur) ridge forming the anterior edge of -the trochanter. The _obturator ridge_ is a short, blunt, longitudinal -ridge forming the posterior edge of the trochanter. The _anterior -intermuscular line_ is a slight ridge extending distally from the -trochanteric ridge. The _posterolateral intermuscular line_ is a slight -ridge extending distally from the obturator ridge. The _posterior -intermuscular line_ is a slight, longitudinal ridge on the mid-posterior -surface of the femur. The _internal condyle_ is a large rounded -articular prominence on the medial side of the distal end of the femur. -On the lateral side of the distal end of the femur are two articular -prominences--the lateralmost, smaller one is the _fibular condyle_, -separated by the _fibular groove_ (visible from posterior aspect only) -from the larger and more medial _external condyle_. The _popliteal area_ -is a depression on the posterior surface of the distal part of the femur -immediately proximal to the condyles. - - -TIBIOTARSUS AND FIBULA - -The _inner cnemial crest_ is pronounced and directed anteriorly on the -anterior surface of the proximal end of the tibiotarsus. The _outer -cnemial crest_ is pronounced and directed anterolaterally on the -anterolateral surface of the proximal end of the tibiotarsus. The -_rotular crest_ is transverse and forms the anterior border of the -proximal end of the tibiotarsus; the crest extends between the dorsal -ends of the two cnemial crests and also extends medial to the inner -cnemial crest. The _fibular crest_ is longitudinal on the lateral -surface of the tibiotarsus and fuses with the middle part of the fibula. -The _fibular tubercle_ is small and on the lateral surface of the fibula -near the level of the middle of the fibular crest. The _anteromedial -intermuscular line_ is a slight ridge extending from the inner cnemial -crest down the anteromedial surface of the tibiotarsus. The -_anterolateral intermuscular line_ is a slight ridge extending from the -fibular crest down the anterolateral surface of the tibiotarsus. The -_supratendinal bridge_ is a transverse bony arch over a longitudinal -groove near the distal end of the anterior surface of the tibiotarsus. - - -TARSOMETATARSUS - -The _hypotarsus_ is a large, pronounced, squarish protuberance on the -posterior surface of the proximal end of the tarsometatarsus and -contains grooves and canals for the passage of the flexor tendons. The -longitudinal ridges forming the lateral and medial edges of the -posterior surface of the hypotarsus are termed _calcaneal ridges_. The -_posterior metatarsal crest_ is long and sharp; it is continuous with -the medial calcaneal ridge that extends most of the way down the -posterior surface of the tarsometatarsus medial to the midline; there is -an opening between this crest and the tarsometatarsus immediately distal -to the hypotarsus. The _medial metatarsal depression_ is large; it is on -the medial surface of the proximal end of the tarsometatarsus. The -_anterior metatarsal groove_ is a longitudinal groove in the midline of -the proximal part of the anterior surface of the tarsometatarsus. The -three _trochleae_ are large rounded articular prominences at the distal -end of the tarsometatarsus; there is one at the base of each of the -digits II, III, and IV. The term _distal foramen_ (as used by Howard) -refers to a short, anteroposteriorly directed canal that perforates the -tarsometatarsus a short distance proximal to the intertrochlear notch -between the trochleae for digits III and IV. Beginning at the middle of -this canal and extending distally at a right angle to it is the -_intertrochlear canal_, which opens via the terminal foramen into the -intertrochlear notch between the trochleae for digits III and IV. - - -_Nerves_ - -For ease of description I have coined terms for the major divisions of -the femoral and sciatic nerves. - - -_Muscles_ - -My terminology follows that of Fisher (1946) and Fisher and Goodman -(1955) except for Mm. femoritibialis externus, flexor cruris lateralis -(accessory head), and obturator internus et externus. Fisher (1946:547) -states that most of his names for the hip and thigh muscles are those of -Howell (1938) and the names for the shank and foot muscles are those of -Hudson (1937). Fisher deviates, without explanation, from Howell's -terminology in respect to Mm. vastus medialis and femoritibialis -internus, M. caudofemoralis, M. flexor cruris lateralis, and Mm. -obturator internus and obturator externus. Fisher's synonymy of these -muscles (1946: table 42) is in error. Fisher understandably deviates -from Hudson in respect to Mm. extensor brevis digiti III and extensor -proprius digiti III (see Holmes, 1962), although Fisher's synonymy is in -error here. See my table 1. - - I am not using Fisher and Goodman's term femoritibialis externus; - this muscle is here considered as a part of M. vastus lateralis. A - great deal of confusion surrounds the terminology of the muscle - complex here termed Mm. vastus lateralis and vastus medialis. - Hudson (1937), Hudson, _et al._ (1959), Fisher (1946), and Fisher - and Goodman (1955) have used different terminology for this - complex. Most of the confusion stems from Gadow's (1891) unclear - description of this complex, which he subdivided into two units - termed Mm. femori-tibialis externus and femori-tibialis medius. - Many birds have three parts to this complex. It is difficult to - determine how to apply Gadow's two terms to these three parts. As - nearly as I can determine, the correct method is that of Hudson, - _et al._ (1959); but because Gadow's terms have been used in - different ways (even by the same worker), it seems best to abandon - these terms. Berger (1956:272) believes that the muscle unit that - Fisher and Goodman term M. femoritibialis externus represents a - head of M. vastus lateralis; I am accepting his opinion. For the - three parts of the complex under discussion, I am using the terms - M. vastus medialis and M. vastus lateralis pars lateralis and pars - postica. - - Fisher (Fisher, 1946; Fisher and Goodman, 1955) considers the - muscle here termed M. femorocruralis as an accessory head of M. - flexor cruris lateralis. The two muscle units in question are - closely associated; they insert broadly on opposite sides of a - common tendinous raphe. Howell (1938:73) considers this to be a - secondary fusion of unrelated muscles. Romer (1927:366) states that - in the chick embryo M. femorocruralis is in reality a shank muscle - that migrates into the thigh during development. Therefore, - Fisher's usage of a single name for these two unrelated muscles is - unsatisfactory. I am using Howell's terminology in which the name - flexor cruris lateralis represents the main head only of Fisher's - M. flexor cruris lateralis and the name femorocruralis represents - Fisher's accessory head. - - Gadow (1891) divides the obturator complex into two muscles (or - muscle groups), which he terms M. obturator and Mm. accessorii M. - obturatoris. He states that the former is homologous with the - mammalian obturator internus and the latter with the obturator - externus. Hudson (1937), accepting Gadow's homologies, renamed - these muscles M. obturator internus and M. obturator externus. - Nearly all subsequent workers have followed Hudson's terminology, - with its implication that these muscles are homologous with the - mammalian muscles of the same name. Howell (1938) is an exception. - He points out (pp. 78, 79) that the obturator internus of Hudson is - homologous with the obturator externus of mammals. His evidence is - convincing: "In origin the obturator is somewhat suggestive of the - mammalian obturator internus, for which it has uniformly been - mistaken. That the latter interpretation is incorrect, however, is - attested by the facts that it receives twigs of n. obturatorius - within the pelvis, passes _through_ the obturator foramen rather - than dorsal to the border of the ischium, and it is segregated from - any muscle with tibial innervation. Insertion has shifted only to a - slight and unimportant degree as compared with that of the - mammalian obturator externus, and beyond question it is the - equivalent of that muscle. The stimulus for a longer muscle, has - been the same, resulting in the extension of origin to within the - pelvis of the externus in birds and the internus in mammals, but - the obturator internus is an extension of a part of the gemellus - mass and this does not occur in any vertebrate class but Mammalia." - Howell applies the term M. obturator to the entire obturator - complex. - -Romer (1927), studying the development of the thigh musculature in chick -embryos, concluded that the entire obturator complex is homologous with -the mammalian obturator externus plus quadratus femoris. He considered -the avian M. flexor ischiofemoralis to be the homologue of the mammalian -obturator internus. - -Gadow, in his work on the ratites (1880:34), states that M. obturator -(obturator internus of Hudson) cannot be homologous to the mammalian -obturator internus, but must represent the obturator externus. His -reasoning is as follows: "Als M. pectineus kann man diesen Muskel nicht -auffassen, da er auf der Aussenfläche des Trochanter major inserirt, -ferner auch nicht als M. obturator internus der menschlichen Anatomie, -da er nicht vom Plexus ischiadicus, sondern vom Plexus cruralis aus -innervirt wird. Seiner Innervation und Insertion nach wäre er nur mit -dem M. obturator externus zu vergleichen, wobei er seinen Ursprung im -Verhältniss zum Menschen nur bedeutend weiter auf das Os ischii und Os -pubis distalwärts ausgedehnt hätte und so allerdings der Lage nach mit -Ausnahme seines Insertionsdrittels ein 'internus' geworden wäre." - -Since Gadow gives different homologues for M. obturator in two of his -works (1880 and 1891), one would suspect that he had changed his opinion -in the interim; however, there is no evidence that he did so. In 1880 he -gives supporting evidence (quoted above) for his view; in 1891 he does -not. After describing (1891:173) how the origin of M. obturator in bird -ancestors presumably migrated from a location outside the pelvis to a -position inside the pelvis prior to the meeting of the pubis and ischium -external to the muscle, he states: "Eine ähnliche Entwicklung ist für -den _Obturator internus_ der Säugethiere anzunehmen, welchem der _M. -obturator_ der Vögel entspricht." A similar development in mammals is -impossible, owing to the different relationship of the muscle to the -pelvic bones in this class. Gadow says nothing more about the mammalian -homologue of M. obturator. In view of this discrepancy, Gadow can hardly -be considered as a supporter of the idea that the avian M. obturator is -homologous with the mammalian obturator internus. - -The evidence is conclusive, it seems to me, that the obturator internus -of Hudson is not homologous with the mammalian obturator internus. -Therefore, the term obturator internus is inappropriate for the avian -muscle and must be abandoned. I shall follow Howell (1938) in naming the -entire obturator complex M. obturator. This term, of course, is not used -in the sense in which it is used by Gadow. The use of the term obturator -externus for the entire complex is avoided because it may not correspond -exactly to the mammalian obturator externus. As mentioned previously, -Romer considers the avian muscle to be homologous not only with the -mammalian obturator externus but also with the quadratus femoris. - -I am following the policy of Wilcox (1948) and Berger (1952) in -latinizing the term anterior, changing it to anticus. When preceded by -the feminine word pars, the feminine ending is used (antica). - -In table 1 my terminology is compared with that of Fisher and Goodman -(1955), Howell (1938), Hudson (1937), and Gadow (1891). The terminology -of Fisher (1946) is identical with that of Fisher and Goodman (1955) -except that in his earlier work Fisher did not describe or name M. -femoritibialis externus, and M. lumbricales of his earlier work is not -mentioned in his later work. The terminology of Hudson, _et al._ (1959) -is identical with that of Hudson (1937) except that the manner in which -the femoritibialis complex is subdivided is identical with that of Gadow -(1891) and different from that in Hudson's earlier work; also the -abbreviations p. ext. and p. int. are substituted in his later paper for -pars anterior and pars posterior, respectively, of M. adductor longus et -brevis. - - - - -ACKNOWLEDGMENTS - - -I gratefully acknowledge the generous help of Professor A. Byron -Leonard, under whose guidance this study was conducted and thank -Professor E. Raymond Hall, Professor Howard A. Matzke, and Dr. Irwin -Baird for numerous helpful suggestions and criticisms. - -For help in collecting specimens I thank J. R. Alcorn, W. C. Glazener -(through the courtesy of the Texas Game and Fish Commission), Dr. -Harrison B. Tordoff, Jerry Tash, William Brecheisen, and Louis -Brecheisen. I thank also Edwin Gebhard of the Kansas Forestry, Fish and -Game Commission for help in locating the Lesser Prairie Chickens. - -I am grateful for the assistance of Mrs. Chester Alexander and Dr. L. C. -Dahl in translating a Russian and a Dutch reference, and thank George -Young and James Bee for making equipment used in my study. - -All of the original drawings except fig. 1 were made by me, although the -final inking of figs. 12 through 19 was done by Bret Waller. Fig. 1 was -drawn by Kay Swearingen. - -I was aided in this study during the summer of 1960 by a research grant -from the University of Kansas. - - - - -SKELETON - - -Although no special study was made of the skeleton, certain conspicuous -variations are discussed here. - -There are a few pronounced differences between the pelvis of -_Tympanuchus_ and that of _Pedioecetes_. Whereas in the former the thick -lateral iliac process has a pronounced overhang with the ventral edge -lateral to the ischium (fig. 1), in _Pedioecetes_ there is no overhang -at all and the edge of this process is much thinner. The ischium in -_Pedioecetes_ is wider (in dorsoventral extent), especially posteriorly, -than in _Tympanuchus_. In _Tympanuchus_ the posteroventral margin of the -ischium is rounded and is free from the pubis, whereas in _Pedioecetes_ -it is pointed and fused with the pubis. - -In _Tympanuchus cupido_ (both subspecies) the lateral iliac process -extends farther ventrally than in _T. pallidicinctus_, approaching or -extending ventral to the level of the pubis in the former species; also -the edge of this process is thicker in _T. cupido_. - -All specimens studied have a single synsacro-thoracic vertebra. The -number of combined synsacro-thoraco-lumbar and synsacro-lumbar vertebrae -is eight in each specimen of _Tympanuchus_ and in one specimen of -_Pedioecetes phasianellus jamesi_ and is seven in three specimens of the -latter. In most specimens of _Tympanuchus_ there are three -synsacro-thoraco-lumbar and five synsacro-lumbar vertebrae, although in -two specimens (_T. pallidicinctus_) there are four of each group; in one -of these latter two specimens the parapophysis on one side of the fourth -synsacro-thoraco-lumbar vertebra is small. The first (of five) -synsacro-lumbar vertebra has a rudimentary parapophysis on one side in -one specimen of _Tympanuchus_ and on both sides in another specimen. One -specimen of _Pedioecetes phasianellus jamesi_ has five synsacro-lumbar -vertebrae and the others have four; all have three -synsacro-thoraco-lumbar vertebrae. - - - - -NERVES - - -For each nerve (or plexus) the condition found in most specimens of the -Lesser Prairie Chicken (_T. pallidicinctus_) is described first. -Following this, variations from the typical _T. pallidicinctus_ -condition are given for _T. pallidicinctus_, then for _T. cupido_ (both -subspecies considered together), and finally for _P. p. jamesi_. - - -=_Lumbosacral Plexus_=, Figs. 2, 3 - -_T. pallidicinctus_ - -DESCRIPTION.--Eight spinal nerves contribute to the lumbosacral plexus. -These are the second through the ninth synsacral spinal nerves (S2 to -S9). The entire ventral ramus of each of these nerves, excepting S2 and -S9, contributes to this plexus. The ventral ramus of S2 divides into two -branches, only the posterior of which contributes to the plexus; the -anterior branch directly innervates muscles of the abdominal wall (as -does the entire ventral ramus of S1). The ventral ramus of S9 divides -into two branches, only the anterior of which contributes to this -plexus; the posterior branch contributes to the more posteriorly -situated pudendal plexus. - -Each root of the plexus corresponds to a single spinal nerve except one -spinal nerve (S5--the furcal) that contributes a root to both the -femoral nerve and the sciatic nerve; thus typically the plexus has nine -roots (but see below). The four anteriormost roots (S2 to S5) contribute -to the femoral nerve, although the contribution from S2 is small. S3 and -S4 contribute to the obturator nerve. The five posteriormost roots (S5 -to S9) contribute to the sciatic nerve, although the contribution from -S9 is relatively small. - -INDIVIDUAL VARIATION.--In all specimens (of all species) examined, the -right and left sides of the plexus in any one individual were -practically identical. In T.p. 2 (fig. 2B), there appear to be two -furcal nerves; S5 is typical, but a small branch of S4 apparently also -contributes to the sciatic nerve. In T.p. 5, S9 is unique in dividing -into three branches; the anterior two join the sciatic nerve separately; -the posterior one joins the pudendal plexus as usual. - -_T. cupido_ - -INDIVIDUAL VARIATION.--S2 or S5, or both, may contribute to a limited -extent to the obturator nerve. In T.c.p. 3 (fig. 3A) and T.c.a. 1 and 2, -much of the plexus has shifted one segment anteriorly, relative to the -synsacral vertebrae (the so-called prefixed condition); the roots of the -femoral nerve are S2, S3, and S4 (all large); the furcal nerve is S4 (in -T.c.a. 1, S5 gives an extremely small root to the femoral nerve, thus -making two furcal nerves); six roots (S4 to S9) contribute to the -sciatic nerve; S3 and S4 remain as the main contributors to the -obturator nerve except in T.c.a. 2 in which only S2 and S3 contribute to -it. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In P.p. 1, the plexus resembles the typical -condition in _T. pallidicinctus_. In P.p. 2, 3, and 4, the plexus is -prefixed. P.p. 2 resembles T.c.p. 3. In P.p. 3 and 4 (fig. 3B) there are -two furcal nerves (S4 and S5); S2 to S4 are the main contributors to the -femoral nerve; only S2 and S3 contribute to the obturator nerve; S4 to -S9 contribute to the sciatic nerve (the anteriormost and posteriormost -roots are small). - - -=_Femoral Nerve_=, Figs. 4, 5 - -_T. pallidicinctus_ - -DESCRIPTION.--The femoral nerve is short, dividing inside the pelvis -into six major divisions--anterior, middle, posterior, anterodorsal, -dorsal, and posterodorsal. The anterodorsal and posterodorsal divisions -are short, failing to extend so far laterally as the inguinal ligament; -the posterodorsal division is also small and is usually covered by other -divisions and is not visible when viewed from the ventral side. - -The anterior division passes ventral to Mm. iliotrochantericus medius -and iliacus and dorsal to the anterior end of the inguinal ligament. The -division branches into two parts. The anterior part extends around the -posterior border of M. extensor iliotibialis anticus and sends several -twigs to the lateral surface of this muscle. The posterior part passes -between the proximal parts of Mm. extensor iliotibialis anticus and -extensor iliotibialis lateralis and supplies the skin. - -The middle division passes ventral to Mm. iliotrochantericus medius and -iliacus and dorsal to the inguinal ligament. The division branches into -a large but variable number of parts. A variable number of branches -(usually two) pass posterior to M. extensor iliotibialis anticus and -penetrate the medial surface of M. extensor iliotibialis lateralis. -Several branches supply the fused Mm. vastus lateralis and vastus -medialis. The posteriormost branch of this division passes between Mm. -ambiens and vastus medialis, giving twigs to the lateral surface of M. -ambiens, and sometimes also to the medial surface of M. vastus medialis, -and terminates in M. femoritibialis internus. - -The posterior division, which does not subdivide, spirals completely -around M. psoas (passing in turn anterior, dorsal, posterior, and -ventral to it) and gives twigs into this muscle. This nerve then extends -distally into the proximal part of the shank and there has a nonmuscular -termination. - -The short, thick anterodorsal division, partly covered by the anterior -division, turns dorsally and passes through the femoral notch of the -ilium and penetrates the deep surface of M. gluteus profundus. - -The slender dorsal division passes ventral to M. iliotrochantericus -medius and dorsal to the inguinal ligament and penetrates the ventral -surface of M. iliacus. - -The small, short posterodorsal division penetrates the ventral surface -of M. iliotrochantericus medius. - -INDIVIDUAL VARIATION.--In two legs the anterior division gives a twig or -two twigs to M. extensor iliotibialis lateralis. The dorsal division may -fuse proximally with either the anterior or middle division, thus -appearing to be a branch of one of these divisions. In one leg (fig. -5A), there are two separate branches (both fused with the middle -division) to M. iliacus. On both sides of one specimen (fig. 5A), the -anteriormost branch of the middle division, which supplies M. extensor -iliotibialis lateralis, gives off a twig that anastomoses with the -branch of the anterior division that supplies M. extensor iliotibialis -anticus. On both sides of another specimen, the anterodorsal division -passes lateral to the anterior end of M. iliotrochantericus medius -instead of through the femoral notch, which is lacking. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In three legs, the anterior division gives twigs -into M. extensor iliotibialis lateralis. The dorsal division is fused -proximally with the middle division in one instance. In three cases, a -twig from the middle division anastomoses with the branch of the -anterior division supplying M. extensor iliotibialis anticus. In the -example shown in fig. 5B, a twig comes off the cutaneous branch of the -anterior division, perforates the ventral part of M. iliacus, and -rejoins the cutaneous branch. In both legs of one specimen, the -cutaneous branch of the anterior division perforates the anterior edge -of M. extensor iliotibialis lateralis instead of passing between the -latter and M. extensor iliotibialis anticus. The posteriormost branch of -the middle division, which terminates in M. femoritibialis internus, -perforates the medial part of M. vastus medialis in one leg. In another -leg, one of the branches to the fused Mm. vastus lateralis and vastus -medialis sends a twig into M. extensor iliotibialis lateralis. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In three legs, the anterior branch of the -anterior division is cutaneous and the posterior branch supplies M. -extensor iliotibialis anticus. The dorsal division may fuse proximally -with either the anterior or middle division. In one leg (fig. 4B), there -are two branches to M. iliacus, one associated with the anterior -division and one with the middle division. - - -=_Obturator Nerve_= - -_T. pallidicinctus_ - -DESCRIPTION.--The long slender obturator nerve passes along the oblique -iliac crest and divides into several branches immediately before -reaching the obturator foramen. One or two branches, which do not pass -through the foramen, penetrate the superficial surface of M. obturator -pars postica. Several small branches (variable in number and -arrangement) pass through the obturator foramen and supply pars -ventralis, pars dorsalis, and pars antica of M. obturator. When pars -ventralis and pars dorsalis are fused, one branch perforates the -proximal end of this mass and reaches pars antica. One large branch -passes through the obturator foramen dorsal to the tendon of M. -obturator pars postica, then turns ventrally, passing lateral to the -latter; the branch passes between Mm. adductor superficialis and -adductor profundus and gives twigs to each of these two muscles. - -INDIVIDUAL VARIATION.--None of significance in any of the three species. - - -=_Sciatic Nerve_=, Figs. 6, 7, 8, 9 - -_T. pallidicinctus_ - -DESCRIPTION.--The sciatic nerve passes through the anterior part of the -ilio-ischiatic fenestra. Several branches diverge from the nerve -immediately after it emerges from the fenestra. The main trunk of the -nerve then extends distally through the thigh deep to M. extensor -iliofibularis and superficial (lateral) to Mm. flexor ischiofemoralis, -caudofemoralis, adductor superficialis, and femorocruralis. The main -trunk subdivides into two large nerves--peroneal and tibial--that are -adjacent and bound to each other throughout the thigh; the peroneal -nerve lies anterior to the tibial. At the distal end of the thigh the -main trunk splits grossly into two large branches that diverge and enter -the shank. This division does not represent the separation between -peroneal and tibial nerves, as is sometimes assumed; the anterior branch -includes a part of the tibial nerve as well as the entire peroneal -nerve. - -A longitudinal groove is visible grossly on the lateral surface of the -main trunk, except at the proximal end; distally a second groove is -visible posterior to the first one (fig. 6). The long anterior groove -indicates the boundary between the peroneal and tibial nerves; this -groove may disappear distally, although the posterior groove is always -visible distally. The posterior groove, which is continuous with the -division of the sciatic nerve into anterior and posterior branches, -represents the boundary between two divisions of the tibial nerve. (This -is discussed in detail below.) In the middle of the thigh the peroneal -and tibial nerves are enclosed in separate connective tissue sheaths, -although the two sheaths are fused together; the point of fusion is -marked by the anterior groove. If the two sheaths are slit open, the two -nerves can be removed and can be seen to be entirely separate. In the -proximal part of the main trunk the peroneal and tibial components are -enclosed in a single sheath and appear as an undivided trunk; but if the -sheath is removed, the two components can be pulled apart rather easily, -although there may be some intermingling of a few fibers. This -separation can be extended to a point proximal to the origin of all the -branches of the sciatic nerve; thus it can be determined which branches -arise from the peroneal component and which from the tibial. (These -branches arise from the sciatic nerve as, or immediately before, the -nerve passes through the ilio-ischiatic fenestra; since this level of -the intact nerve could not be adequately observed, it was necessary to -cut the nerve inside the pelvis and pull the intrapelvic part of the -nerve out through the ilio-ischiatic fenestra. In doing this, care had -to be taken to avoid damaging the most proximal branches.) - -Three main branches arise from the peroneal component (apart from the -main trunk) and two from the tibial. Including the peroneal and tibial -components of the main trunk, the sciatic nerve can be divided into -seven major divisions--anterior peroneal, middle peroneal, dorsal -peroneal, posterior or main peroneal (contributes to main trunk), -anterior or main tibial (contributes to main trunk), middle tibial, and -posterior tibial. Farther distally, the posterior peroneal division -becomes the peroneal nerve and the anterior tibial division becomes the -tibial nerve. For descriptive purposes, the term peroneal (or tibial) -_nerve_ will be applied only where the nerve is enclosed in its own -sheath, but regardless of whether or not the sheath is fused with -another; proximal to this, where the separation may not be precise, the -terms peroneal (or tibial) _division_ or _component_ will be used. - -The small anterior peroneal division arises from the anterior edge of -the sciatic nerve. Immediately after emerging from the ilio-ischiatic -fenestra, the division turns anteriorly and passes deep to M. -piriformis, to which the division gives a twig (in some cases more than -one twig), then continues forward to supply the posterior part of M. -gluteus profundus. - -The middle peroneal division branches into two parts. One part -penetrates the deep surface of the anteroproximal part of M. extensor -iliofibularis. The other part emerges between the proximal ends of Mm. -extensor iliofibularis and vastus lateralis and penetrates the deep -surface of M. extensor iliotibialis lateralis. - -The dorsal peroneal division arises from the posterodorsal part of the -peroneal component, then angles posteriorly, crossing the dorsal surface -of the anterior tibial division and superficially appears to arise from -the tibial component. The dorsal peroneal division usually subdivides -into two unequal branches, both of which penetrate the deep surface of -the proximal end of M. extensor iliofibularis. - -The large middle tibial division soon subdivides into two branches that -pass posterodistally lateral to M. flexor ischiofemoralis. One branch -(usually the anterior one) passes lateral to M. caudofemoralis (both -heads) and emerges between Mm. extensor iliofibularis and flexor cruris -lateralis and enters the skin. The other branch passes deep to M. -caudofemoralis pars iliofemoralis, and divides into several branches. -Several tiny branches penetrate the deep surface of M. caudofemoralis -pars iliofemoralis. Another branch also enters the substance of the -latter and emerges from the ventral edge of it, giving a twig to pars -caudifemoralis, then passes lateral to pars caudifemoralis and enters M. -flexor cruris lateralis. Still another branch passes deep to both heads -of M. caudofemoralis and enters the anterior part of M. flexor cruris -medialis. - -The small posterior tibial division arises from the posterior edge of -the sciatic nerve. The division diverges from the remainder of the -nerve, as the latter passes through the ilio-ischiatic fenestra, and -penetrates the dorsal surface of M. flexor ischiofemoralis. - -Below the middle of the main trunk a bundle of fibers of moderate size -separates from the anterior edge of the tibial nerve, leaves the tibial -sheath, and enters its own sheath, lying superficially between the -tibial and peroneal sheaths (fig. 6). At the distal end of the thigh the -sheath enclosing this bundle of fibers remains fused with the posterior -edge of the peroneal nerve and passes with the latter (diverging from -the remainder of the tibial nerve) through the tendinous guide loop for -M. extensor iliofibularis, and then diverges from the peroneal nerve. -Since this bundle of fibers is distributed with the peroneal nerve, and -since the origin of the bundle may be easily overlooked, it has -sometimes been misinterpreted as a branch of the peroneal nerve, whereas -it almost certainly is a branch of the tibial nerve; this bundle will -here be termed the paraperoneal branch of the tibial nerve. - -A small but long branch separates from the posterior edge of the -proximal end of the tibial nerve or from the tibial component proximal -to this and extends distally for some distance adjacent to the tibial -nerve, then passes posterodistally between Mm. extensor iliofibularis -and flexor cruris lateralis and supplies the skin. - -A small branch separates from the anterior edge of the peroneal nerve a -short distance above the distal end of the main trunk and passes -distolaterally between Mm. extensor iliotibialis lateralis and extensor -iliofibularis and supplies the skin. - -A twig comes off the medial surface of the tibial nerve near the distal -end of the main trunk, passes anteriorly deep to the peroneal nerve, and -penetrates the lateral surface of M. femorocruralis; in some cases two -twigs enter this muscle. - -INDIVIDUAL VARIATION.--In one leg (fig. 7), the twig to M. -caudofemoralis pars caudifemoralis arises more proximally than usual and -perforates pars iliofemoralis independently of the branch to M. flexor -cruris lateralis. The nerve supplying M. flexor cruris lateralis does -not perforate M. caudofemoralis pars iliofemoralis, but passes deep to -it in three legs. In half the legs, the paraperoneal branch of the -tibial nerve, after extending a short distance in its own sheath, enters -the sheath of the peroneal nerve and appears grossly to unite with it; -if, however, the sheath is slit open, the paraperoneal branch can be -easily pulled apart from the posterior edge of the peroneal nerve; the -paraperoneal branch is again enclosed in its own sheath at the distal -end of the thigh. In one leg, the cutaneous branch of the peroneal nerve -perforates the posteroproximal part of M. gastrocnemius pars externa; in -three others, this branch is absent. In one of these last three legs -(fig. 7), the distal cutaneous branch of the tibial nerve is also -absent. In three legs (of different specimens), a minute twig from the -middle tibial division passes posteriorly deep to M. caudofemoralis pars -caudifemoralis toward the tail (fig. 7); this twig joins the pudendal -plexus in one leg; in the other two the twig could not be traced to its -termination. Minute twigs come off the peroneal nerve near the middle of -the thigh and enter M. extensor iliofibularis in some legs. In a few -cases, a minute nonmuscular twig arises from the peroneal nerve near the -distal end of the main trunk and passes anteriorly deep to M. vastus -lateralis pars postica (fig. 7). - -_T. cupido_ - -INDIVIDUAL VARIATION.--In several legs, the nerve supplying M. flexor -cruris lateralis does not perforate M. caudofemoralis pars -iliofemoralis, but passes deep to it. The branch to M. flexor cruris -medialis arises from the posterior (rather than the middle) tibial -division in one instance (fig. 8). In one leg, a minute twig from the -middle tibial division passes posteriorly and joins the pudendal plexus; -in another, a similar twig is present but could not be traced to its -termination. In some specimens, minute twigs come off the peroneal nerve -near the middle of the thigh and enter M. extensor iliofibularis. In one -leg, a nonmuscular twig arises from the base of the cutaneous branch of -the peroneal nerve and passes anteriorly deep to M. vastus lateralis -pars postica. In another leg (fig. 8), a tiny additional twig arises -from the posterior edge of the tibial nerve and subdivides, one branch -joining the cutaneous branch of the middle tibial division and the other -joining the distal cutaneous branch of the tibial nerve. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In both legs of one specimen, the branch to M. -flexor cruris medialis arises from the posterior (rather than the -middle) tibial division; in three legs, this branch arises as an -independent division of the tibial nerve (fig. 6). (Only in one leg does -this branch arise as in _T. pallidicinctus_.) The branch to M. flexor -cruris medialis perforates the lateral part of M. flexor ischiofemoralis -in one instance. In all legs except one (nerve possibly destroyed), a -second twig to M. flexor ischiofemoralis arises from the branch to M. -flexor cruris medialis (fig. 6). In one leg (fig. 9), an additional -branch, arising as an independent division of the sciatic nerve, enters -M. extensor iliofibularis distal to the point of entrance of the dorsal -peroneal division; this extra branch arises posterior (adjacent) to the -dorsal peroneal division, but it could not be determined with certainty -whether it arises from the peroneal or tibial component. A minute twig -from the branch to M. flexor cruris medialis passes posteriorly and -joins the pudendal plexus in one leg (fig. 6); in another, a similar -twig is present but could not be traced to its termination. In nearly -all the legs, minute twigs come off the peroneal nerve near the middle -of the thigh and enter M. extensor iliofibularis (fig. 6). In both legs -of one specimen, the paraperoneal branch enters the peroneal sheath -(although separable from the peroneal nerve). The distal branch to M. -femorocruralis gives off a long twig to M. gastrocnemius pars media in -one instance (fig. 6). - - -=_Peroneal Nerve_=, Fig. 10 - -_T. pallidicinctus_ - -DESCRIPTION.--The branch that is given off in the thigh has been -discussed above. The peroneal nerve passes, with the paraperoneal branch -of the tibial nerve, through the guide loop for M. extensor -iliofibularis. The peroneal nerve diverges from the paraperoneal branch -and passes along the anterior (proximal) edge of the tendon of M. -extensor iliofibularis medial to the common tendon of the lateral heads -of Mm. flexor perforatus digiti IV and flexor perforatus digiti II and -lateral to the common tendon of the anterolateral heads of Mm. flexor -perforatus digiti IV, flexor perforatus digiti II, and flexor perforatus -digiti III. - -The peroneal nerve soon gives off a spray of branches that supplies the -following: femoral head of M. tibialis anticus, tibial head of M. -tibialis anticus (branch passes deep to femoral head), M. extensor -digitorum longus (branch passes deep to tibial head of M. tibialis -anticus), and M. peroneus longus. A part of the nerve may or may not -pass through a notch in the proximal end of the lateral head of M. -flexor digitorum longus. The nerve then extends distally along the -anterolateral edge of the latter muscle and subdivides into two long -branches. Gadow (1891) termed these branches the superficial peroneal -and the deep peroneal; his terminology will be used here. - -The superficial peroneal branch, after giving off, near its proximal -end, one or two twigs into M. peroneus brevis, passes lateral to the -retinaculum for the tendon of M. tibialis anticus, then across the -intratarsal joint lateral to the latter, then lateral to the insertion -of M. tibialis anticus, where the branch subdivides. One of the two -resulting branches gives one or two twigs into M. extensor brevis digiti -IV, then terminates nonmuscularly in the digits. The other branch passes -between the main and accessory insertions of M. tibialis anticus and -joins the branch of the deep peroneal which supplies M. abductor digiti -II. (See next paragraph.) - -The deep peroneal branch passes through the retinaculum for the tendon -of M. tibialis anticus, lying lateral, then deep, then medial to the -latter; it crosses the intratarsal joint medial to the latter. -Immediately above the insertion of M. tibialis anticus, the deep -peroneal branch divides, one branch passing on each side of the main -insertion. The branch passing lateral to the main insertion passes -between the latter and the accessory insertion (medial to the latter) -and is joined by a branch of the superficial peroneal nerve. This fused -branch extends distally between Mm. extensor hallucis longus and -extensor brevis digiti IV and medial to M. extensor brevis digiti III, -giving twigs into the latter and into M. abductor digiti II before -terminating nonmuscularly in the digits. The branch of the deep peroneal -nerve that passes medial to the main insertion of M. tibialis anticus -gives one or two twigs into the proximal head of M. extensor hallucis -longus, then terminates nonmuscularly in the digits. - -INDIVIDUAL VARIATION.--In four legs, the branch of the superficial -peroneal nerve that usually joins the lateral branch of the deep -peroneal nerve is lacking (fig. 10B). In these legs it can be seen that -Mm. extensor brevis digiti III and abductor digiti II are supplied by -the deep peroneal nerve. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In two legs, the same branch that gives twigs -into the proximal head of M. extensor hallucis longus also sends a twig -into the distal head of this muscle (fig. 10C). - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_Tibial Nerve_=, Fig. 11 - -_T. pallidicinctus_ - -DESCRIPTION.--The branches given off in the thigh have been discussed in -the account of the sciatic nerve. At the distal end of the thigh the -peroneal nerve and the paraperoneal branch of the tibial nerve diverge -from the remainder of the tibial nerve and pass through the tendinous -guide loop for M. extensor iliofibularis whereas the remainder of the -tibial nerve does not. This main part of the tibial nerve immediately -divides into three main divisions--lateral, posterior, and medial. - -The lateral division passes between Mm. flexor perforatus digiti IV and -gastrocnemius pars externa and subdivides into two branches, one of -which penetrates the medial surface of M. gastrocnemius pars externa. -The other branch passes deep to the latter and sends twigs into the -posterior head of M. flexor perforans et perforatus digiti II, then -passes deep to the latter and enters M. flexor perforans et perforatus -digiti III. - -The posterior division sends a branch into the medial head of M. flexor -perforatus digiti IV, then passes between the latter and the medial head -of M. flexor perforatus digiti III, and extends distally giving off -twigs to each of the three heads of M. flexor perforatus digiti IV, to -each of the two heads of M. flexor perforatus digiti III, and to each of -the three heads of M. flexor perforatus digiti II. The number and -arrangement of these twigs is variable. - -The medial division passes medial to the medial head of M. flexor -perforatus digiti III, sends a twig to the lateral surface of M. -gastrocnemius pars media, then passes into the shank musculature between -Mm. plantaris and flexor hallucis longus, and sends a branch along the -medial edge of M. flexor hallucis longus that gives several twigs into -this muscle before terminating nonmuscularly. A small branch extends to -M. popliteus, another to M. plantaris, and another to the posterior head -of M. flexor digitorum longus. A nonmuscular branch passes between the -medial and posterior heads of M. flexor digitorum longus and extends -distally deep to this muscle. A long branch gives off near its proximal -end a variable number of twigs that pass deep to M. plantaris and enter -M. gastrocnemius pars interna; the branch then extends distally along -the lateral edge of M. plantaris and terminates nonmuscularly. - -The paraperoneal branch diverges from the peroneal nerve, passing medial -and then distal to the insertion of M. extensor iliofibularis, whereas -the peroneal nerve passes proximal and then lateral to this insertion. -The paraperoneal branch passes deep to the lateral heads of Mm. flexor -perforatus digiti IV and flexor perforatus digiti II and superficial to -the tendon of the anterolateral head of M. flexor perforatus digiti IV -and then passes distally along the anterolateral borders of the latter -and the lateral head of M. flexor perforatus digiti III and the -posterolateral border of M. flexor digitorum longus. This branch is thus -separated from the peroneal nerve by M. flexor digitorum longus and by -the fibula; the branch passes along the lateral surface of the tibial -cartilage, continues lateral to the hypotarsus, then turns medially -before extending distally between Mm. abductor digiti IV and flexor -hallucis brevis, sending twigs into each of these muscles and a long -twig into M. lumbricalis before terminating nonmuscularly. - -INDIVIDUAL VARIATION.--In T.p. 3L,R (fig. 11B), an extra branch arises -from the tibial nerve as a separate (fourth) division; it enters the -medial head of M. flexor perforatus digiti IV and also gives off a twig -that anastomoses with the posterior division (left leg) or with the -first branch of the posterior division (right leg). In T.p. 3R (fig. -11B), a large extra branch arises from the proximal part of the medial -division and passes medial and then deep to the medial head of M. flexor -perforatus digiti III, perforates the tendinous part of the medial head -of M. flexor perforatus digiti II, and joins the posterior division -(lateral to the medial head of M. flexor perforatus digiti III). A -similar branch is found in T.p. 3L except that it arises from the -proximal part of the posterior (rather than the medial) division. In -T.p. 3R (fig. 11B), the branch to M. gastrocnemius pars externa arises -so far proximally that it appears as a separate (fifth) division of the -tibial nerve. In two legs, the branch of the medial division that -supplies M. gastrocnemius pars media sends a twig into the distal end of -M. femorocruralis (fig. 11A). - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, an extra branch of the medial -division arises immediately distal to the branch to M. gastrocnemius -pars media and enters the proximal end of the medial head of M. flexor -perforatus digiti III. In one instance, the branch to M. gastrocnemius -pars interna passes through a gap in the origin of M. plantaris rather -than distal to the origin of the latter. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The branch to M. gastrocnemius pars interna gives -a minute twig to the deep surface of the free belly of M. plantaris in -one leg. - -[Illustration: FIG. 2. Ventral views of the lumbosacral plexus of -_Tympanuchus pallidicinctus_. Sympathetic ganglionated chain removed. -Numbers indicate synsacral spinal nerves. × 2. A. T.p. 1L. B. T.p. 2L.] - -[Illustration: FIG. 3. Ventral views of the lumbosacral plexus. -Sympathetic ganglionated chain removed. Numbers indicate synsacral -spinal nerves. × 2. A. _Tympanuchus cupido pinnatus_ 3L. B. _Pedioecetes -phasianellus jamesi_ 4L.] - -[Illustration: FIG. 4. Semidiagrammatic ventral views of the femoral -nerve, showing the distribution of the branches. × 3. 1,2, M. extensor -iliotibialis anticus; 3, cutaneous; 4-6, M. extensor iliotibialis -lateralis; 7,8, M. iliacus; 9, M. gluteus profundus; 10-12, fused Mm. -vastus lateralis and vastus medialis; 13,14, M. vastus medialis; 15, M. -ambiens; 16, M. femoritibialis internus; 17, nonmuscular; 18, M. psoas; -19, M. iliotrochantericus medius. A. _Tympanuchus cupido pinnatus_ 3L. -B. _Pedioecetes phasianellus jamesi_ 3L.] - -[Illustration: FIG. 5. Semidiagrammatic ventral views of the femoral -nerve, showing the distribution of the branches. × 3. 1,2, M. extensor -iliotibialis anticus; 3, cutaneous; 5,6, M. extensor iliotibialis -lateralis; 7,8, M. iliacus; 9, M. gluteus profundus; 10,11, fused Mm. -vastus lateralis and vastus medialis; 13, M. vastus medialis; 15, M. -ambiens; 16, M. femoritibialis internus; 17, nonmuscular; 18, M. psoas; -19, M. iliotrochantericus medius. A. _Tympanuchus pallidicinctus_ 2L. B. -_Tympanuchus cupido attwateri_ 1R.] - -[Illustration: FIG. 6. Semidiagrammatic dorsolateral view of the sciatic -nerve of _Pedioecetes phasianellus jamesi_ 3R, showing the distribution -of the branches. × 2-1/2. 1, M. gluteus profundus; 2, M. piriformis; 3, -M. extensor iliotibialis lateralis; 4-7, M. extensor iliofibularis; 8, -M. flexor cruris medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. -flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; -13-15, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor -ischiofemoralis; 18,19, M. femorocruralis (branch of tibial nerve); 20, -cutaneous; 21, M. gastrocnemius pars media (branch of tibial nerve); 22, -cutaneous.] - -[Illustration: FIG. 7. Semidiagrammatic dorsolateral view of the sciatic -nerve of _Tympanuchus pallidicinctus_ 2L, showing the distribution of -the branches. × 2-1/2. 1, M. gluteus profundus; 2, M. piriformis; 3, M. -extensor iliotibialis lateralis; 4, 7, M. extensor iliofibularis; 8, M. -flexor cruris medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. -flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; -13-15, M. caudofemoralis pars iliofemoralis; 17, M. flexor -ischiofemoralis; 18, M. femorocruralis (branch of tibial nerve); 22, -cutaneous; 23, nonmuscular (branch of peroneal nerve).] - -[Illustration: FIG. 8. Semidiagrammatic dorsolateral view of the sciatic -nerve of _Tympanuchus cupido pinnatus_ 3L, showing the distribution of -the branches. × 2-1/2. 1, M. gluteus profundus; 2, M. piriformis; 3, M. -extensor iliotibialis lateralis; 4,7, M. extensor iliofibularis; 8, M. -flexor cruris medialis; 9, cutaneous; 11, M. flexor cruris lateralis; -12, M. caudofemoralis pars caudifemoralis; 13, M. caudofemoralis pars -iliofemoralis; 17, M. flexor ischiofemoralis; 18, M. femorocruralis -(branch of tibial nerve); 20, cutaneous; 22, cutaneous.] - -[Illustration: FIG. 9. Semidiagrammatic dorsolateral view of the sciatic -nerve of _Pedioecetes phasianellus jamesi_ 3L, showing the distribution -of the branches. × 2-1/2. 1, M. gluteus profundus; 2, M. piriformis; 3, -M. extensor iliotibialis lateralis; 4,5,7, M. extensor iliofibularis; 8, -M. flexor cruris medialis; 9, cutaneous; 11, M. flexor cruris lateralis; -13,14, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor -ischiofemoralis; 18,19, M. femorocruralis (branch of tibial nerve); 20, -cutaneous; 22, cutaneous.] - -[Illustration: FIG. 10. A,B. Semidiagrammatic drawings of the peroneal -nerve of _Tympanuchus pallidicinctus_ 1L, showing the distribution of -the branches. × 2. C. Semidiagrammatic drawing of the distal part of the -peroneal nerve of _Tympanuchus cupido attwateri_ 1R, showing the -distribution of the branches. × 2. 1,2, M. tibialis anticus (tibial -head); 3,4, M. tibialis anticus (femoral head); 5, M. extensor digitorum -longus; 6, nonmuscular; 7,8, M. peroneus longus; 9, M. peroneus brevis; -10,11, M. extensor hallucis longus (proximal head); 12, M. extensor -hallucis longus (distal head); 13-15, nonmuscular (to toes); 16, M. -abductor digiti II; 17, M. extensor brevis digiti III; 18, M. extensor -brevis digiti IV.] - -[Illustration: FIG. 11. A,B. Semidiagrammatic drawings of the tibial -nerve (excluding the paraperoneal branch) of _Tympanuchus -pallidicinctus_, showing the distribution of the branches. × 2. A. T.p. -1L. B. T.p. 3R. C. Semidiagrammatic drawing of the distal part of the -paraperoneal branch of the tibial nerve of _Pedioecetes phasianellus -jamesi_ 2L, showing the distribution of the branches. × 2. 1, M. -femorocruralis; 2, M. gastrocnemius pars media; 3, M. popliteus; 4, M. -plantaris; 5, M. flexor digitorum longus; 6-8, nonmuscular; 9-11, M. -gastrocnemius pars interna; 12,13, M. flexor hallucis longus; 14-16, M. -flexor perforatus digiti IV (medial head); 17, M. flexor perforatus -digiti III (medial head); 18-20, M. flexor perforatus digiti II; 21, M. -flexor perforatus digiti IV (lateral head); 22-24, M. flexor perforatus -digiti IV (anterolateral head); 25, M. flexor perforatus digiti III -(anterolateral head); 26, M. flexor perforans et perforatus digiti III; -27,28, M. flexor perforans et perforatus digiti II; 29, M. gastrocnemius -pars externa; 30,31, M. abductor digiti IV; 32,33, M. flexor hallucis -brevis; 34,35, nonmuscular (to toes).] - - - - -MUSCLES - - -In the accounts of the muscles the name used by Hudson, _et al._ (1959) -for each muscle is given in parentheses after the name used by me if the -two differ. - -In the account of each muscle, the description of the condition found in -most specimens of the Lesser Prairie Chicken (_T. pallidicinctus_) is -given first. This is hereafter referred to as the typical condition for -_T. pallidicinctus_. Then any individual variations found within this -species are given. Under the heading _T. cupido_ any constant -differences between this species and typical _T. pallidicinctus_ are -given first, and any individual variations found within the species _T. -cupido_ (both subspecies considered together) are given second. Under -the heading _P. p. jamesi_ any constant differences between this -subspecies and the typical condition for _T. pallidicinctus_ (thus these -differences are not necessarily constant between the two genera) are -given first, and any individual variations found within the subspecies -_P. p. jamesi_ are given second. - -In the bird embryo, according to the studies of Romer (1927) and Wortham -(1948), the muscles within each segment of the leg differentiate from -distinct dorsal or ventral mesenchymal masses. Presumably these -represent the primitive dorsal extensor and ventral flexor muscle -masses. The list below indicates the ontogenetic origin of the avian leg -muscles, according to the studies of Romer and Wortham. The individual -muscles are discussed in the order in which they are listed below. - -Dorsal muscles of thigh - - M. extensor iliotibialis lateralis M. extensor iliofibularis - M. extensor iliotibialis anticus M. piriformis - M. ambiens M. gluteus profundus - M. vastus lateralis M. iliacus - M. vastus medialis M. iliotrochantericus medius - M. femoritibialis internus M. psoas - - -Ventral muscles of thigh - - M. flexor cruris lateralis M. adductor superficialis - M. flexor cruris medialis M. adductor profundus - M. caudofemoralis M. obturator - M. flexor ischiofemoralis M. femorocruralis - - -Ventral muscles of shank - - M. gastrocnemius M. flexor perforatus digiti III - M. flexor perforans et perforatus M. flexor perforatus digiti II - digiti II M. flexor hallucis longus - M. flexor perforans et perforatus M. plantaris - digiti III M. flexor digitorum longus - M. flexor perforatus digiti IV M. popliteus - - -Dorsal muscles of shank - - M. peroneus longus M. extensor digitorum longus - M. tibialis anticus M. peroneus brevis - - -Dorsal muscles of foot - - M. extensor hallucis longus M. extensor proprius digiti III - M. abductor digiti II M. extensor brevis digiti IV - M. extensor brevis digiti III - -Ventral muscles of foot - - M. lumbricalis (M. adductor digiti II--not - M. abductor digiti IV present) - M. flexor hallucis brevis (M. adductor digiti IV--not - present) - -[Illustration: FIG. 12. _Tympanuchus pallidicinctus_ 2L. Lateral view of -the superficial muscles of the left leg. × 1.] - -=_M. Extensor Iliotibialis Lateralis_= (M. iliotibialis), Figs. 12, 13, -20F, G - -_T. pallidicinctus_ - -[Illustration: FIG. 13. _Tympanuchus pallidicinctus_ 2L. Medial view of -the superficial muscles of the left leg. × 1. Articular capsule shown by -concentrically arranged dashes.] - -GENERAL DESCRIPTION AND RELATIONS.--Most superficial muscle on lateral -surface of thigh; broad, flat, and triangular; bounded anteriorly by M. -extensor iliotibialis anticus and posteriorly by M. flexor cruris -lateralis; posterior part considerably thicker than anterior part; -anteroproximal and centrodistal parts aponeurotic; extreme -posteroproximal corner also aponeurotic (could be considered tough sheet -of connective tissue intimately fused with M. extensor iliotibialis -lateralis, rather than part of muscle itself; see fig. 20F); latter -aponeurosis, as well as adjacent fleshy fibers, overlapped by M. flexor -cruris lateralis; this aponeurosis fused with posterior end of -underlying M. caudofemoralis pars iliofemoralis; centrodistal -aponeurosis tightly fused to underlying Mm. vastus lateralis and vastus -medialis; fleshy fibers posterior to this aponeurosis also fused with M. -vastus lateralis, although posterior third of muscle free; fleshy part -anterior to this aponeurosis bound by tough connective tissue to -underlying M. vastus medialis, although no fusion of fibers; anterior -edge tightly bound by strong connective tissue to M. extensor -iliotibialis anticus, with some fusion of fibers (proximally); -posteroproximal corner bound by tough connective tissue to adjacent -muscles; anteroproximal aponeurosis fused with aponeurotic -anteroproximal part of underlying M. extensor iliofibularis. Continuous -proximal aponeurosis of M. extensor iliotibialis anticus and of M. -extensor iliotibialis lateralis underlain by tough fascial sheet -overlying M. gluteus profundus; anterior part of this fascia tightly -fused to latter muscle but free from overlying aponeurosis; posterior -part of this fascia tightly fused to overlying aponeurosis but free from -M. gluteus profundus; middle part of fascia fused to both aponeurosis -and M. gluteus profundus. - -[Illustration: FIG. 14. _Tympanuchus pallidicinctus_ 2L. Lateral view of -the muscles of the left leg. The following muscles have been removed: -extensor iliotibialis lateralis, extensor iliotibialis anticus, -gastrocnemius pars externa and pars interna, and peroneus longus. × 1.] - -[Illustration: FIG. 15. _Tympanuchus pallidicinctus_ 2L. Medial view of -the muscles of the left leg. The following muscles have been removed: -extensor iliotibialis lateralis, extensor iliotibialis anticus, ambiens, -flexor cruris lateralis (in part), flexor cruris medialis (in part), -gastrocnemius pars externa and pars interna, and peroneus longus. × 1.] - -ORIGIN.--Approximately the anterior half attaches by an extensive -aponeurosis, which is continuous anteriorly with that of M. extensor -iliotibialis anticus, to the anterior iliac crest, ending posteriorly at -the anterior end of the lateral iliac process; the posterior part -attaches fleshily to the edge of the entire lateral iliac process and -(posterior few mm.) aponeurotically to the entire lateral ischiatic -ridge. The proximal part of the belly is much thicker than the fleshy -origin. Two accessory aponeuroses associate with the anterior part of -the muscle; the proximal one of these comes off the deep surface several -mm. distal to the proximal end of the fleshy belly and passes medially -between Mm. gluteus profundus and iliacus, fusing to both these muscles, -and attaches to the lateral edge of M. iliotrochantericus medius and to -the lateral edge of the ilium anterior to the latter; the aponeurosis -actually splits into two sheets at the edge of M. iliotrochantericus -medius; these sheets fuse to the dorsal and ventral surfaces of the -latter muscle, enclosing it; the part of this aponeurosis between Mm. -iliacus and iliotrochantericus medius is strongly fused with the -underlying body wall. The distal accessory aponeurosis (sometimes weak) -comes off the deep surface several mm. distal to the proximal one and -passes medially along the ventral surface of M. iliacus, fusing with the -latter, then joining the proximal accessory aponeurosis medial to M. -iliacus. - -INSERTION.--The muscle inserts by a broad aponeurosis strongly fused to -the underlying Mm. vastus lateralis and vastus medialis; the aponeurosis -contributes superficially to the patellar tendon, attaching to the -lateral half of the rotular crest. - -[Illustration: FIG. 16. _Tympanuchus pallidicinctus_ 2L. Lateral view of -the muscles of the left leg. The following muscles, in addition to those -listed for Fig. 14, have been removed: ambiens, vastus lateralis pars -lateralis, vastus medialis (except for part of patellar tendon), -extensor iliofibularis, flexor cruris lateralis (in part), flexor -perforans et perforatus digiti II, and flexor perforans et perforatus -digiti III. × 1.] - -INNERVATION.--A variable number of branches (usually two) of the middle -division of the femoral nerve pass ventral to M. iliacus and between Mm. -extensor iliotibialis anticus and vastus medialis and enter the deep -surface of the anteroproximal part of the muscle. The branch of the -middle peroneal division of the sciatic nerve emerges between the -proximal ends of Mm. extensor iliofibularis and vastus lateralis and -sends twigs into the deep surface of M. extensor iliotibialis lateralis. - -INDIVIDUAL VARIATION.--In two legs, the nerve supplying M. extensor -iliotibialis anticus gives twigs into M. extensor iliotibialis -lateralis. - -_T. cupido_ - -DIFFERENCES FROM _T. pallidicinctus_.--The fleshy origin from the -lateral iliac process is considerably thicker (reflected in a thicker -lateral iliac process). - -INDIVIDUAL VARIATION.--In three legs the nerve supplying M. extensor -iliotibialis anticus gives twigs into M. extensor iliotibialis -lateralis. In another leg one of the branches to the fused Mm. vastus -lateralis and vastus medialis sends a twig into M. extensor iliotibialis -lateralis. - -[Illustration: FIG. 17. _Tympanuchus pallidicinctus_ 2L. Lateral view of -the muscles of the left leg. The following muscles, in addition to those -listed for Fig. 16, have been removed: vastus lateralis pars postica, -gluteus profundus, flexor cruris medialis (in part), caudofemoralis, -flexor perforatus digiti IV, and tibialis anticus. × 1.] - - -_P. p. jamesi_ - -[Illustration: FIG. 18. _Tympanuchus pallidicinctus_ 2L. Lateral view of -the muscles of the left leg. The following muscles, in addition to those -listed for Fig. 17, have been removed: patellar tendon, iliacus, -iliotrochantericus medius, flexor cruris lateralis, flexor cruris -medialis, flexor ischiofemoralis, adductor superficialis, -femorocruralis, gastrocnemius pars media, flexor perforatus digiti III, -flexor perforatus digiti II, flexor hallucis longus, plantaris, flexor -digitorum longus, popliteus, and extensor digitorum longus. × 1.] - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The posteroproximal -aponeurosis is more extensive, resulting in a narrower proximal fleshy -end (fig. 20G); the fleshy fibers adjacent to this aponeurosis are not -overlapped by M. flexor cruris lateralis. There is a fusion of fibers -between the anterodistal fleshy part of M. extensor iliotibialis -lateralis and the underlying M. vastus medialis, but there is no fusion -of fibers between the anterior edge of M. extensor iliotibialis -lateralis and M. extensor iliotibialis anticus. The connective tissue -binding the posteroproximal corner to adjacent muscles is stronger. The -fleshy part of the origin is narrower, partly tendinous, and much -thinner (reflected in a thin lateral iliac process). The proximal border -is much more nearly straight, owing to a less pronounced lateral iliac -process. The distal accessory aponeurosis is absent. - -[Illustration: FIG. 19. _Tympanuchus pallidicinctus_ 2L. A. Posterior -view of the muscles of the left shank. The following shank muscles, in -addition to those listed for Fig. 17, have been removed: gastrocnemius -pars media, flexor perforatus digiti III, and flexor perforatus digiti -II. × 1. B. Posterior view of the proximal end of the shank, showing the -most deeply situated muscle. × 1. C. Lateral view of the head of the -left femur and the middle part of the pelvis, showing the deepest part -of M. obturator. × 1. D. Medial view of the posteroventral part of the -left side of the pelvis, showing the intrapelvic part of M. obturator. × -1. E. Anterior view of the left tarsometatarsus, showing the dorsal -intrinsic muscles of the foot. × 1-1/2. F. Posterior view of the left -tarsometatarsus, showing the ventral intrinsic muscles of the foot. × -1-1/2.] - -INDIVIDUAL VARIATION.--The muscle is usually somewhat fused to the -posteroproximal and anteroproximal fleshy corners of the underlying M. -extensor iliofibularis. - - -=_M. Extensor Iliotibialis Anticus_= (M. sartorius), Figs. 12, 13 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Anteriormost muscle of thigh; long -and strap-shaped; proximal part entirely anterior (adjacent) to M. -extensor iliotibialis lateralis; posterior edge of middle part medial to -latter muscle; distal part mostly medial to Mm. extensor iliotibialis -lateralis and vastus medialis; proximal part aponeurotic, continuous -posteriorly with anteroproximal aponeurosis of M. extensor iliotibialis -lateralis; anterior edge of M. extensor iliotibialis lateralis bound by -strong connective tissue to adjacent part of M. extensor iliotibialis -anticus; some fusion of fibers (proximally) between these two muscles; -anteroproximal corner of fleshy part of muscle sometimes fused to -underlying anterior edge of ilium and fascia covering body wall -musculature adjacent (anterior) to ilium. - -ORIGIN.--The muscle arises aponeurotically from the anterior part of the -anterior iliac crest and (anteroproximal corner) from the anterior end -of the median dorsal ridge. - -INSERTION.--The flat tendon, continuous posteriorly with the superficial -tendon of M. femoritibialis internus, fuses to the tendon of M. vastus -medialis, contributing superficially to the medial part of the patellar -tendon, which attaches to the medial half of the rotular crest; most of -the tendon is overlapped by the edge of M. gastrocnemius pars interna. - -INNERVATION.--A branch of the anterior division of the femoral nerve -gives twigs into the lateral surface of the posterior part. - -INDIVIDUAL VARIATION.--In two legs, a twig from the anteriormost branch -of the middle division of the femoral nerve anastomoses with the typical -branch to M. extensor iliotibialis anticus. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In several legs, the anterior edge of origin -extends forward onto the neural spine of the last free thoracic -vertebra. A twig from the middle division of the femoral nerve -anastomoses with the typical branch to M. extensor iliotibialis anticus -in three legs. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--There is no fusion of -fibers between M. extensor iliotibialis anticus and M. extensor -iliotibialis lateralis. - -INDIVIDUAL VARIATION.--The anterior edge of origin extends forward onto -the neural spine of the last free thoracic vertebra in some legs. - -[Illustration: FIGURE 20. Explanation on opposite page.] - -EXPLANATION OF FIGURE 20 - -A-D. Dorsal views of M. iliotrochantericus medius, showing its -relationship to femoral notch. × 1. In D, note absence of femoral notch -and location of branch of femoral nerve. A. _Tympanuchus pallidicinctus_ -2L. B. _T. cupido pinnatus_ 4L. C. _Pedioecetes phasianellus jamesi_ 1L. -D. _T. pallidicinctus_ 3L. - -E. Medial view of distal end of M. flexor cruris medialis of _P. p. -jamesi_ 4L. × 1. Part of insertion is covered by medial collateral -ligament. - -F,G. Lateral views of posteroproximal corner of M. extensor iliotibialis -lateralis (removed from specimen). × 1. F. _T. pallidicinctus_ 2L. G. -_P. p. jamesi_ 3L. - -H,I. Dorsolateral views of M. piriformis. × 1. H. _P. p. jamesi_ 1L. I. -_T. cupido attwateri_ 1L. - -J. Lateral view of M. caudofemoralis pars caudifemoralis (removed from -specimen) of _T. c. pinnatus_ 4L. × 1. - -K. Lateral view of extrapelvic part of M. obturator of _T. -pallidicinctus_ 3L (bones not shown). × 2. - -L,M. Region surrounding obturator foramen of _T. pallidicinctus_ 3L, -showing points of attachment of three parts of M. obturator (muscles -removed). × 3. L. Lateral view. M. Medial view. - -N. Anterior view of left tarsometatarsus of _P. p. jamesi_ 4L, showing -dorsal intrinsic muscles of foot. × 1-1/2. Tendon of M. extensor -digitorum longus has been removed. - - -=_M. Ambiens_=, Figs. 13, 16, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thin and elongate; on medial surface -of thigh; broadest above middle of belly; belly narrowed distally, -forming long slender tendon passing lateral to distal part of M. -extensor iliotibialis anticus; bounded anterolaterally by M. vastus -medialis and posterolaterally by Mm. femoritibialis internus and psoas -(proximally). - -ORIGIN.--The muscle arises by a short flat tendon from the pectineal -process. - -INSERTION.--The long slender tendon enters an elongate channel within -the patellar tendon; the point of entrance is at the proximal end of the -latter tendon just medial to the patella; the tendon passes -distolaterally (within the channel) below the patella and emerges from -the distolateral edge of the patellar tendon and then extends distally -along the anterolateral surface of the head of the fibula, superficial -to the fibular arm of the guide loop for M. extensor iliofibularis, and -joins the anterolateral surface of the common tendon of origin of the -anterolateral heads of Mm. flexor perforatus digiti III, flexor -perforatus digiti IV, and flexor perforatus digiti II; the point of -junction is usually immediately proximal to the proximal end of the -lateral head of M. flexor digitorum longus. - -INNERVATION.--The branch of the middle division of the femoral nerve -that supplies M. femoritibialis internus gives off a tiny twig or twigs -that penetrate the lateral surface of the proximal part of M. ambiens. - -INDIVIDUAL VARIATION.--None of significance in _T. pallidicinctus_ or in -_P. p. jamesi_; in _T. cupido_ the origin is partly fleshy in one leg. - - -=_M. Vastus Lateralis_= (M. femoritibialis externus + part of M. -femoritibialis medius), Figs. 14, 16 - -Fisher and Goodman (1955) apply the name femoritibialis externus to the -muscle unit that I here term the pars postica of M. vastus lateralis. -The reasons for this change are discussed in the section on terminology. - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thick; on lateral surface of femur -deep to M. extensor iliotibialis lateralis; anterior to M. extensor -iliofibularis and lateral to M. vastus medialis; much of lateral -surface, except proximal part, fused with overlying M. extensor -iliotibialis lateralis; deep surface of anterior half fused with M. -vastus medialis; proximal part overlapping, but usually not fusing with, -insertions of Mm. iliacus and caudofemoralis; partially separable into -two parts--pars lateralis and pars postica, former constituting main -part of muscle; latter considerably smaller and situated deep to -posterodistal part of pars lateralis, except for posterodistal part -extending posterior to edge of pars lateralis; proximal part of pars -postica strongly fused with pars lateralis; posterodistal tendinous edge -of pars lateralis fused or not fused with lateral surface of pars -postica; proximal end (narrow) of pars postica tendinous and variable in -length. - -ORIGIN.--_Pars lateralis_: This arises fleshily from most of the lateral -surface and (distally) from the anterior surface of the femur, extending -anteriorly to the anterior intermuscular line, fusing with M. vastus -medialis, and extending posteriorly to the posterolateral intermuscular -line (proximally) and the origin of pars postica (distally); the -proximal end begins at the level of the distal edge of the insertion of -M. iliotrochantericus medius, contacting the insertions of Mm. -iliotrochantericus medius, piriformis, and flexor ischiofemoralis, and -terminates distally at the level of the proximal ends of the femoral -condyles. - -_Pars postica_: This arises fleshily and tendinously (proximal end and -deep surface) from the posterolateral surface of approximately the -distal half of the femur, extends posteromedially to the posterolateral -intermuscular line where it contacts the origin of M. femorocruralis, -and extends anteriorly to the level of a line drawn diagonally across -the femur from the proximal end of the origin (at the posterolateral -intermuscular line) to the proximal end of the external condyle; the -distal end is anterior (adjacent) to the attachment of the proximal arm -of the tendinous guide loop for M. extensor iliofibularis; the origin is -adjacent to, but distinct from, the origin of pars lateralis. - -INSERTION.--_Pars lateralis_ is fused indistinguishably with M. vastus -medialis; these two muscles form the main (middle) part of the patellar -tendon, which also receives contributions from pars postica and Mm. -femoritibialis internus, extensor iliotibialis lateralis, and extensor -iliotibialis anticus; the patellar tendon attaches to the entire rotular -crest of the tibia; the patella is situated in the proximal part of this -tendon; some deep fleshy fibers of M. vastus lateralis pars lateralis -and M. vastus medialis attach to the proximal edge of the patella. _Pars -postica_ forms a short narrow tendon that fuses to the lateral part of -the tendon of pars lateralis, forming the lateralmost part of the -patellar tendon. A broad flat vinculum extends from the lateral surface -of the femorofibular fascia (defined under M. flexor perforans et -perforatus digiti II) to the deep surface of the lateral part of the -patellar tendon; a similar vinculum extends from the medial surface of -the internal condyle to the deep surface of the medial part of the -patellar tendon. - -INNERVATION.--Two or more branches of the middle division of the femoral -nerve penetrate the anterior surface of the fused Mm. vastus lateralis -(pars lateralis) and vastus medialis; short twigs emerge from the deep -surface of pars lateralis and penetrate the superficial surface of the -anteroproximal part of pars postica. - -INDIVIDUAL VARIATION.--The proximal ends of M. vastus medialis and M. -vastus lateralis are usually separated by a deep notch. In some legs, a -small bundle of fibers forming the anteroproximal part of M. vastus -lateralis attaches to the lateral surface of M. vastus medialis anterior -to this notch. - -_T. cupido_ - -INDIVIDUAL VARIATION.--One leg shows the same variation found in _T. -pallidicinctus_ (see above). In several legs, pars lateralis does not -extend so far proximally as usual, but begins at the level of insertion -of M. piriformis (does not contact the insertion of M. -iliotrochantericus medius) and may not overlap M. iliacus. In a few -legs, no vincula are associated with the patellar tendon. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--Pars lateralis often begins proximally at the -level of the insertion of M. piriformis. - - -=_M. Vastus Medialis_= (Part of M. femoritibialis medius), Figs. 13, 14, -15 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thick; on anteromedial surface of -femur medial to anterior part of M. vastus lateralis pars lateralis; -bounded medially by Mm. ambiens and extensor iliotibialis anticus -(distally); bounded posteromedially by M. femoritibialis internus; -proximal part medial to posterior ends of Mm. iliacus, -iliotrochantericus medius, and gluteus profundus; lateral surface, -except proximal part, fused with anterior part of M. vastus lateralis -pars lateralis; part of lateral surface of M. vastus medialis covered by -sheet of fascia attaching to anterior intermuscular line; M. vastus -lateralis separable from this fascia, but fascia absent anteriorly and -distally and these two muscles indistinguishably fused. - -ORIGIN.--The proximal third is attached narrowly by its lateral edge; -the distal two thirds is attached broadly by its entire deep surface. -The proximal third arises tendinously from the trochanteric ridge and -the proximal end of the anterior intermuscular line and fleshily from a -narrow area of the femur adjacent (medial) to the latter; the distal -part arises tendinously from the anterior intermuscular line and -fleshily from a broad adjacent area on the anteromedial surface of the -femur, terminating distally at the level of the proximal end of the -internal condyle; the posterior edge contacts the origin of M. -femoritibialis internus. - -INSERTION.--Attachment is in common with M. vastus lateralis pars -lateralis, which see. - -INNERVATION.--Two or more branches of the middle division of the femoral -nerve penetrate the anterior surface of the fused Mm. vastus medialis -and vastus lateralis pars lateralis; a variable number of branches of -the same division penetrate the medial surface of the proximal part of -M. vastus medialis. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Femoritibialis Internus_=, Figs. 13, 15 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Elongate; on posteromedial surface -of femur; bounded anteriorly by M. vastus medialis and posteriorly by M. -adductor profundus (overlapping anterior edge of latter); anteroproximal -part lateral to M. ambiens; anterodistal corner deep to distal end of M. -extensor iliotibialis anticus; distal part of muscle split into -superficial and deep layers; superficial layer thin, narrow, and -tendinous except for proximal end; deep layer wider, much thicker, and -fleshy except for distal end taking form of flat tendon; anterior edge -of latter somewhat fused to medial edge of tendon of M. vastus medialis; -deep layer widest near distal end of fleshy part; posterior edge of -superficial layer fused to underlying deep layer, and anterior edge -fused to (continuous with) posterior edge of tendon of M. extensor -iliotibialis anticus. - -ORIGIN.--The origin is mostly fleshy from the posteromedial surface of -the femur between the origin of M. vastus medialis and the posterior -intermuscular line, terminating immediately proximal to the internal -condyle. - -INSERTION.--The tendons of both superficial and deep layers attach to -the medial part of the rotular crest, forming the medialmost part of the -patellar tendon. - -INNERVATION.--The posteriormost branch of the middle division of the -femoral nerve penetrates the medial surface of the muscle near the -proximal end. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Extensor Iliofibularis_= (M. biceps femoris), Figs. 12, 14, 16, 17 - -The term extensor in the name of this muscle does not refer to its -function. Howell (1938) used the term extensor to indicate derivation of -the muscle from the primitive dorsal extensor muscle mass. (Likewise he -used the term flexor to indicate derivation from the primitive ventral -flexor muscle mass.) - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Deep to M. extensor iliotibialis -lateralis and posterior to femur; broad proximally and narrow distally; -posterior to M. vastus lateralis and anterior to proximal part of M. -flexor cruris lateralis (superficial to distal part of latter); -anteroproximal part aponeurotic, fused to deep surface of aponeurosis of -M. extensor iliotibialis lateralis; proximal part of aponeurosis of M. -extensor iliofibularis also fused to dorsal edges of underlying Mm. -gluteus profundus and piriformis. - -ORIGIN.--The posterior part is fleshy from the ventromedial surface of -the entire lateral iliac process; the anterior part is aponeurotic from -the posterior part of the anterior iliac crest. - -INSERTION.--The tendon forms along the posterodistal edge of the belly -and continues beyond the end of the belly as a cylindrical tendon that -passes through the tendinous guide loop (the belly terminates -approximately at the level of the guide loop), then extends -anterodistally into the shank musculature; the tendon passes between the -medial and lateral heads of M. flexor perforatus digiti IV, between the -medial and lateral heads of M. flexor perforatus digiti II, lateral to -the common tendon of the anterolateral heads of Mm. flexor perforatus -digiti IV, flexor perforatus digiti II, and flexor perforatus digiti -III, and between the posterior and lateral heads of M. flexor digitorum -longus, attaching to the fibular tubercle. - -The tendinous guide loop has three arms--proximal femoral, distal -femoral, and fibular; the proximal and distal femoral arms unite -posterior to the tendon of M. extensor iliofibularis; the proximal arm -is medial to, and the distal arm is lateral to, the latter; the fibular -arm joins the distal edge of the distal arm lateral to the tendon of M. -extensor iliofibularis. The proximal arm extends anteroproximally -lateral to the medial head of M. flexor perforatus digiti IV and medial -to M. vastus lateralis pars postica, attaching to a narrow line on the -anterolateral surface of the femur a short distance proximal to the -external condyle and adjacent (posterior) to the origin of M. vastus -lateralis pars postica. The distal arm extends anteriorly medial to the -posterior head of M. flexor perforans et perforatus digiti II and medial -to M. vastus lateralis pars postica, attaching in common with the tendon -of origin of M. gastrocnemius pars externa to a small oval area on the -posterolateral surface of the femur a short distance proximal to the -fibular groove; the arm is also fused to the underlying articular -capsule. The fibular arm (broadest of the three) passes deep to, and -fused with, the common tendon of origin of the lateral heads of Mm. -flexor perforatus digiti IV and flexor perforatus digiti II, superficial -to the common tendon of origin of the anterolateral heads of Mm. flexor -perforatus digiti IV, flexor perforatus digiti II, and flexor perforatus -digiti III, and deep to the tendon of M. ambiens, attaching broadly to a -narrow line on the anterolateral surface of the proximal part of the -fibula; the arm is also fused to the underlying articular capsule. - -INNERVATION.--A branch of the middle peroneal division of the sciatic -nerve sends twigs to the deep surface of the anteroproximal part; the -dorsal peroneal division of the sciatic nerve penetrates the deep -surface of the proximal end. - -INDIVIDUAL VARIATION.--In some instances a variable number of twigs -arises from the peroneal nerve near the middle of the thigh and enters -the deep surface of the muscle. They are difficult to expose without -breaking and may have been overlooked in some specimens. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The same variation is found as in _T. -pallidicinctus_ (see above). In one leg, the tendon of insertion -bifurcates into proximal and distal arms before attaching. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--It arises from the -ventral rather than the ventromedial surface of the lateral iliac -process (there is no ventromedial surface to this process). - -INDIVIDUAL VARIATION.--In nearly all of the legs, minute twigs to M. -extensor iliofibularis come off the peroneal nerve near the middle of -the thigh. The insertional tendon tends toward doubleness in two legs. - - -=_M. Piriformis_= (M. gluteus medius et minimus), Figs. 16, 20H, I - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Small, thin, and triangular; lateral -to antitrochanter and posterior part of trochanter; deep to M. extensor -iliofibularis and posterior (adjacent) to M. gluteus profundus; distal -half (or more) tendinous. - -ORIGIN.--The muscle arises fleshily from the posterior end of the -anterior iliac crest (ventral to the origins of Mm. extensor -iliotibialis lateralis and extensor iliofibularis) beginning adjacent to -the posterior end of M. gluteus profundus. - -INSERTION.--The flat tendon narrows, overlaps the anteroproximal corner -of insertion of M. flexor ischiofemoralis, and attaches to the lateral -surface of the proximal part of the femur immediately anterior to the -insertion of M. flexor ischiofemoralis and posterior to the proximal end -of M. vastus lateralis; the attachment is posterodistal to the insertion -of M. iliotrochantericus medius and posteroproximal to the insertion of -M. iliacus. - -INNERVATION.--The small anterior peroneal division of the sciatic nerve -turns anteriorly immediately after emerging from the ilio-ischiatic -fenestra and passes deep to M. piriformis, giving twigs to the deep -surface. - -INDIVIDUAL VARIATION.--In both legs of one specimen, the insertion does -not overlap the insertion of M. flexor ischiofemoralis. The -posteroproximal corner of the muscle is tendinous in one leg. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The anterior border is somewhat fused with the -posterior edge of M. gluteus profundus in one leg, while in another -there is a slight gap between the origins of M. gluteus profundus and M. -piriformis. In one leg, the posterior edge of the origin is aponeurotic. -On both sides of one specimen, an accessory tendinous band arises -several mm. posterior to the main part of M. piriformis and joins the -proximal part of the insertional tendon, thus forming a Y-shaped unit -(fig. 20I); the accessory tendon arises from the anterior end of the -lateral iliac process (left side) or from the anterior part of the -lateral iliac fossa (right side). The insertion may be proximal (rather -than posterior) to the proximal end of M. vastus lateralis. In one leg, -the insertional tendon is partly fused to the insertional tendon of M. -flexor ischiofemoralis. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--There is often a gap between the origins of M. -gluteus profundus and M. piriformis. In one leg (fig. 20H), the -posteroproximal corner of the muscle is aponeurotic. The insertion is -often proximal (rather than posterior) to the proximal end of M. vastus -lateralis. In one instance, the insertion does not overlap the insertion -of M. flexor ischiofemoralis. - - -=_M. Gluteus Profundus_= (M. iliotrochantericus posterior), Figs. 14, 16 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Large and thick; covering -dorsolateral surface of entire preacetabular part of ilium; deep to Mm. -extensor iliotibialis lateralis and extensor iliotibialis anticus; -bounded posteriorly by M. piriformis and ventrally by M. iliacus; -ventral edge fused with anterior part of latter and with proximal -accessory aponeurosis of M. extensor iliotibialis lateralis; tough sheet -of fascia strongly fused to anterior two thirds of lateral surface; -posterior to this, fascia overlying muscle but not attaching to it; -posterior half of fascia fused to overlying aponeurosis of M. extensor -iliotibialis lateralis; deep surface of muscle somewhat fused to -proximal part of M. iliotrochantericus medius. - -ORIGIN.--The superficial surface is tendinous from the entire anterior -iliac crest except the posterior end and from the crest forming the -anterior and anterolateral edges of the ilium; the muscle arises -fleshily from the entire dorsolateral surface of the preacetabular ilium -as far posteriorly as the level of the pectineal process; the dorsal -edge is adjacent (anterior) to the origin of M. piriformis. - -INSERTION.--The attachment is by a short, wide, thick tendon to a curved -line (convex anteriorly) on the lateral surface of the femoral -trochanter. - -INNERVATION.--The anterodorsal division of the femoral nerve turns -dorsally through the femoral notch of the ilium and penetrates the deep -surface of the ventral part of the muscle midway of its length; the -anterior peroneal division of the sciatic nerve passes deep to M. -piriformis and terminates near the posterodorsal edge of M. gluteus -profundus. - -INDIVIDUAL VARIATION.--On both sides of one specimen, the branch from -the femoral nerve passes lateral to the extreme anteroproximal corner of -M. iliotrochantericus medius instead of through the femoral notch. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, the insertional tendon is strongly -fused to the insertional tendon of M. iliotrochantericus medius. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Iliacus_= (M. iliotrochantericus anterior), Figs. 13, 14, 15, 16, -17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Adjacent ventrally to ventrolateral -edge of M. gluteus profundus; lateral edge much thicker than medial -edge; deep to M. extensor iliotibialis lateralis and anterolateral to M. -iliotrochantericus medius; distal (posterior) end passing between -proximal ends of Mm. vastus medialis and vastus lateralis pars -lateralis; insertion overlapped by latter; dorsal surface of anterior -part fused with ventrolateral edge of M. gluteus profundus and with -ventral surface of proximal accessory aponeurosis of M. extensor -iliotibialis lateralis; ventral surface partly fused with distal -accessory aponeurosis of latter muscle. - -ORIGIN.--The origin is fleshy and tendinous from the lateral edge of the -anterior part of the ilium. - -INSERTION.--The attachment is by a short flat tendon to the lateral -surface of the femur distal to the trochanter and anterodistal to the -insertion of M. piriformis and deep to the proximal part of M. vastus -lateralis pars lateralis. - -INNERVATION.--The dorsal division of the femoral nerve penetrates the -ventral surface. - -INDIVIDUAL VARIATION.--The dorsal division of the femoral nerve may fuse -proximally with either the anterior or middle division. In one leg, -there are two separate branches to the muscle. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The insertion may not be overlapped by M. vastus -lateralis. The dorsal division of the femoral nerve is fused proximally -with the middle division in one leg. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The fleshy origin is -wider. - -INDIVIDUAL VARIATION.--The dorsal division of the femoral nerve may fuse -proximally with either the anterior or middle division. In one leg, -there are two branches to M. iliacus, one fused with the anterior -division and the other with the middle division. - - -=_M. Iliotrochantericus Medius_=, Figs. 17, 20A, B, C, D - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Small and triangular; ventral to -posterior half of M. gluteus profundus; all but posteroventral corner -deep to latter; posteromedial to M. iliacus, anterior to neck of femur, -and dorsolateral (adjacent proximally) to M. psoas; proximal end notched -at level of femoral notch for passage of anterodorsal division of -femoral nerve; part anterior to femoral notch mainly tendinous; dorsal -surface of proximal part somewhat fused to M. gluteus profundus, -proximal accessory aponeurosis of M. extensor iliotibialis lateralis -split into two sheets enclosing and fusing with M. iliotrochantericus -medius, ultimately attaching to lateral edge of ilium in common with -origin of latter muscle. - -ORIGIN.--The muscle arises from the ventrolateral surface of the ilium -anterior to the acetabulum and posterior to the origin of M. iliacus; -the anterior part attaches to the ventrolateral edge of the ilium and -the posterior part attaches just above the ventral edge. The muscle is -not attached to the concavity of the femoral notch (the origin is -notched here). The part attaching anterior to the femoral notch is -narrow, tendinous, and continuous anteriorly with the accessory -aponeurosis of M. extensor iliotibialis lateralis (thus the anterior -border of the muscle cannot be exactly delimited). The part attaching -posterior to the femoral notch is wider and fleshy (fig. 20A). - -INSERTION.--The short flat tendon attaches to the lateral surface of the -distal end of the trochanter slightly anterior and immediately distal to -the insertion of M. gluteus profundus; the attachment is proximal to the -origin of M. vastus lateralis, anteroproximal to the insertion of M. -piriformis, and several mm. proximal to the insertion of M. iliacus. - -INNERVATION.--The small posterodorsal division of the femoral nerve -penetrates the ventral surface. - -INDIVIDUAL VARIATION.--On both sides of one specimen, the femoral notch -is absent and the proximal end of the muscle is not notched; the -proximal part is entirely fleshy and the anterior border is well defined -(fig. 20D). - -_T. cupido_ - -INDIVIDUAL VARIATION.--The part attaching anterior to the femoral notch -has a fleshy origin in one leg (fig. 20B), but in another, no part -attaches anterior to the femoral notch (thus the muscle is not notched). -In one leg, the insertional tendon is strongly fused to, and continuous -with, the ventral edge of the insertional tendon of M. gluteus -profundus. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The part attaching anterior to the femoral notch -may be mainly or entirely fleshy. In one leg, the part attaching -anterior to the femoral notch is entirely separate from, although -overlapped by, the main part of the muscle for the entire length of the -fleshy belly (fig. 20C); both parts have a common insertional tendon. - - -=_M. Psoas_= (M. iliacus), Figs. 13, 15, 18 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Small and slender; on medial aspect -of proximal end of thigh lateral to proximal end of M. ambiens; -ventromedial to M. iliotrochantericus medius; proximal end visible from -inside pelvis (medial to inguinal ligament); passes dorsolateral to -inguinal ligament. - -ORIGIN.--The muscle arises fleshily from the ventrolateral edge of the -ilium posterior to the femoral notch and ventral (adjacent) to the -origin of M. iliotrochantericus medius. - -INSERTION.--The attachment is tendinous to the medial surface of the -femur a short distance proximal to the origin of M. femoritibialis -internus. - -INNERVATION.--The posterior division of the femoral nerve, which spirals -completely around M. psoas, gives several twigs into the proximal part. - -INDIVIDUAL VARIATION.--None of significance. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In two legs the insertion is partly fleshy. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In one leg the insertion is partly fleshy. The -posterior division of the femoral nerve perforates the muscle in one -instance. - - -=_M. Flexor Cruris Lateralis_= (M. semitendinosus), Figs. 12, 13, 14, -15, 16, 17 - -This muscle represents only the main head of the muscle for which Fisher -and Goodman (1955) used the same name. Their accessory head of M. flexor -cruris lateralis is here termed M. femorocruralis. - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Large, thick, and strap-shaped; on -posterior surface of thigh; proximal part bounded anteriorly by Mm. -extensor iliotibialis lateralis and extensor iliofibularis; anterodistal -part deep to latter; bounded medially by Mm. caudofemoralis (proximally) -and flexor cruris medialis (distally); proximal end much narrower than -remainder and posterior to ilium; fused to underlying tough membrane, -which forms body wall posterior to ilium; proximal half of narrow part -aponeurotic; distal part of muscle posterior to M. femorocruralis; -separated from latter by common raphe to which both attach; caudal -muscle (M. transversoanalis) attached aponeurotically to superficial -surface of posteroproximal fleshy part of M. flexor cruris lateralis. - -ORIGIN.--The origin is tendinous (superficial surface) and fleshy from -the entire dorsolateral iliac ridge and fleshy from an area of the ilium -below this ridge, also tendinous from the posterior edge of the ilium -medial to the dorsolateral iliac ridge, and also tendinous from the -transverse processes of the first free caudal vertebra and the vertebra -either anterior or posterior to the latter. - -INSERTION.--M. flexor cruris lateralis and M. femorocruralis insert -broadly on opposite sides of a long tendinous raphe that extends -parallel to, but some distance posterior to, the distal half of the -femur; the distal end of this tendon broadens somewhat and fuses to the -medial surface of M. gastrocnemius pars media (continuous with the -tendon of the latter); the superficial part of this tendon continues -toward the tibiotarsus, soon fusing to the deep surface of the overlying -tendon of M. flexor cruris medialis; thus the common tendon of M. flexor -cruris lateralis and M. femorocruralis insert in common with both M. -flexor cruris medialis and M. gastrocnemius pars media. - -INNERVATION.--A branch of the middle tibial division of the sciatic -nerve enters the substance of M. caudofemoralis pars iliofemoralis, and -emerges near its ventral edge, then passes lateral to M. caudofemoralis -pars caudifemoralis and enters the anterior part of M. flexor cruris -lateralis. - -INDIVIDUAL VARIATION.--In three legs, the nerve does not perforate M. -caudofemoralis pars iliofemoralis, but passes deep to it. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, a small accessory slip arises from -the ventrolateral surface of the caudal musculature and joins the -posterior edge of the main part of M. flexor cruris lateralis a short -distance dorsal to the pubis. In several legs, the nerve does not -perforate M. caudofemoralis pars iliofemoralis, but passes deep to it. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The muscle is wider. The -extreme proximal end is fleshy up to its origin, which is fleshy and -tendinous from the vertebrae. The common insertional tendon of M. flexor -cruris lateralis and M. femorocruralis fuses with the distal end of the -fleshy part (instead of tendon) of M. flexor cruris medialis. - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Flexor Cruris Medialis_= (M. semimembranosus), Figs. 12, 13, 14, -15, 16, 17, 20E - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Most posterior muscle on medial -surface of thigh; long and strap-shaped; bounded anteriorly by M. -adductor profundus; posteroproximal corner of latter medial to -anteroproximal part of M. flexor cruris medialis; bounded laterally by -Mm. caudofemoralis (proximally) and flexor cruris lateralis (distally); -anteroproximal corner adjacent to posteroventral corner of M. flexor -ischiofemoralis and lateral to extreme posteroproximal corner of M. -adductor superficialis; distal end tendinous, extending into proximal -part of shank; bounded medially by M. gastrocnemius pars interna and -laterally by Mm. gastrocnemius pars media and plantaris. - -ORIGIN.--The muscle arises by a wide flat tendon from a narrow line on -the lateral surface of the ischium dorsal to the ventral ischiatic -tubercle. - -INSERTION.--The wide flat tendon attaches to a narrow line on the medial -surface of the proximal part of the tibiotarsus a short distance -anterior to the proximal part of M. plantaris and deep to M. -gastrocnemius pars interna; the proximal end attaches immediately -anterior to the distal end of the medial collateral ligament. Part of -the common tendon of Mm. flexor cruris lateralis and femorocruralis -fuses with the lateral surface of the tendon of M. flexor cruris -medialis, inserting in common with it. - -INNERVATION.--A branch of the middle tibial division of the sciatic -nerve passes deep to both heads of M. caudofemoralis and enters the -anterior part of M. flexor cruris medialis. - -INDIVIDUAL VARIATION.--In several legs, the anterior edge of the -proximal part fits into a deep longitudinal groove in the posterior edge -of the proximal part of M. adductor superficialis; the two muscles fuse -slightly at this point. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In two legs, the extreme posterior end of the -origin is from the pubis. In two others, the proximal end is separated -by a slight gap from M. adductor superficialis. The nerve arises from -the posterior (rather than middle) tibial division in one leg. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The origin is wider; the -posterior third to half of the origin is fleshy. The entire origin is -from a strongly curved line, the middle part of which attaches to the -ventral edge of the ischium posterior to the ventral ischiatic tubercle. -The insertion is wider. The insertional tendon attaches posterior -(rather than anterior) to the distal end of the medial collateral -ligament; the proximal end of the insertion attaches to the articular -capsule (fig. 20E). The insertional tendon is shorter; as a result, the -common tendon of Mm. flexor cruris lateralis and femorocruralis fuses -with the distal end of the fleshy belly (instead of the tendon) of M. -flexor cruris medialis. - -INDIVIDUAL VARIATION.--In two thirds of the legs, the proximal part of -the insertion is fleshy rather than tendinous. In one leg, the middle -part of the insertional tendon splits into two sheets, one attaching -anterior to and one attaching posterior to the distal end of the medial -collateral ligament. The nerve may arise from the posterior tibial -division (two legs), from the middle tibial division (one leg), or as an -independent division of the tibial nerve (three legs). In one leg, the -nerve perforates the lateral part of M. flexor ischiofemoralis. - - -=_M. Caudofemoralis_= (M. piriformis), Figs. 12, 13, 14, 15, 16, 20J - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Posterior to proximal part of shaft -of femur and deep to M. extensor iliofibularis; posterior part deep to -M. flexor cruris lateralis; bounded medially by Mm. flexor -ischiofemoralis (dorsally), flexor cruris medialis (posteriorly), and -adductor superficialis (anteroventrally); anterior end distal to -anterior end of M. flexor ischiofemoralis; two distinct heads--pars -iliofemoralis and pars caudifemoralis; _pars iliofemoralis_ dorsal to -pars caudifemoralis; posteroventral corner of former overlapped by -latter; pars iliofemoralis wider and much shorter than pars -caudifemoralis; extreme posterior end of pars iliofemoralis fused to -overlying posteroproximal aponeurosis of M. extensor iliotibialis -lateralis; small part of ventral edge sometimes fused with underlying -tendinous posteroproximal corner of M. flexor cruris medialis; entirely -fleshy except for small triangular tendinous area along dorsal margin at -point where branch of middle tibial division of sciatic nerve passes -deep to muscle; _pars caudifemoralis_ long, thin, narrow, and -strap-shaped; overlapping posteroventral corner of ischium; posterior -end of fleshy belly narrowed and forming long slender tendon passing -into caudal musculature; anterior end forming short narrow tendon fused -to deep surface of ventral edge of pars iliofemoralis relatively near -insertion; tendon continuous to insertion; fleshy anterodorsal corner of -pars caudifemoralis slightly overlapped by ventral edge of pars -iliofemoralis; some form of connection usually present between anterior -part of M. caudofemoralis pars caudifemoralis and dorsal end of raphe -between Mm. flexor cruris lateralis and femorocruralis, most often -consisting of narrow weak tendon. - -ORIGIN.--_Pars iliofemoralis_: This arises fleshily from the -ventromedial surface of the posterior part of the lateral iliac process, -from the entire lateral ischiatic ridge, and from the lateral surface of -the ischium anterior to this ridge nearly as far forward as the -posterior edge of origin of M. flexor ischiofemoralis; the -posteroventral corner reaches the ventral edge of the ischium and -usually attaches to the ischiopubic membrane posterior to M. flexor -cruris medialis. _Pars caudifemoralis_: This arises by a narrow tendon -from the ventral surface of a broad, thick, tendinous sheet ventral to -the pygostyle, which, in turn, attaches to the ventral surface of the -pygostyle. - -INSERTION.--The common belly formed by the union of the two heads -narrows (width variable) and attaches to the posterolateral surface of -the femur distal to the level of insertion of M. iliacus and in contact -with the posterior edge of origin of M. vastus lateralis pars lateralis; -the dorsal part is fleshy and the ventral part is tendinous. - -INNERVATION.--A branch of the middle tibial division of the sciatic -nerve gives several twigs to the deep surface of pars iliofemoralis; -another twig enters the substance of pars iliofemoralis and emerges from -the ventral edge of the latter, then enters the dorsal edge of pars -caudifemoralis. The latter twig was not found in all legs, but was -probably destroyed during dissection. - -INDIVIDUAL VARIATION.--The tendinous area in the dorsal margin of pars -iliofemoralis is lacking in one leg and extremely small in some others. -In both legs of one specimen, the connection between M. caudofemoralis -pars caudifemoralis and the raphe between Mm. flexor cruris lateralis -and femorocruralis consists of a small (11 × 2 mm.) but well developed -and entirely fleshy muscle slip (fig. 16). In one leg, the ventral third -of this connection is fleshy, the remainder tendinous; in another, this -connection is completely lacking. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The tendinous area in the dorsal margin of pars -iliofemoralis is lacking in one leg. The connection between pars -caudifemoralis and the raphe between Mm. flexor cruris lateralis and -femorocruralis is lacking in several legs. A conspicuous variation -occurring in three legs is the presence of a tendinous area in the belly -of pars caudifemoralis, dividing the latter into proximal and distal -parts (fig. 20J). In one leg, the posteroventral corner of pars -iliofemoralis arises from the pubis. The origin of pars caudifemoralis -in three legs is directly from the anteroventral surface of the -pygostyle. In one instance, the insertional tendon of pars -caudifemoralis is long and extremely slender and extends for some -distance in a groove on the medial surface of pars iliofemoralis before -fusing with the latter. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--There is no connection at -all between pars caudifemoralis and the raphe between Mm. flexor cruris -lateralis and femorocruralis. The posteroventral corner of pars -iliofemoralis is some distance dorsal to the ventral edge of the ischium -and, therefore, does not attach to the ischiopubic membrane. - -INDIVIDUAL VARIATION.--The insertion (narrow) is entirely tendinous in -one leg. - - -=_M. Flexor Ischiofemoralis_= (M. ischiofemoralis), Figs. 16, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thick; on lateral surface of -anterior part of ischium; posterior end in lateral iliac fossa; deep to -Mm. extensor iliofibularis and caudofemoralis pars iliofemoralis; -overlapping ventral extrapelvic part of M. obturator and anteroproximal -part of M. adductor superficialis (slightly fused to proximal edge of -latter); posteroventral corner contacting anteroproximal corner of M. -flexor cruris medialis; extreme anterodorsal corner usually overlapped -by tendon of M. piriformis. - -ORIGIN.--The muscle arises fleshily from a large area on the lateral -surface of the ischium extending ventrally to the origin of M. adductor -superficialis, anteriorly to the level of the posterior end of the -obturator foramen, dorsally to the ventral border of the ilio-ischiatic -fenestra and to the depth of the lateral iliac fossa, and posteriorly -approximately to the level of the ventral ischiatic tubercle. - -INSERTION.--The short flat tendon attaches to the lateral surface of the -femur immediately posterior to the insertion of M. piriformis. - -INNERVATION.--The posterior tibial division of the sciatic nerve -penetrates the dorsal surface. - -INDIVIDUAL VARIATION.--The ventral part of the insertion may be fleshy. - -_T. cupido_ - -INDIVIDUAL VARIATION.--None of significance. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In all the legs except one, an additional twig -arises from the branch to M. flexor cruris medialis and penetrates the -lateral surface of M. flexor ischiofemoralis. The ventral part of the -insertion is fleshy in one leg. - - -=_M. Adductor Superficialis_= (M. adductor longus et brevis, pars -externa), Figs. 14, 16, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Posterior to femur, lateral to M. -adductor profundus, and medial to Mm. flexor ischiofemoralis, -caudofemoralis, and femorocruralis; proximal end (fleshy) fused to -proximal tendinous end of M. adductor profundus. - -ORIGIN.--The origin is fleshy and tendinous from the proximal end of the -lateral surface of M. adductor profundus and from a narrow line on the -ischium adjacent (dorsal) to the origin of the latter; the posterior -part of the origin sometimes extends farther dorsally on the lateral -surface of the ischium; the origin does not extend so far anteriorly nor -so far posteriorly as the origin of M. adductor profundus; the anterior -edge is at the posterior border of the obturator foramen. - -INSERTION.--The attachment is fleshy and thick (distal end thin) to the -posterior surface of the middle part of the femur between the posterior -and posterolateral intermuscular lines; the attachment is adjacent -(lateral) to the insertion of M. adductor profundus and adjacent -(medial) to the origins of Mm. vastus lateralis (proximally) and -femorocruralis (distally); the proximal edge is approximately at the -level of the distal edge of the insertion of M. caudofemoralis. - -INNERVATION.--A branch of the obturator nerve emerges from the obturator -foramen dorsal to the tendon of insertion of M. obturator pars postica, -turns ventrally (crossing latter), and passes deep to the anteroproximal -corner of M. adductor superficialis, extending posterodistally between -the adductor muscles and giving twigs to the medial surface of M. -adductor superficialis and to the lateral surface of M. adductor -profundus. - -INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles -are so firmly fused together in some cases that the boundaries cannot be -identified at this point. In several legs, there is a deep longitudinal -groove in the posterior edge of the proximal part of the muscle into -which the anterior edge of M. flexor cruris medialis fits. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In some cases, the anterior edges of the two -adductor muscles are firmly fused together. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL T. PALLIDICINCTUS.--The origin is narrower. - -INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles -may be fused together. In one leg, the entire muscle is -indistinguishably fused with M. adductor profundus and they appear as a -single muscle. - - -=_M. Adductor Profundus_= (M. adductor longus et brevis, pars interna), -Figs. 13, 15, 17, 18 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Broad; on medial surface of thigh -immediately posterior to femur; bounded posteriorly by M. flexor cruris -medialis (medial to anteroproximal corner of latter), anteriorly by M. -femoritibialis internus (anterior edge overlapped by latter), and -laterally by Mm. adductor superficialis and femorocruralis; proximal end -tendinous (except anterior edge), fused to proximal fleshy end of M. -adductor superficialis. - -ORIGIN.--The muscle arises tendinously from the ventral edge of the -ischium extending from the posterior border of the obturator foramen to -the ventral ischiatic tubercle and (anterior edge) fleshily from the -lateral surface of the pubis ventral to the obturator foramen; the -origin is adjacent (ventral) to the origin of M. adductor -superficialis. - -INSERTION.--The attachment is fleshy and tendinous from the posterior -intermuscular line and (proximally and distally) from a narrow adjacent -area. Proximally there are often two approximately parallel lines a -short distance apart, representing points of attachment of the lateral -and medial edges of the muscle; if there is only one line proximally, it -may represent the attachment of either the lateral or medial edge of the -muscle; distally there is usually only one line, representing the -lateral edge of the muscle. The distal end extends onto the posterior -surface of the proximal part of the internal condyle, and is adjacent -(lateral) to the origin of M. femoritibialis internus, adjacent (medial) -to Mm. adductor superficialis and femorocruralis, and adjacent -(proximal) to M. gastrocnemius pars media. - -INNERVATION.--See M. adductor superficialis. - -INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles -are strongly fused together in some cases. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The anterior edge may be fused with that of M. -adductor superficialis. The distal end is sometimes slightly fused with -M. gastrocnemius pars media. In one leg, the proximal two thirds of the -insertion is entirely tendinous, whereas in another the distal end of -the insertion is tendinous. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The anterior edge (in one leg the entire muscle) -in some legs fuses with that of M. adductor superficialis. - - -=_M. Obturator_= (M. obturator externus + M. obturator internus), Figs. -16, 17, 18, 19C, D, 20K, L, M - -I am adopting the single name M. obturator for the complex that Fisher -(Fisher, 1946; Fisher and Goodman, 1955) subdivides into Mm. obturator -externus and obturator internus. The reasons for this change are given -in the section on terminology. - -For ease of description, it is desirable to apply names to the -subdivisions of M. obturator. It has been customary to divide the -obturator complex into two parts--an obturator internus and an obturator -externus; the latter has often been further subdivided. The evidence -given below demonstrates that a primary division of the complex into -only two parts is unsatisfactory. - -I strongly suspect that comparable parts of the obturator complex have -been considered a part of the "internus" in some birds and a part of the -"externus" in others. In their work on the Galliformes, Hudson, _et al._ -(1959) subdivide the obturator complex into only two -divisions--obturator externus and obturator internus. The extrapelvic -part of this complex that arises from the rim of the obturator foramen -and inserts in common with the stout tendon of the main intrapelvic part -of the obturator internus is considered by them to be a part of the -obturator internus. Their obturator externus lies anterior and deep to -the extrapelvic part of the obturator internus and inserts separately -from the latter. (I also have found this same arrangement in -_Tympanuchus_ and _Pedioecetes_.) - -Berger (1952), in his description of the Black-billed Cuckoo (_Coccyzus -erythrophthalmus_), also divides the obturator complex into an obturator -internus and an obturator externus; the latter he subdivides into a -dorsal and a ventral part. He states (p. 530) that he did not find any -measurable differences in myology between _C. erythrophthalmus_ and _C. -americanus_. In order better to compare this arrangement with that in -_Tympanuchus_, I have examined two specimens of _C. americanus_. My -findings in the latter differ from Berger's description (p. 541) in one -respect. Whereas Berger states that the dorsal and ventral parts of M. -obturator externus are distinct except at their origin, I find them -fused for their entire length; the muscle fibers that connect these two -parts lie deep to the tendon of M. obturator internus. The origin of all -parts of the complex in _Coccyzus_ is similar to that in _Tympanuchus_. -The only notable difference in configuration is that the part in -_Coccyzus_ that appears to correspond to the obturator externus of -Hudson, _et al._ (1959) is not separate from the remainder of the -extrapelvic part of the muscle. Berger (1952) considers all parts of the -muscle having an extrapelvic origin to make up the obturator externus. -It appears to me that the dorsal part and a part of the ventral part of -the obturator externus of Berger correspond to the extrapelvic fleshy -part of the obturator internus of Hudson, _et al._ - -From my limited study, it seems to me to be desirable to recognize four -subdivisions of the obturator complex, for which I propose the terms -pars antica, pars dorsalis, pars ventralis, and pars postica. These -parts exhibit various degrees of fusion in different groups of birds and -some parts appear to be absent in certain birds. A study of a wide -variety of birds will be required to determine whether or not a -subdivision into the four parts proposed here is suitable for birds as a -whole. - -Applying these terms to _Coccyzus_, pars postica is equivalent to the -entire obturator internus of Berger (1952). Pars dorsalis is apparently -equivalent to the dorsal part of Berger's obturator externus. The -ventral part of the obturator externus of Berger represents the fused -pars antica and pars ventralis. - -The main parts of the obturator muscle appear to be pars postica and -pars antica. Pars dorsalis and pars ventralis are more variable; in -_Coccyzus_ these two parts are closely associated with pars antica -whereas in _Tympanuchus_ they are most closely associated with pars -postica. Apparently pars dorsalis and pars ventralis may be absent in -some birds. - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Deeply situated immediately -posterior to head of femur; part extending through obturator foramen and -lying inside pelvis; extrapelvic part deep to Mm. flexor ischiofemoralis -and piriformis; muscle partially divisible into four parts--pars antica, -pars dorsalis, pars ventralis, and pars postica (fig. 20K); _pars -postica_: mostly inside pelvis; much larger than other parts; broad -(narrow anteriorly); on medial surface of ischium; composed of several -fascicles; anterior end forming narrow, heavy tendon (with some fleshy -fibers on posterior part of deep surface) passing through obturator -foramen; anteriormost fleshy fibers of ventralmost fascicle fused with -pars ventralis; _pars ventralis_: essentially extrapelvic (see origin); -mostly ventral to tendon of pars postica; superficial to pars antica; -fused to anterior fleshy part of pars postica; anterodorsal edge usually -adjacent to, and often slightly fused with, ventral edge of pars -dorsalis (deep to tendon of pars postica); _pars dorsalis_: entirely -extrapelvic; mostly dorsal to tendon of pars postica; superficial to -dorsal part of pars antica; _pars antica_: extremely short but -relatively thick; entirely fleshy; entirely extrapelvic; between -obturator foramen and head of femur; anterior surface adjacent to -articular capsule; almost completely covered by other parts of muscle; -proximal end of posterior surface often slightly fused with adjacent -parts of pars ventralis and pars dorsalis. - -ORIGIN.--_Pars postica_: This arises fleshily from the medial surface of -the entire ischium except the posterior end, from the dorsomedial and -medial surfaces of the anterior half of the pubis as far forward as the -obturator foramen, from the internal ilio-ischiatic crest, from the -medial surface of the ilium for a short distance posterior to this -crest, and from the iliac recess; the posteroventral corner usually -arises from the medial surface of the ischiopubic membrane. _Pars -ventralis_: This arises fleshily from the dorsomedial edge of the -ventral border of the obturator foramen (fig. 20M) and (narrowly) from -the anterior border of the foramen; this part may or may not arise from -the lateral surface of the anteroventral border of the foramen and is -usually adjacent along the anterior border of the foramen to pars -dorsalis; _pars ventralis_ is continuous along the ventral border of the -foramen with the intrapelvic origin of pars postica. _Pars dorsalis_: -This arises fleshily from the lateral surface of the anterodorsal border -of the foramen (fig. 20L) and may extend posteriorly along the dorsal -border of the foramen. _Pars antica_: This arises fleshily from the -depresssed area anterior to the obturator foramen (adjacent to pars -dorsalis and pars ventralis); the posteroventral corner may arise from -the lateral surface of the anteroventral border of the obturator foramen -(ventral to the anterior end of pars ventralis; fig. 20L). - -INSERTION.--_Pars postica_: Several tendinous bands (intrapelvic) -converge and coalesce, forming a single strong tendon that passes -through the obturator foramen and attaches to the lateral surface of the -femoral trochanter a short distance posterior to the insertion of M. -gluteus profundus and proximal to the insertion of M. flexor -ischiofemoralis. _Pars ventralis_: The attachment is fleshy and -tendinous to the ventral edge and the deep surface of the tendon of pars -postica. _Pars dorsalis_: The attachment is fleshy and tendinous to the -dorsal edge of the tendon of pars postica. _Pars antica_: The attachment -is fleshy to the posterior surface of the proximal end of the femur -several mm. posterior to the insertion of pars postica; the lateral edge -attaches to the obturator ridge. - -INNERVATION.--The muscle is supplied by the obturator nerve; several -twigs, which do not pass through the obturator foramen, penetrate the -anterior part of the medial surface of pars postica; several twigs pass -through the obturator foramen and supply pars dorsalis, pars ventralis, -and pars antica. - -INDIVIDUAL VARIATION.--In some cases the origin of pars postica does not -include the dorsal end of the internal ilio-ischiatic crest nor the -ilium posterior to it. Tiny but distinct accessory slips are sometimes -present. In one leg a tendinous slip of pars antica extends beyond the -remainder of the muscle and inserts independently on the trochanter -close to the insertion of pars postica. In another leg, a fleshy and -tendinous slip of pars antica attaches to the deep surface of the -insertional tendon of pars postica. In still another leg, a fleshy and -tendinous slip of pars dorsalis inserts adjacent (anterior) to the -dorsal edge of the insertion of pars antica. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The variations are similar to those given above -for _T. pallidicinctus_ except that there is no slip of pars antica -attaching to the tendon of pars postica. - -_P. p. jamesi._ - -INDIVIDUAL VARIATION.--There are variations similar to those given above -for _T. pallidicinctus_ except that there is no independent slip of pars -antica attaching on the trochanter close to the insertion of pars -postica. Pars dorsalis may be quite small. In several legs, pars -dorsalis is more closely associated with pars antica than with pars -postica; in one of these, pars dorsalis is indistinguishably fused with -pars antica (inserting with the latter) except for a few fibers which -insert with pars postica. - - -=_M. Femorocruralis_= (M. accessorius semitendinosi), Figs. 14, 15, 16, -17 - -Fisher (Fisher, 1946; Fisher and Goodman, 1955) considers this muscle as -an accessory head of M. flexor cruris lateralis. The reasons for this -change in terminology are given in the section on terminology. - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Short and broad; posterior to distal -part of femur; deep to Mm. extensor iliofibularis and vastus lateralis -pars postica; bounded posteriorly by M. flexor cruris lateralis, -medially by Mm. adductor superficialis and adductor profundus, and -distally by M. gastrocnemius pars media; fused to a variable degree with -the latter (in some cases these two muscles fused firmly together, -appearing as single muscle); distal and medial to proximal end of M. -flexor perforatus digiti IV. - -ORIGIN.--The muscle arises fleshily (thin proximally, thick distally) -from the posterior surface of approximately the distal half of the femur -between the posterior and posterolateral intermuscular lines. The -ventral end is continuous with the origin of M. gastrocnemius pars -media, adjacent (medial) to the origin of M. vastus lateralis pars -postica, and adjacent (lateral) to the insertions of Mm. adductor -superficialis and adductor profundus. - -INSERTION.--The attachment is to the tendinous raphe in common with M. -flexor cruris lateralis (which see). - -INNERVATION.--One or two tiny branches come off the tibial nerve near -the distal end of the main trunk of the sciatic nerve, pass anteriorly -deep to the peroneal nerve, and penetrate the lateral surface. - -INDIVIDUAL VARIATION.--In two legs, the branch of the medial division of -the tibial nerve which supplies M. gastrocnemius pars media sends a twig -to the lateral surface of the distal end of M. femorocruralis (in -addition to the usual innervation). - -_T. cupido_ - -INDIVIDUAL VARIATION.--None of significance. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The muscle is much wider, -extending farther proximally on the femur. - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Gastrocnemius_=, Figs. 12, 13, 15 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Divided into three distinct, widely -separated parts--pars externa, pars interna, and pars media; _pars -externa_: large; on posterolateral surface of shank; narrow proximally -and distally; bounded anterolaterally by M. flexor perforans et -perforatus digiti II and anteromedially by medial head of M. flexor -perforatus digiti III; completely separate from pars interna and media -except for common tendon of insertion; _pars interna_: large; on -anteromedial surface of shank; narrow distally; bounded anterolaterally -by M. peroneus longus and posteromedially by pars media (proximally) and -medial head of M. flexor perforatus digiti III; broad sheet of tough -connective tissue extending between distal parts of pars externa and -pars interna; covering underlying M. flexor perforatus digiti III -(medial head), somewhat fused with anteroproximal edge of M. peroneus -longus; _pars media_: small and short; on medial surface of proximal -part of shank; deep to tendon of insertion of M. flexor cruris medialis; -bounded anteromedially by pars interna, posterolaterally by medial head -of M. flexor perforatus digiti III, and proximally by M. femorocruralis; -fused to latter, and boundary between the two difficult to locate. - -ORIGIN.--_Pars externa_: The short cylindrical tendon fuses with the -anterior half of the distal arm of the tendinous guide loop for M. -extensor iliofibularis and attaches in common with the latter to the -posterolateral surface of the femur immediately proximal to the fibular -condyle; the attachment is proximal (adjacent) to the origin of M. -flexor perforans et perforatus digiti II and distal (adjacent) to the -origin of M. flexor perforatus digiti IV and is fused to the articular -capsule. - -_Pars interna_: The proximal end is partly separable into two layers--a -superficial longer one and a deep shorter one. The superficial layer -attaches fleshily to the ventral part of the anterior surface of the -patella and to the medial half of the superficial surface of the -patellar tendon; this layer slightly overlaps the distal fleshy end of -M. extensor iliotibialis anticus. The deep layer (overlapped by the -superficial layer) attaches to the medial surface of the inner cnemial -crest, to the rotular crest medial to the latter, to the medial surface -of the proximal part of the tibiotarsus, and (posteroproximal corner) to -the distomedial edge of the patellar tendon and to the articular capsule -posteromedial to the rotular crest; the entire ventral edge is -tendinous, the remainder fleshy. - -_Pars media_: This arises fleshily from an oblique line beginning at the -distal end of the origin of M. femorocruralis (continuous with the -latter) and extending distomedially across the proximal part of the -popliteal area to the proximal edge of the internal condyle, then -attaching to the adjacent part of the articular capsule; this part is -adjacent (distal) to the insertion of M. adductor profundus and adjacent -(proximomedial) to the medial head of M. flexor perforatus digiti IV. - -INSERTION.--_Pars media_ narrows distally with a narrow tendon along the -posterior edge of the fleshy belly; approximately one third of the way -down the tibiotarsus the fleshy part terminates and the tendon joins the -posterior edge of pars interna, continuing distally in this position. -The ossified tendon on the superficial surface of the distal part of -_pars interna_, continuous posteriorly with the tendon of pars media, is -joined approximately two thirds of the way down the tibiotarsus by the -tendon of pars externa; the fleshy belly of pars interna ends just below -the junction. The ossified tendon on the superficial surface of the -distal part of _pars externa_ extends beyond the fleshy belly and -becomes flexible before joining the tendon of pars interna and media. -The common tendon (partly ossified) extends along the posterior surface -of the tibiotarsus and widens as it passes posterior to the tibial -cartilage, bound to the latter by a thin tough sheet of connective -tissue which attaches to the edges of the tibial cartilage, thus forming -a sheath for the tendon; the tendon attaches by its edges to the -posterior edges of the calcaneal ridges of the hypotarsus, then -continues distally (much reduced in thickness) along the posterior -surface of the tarsometatarsus, enclosing the flexor tendons; the -lateral edge of the tendon attaches to the posterolateral edge of the -tarsometatarsus, terminating immediately above the level of the hallux; -the medial edge attaches to the edge of the posterior metatarsal crest; -the tendon terminates as a thin sheet that attaches to the fascia on the -sole of the foot. (Hudson, _et al._, 1959 consider the posterior -metatarsal crest to be an ossified part of the tendon of M. -gastrocnemius.) - -INNERVATION.--A branch of the lateral division of the tibial nerve -penetrates the proximal part of the medial surface of pars externa. One -or two branches of the medial division of the tibial nerve pass deep to -M. plantaris and penetrate the deep surface of the posterior part of -pars interna. The most proximal branch of the medial division of the -tibial nerve penetrates the lateral surface of pars media. - -INDIVIDUAL VARIATION.--None of significance. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, the lateral edge of pars interna -overlaps the proximomedial edge of M. peroneus longus; some fibers -attach to the lateral surface of the inner cnemial crest. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The proximal end of pars -interna does not reach the patella. - -INDIVIDUAL VARIATION.--In one leg, an additional twig to pars media -arises from the distal branch to M. femorocruralis. - - -=_M. Flexor Perforans et Perforatus Digiti II_=, Figs. 12, 14 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Long, slender, and Y-shaped; on -lateral surface of shank; the two heads enclosing M. flexor perforans et -perforatus digiti III; _posterior head_ bounded posteriorly by M. -gastrocnemius pars externa; extreme proximal end deep to M. vastus -lateralis pars postica; anterior surface fused to posterior surface of -M. flexor perforans et perforatus digiti III; deep surface fused to -tendinous part of lateral head of M. flexor perforatus digiti IV; -_anterior head_ tendinous except for extreme distal end; covered by, and -fused to, posterior edge of M. peroneus longus; fused to anterior -surface of M. flexor perforans et perforatus digiti III; two heads join -above middle of shank; anteroproximal and posterodistal parts of common -belly usually tendinous. - -ORIGIN.--_Anterior head_: This arises by a narrow tendon (partly -ossified) from the distal tip of the outer cnemial crest. The tendon is -so intimately fused with a connective tissue sheet fused to the deep and -posterior surfaces of M. peroneus longus and to the anterior surface of -M. flexor perforans et perforatus digiti III that M. flexor perforans et -perforatus digiti II could be considered to arise from these two -muscles. _Posterior head_: This arises mostly fleshily from the lateral -surface of a compound sheet of tough connective tissue formed by the -fusion of the tendinous posteroproximal corner of M. flexor perforans et -perforatus digiti III, the proximal parts of the tendons of origin of -the lateral heads of Mm. flexor perforatus digiti IV and flexor -perforatus digiti II, the fibular and distal arms of the guide loop for -M. extensor iliofibularis, and the lateral part of the articular -capsule; a part of the common tendon of origin of the anterolateral -heads of Mm. flexor perforatus digiti III, flexor perforatus digiti IV, -and flexor perforatus digiti II also contributes to this sheet, which -attaches to the lateral surface of the external condyle of the femur and -to the anterolateral surface of the head of the fibula; for convenience -in description, this complex connective tissue sheet will hereafter be -termed the _femorofibular fascia_. The anteroproximal corner of the -posterior head of M. flexor perforans et perforatus digiti II often -attaches to the lateral surface of the vinculum that passes from the -femorofibular fascia to the deep surface of the patellar tendon; the -extreme proximal end usually attaches fleshily to a small area on the -femur immediately proximal to the fibular condyle and adjacent (distal) -to the attachment of the distal arm of the guide loop for M. extensor -iliofibularis. - -INSERTION.--The common belly terminates approximately two thirds of the -way down the shank; the slender ossified tendon begins along the -posteromedial edge of the common belly, continues distally along the -posterior surface of the shank, and becomes flexible before passing -through the canal in the tibial cartilage that lies posteromedial to the -canal for M. flexor digitorum longus. The tendon passes with the tendon -of M. flexor perforatus digiti II (medial to the latter) through a canal -in the hypotarsus (see M. flexor perforatus digiti II); just below the -hypotarsus, the tendon becomes superficial to the tendon of M. flexor -perforatus digiti II and farther distally becomes lateral and finally -deep to the latter; the tendon is ossified for most of the length of the -tarsometatarsus. At the distal end of this bone, the tendon expands -before passing onto the ventral surface of digit II between the tendons -of Mm. flexor perforatus digiti II and flexor digitorum longus; at the -level of the first phalanx, the edges of the tendon extend dorsally -around the tendon of M. flexor digitorum longus and fuse, forming a -sheath around the latter; the latter emerges from the sheath near the -distal end of the first phalanx; the tendon attaches to the proximal end -of the subarticular cartilage ventral to the first interphalangeal joint -(the strongest attachment is on the medial side). - -INNERVATION.--The lateral division of the tibial nerve sends twigs into -the posteromedial edge of the posterior head. - -INDIVIDUAL VARIATION.--In one leg, the fleshy part of the anterior head -is unusually long. In another leg, the anterior head is entirely -tendinous. In one leg, a bundle of fibers of the posterior head attaches -to the deep surface of the distal part of the patellar tendon. In one -leg, near the middle of the tarsometatarsus a rather long and narrow but -thick and strong vinculum arises from the tendon of M. flexor perforatus -digiti II and, farther distally, joins the tendon of M. flexor perforans -et perforatus digiti II. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, the posterior head arises in part -from the distolateral edge of the patellar tendon and in another, in -part from the superficial surface of the distolateral corner of the -patellar tendon. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Flexor Perforans et Perforatus Digiti III_=, Figs. 12, 14 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thick, bipinnate; on lateral surface -of proximal part of shank between two heads of M. flexor perforans et -perforatus digiti II; bounded anteriorly by M. peroneus longus; anterior -surface fused with tendinous anterior head of M. flexor perforans et -perforatus digiti II; anterolateral edge somewhat fused to posterior -edge of M. peroneus longus superficial to latter tendon; posterior -surface fused to posterior head of M. flexor perforans et perforatus -digiti II; distal part of belly covered by common belly of latter -muscle; posteromedial edge fused to underlying lateral head of M. flexor -perforatus digiti IV; anteromedial edge usually somewhat fused to -underlying M. flexor digitorum longus. - -ORIGIN.--The origin is fleshy and tendinous from the edge of the outer -cnemial crest and fleshy from the superficial surface of the -distolateral part of the patellar tendon; the posteroproximal corner -arises tendinously from the femorofibular fascia. - -INSERTION.--The belly narrows abruptly, terminating approximately at the -middle of the shank; the slender ossified tendon extends posterodistally -along the shank, becoming flexible before passing posterior to the -tibial cartilage deep to the tendon of M. gastrocnemius, medial to the -tendon of M. flexor perforatus digiti IV, and superficial to the medial -half of the tendon of M. flexor perforatus digiti III; a thin sheet of -connective tissue covers the tendon and attaches by its edges to the -underlying tendon of M. flexor perforatus digiti III (thus the latter -tendon forms a sheath for the tendon of M. flexor perforans et -perforatus digiti II); the tendon is ossified for most of the length of -the tarsometatarsus; at midlength of the latter, the tendon lies between -the tendons of Mm. flexor perforatus digiti IV and flexor perforatus -digiti III; near the distal end of the tarsometatarsus, the tendon -becomes lateral and then deep to the tendon of M. flexor perforatus -digiti III and is connected by a vinculum to the latter (which see). The -tendon enters the ventral surface of digiti III between the tendons of -Mm. flexor perforatus digiti III and flexor digitorum longus; after -sending a dorsal slip (lateral to the tendon of M. flexor digitorum -longus) to the subarticular cartilage ventral to the first -interphalangeal joint, the tendon divides into two branches, between -which emerges the tendon of M. flexor digitorum longus; the lateral -branch attaches to the subarticular cartilage of the second -interphalangeal joint and to the lateral surface of the distal end of -the second phalanx; the medial branch has similar attachments on the -medial side of the digit. - -INNERVATION.--A branch of the lateral division of the tibial nerve -passes deep to the posterior head of M. flexor perforans et perforatus -digiti II and enters the posteromedial edge of M. flexor perforans et -perforatus digiti III. - -INDIVIDUAL VARIATION.--In both legs of one specimen, the part arising -from the femorofibular fascia appears as a distinct but short accessory -head. There is no significant individual variation in _T. cupido_ or _P. -p. jamesi_. - - -=_M. Flexor Perforatus Digiti IV_=, Figs. 14, 16 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--On posterolateral aspect of shank -deep to M. gastrocnemius pars externa; bounded medially by medial head -of M. flexor perforatus digiti III, anterolaterally by posterior head of -M. flexor perforans et perforatus digiti II, and anteriorly by M. flexor -digitorum longus; divided into three heads--medial (largest), lateral, -and anterolateral (smallest); tendon of insertion of M. extensor -iliofibularis passing between medial and lateral heads; proximal and -anteroproximal parts of _lateral head_ an extremely thin, flat tendon; -anterodistal part of tendon fused to lateral surface of fleshy part of -underlying lateral head of M. flexor perforatus digiti II; proximal part -of tendon fused indistinguishably to tendinous part of underlying -lateral head of M. flexor perforatus digiti II; fleshy part of -_anterolateral head_ anterodistal to lateral head; proximal part of -former a long slender tendon anterior to lateral head; anterior surface -of anterolateral head (both fleshy and tendinous parts) fused to tendon -of anterolateral head of M. flexor perforatus digiti III; deep surface -fused to underlying anterolateral head (fleshy) of M. flexor perforatus -digiti II; common tendon of anterolateral heads of M. flexor perforatus -digiti IV and M. flexor perforatus digiti III passing medial to tendon -of insertion of M. extensor iliofibularis, to peroneal nerve, and to -fibular arm of guide loop for M. extensor iliofibularis; tendon of M. -ambiens inserting on anterolateral surface of this common tendon; -_medial head_ entirely fleshy; medial surface fused to medial head of M. -flexor perforatus digiti III; deep surface fused to medial edge of -underlying medial head of M. flexor perforatus digiti II; medial and -lateral heads joined, forming bipinnate belly (pinnate structure most -evident on deep surface); anterolateral head joined to distolateral part -of belly. - -ORIGIN.--The _medial head_ attaches fleshily to the proximal part of the -popliteal area proximal (adjacent) to the origin of M. flexor hallucis -longus and distolateral to the distal end of the origin of M. -femorocruralis; the attachment extends laterally onto the posterolateral -surface of the femur proximal (adjacent) to the common attachment of M. -gastrocnemius pars externa and the distal arm of the guide loop for M. -extensor iliofibularis; the medial edge of the origin is fused with part -of the tendinous origin of the medial head of M. flexor perforatus -digiti III. - -The broad flat common tendon of the _lateral head_ and the lateral head -of M. flexor perforatus digiti II fuses to the superficial surface of -the fibular arm of the guide loop for M. extensor iliofibularis and -contributes to the femorofibular fascia; consequently the ultimate -origin would be the external femoral condyle and the head of the fibula. - -The slender common tendon of the _anterolateral head_ and the -anterolateral heads of Mm. flexor perforatus digiti II and flexor -perforatus digiti III passes deep to the insertional tendon of M. -extensor iliofibularis and to the fibular arm of the guide loop for the -latter muscle (to which it partly fuses); the tendon attaches to a -narrow line on the head of the fibula adjacent to the attachment of the -fibular arm of the guide loop and to the deep part of the femorofibular -fascia. - -INSERTION.--The slender ossified tendon becomes flexible before it -passes posterior to the tibial cartilage deep to the tendon of M. -gastrocnemius, lateral to the tendon of M. flexor perforans et -perforatus digiti III, and superficial to the lateral half of the tendon -of M. flexor perforatus digiti III; a thin sheet of connective tissue -covers the tendon and attaches by its edges to the underlying tendon of -M. flexor perforatus digiti III (thus the latter tendon forms a sheath -for the tendon of M. flexor perforatus digiti IV; this sheath is -separate from a similar sheath surrounding the tendon of M. flexor -perforans et perforatus digiti III); the tendon is again ossified where -it passes along the posterolateral surface of the tarsometatarsus -posterolateral to the tendon of M. flexor perforans et perforatus digiti -III; near the distal end of the tarsometatarsus the tendon becomes -flexible and expands greatly in width and thickness, and sends a small -slip dorsally, medial to the underlying tendons, that attaches to the -subarticular cartilage ventral to the trochlea for digit IV; sometimes -this slip is continuous with the retinaculum ventral to the tendon at -the level of the proximal end of the digit. Several more or less -distinct sheets of tough connective tissue lie ventral to all of the -flexor tendons at the level of the trochleae and the proximal end of the -digits, holding them in place. The tendon narrows as it passes onto the -ventral surface of digit IV and soon divides into three branches; the -tendon of M. flexor digitorum longus emerges between the medial and -middle branches. The lateral branch attaches to the subarticular -cartilage ventral to the first interphalangeal joint and is also bound -by connective tissue to the ventrolateral surface of the first phalanx. -A dorsal slip arises at the point of divergence of the lateral and -middle branches and attaches to the subarticular cartilage of the first -interphalangeal joint. The middle branch attaches to the subarticular -cartilage of the second joint. The medial branch, after sending dorsal -slips to each of the first two subarticular cartilages, attaches to the -subarticular cartilage of the third interphalangeal joint. - -INNERVATION.--The posterior division of the tibial nerve sends a branch -into the posterior edge of the medial head, then passes between the -latter and the medial head of M. flexor perforatus digiti III; as it -extends distally it gives off twigs to the medial surface of the medial -head, to the deep surface of the lateral head, and to the deep surface -of the anterolateral head. - -INDIVIDUAL VARIATION.--In one leg, an additional branch arises from the -tibial nerve at the level of origin of the posterior division and enters -the posterior surface of the medial head; a twig from this branch -anastomoses with the first twig of the posterior division to the same -head; a branch of the medial division joins the posterior division -distal to the origin of the twigs to the medial head but proximal to the -origin of the twigs to the other heads. - -_T. cupido_ - -INDIVIDUAL VARIATION.--None of significance. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In four legs, a tiny vinculum connects with the -tendon of M. flexor digitorum longus (which see). - - -=_M. Flexor Perforatus Digiti III_=, Figs. 13, 14, 15, 16, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Divided into two widely separated -heads--medial and anterolateral--with completely separate bellies but -with common insertional tendon; small _anterolateral head_ on lateral -aspect of thigh deep to M. flexor perforans et perforatus digiti II and -posterior to M. flexor digitorum longus; fleshy part of head -distolateral to belly of M. flexor perforatus digiti IV; fleshy part -fused to lateral edge of belly of M. flexor perforatus digiti II; -proximal part of head a slender ossified tendon fused to anterior edge -of both fleshy and tendinous parts of anterolateral head of M. flexor -perforatus digiti IV and to lateral edge of anterolateral head of M. -flexor perforatus digiti II; this tendon passing deep to tendon of -insertion of M. extensor iliofibularis and to peroneal nerve; large -_medial head_ on posteromedial surface of thigh anterior to medial edge -of M. gastrocnemius pars externa, lateral to M. gastrocnemius pars -media, and medial to M. flexor perforatus digiti IV; fused to medial -surface of medial head of latter and to medial edges of Mm. flexor -perforatus digiti II and flexor hallucis longus; proximal end of head -tendinous. - -ORIGIN.--The _medial head_ attaches tendinously to the medial part of -the popliteal area in common with the medial head of M. flexor -perforatus digiti II and with the medial edges of Mm. flexor perforatus -digiti IV (medial head) and flexor hallucis longus; and is also fused to -the articular capsule. The _anterolateral head_ arises in common with -the anterolateral heads of Mm. flexor perforatus digiti II and flexor -perforatus digiti IV (see account of latter). - -INSERTION.--The short unossified tendon of the anterolateral head and -the longer ossified tendon of the medial head join (after the latter -becomes flexible) a short distance above the tibial cartilage, forming a -broad flat common tendon that passes posterior to the tibial cartilage -(in a shallow groove of the latter); the main part of the tendon is deep -to the tendons of Mm. flexor perforatus digiti IV and flexor perforans -et perforatus digiti III, but forms separate thin sheaths around these -two tendons at the level of the tibial cartilage. A thin sheet of -connective tissue covers these three tendons and attaches by its edges -to the tibial cartilage, forming a sheath for them. These three tendons -pass through the superficial groove in the hypotarsus deep to the tendon -of M. gastrocnemius; the tendon of M. flexor perforatus digiti III is -ossified for most of the length of the tarsometatarsus; a short distance -below the hypotarsus, the anterior branch of the tendon of M. peroneus -longus attaches broadly to the lateral edge of the tendon of M. flexor -perforatus digiti III. In the proximal part of the tarsometatarsus the -tendon is deep to the tendon of M. flexor perforans et perforatus digiti -III, but farther distally becomes medial and then superficial to the -latter and lateral to the tendon of M. flexor perforans et perforatus -digiti II; near the distal end of the tarsometatarsus a narrow but -strong vinculum extends from the lateral edge of the tendon somewhat -distally to the lateral edge of the tendon of M. flexor perforans et -perforatus digiti III. At the distal end of the tarsometatarsus the -tendon expands before entering the ventral surface of digit III where it -soon divides into two branches, between which emerge the tendons of Mm. -flexor perforans et perforatus digiti III and flexor digitorum longus; -the lateral branch attaches to the subarticular cartilage ventral to the -first interphalangeal joint and to the lateral surface of the distal end -of the first phalanx; the medial branch has similar attachments on the -medial side of the digit. - -INNERVATION.--The posterior division of the tibial nerve passes between -the medial heads of M. flexor perforatus digiti III and M. flexor -perforatus digiti IV and sends a twig to the lateral surface of the -former, then passes deep to the common belly of M. flexor perforatus -digiti IV and sends a twig to the posterior surface of the anterolateral -head of M. flexor perforatus digiti III. - -INDIVIDUAL VARIATION.--None of significance. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, an extra branch (immediately distal -to the branch to M. gastrocnemius pars media) of the medial division of -the tibial nerve penetrates the medial surface of the proximal end of -the medial head. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Flexor Perforatus Digiti II_=, Figs. 15, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Bipinnate; on posterior aspect of -shank deep to M. flexor perforatus digiti IV and between two heads of M. -flexor perforatus digiti III; bounded anteriorly by Mm. flexor digitorum -longus and flexor hallucis longus; proximal part divided into three -small heads--medial, lateral, and anterolateral; medial and proximal -parts of _medial head_ tendinous and extremely thin except for ossified -medial edge; proximal part of _lateral head_ tendinous and lateral to -insertional tendon of M. extensor iliofibularis; both tendinous and -fleshy parts fused to overlying tendon of M. flexor perforatus digiti -IV; narrow _anterolateral head_ fused to overlying anterolateral head of -latter muscle and (anterolateral edge) to ossified tendon of -anterolateral head of M. flexor perforatus digiti III; lateral edge of -common belly fused to latter head; medial edge of muscle fused to medial -heads of Mm. flexor perforatus digiti IV and flexor perforatus digiti -III and to M. flexor hallucis longus. - -ORIGIN.--The _medial head_ attaches by a slender ossified tendon to the -medial part of the popliteal area in common with the medial head of M. -flexor perforatus digiti III and with the medial edges of Mm. flexor -perforatus digiti IV (medial head) and flexor hallucis longus; this -head is also fused to the articular capsule. The above-mentioned -ossified part of the tendon is situated at the junction of M. flexor -perforatus digiti II and M. flexor perforatus digiti III (medial head) -and could be considered to be a part of the latter rather than the -former. The flat tendon of the _lateral head_ arises in common with the -lateral head of M. flexor perforatus digiti IV (which see). The -_anterolateral head_ arises in common with the anterolateral heads of -Mm. flexor perforatus digiti IV and flexor perforatus digiti III (see -former). - -INSERTION.--The short, slender, ossified tendon becomes flexible and -passes through the canal in the tibial cartilage that lies medial to the -canal for M. flexor hallucis longus and lateral to the canals for Mm. -flexor digitorum longus and flexor perforans et perforatus digiti II. -The tendon passes with the tendon of M. flexor perforans et perforatus -digiti II (lateral to latter) through the canal in the hypotarsus that -is deep to the groove for M. flexor perforatus digiti III and -superficial to the canal for M. flexor digitorum longus; the former -canal has a bony floor and sides but a fibrous roof; a fibrous partition -subdivides the proximal half of this canal, forming a separate channel -for each tendon. The tendon is ossified for most of the length of the -tarsometatarsus and is situated lateral (adjacent) to the posterior -metatarsal crest; immediately below the hypotarsus, the tendon becomes -situated deep to the tendon of M. flexor perforans et perforatus digiti -II and farther distally becomes situated medial and finally superficial -to the latter; at the distal end of the tarsometatarsus the tendon -expands greatly and its edges (thick) pass dorsally around the -underlying flexor tendons and become continuous with the subarticular -cartilage ventral to the trochlea for digit II. The tendon extends onto -the ventral surface of digit II and attaches by its edges to the -ventromedial and ventrolateral surfaces of the proximal part of the -first phalanx (the lateral edge extending farthest distally); the -tendons of Mm. flexor perforans et perforatus digiti II and flexor -digitorum longus emerge from the distal end of the tendon of M. flexor -perforatus digiti II. - -INNERVATION.--The posterior division of the tibial nerve passes between -the medial heads of Mm. flexor perforatus digiti III and flexor -perforatus digiti IV and gives a twig to the superficial surface of each -of the three heads of M. flexor perforatus digiti II and sometimes gives -another twig to the superficial surface of the distal part of the common -belly. - -INDIVIDUAL VARIATION.--In one leg, a vinculum connects the tendon with -that of M. flexor perforans et perforatus digiti II (which see). - -_T. cupido_ - -INDIVIDUAL VARIATION.--The canal in the hypotarsus through which the -tendon passes has a bony (instead of fibrous) roof in one leg. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The variation given above for _T. cupido_ is -found in both legs of one specimen. - - -=_M. Flexor Hallucis Longus_=, Figs. 15, 19A - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Elongate and tapering; on posterior -aspect of shank deep to M. flexor perforatus digiti II and to proximal -end of medial head of M. flexor perforatus digiti IV; bounded -anterolaterally by M. flexor digitorum longus and anteromedially by M. -plantaris; tendinous anteromedial surface of proximal end fused to -common tendon of origin of medial heads of Mm. flexor perforatus digiti -III and flexor perforatus digiti II; belly ending approximately halfway -down shank. - -ORIGIN.--The origin is fleshy and tendinous (anteromedial surface) from -the popliteal area immediately distal to the origin of the medial head -of M. flexor perforatus digiti IV, extending laterally to the area -immediately proximal to the external femoral condyle (medial to the -origin of M. gastrocnemius pars externa); the muscle also arises from -the proximal end of the posterior part of the articular capsule. - -INSERTION.--The slender ossified tendon becomes flexible and passes -through the canal in the tibial cartilage that lies lateral to the canal -for M. flexor perforatus digiti II, then passes through a slight groove -in the lateral surface of the hypotarsus and becomes ossified again; -midway of the tarsometatarsus, the tendon becomes superficial to the -tendon of M. flexor digitorum longus and is connected with the latter by -an extensive vinculum, which extends from the deep surface and lateral -edge of the tendon of M. flexor hallucis longus distally to the -superficial surface of the tendon of M. flexor digitorum longus; the -tendon continues, unossified and considerably reduced in size, distally -medial to the tendon of M. flexor digitorum longus, and passes through -the flexor groove of the first metatarsal anterolateral (adjacent) to -the tendon of M. flexor hallucis brevis, then passes deep to the -terminal expansion of the latter onto the ventral surface of the hallux; -the tendon emerges from under the end of the tendon of M. flexor -hallucis brevis and attaches to the ventral surface of the ungual -phalanx; a weak dorsal slip attaching to the ventral surface of the -distal end of the first phalanx is usually present. - -INNERVATION.--A branch of the medial division of the tibial nerve passes -along the medial edge of the muscle, giving several twigs into it. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Plantaris_=, Figs. 15, 19A - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Elongate and tapering; on -posteromedial surface of tibiotarsus; bounded medially by M. -gastrocnemius pars interna and tendon of M. flexor cruris medialis, -posteriorly by M. gastrocnemius pars media and medial head of M. flexor -perforatus digiti III, posterolaterally by M. flexor hallucis longus; -medial to M. flexor digitorum longus; anterolateral surface of proximal -end often slightly overlapping and fused to posterior surface of medial -end of M. popliteus; belly terminating above middle of shank. - -ORIGIN.--The origin is fleshy and tendinous (distal edge only) from an -elongate area on the posteromedial surface of the proximal end of the -tibiotarsus adjacent to the insertion of M. popliteus. - -INSERTION.--The long, slender, ossified tendon extends along the -posteromedial aspect of the tibiotarsus and becomes flexible just before -attaching to the proximomedial part of the tibial cartilage. The tibial -cartilage is a large, mostly cartilaginous pad fitting closely over the -posterior surface of the intratarsal joint; the distomedial corner is -ossified. This cartilage is perforated by the tendons of several flexor -muscles; the distal end of the cartilage attaches to the posteroproximal -corner of the tarsometatarsus. - -INNERVATION.--A branch of the medial division of the tibial nerve -penetrates the lateral surface. - -INDIVIDUAL VARIATION.--In one leg, a small bundle of fibers separates -from the proximal end of the muscle, forming a short accessory head -which attaches, separately from the remainder, to the articular capsule -posteroproximal to the main origin; a blood vessel passes between the -main and accessory heads. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, a small bundle of fibers arises from -the medial collateral ligament. In another leg, the nerve to M. -gastrocnemius pars interna passes through a gap in the origin of M. -plantaris rather than distal to its origin. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The nerve branch supplying M. gastrocnemius pars -interna gives a minute twig to the deep surface of the free belly of M. -plantaris in one instance. - - -=_M. Flexor Digitorum Longus_=, Figs. 14, 16, 17, 19A - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Relatively broad; bipinnate; on -posterolateral surface of tibiotarsus; bounded posteromedially by M. -flexor hallucis longus, posteriorly by M. flexor perforatus digiti II -and anterolateral head of M. flexor perforatus digiti III, laterally by -Mm. flexor perforans et perforatus digiti III and flexor perforans et -perforatus digiti II, and anterolaterally by Mm. peroneus brevis and -tibialis anticus; anterior surface of lateral part of distal half of -common belly fused to M. peroneus brevis; divided into three -heads--posterior (largest), lateral, and medial; _posterior head_ on -posterior surface of head of fibula; overlapping and fused to lateral -end of M. popliteus; proximomedial corner deep to latter; _lateral head_ -on lateral surface of fibula; lateral and posterior heads separated by -insertion of M. extensor iliofibularis; these two heads joined -immediately distal to insertion of latter; _medial head_ on posterior -surface of tibiotarsus; group of blood vessels and nerves passing -between medial and posterior heads; these two heads joined several mm. -distal to junction of lateral and posterior heads; deep surface of -insertional tendon near distal end of tarsometatarsus serving as origin -for M. lumbricalis. - -ORIGIN.--_Posterior head_: This arises fleshily from the posterior -surface of the fibula beginning almost at the proximal end and from the -medial surface of the fibula beginning deep to the distal part of M. -popliteus. _Lateral head_: This arises fleshily (sometimes partly -tendinously) from the lateral surface of the fibula proximal to the -fibular tubercle. Some fibers arise from the distal edge of the tendon -of insertion of M. extensor iliofibularis. _Medial head_: This arises -fleshily from the posterior surface of the tibiotarsus just medial to -the distal part of the posterior head, distal to M. popliteus, and -either lateral or distolateral to the origin of M. plantaris. Distal to -the junction of the three heads, the muscle arises fleshily from the -posterior surface of the tibiotarsus (except the distal part) and from -the medial and posterior surfaces of the fibula. - -INSERTION.--The slender ossified tendon becomes flexible and passes -through the canal in the tibial cartilage that lies anterolateral to the -canal for M. flexor perforans et perforatus digiti II and anteromedial -to the canal for M. flexor perforatus digiti II, then passes through the -bony canal of the hypotarsus that is deep to all the other flexor -tendons; the tendon ossifies again and lies adjacent (lateral) to the -posterior metatarsal crest; the vinculum from the tendon of M. flexor -hallucis longus fuses extensively to the superficial surface of the -present tendon a short distance below the midpoint of the -tarsometatarsus; the tendon is considerably broader below this point -than above it. At the level of the first metatarsal, the tendon divides -into three branches (unossified) that diverge, each passing through a -groove on the ventral surface of the subarticular cartilages ventral to -the trochleae, then pass onto the ventral surfaces of digits II, III, -and IV. On _digit IV_ the tendon gives off two dorsal fibro-elastic -slips before attaching to the ventral surface of the ungual phalanx; one -slip attaches to the subarticular cartilage ventral to the third -interphalangeal joint, the other to the subarticular cartilage of the -fourth joint and may also attach in part to the distal end of the fourth -phalanx. On _digit III_ the tendon gives off two dorsal slips before -attaching to the ventral surface of the ungual phalanx; one slip -attaches to the subarticular cartilage of the second interphalangeal -joint, the other to the subarticular cartilage of the third joint and -may also attach in part to the distal end of the third phalanx. On -_digit II_ the tendon gives off one dorsal slip before attaching to the -ventral surface of the ungual phalanx; the slip attaches to the -subarticular cartilage of the second interphalangeal joint and may also -attach in part to the distal end of the second phalanx. - -INNERVATION.--A branch of the medial division of the tibial nerve -penetrates the medial surface of the posterior head. - -INDIVIDUAL VARIATION.--In half the legs, the proximal end of the lateral -head is notched for the passage of the peroneal nerve; the main part of -the head lies medial to this nerve; the short fleshy slip lateral to -this nerve arises by a long, slender, and extremely weak tendon from -connective tissue surrounding the femorotibiotarsal joint. In one leg, a -bundle of fibers separates from the lateral head and attaches to the -terminal four mm. of the anterior (proximal) edge of the tendon of M. -extensor iliofibularis. Each of the following variations occurs in -several legs: a third dorsal slip on digit IV attaches to the distal end -of the fourth phalanx in some legs and to the subarticular cartilage of -the fourth joint in other legs; a third dorsal slip on digit III -attaches to the distal end of the third phalanx in some legs and to the -subarticular cartilage of the third joint in other legs; a second dorsal -slip on digit II attaches to the distal end of the second phalanx in -some legs and to the subarticular cartilage of the second joint in other -legs. - -_T. cupido_ - -INDIVIDUAL VARIATION.--The dorsal slips of insertion show variations -similar to those noted above for _T. pallidicinctus_. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--In one leg, the proximal end of the lateral head -is notched for the passage of the peroneal nerve. The dorsal slips of -insertion show variations similiar to those given above for _T. -pallidicinctus_. In four legs, a tiny vinculum extends from the lateral -edge of the branch of the tendon on digit IV to the lateral edge of the -underlying medial branch of the tendon of M. flexor perforatus digiti IV -at the level of the second phalanx. - - -=_M. Popliteus_=, Fig. 19B - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Extremely short but relatively broad -and thick; on posterior surface of proximal end of tibiotarsus; -extending distomedially from proximal part of fibula; deep to M. flexor -hallucis longus; lateral end overlapped by, and fused to, posterior head -of M. flexor digitorum longus; medial end often slightly overlapped by, -and fused to, M. plantaris; medial end (insertion) much wider than -lateral end (origin). - -ORIGIN.--The origin is fleshy and tendinous (superficial surface) from -the medial surface of the fibula near the proximal end. - -INSERTION.--The attachment is fleshy to the posterior surface of the -proximal end of the tibiotarsus adjacent (lateral) to the origin of M. -plantaris. - -INNERVATION.--A branch of the medial division of the tibial nerve -penetrates the posterior surface. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Peroneus Longus_=, Figs. 12, 13 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Large; on anterolateral surface of -shank; bounded medially by M. gastrocnemius pars interna and -posterolaterally by Mm. flexor perforans et perforatus digiti III and -flexor perforans et perforatus digiti II; proximal three fourths of -posteromedial part (covered by M. gastrocnemius pars interna) -aponeurotic and tightly fused to medial surfaces of underlying Mm. -tibialis anticus and extensor digitorum longus; proximal part of fleshy -belly somewhat fused to anterior surface of underlying M. tibialis -anticus; posterolateral surface strongly fused to aponeurotic medial -head of M. flexor perforans et perforatus digiti II and slightly fused -to anterolateral edge of M. flexor perforans et perforatus digiti III. - -ORIGIN.--The muscle arises by fleshy and tendinous fibers from the edges -of the inner and outer cnemial crests; the extreme proximal end arises -either fleshily or aponeurotically from the rotular crest between the -cnemial crests; the posteromedial edge (aponeurotic except distal one -fourth fleshy) arises from the anteromedial intermuscular line. - -INSERTION.--The narrow ossified tendon on the superficial surface of the -distal part of the fleshy belly extends several mm. beyond the belly -where it becomes flexible and divides into two branches. The short, -broad posterior branch attaches broadly to the proximolateral corner of -the tibial cartilage. The narrow anterior branch passes along the -lateral surface of the tibiotarsus, through a strong retinaculum -immediately proximal to the external condyle, and crosses the lateral -surface of the joint, where it is covered by connective tissue nearly as -tough as, and continuous with, the retinaculum; the tendon attaches -broadly to the lateral edge of the ossified tendon of M. flexor -perforatus digiti III a short distance below the hypotarsus. - -INNERVATION.--The peroneal nerve sends twigs to the deep surface. - -INDIVIDUAL VARIATION.--In both legs of two specimens, the extreme -proximal end extends proximal to the rotular crest and attaches fleshily -to the superficial surface of the distal end of the patellar tendon. - -_T. cupido_ - -INDIVIDUAL VARIATION.--None of significance. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--One leg shows the variation described above for -_T. pallidicinctus_. - - -=_M. Tibialis Anticus_=, Figs. 14, 15, 16, 19E, 20N - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Thick; on anterior aspect of thigh -deep to M. peroneus longus; bounded posteriorly by M. extensor digitorum -longus and posterolaterally by Mm. flexor digitorum longus and peroneus -brevis; divided into two heads--tibial and femoral; small femoral head -adjacent to posterolateral surface of much larger tibial head; two heads -joined near midpoint of fleshy part of muscle, forming bipinnate belly -(pinnate structure most evident on deep surface); proximal part of -femoral head situated between outer cnemial crest and head of fibula; -proximal part of anterior surface of tibial head somewhat fused to -overlying M. peroneus longus; medial surface fused to aponeurosis of -latter. - -ORIGIN.--_Tibial head_: This arises by fleshy and tendinous fibers from -the edge of the inner cnemial crest, from the rotular crest between the -inner and outer cnemial crests, and from the anterior surface, distal -edge, and posterior surface of the outer cnemial crest; the attachment -may or may not extend onto the superficial surface of the distal part of -the patellar tendon; the attachment is adjacent to the origin of the -underlying M. extensor digitorum longus. _Femoral head_: This arises by -a slender tendon from the notch in the distal end of the external -condyle of the femur. - -INSERTION.--The slender ossified tendon extends along the anterior -surface of the distal end of the tibiotarsus and passes through a large, -strong, oblique retinaculum (superficial to the supratendinal bridge); -the lateral end of the retinaculum attaches to the lateral end of the -supratendinal bridge; the medial end attaches immediately proximal to -the medial end of the bridge. The tendon widens and becomes flexible as -it passes across the anterior surface of the intratarsal joint, then -narrows and attaches to the tubercle on the anterior surface of the -proximal part of the tarsometatarsus between Mm. extensor hallucis -longus and extensor brevis digiti IV. The distalmost bundle of -tendinous fibers does not attach to the tubercle, but extends distally -along the anterior surface of the tarsometatarsus and attaches to the -latter a few mm. distal to the tubercle, forming an accessory insertion. -A part of the peroneal nerve passes between the main and accessory -insertions. - -INNERVATION.--A variable number of branches of the peroneal nerve -penetrate the lateral surface of the femoral head; a variable number of -branches of the same division pass deep to the femoral head and enter -the posterior edge of the tibial head. - -INDIVIDUAL VARIATION.--- In one leg, the accessory insertion is absent. - -_T. cupido_ - -INDIVIDUAL VARIATION.--None of significance. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The origin of the tibial -head does not extend onto the patellar tendon. - -INDIVIDUAL VARIATION.--The accessory insertion is absent in one leg. - - -=_M. Extensor Digitorum Longus_=, Figs. 15, 17 - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Bipinnate; on anterior surface of -tibiotarsus deep to M. tibialis anticus; bounded laterally by M. -peroneus brevis; lateral edge usually slightly fused to proximal half of -latter; medial surface fused to aponeurosis of M. peroneus longus. - -ORIGIN.--The muscle arises fleshily from the lateral surface of the -inner cnemial crest, from the rotular crest between the cnemial crests -(deep to the attachment of M. tibialis anticus), from the basal (medial) -half of the anterior surface of the outer cnemial crest, and from the -anterior surface of the tibiotarsus (except the distal part) between the -anteromedial and anterolateral intermuscular lines; proximal to the -anterolateral intermuscular line, the origin usually extends almost to -the lateral edge of the tibiotarsus. - -INSERTION.--The ossified tendon extends along the mid-anterior surface -of the distal part of the tibiotarsus deep to the tendon of M. tibialis -anticus and passes under the supratendinal bridge, becoming flexible and -widening slightly as it crosses the anterior surface of the intratarsal -joint; the tendon narrows again and passes through a small but strong -retinaculum on the anterior surface (medial to midline) of the proximal -part of the tarsometatarsus; the retinaculum is immediately proximal and -medial to the insertion of M. tibialis anticus. The tendon ossifies -again as it passes down the anterior surface of the tarsometatarsus and -bifurcates near the midpoint of the latter; the lateral branch soon -bifurcates again; of these three branches, which are ossified for some -distance, the lateral one passes onto the dorsal surface of digit IV, -the middle one passes onto the dorsolateral surface of digit III, and -the medial one subdivides (at the level of the trochleae) into three -branches--one passing onto the dorsal surface of digit III and two -passing onto the dorsal surface of digit II. At the level of the -metatarsophalangeal joints, all of these tendons are interconnected by -strong sheets of connective tissue and it is often difficult exactly to -delimit the tendons at this level. On the digits, tough connective -tissue binds the tendons to the phalanges; this is most pronounced at -the interphalangeal joints. The tendons are distinct on the first -phalanx of each digit, but are often poorly defined farther distally. On -_digit IV_ the tendon subdivides into branches that attach to the -proximal ends of the ungual, fourth, third, and (usually) second -phalanges. On _digit III_ the lateralmost tendon bifurcates, with one -branch attaching to the ungual phalanx and the other to the proximal end -of the third phalanx; the medial tendon attaches to the proximal end of -the second phalanx. On _digit II_ the originally medial tendon passes -underneath and then lateral to the other tendon and attaches to the -ungual phalanx; the other tendon attaches to the proximal end of the -second phalanx. - -INNERVATION.--One or more branches of the peroneal nerve enter the -lateral edge. - -INDIVIDUAL VARIATION.--In four legs, the lateral branch of the -trifurcated tendon is not ossified at all. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In a few cases, the muscle does not come in -contact with M. peroneus brevis. - -_P. p. jamesi_ - -DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The belly is shorter. The -lateral branch of the tendon on the tarsometatarsus is not ossified -(true also of some legs of _Tympanuchus_). - -INDIVIDUAL VARIATION.--In several legs, the muscle also arises from the -distal part of the posterior surface of the outer cnemial crest. - - -=_M. Peroneus Brevis_=, Figs. 14, 16, 17, 18, 19A - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Small; on lateral surface of distal -part of tibiotarsus; mainly anterior to fibula; bounded posteriorly and -laterally by M. flexor digitorum longus (fused with latter), anteriorly -by M. tibialis anticus, and anteromedially by M. extensor digitorum -longus (usually slightly fused to latter). - -ORIGIN.--The muscle arises by fleshy and tendinous fibers from the -medial and anterior surfaces of the fibula beginning a short distance -below the distal end of the fibular crest and from the anterolateral -surface of the tibiotarsus anterior to the fibula; the anteromedial edge -attaches to the anterolateral intermuscular line. - -INSERTION.--The short, slender, ossified tendon passes along the -anterolateral surface of the tibiotarsus and through a retinaculum -immediately proximal and anteromedial to the retinaculum for the -anterior branch of the tendon of M. peroneus longus; the tendon becomes -flexible and widens as it passes across the lateral surface of the -intratarsal joint deep to the tendon of M. peroneus longus, turning -posteriorly and attaching to the proximolateral corner of the -hypotarsus. - -INNERVATION.--The superficial peroneal branch of the peroneal nerve -gives one or two twigs to the anterior surface of the proximal part. - -INDIVIDUAL VARIATION.--None of significance. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In a few legs, the muscle does not come in -contact with M. extensor digitorum longus. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Extensor Hallucis Longus_=, Figs. 19E, 20N - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; proximal part -on anterior surface of tarsometatarsus medial to anterior metatarsal -groove; near midlength of tarsometatarsus, muscle twisted onto medial -surface of latter; divisible into two heads--proximal and distal; belly -of proximal head (largest) ending at level of twisting onto medial -surface of bone; short distal head beginning at this point deep to -tendon of proximal head and soon joining latter tendon. - -ORIGIN.--_Proximal head_: This arises fleshily from the anterior surface -of approximately the proximal half of the tarsometatarsus medial to the -anterior metatarsal groove; the proximal end is partly medial to and -partly deep to the retinaculum for M. extensor digitorum longus; some -fibers arise from the extreme distal edge of the main insertion of M. -tibialis anticus; the distal end of the belly is unattached. _Distal -head_: This arises fleshily from the medial surface of the -tarsometatarsus proximal to the first metatarsal and deep to the tendon -of the proximal head. - -INSERTION.--The slender tendon of the proximal head, which begins along -the medial edge of the distal part of the belly, soon fuses with the -superficial surface of the distal head (ossified here); the common -tendon (unossified) passes onto the dorsal (proximal) surface of the -first metatarsal, where it passes through a retinaculum, then passes -along the dorsal surface of the hallux (bound by strong connective -tissue to the metatarsophalangeal joint), attaching to the dorsal -surface of the ungual phalanx. - -INNERVATION.--The branch of the deep peroneal nerve that passes medial -to the main insertion of M. tibialis anticus gives one or two twigs into -the proximal part of the proximal head. No supply to the distal head was -found, but see below. - -INDIVIDUAL VARIATION.--In one leg, the proximal end of the distal head -is fused to the distal end of the belly of the proximal head, whereas in -three legs, a distinct gap separates the fleshy parts of the two heads. -The following variations, each found in one leg, pertain to the -relationship of the origin of the proximal head to the retinaculum for -M. extensor digitorum longus: the origin does not extend proximally -medial to the retinaculum; the origin does not extend proximally deep to -this retinaculum; a part of the proximal end extends proximally lateral -to this retinaculum (in this instance there is an unusually wide gap -between the retinaculum and the insertion of M. tibialis anticus). In -one leg, the distalmost fibers of the distal head do not join the common -tendon but insert independently on the articular capsule of the -metatarsophalangeal joint (deep to the common tendon). - -_T. cupido_ - -INDIVIDUAL VARIATION.--The relationship between the two heads varies as -follows: the proximal end of the distal head may be fused to the distal -end of the belly of the proximal head; the proximal end of the distal -head may begin anterior (adjacent) to the distal end of the belly of the -proximal head; there may be a distinct gap between the fleshy parts of -the two heads. In two legs, there is no origin from the insertion of M. -tibialis anticus. In one leg, a small accessory bundle of fleshy fibers -arises from the proximal end of the first metatarsal (widely separated -from the origin of the distal head), passes through the retinaculum deep -to the common tendon and attaches to the dorsal surface of the articular -capsule of the metatarsophalangeal joint; thus this bundle is completely -separate from the remainder of the muscle. In two legs, the same nerve -branch that gives twigs into the proximal head also gives off (much -farther distally) a twig that enters the distal head. - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--The proximal end of the distal head may begin -anterior (adjacent) to the distal end of the belly of the proximal head. -In four legs, the origin of the proximal head does not extend proximally -medial to the retinaculum for M. extensor digitorum longus; in one of -these legs, a part of the proximal end extends proximally lateral to -this retinaculum. The distalmost fibers of the distal head do not join -the common tendon but insert independently on the dorsal surface of the -articular capsule of the metatarsophalangeal joint in four legs; in -another leg, the entire distal head has the latter insertion -(consequently the two heads are completely separate). - - -=_M. Abductor Digiti II_= Figs. 19E, 20N - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Short; on medial surface of distal -part of tarsometatarsus; proximal end adjacent (anterior) to distal head -of M. extensor hallucis longus. - -ORIGIN.--The origin is fleshy from the medial surface of the distal part -of the tarsometatarsus anterior (adjacent) to the first metatarsal and -from the anteromedial surface of the basal half of the first metatarsal. - -INSERTION.--The flat tendon passes over the medial surface of the -trochlea for digit II and attaches to the medial surface of the proximal -end of the first phalanx of digit II; the tendon is fused with the -articular capsule. - -INNERVATION.--The compound nerve formed by the fusion of a branch of the -superficial peroneal nerve with a branch of the deep peroneal nerve -gives a twig to the anterolateral edge of the muscle. - -INDIVIDUAL VARIATION.--In some cases, the twig arises from the deep -peroneal branch alone (which is not joined by the superficial peroneal -nerve). - -_T. cupido_ - -INDIVIDUAL VARIATION.--In one leg, some of the fleshy fibers arising -from the first metatarsal insert independently on the medial surface of -the trochlea for digit II (deep to the main part of the muscle). - -_P. p. jamesi_ - -INDIVIDUAL VARIATION.--None of significance. - - -=_M. Extensor Brevis Digiti III_= (M. extensor proprius digiti III), -Figs. 19E, 20N - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Short and relatively broad (narrow -proximally); on mid-anterior surface of distal part of tarsometatarsus; -tendon of insertion fused with articular capsule. - -ORIGIN.--The origin is fleshy from the mid-anterior surface of the -distal part of the tarsometatarsus ending a short distance proximal to -the trochlea for digit III. - -INSERTION.--The flat tendon passes over the trochlea for digit III and -attaches to the dorsal surface of the proximal end of the first phalanx -of digit III. - -INNERVATION.--The compound nerve formed by the fusion of a branch of the -superficial peroneal nerve with a branch of the deep peroneal nerve -gives a twig to the proximal end of the muscle. - -INDIVIDUAL VARIATION.--In some cases, the twig arises from the deep -peroneal branch alone (which is not joined by the superficial peroneal -nerve). The individual variation is insignificant in _T. cupido_ and _P. -p. jamesi_. - - -=_M. Extensor Proprius Digiti III_= (Not found by Hudson, _et al._), -Fig. 20N - -_T. pallidicinctus_ and _T. cupido_ - -Absent in both species. - -_P. p. jamesi_ - -This atypical muscle was found in only two legs (P.p. 1L and 4L). The -following description applies to P.p. 4L (Fig. 20N). - -GENERAL DESCRIPTION AND RELATIONS.--Small but well developed; fleshy -part 1-1/2 × 13 mm.; proximal end narrower; on mid-anterior surface of -tarsometatarsus between Mm. extensor brevis digiti IV and extensor -hallucis longus and mostly proximal to M. extensor brevis digiti III; -tendinous distal part superficial to latter; fleshy belly ending -immediately distal to proximal end of latter. - -ORIGIN.--The origin is fleshy from a narrow elongate area on the -mid-anterior surface of the tarsometatarsus between Mm. extensor brevis -digiti IV and extensor hallucis longus, beginning at the distal end -(bony) of the elongate accessory insertion of M. tibialis anticus. The -distal part of the belly is free. - -INSERTION.--The attachment is by a thin, wide (relative to belly) tendon -to the superficial surface of M. extensor brevis digiti III. - -INNERVATION.--Not found. - -INDIVIDUAL VARIATION.--In P.p. 1L, the muscle is less well developed. -The fleshy belly is 1 × 5 mm. It arises from the lateral edge of M. -extensor hallucis longus. The extremely slender insertional tendon -attaches as above. - - -=_M. Extensor Brevis Digiti IV_=, Figs. 19E, 20N - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Slender and tapering; on lateral -part of anterior surface of tarsometatarsus; length of belly variable; -middle of medial edge in contact with M. extensor hallucis longus. - -ORIGIN.--The origin is fleshy from the lateral part of the anterior -surface of the tarsometatarsus, including the anterior metatarsal -groove. - -INSERTION.--The long slender tendon enters the anterior aperture of the -distal foramen, passes through the intertrochlear canal, emerges from -the terminal foramen, and attaches to the medial surface of the proximal -end of the first phalanx of digit IV. - -INNERVATION.--The superficial peroneal branch of the peroneal nerve -sends a twig into the proximal part of the muscle. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Lumbricalis_=, Fig. 19F - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Small, thin, and strap-shaped; on -mid-posterior surface of distal end of tarsometatarsus deep to tendon of -M. flexor digitorum longus; belly partly fleshy and partly elastic -connective tissue. - -ORIGIN.--The muscle arises from the deep (anterior) surface of the -tendon of M. flexor digitorum longus a short distance proximal to the -trifurcation of the latter. - -INSERTION.--The muscle attaches to the proximal end of the subarticular -cartilage ventral to the trochlea for digit III. - -INNERVATION.--A long but extremely small twig arises from the -paraperoneal branch of the tibial nerve a short distance distal to the -hypotarsus and extends distally along the mid-posterior surface of the -tarsometatarsus (parallel to a larger nonmuscular branch) and enters the -deep surface distal to the middle. It was possible to follow this twig -in only two legs; it was presumably destroyed in the course of -dissection in the others. - -INDIVIDUAL VARIATION.--In some cases, the "muscle" appears grossly to be -entirely connective tissue, although a distinct entity. - -_T. cupido_ - -INDIVIDUAL VARIATION.--In some cases, the "muscle" appears grossly to be -entirely connective tissue. The innervation was found in only one leg, -in which the twig arises more distally than in _T. pallidicinctus_. - -_P. p. jamesi_ - -The innervation was not found. - - -=_M. Abductor Digiti IV_=, Fig. 19F - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; on posterior -surface of tarsometatarsus lateral to midline; in contact with M. flexor -hallucis brevis in midline. - -ORIGIN.--The origin is fleshy from the posterior surface of the -tarsometatarsus lateral to the midline beginning near the proximal end -(lateral to the hypotarsus) and ending at the level of the first -metatarsal. - -INSERTION.--The slender tendon, which begins along the lateral edge of -the distal part of the belly, passes through a retinaculum on the -posterolateral surface of the tarsometatarsus immediately above the -outer trochlea and attaches to the lateral surface of the proximal end -of the first phalanx of digit IV. - -INNERVATION.--The paraperoneal branch of the tibial nerve gives one or -two twigs to the proximal part of the muscle. - -INDIVIDUAL VARIATION.--None of significance in any of the three species -studied. - - -=_M. Flexor Hallucis Brevis_=, Fig. 19F - -_T. pallidicinctus_ - -GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; on posterior -surface of tarsometatarsus medial to midline; belly (except proximal -end) adjacent (lateral) to posterior metatarsal crest; proximal end -passing under latter (immediately distal to hypotarsus) and lying -anteromedial to hypotarsus. - -ORIGIN.--The origin is fleshy from the medial metatarsal depression and -from the posterior surface of the tarsometatarsus between the midline -and the posterior metatarsal crest beginning immediately below the -hypotarsus and ending a short distance above the first metatarsal -(sometimes more proximally). - -INSERTION.--The slender tendon, which begins along the medial edge of -the distal part of the belly, passes through the groove on the -posterodistal surface of the first metatarsal and onto the proximal end -of the ventral surface of the hallux; the tendon widens considerably and -attaches by its edges to the ventral surface of the proximal end of the -first phalanx, forming a short "tunnel" through which the tendon of M. -flexor hallucis longus passes. - -INNERVATION.--The paraperoneal branch of the tibial nerve sends one or -two twigs into the proximal part of the muscle (but distal to the -hypotarsus). - -INDIVIDUAL VARIATION.--In two legs, the muscle arises in part from the -distal end of the lateral calcaneal ridge. The individual variation is -insignificant in _T. cupido_ and _P. p. jamesi_. - - - - -DISCUSSION AND CONCLUSIONS - - -_Analysis of Individual Variation_ - -Considerable individual variation occurs in both the muscles and the -nerves of the leg of the three species studied. The amount of variation -reported by a worker depends in large part on the degree of variation -that he considers significant. - -Individual variation in the muscles and in the nerves will be discussed -separately; that of the muscles (excluding innervation) will be -considered first. - - -Muscles - -Considering the number, rather than degree, of variations, the most -variable muscles are: Mm. flexor digitorum longus, obturator, -caudofemoralis, and extensor hallucis longus. The first-mentioned muscle -exhibits 14 different variations in the specimens studied. Mm. vastus -lateralis, flexor perforans et perforatus digiti II, and piriformis also -showed a considerable number of variations. The following muscles did -not exhibit any variations considered significant in this study: Mm. -vastus medialis, femoritibialis internus, flexor perforatus digiti III, -extensor brevis digiti III, and abductor digiti IV. - -Muscles showing a great _degree_ of individual variation included the -following: M. extensor proprius digiti III was present in two legs of -_Pedioecetes_ but absent in the other legs studied. A fleshy muscle slip -connected M. caudofemoralis pars caudifemoralis with the tendinous raphe -between Mm. flexor cruris lateralis and femorocruralis in two legs, -whereas in others this connection was tendinous or even absent -altogether. M. caudofemoralis pars caudifemoralis had a tendinous area -within the belly in only three legs. A vinculum connected the -insertional tendons of Mm. flexor perforans et perforatus digiti II and -flexor perforatus digiti II in only one leg. The fleshy belly of M. -iliotrochantericus medius was completely split into two parts in one -leg. M. flexor cruris lateralis had an accessory slip arising from the -caudal musculature in one leg. - -Certain individual variations reported in the accounts of the muscles -formed a graduated series, as far as degree is concerned, from the -typical to the extreme condition. Therefore it was difficult or -impossible in some cases to state whether or not certain specimens -exhibited such a variation. Elimination of the doubtful instances of -variation leaves a total of 50 different variations (excluding -variations between species) which can be attributed to a definite number -of specimens. The remainder of the discussion of individual variation in -the muscles concerns these 50 variations. See table 3. - -The typical condition of any structure is considered to be the condition -of that structure in the majority of the legs studied. Some conditions -considered as typical in the present study might not be so considered if -a larger number of specimens had been studied. If exactly half of the -legs of one species shows a particular condition of a structure, the -condition typical for this species is considered (for purposes of the -following discussion) to be that found in the majority of the legs of -the other species. - -In all instances except two (of 50) the typical condition of the muscles -in _T. pallidicinctus_ was also the typical condition in _T. cupido_. -The majority of the legs in _T. cupido_ had an additional dorsal slip on -the tendon of M. flexor digitorum longus in digits II and III. In all -instances except seven the typical condition in _T. pallidicinctus_ was -also the typical condition in _Pedioecetes_. In these seven instances a -variation in the former was the typical condition in the latter. These -were: an additional dorsal slip on the tendon of M. flexor digitorum -longus in each of three digits, a vinculum between the latter and M. -flexor perforatus digiti IV, a partly fleshy insertion of M. flexor -cruris medialis, an unossified lateral branch of the insertional tendon -of M. extensor digitorum longus, and an independent insertion of the -distalmost fibers of the distal head of M. extensor hallucis longus. For -all characters except the number of the dorsal slips on the tendon of M. -flexor digitorum longus in digits II and III, the typical condition in -_T. pallidicinctus_ was also the typical condition for all species -considered together. To facilitate comparison, in the following -discussion all of the above-mentioned characters are considered in all -species as variants from the typical condition. - -Certain legs showed a greater number of variations from the typical -condition than did others. The majority of legs showed from four to -seven variations in the muscles of the leg. The extremes were P.p. 1L, -which showed 11, and T.c.p. 2L, which exhibited only one variation. - -Twenty-three of the 50 variations were found in only one leg (out of -23). It would be expected that if additional specimens were studied, -more kinds of variations would be found. Nine variations were found in -only two legs, five in three legs, five in four legs, and four in five -legs. One variation was found in nine legs, one in ten legs, and two in -12 legs; the last four variations were in the number of dorsal slips of -the insertional tendon of M. flexor digitorum longus in digits II, III, -and IV and in the ossification of the insertional tendon of M. extensor -digitorum longus. - -Five of the variations were found only in specimens in which only one -leg was dissected. Considering only those eight specimens in which both -legs were dissected, five of the 45 variations were found in both legs -of each specimen exhibiting the variation; 28 variations were found in -only one leg of each specimen exhibiting the variation; 12 variations -were found in both legs of some specimens but in only one leg of other -specimens. Of the six muscle features showing the greatest degree of -individual variation (described previously), only two (both pertaining -to M. caudofemoralis) were found in both legs of the specimens -exhibiting the variation. - -For one leg (the one showing the most variations) of each specimen of -which both legs were studied, the number of variations that this leg had -in common with every other leg (of all species) was determined. Then the -number of variations in common between the two legs of one individual -was compared with the number of variations in common between one leg of -this individual and each leg of every other individual. See table 4. One -leg of six of the eight specimens showed at least as many variations in -common with a leg of another individual as with the other leg of the -same individual. The two exceptions were T.p. 2R and T.c.a. 1R. Thus for -most specimens there was as much variation in the muscles between the -right and left legs of one individual as there was between individuals. - -Of the 50 muscle variations seven were found only in _T. pallidicinctus_ -(eight legs), 16 were found only in _T. cupido_ (nine legs), and ten -were found only in _Pedioecetes_ (six legs). Two were found in both -species of _Tympanuchus_ (but not in _Pedioecetes_). Fifteen were found -in both _Tympanuchus_ and _Pedioecetes_; of these, five were found in -all three species studied, eight were shared by _T. pallidicinctus_ and -_Pedioecetes_, and two occurred in _T. cupido_ and _Pedioecetes_. - - -Nerves - -The lumbosacral plexus, femoral nerve, sciatic nerve, and tibial nerve -all showed numerous individual variations. The peroneal nerve, however, -was relatively constant. Variations in the obturator nerve were -considered to be insignificant. See table 5. - -In all instances except one (of 40) the typical condition in _T. -pallidicinctus_ was also the typical condition in _T. cupido_. In most -of the legs of the latter the nerve to M. flexor cruris lateralis did -not perforate M. caudofemoralis. In all instances except four the -typical condition in _T. pallidicinctus_ was also the typical condition -in _Pedioecetes_. These exceptions were: prefixation of the lumbosacral -plexus, six roots of the sciatic nerve, femoral nerve formed mainly from -S2 to S4 and two twigs to M. flexor ischiofemoralis. In all instances -the typical condition in _T. pallidicinctus_ was also the typical -condition for all species considered together. - -Certain legs showed a greater number of variations from the typical -condition of the nerves than did others. The greatest number of -variations was shown by P.p. 3L, which had 12. T.p. 1R and T.c.p. 1L -both showed only one. - -All six variations in the lumbosacral plexus were found on both sides of -each specimen exhibiting the variation. In marked contrast to the other -nerves, there was no significant variation in the lumbosacral plexus -between the right and left sides of one individual. (This might not -always be true, however, if a larger number of specimens were studied.) -Of the variations in the lumbosacral plexus, one was found in only one -specimen (of 15), one was found in three specimens, one in four -specimens, two in six specimens, and one in seven specimens. Of the 34 -variations found in the other nerves, 14 were found in only one leg (of -23), six occurred in two legs, four in three legs, three in four legs, -three in five legs, two in six legs, one in seven legs, and one in nine -legs. - -Four of the variations were found only in specimens in which only one -leg was dissected. Considering only those eight specimens in which both -legs were dissected, and excluding the lumbosacral plexus, ten of the 30 -variations were found in both legs of each specimen exhibiting the -variation; 16 variations were found in only one leg of each specimen -exhibiting the variation; four variations were found in both legs of -some specimens but in only one leg of other specimens. - -The number of variations in common between the two legs of one -individual was compared with the number between individuals in the same -manner as for the muscles; the lumbosacral plexus was excluded from -consideration. See table 6. One leg of six of the eight specimens showed -at least as many variations in common with a leg of another individual -as with the other leg of the same individual. The two exceptions were -T.p. 2L and T.p. 3R. Thus for most specimens there was as much variation -in the nerves other than the lumbosacral plexus between the right and -left legs of one individual as there was between individuals. - -Of the 40 nerve variations (including the lumbosacral plexus) 11 were -found only in _T. pallidicinctus_, seven were found only in _T. cupido_, -and seven were found only in _Pedioecetes_. Four were found in both -species of _Tympanuchus_ (but not in _Pedioecetes_). Eleven were found -in both _Tympanuchus_ and _Pedioecetes_; of these, four were found in -all three species, three were shared by _T. pallidicinctus_ and -_Pedioecetes_ and four occurred in _T. cupido_ and _Pedioecetes_. - -The average number of variations per leg in both muscles and nerves was -11 in _T. pallidicinctus_, nine in _T. cupido_, and 16 in _Pedioecetes_. -The high number in the last is in part the result of these being -variations from the typical condition of _T. pallidicinctus_ (rather -than from _Pedioecetes_). - - -_Analysis of Variation Between Species_ - -No constant differences in the muscles or nerves was found between _T. -cupido pinnatus_ and _T. cupido attwateri_. Only one constant difference -was found between _T. cupido_ and _T. pallidicinctus_: a thicker fleshy -origin of M. extensor iliotibialis lateralis in _T. cupido_ (associated -with a thicker edge of the lateral iliac process). - -Although no constant differences in the nerves were found between -_Pedioecetes_ and _Tympanuchus_ (both species), 17 constant differences -in the muscles were found between these two genera. Seven of these -differences pertain to features of a single muscle--M. flexor cruris -medialis. Compared with the condition in _Tympanuchus_, M. flexor cruris -medialis in _Pedioecetes_ has a wider origin, a partly fleshy (instead -of entirely tendinous) origin, a more pronounced curvature of the line -of origin, a wider insertion, an insertion posterior (rather than -anterior) to the medial collateral ligament, an insertion that attaches -in part to the articular capsule, and a shorter tendon of insertion -(resulting in the fusion of the common insertional tendon of Mm. flexor -cruris lateralis and femorocruralis with the fleshy belly rather than -with the insertional tendon). Other differences include the following. A -more extensive posteroproximal aponeurosis of M. extensor iliotibialis -lateralis in _Pedioecetes_ (resulting in a narrower fleshy origin); a -more nearly straight line of origin of this muscle (associated with a -less pronounced lateral iliac process); a thinner fleshy origin of this -muscle (associated with a thinner edge of the lateral iliac process); a -wider M. flexor cruris lateralis that is fleshy up to the origin from -the vertebrae; a wider fleshy origin of M. iliacus; the origin of M. -caudofemoralis pars iliofemoralis not reaching the ventral edge of the -ischium; a narrower origin of M. adductor superficialis; a wider M. -femorocruralis; and a shorter belly of M. extensor digitorum longus. -Some additional differences between these two genera, which are slight -in degree, are given in the accounts of the muscles. If additional -specimens were studied, some of the differences listed above possibly -would prove to be subject to individual variation and so could not -properly be listed as constant differences between the two genera. - -The picture of the differences between _Tympanuchus_ and _Pedioecetes_ -that the present study presents is radically different from that -presented by the study of Hudson, _et al._ (1959). These authors -reported the following differences between these two genera. (I am using -my terminology.) The origin of M. piriformis is narrower in -_Pedioecetes_ and is more posteriorly situated; the belly of M. extensor -iliotibialis anticus is broader in _Pedioecetes_; the belly of M. -tibialis anticus is longer; the belly of M. peroneus brevis is shorter; -the insertional tendon of the anterolateral head of M. flexor perforatus -digiti III is shorter; the belly of M. flexor digitorum longus is -shorter; only two (rather than three) of the branches of M. extensor -digitorum longus on the tarsometatarsus are ossified; the posterior -metatarsal crest is shorter; M. flexor perforans et perforatus digiti II -has two heads in _Pedioecetes_ but only one in _Tympanuchus_; the roof -over the hypotarsal canal enclosing the tendon of M. flexor digitorum -longus is bony in _Pedioecetes_ but fibrous in _Tympanuchus_; M. flexor -cruris lateralis is wider in _Pedioecetes_; and the origin of M. -femorocruralis is wider. I paid particular attention in my study to -these 13 features given by Hudson, _et al._; of these the only -differences that I found to be constant were the last two. The apparent -reason for this great discrepancy is the small number of legs of -_Tympanuchus_ studied by Hudson, _et al._ They studied eight legs of -_Pedioecetes_ but only two legs of _Tympanuchus_. This emphasizes the -danger of making comparisons based on a very small number of specimens -(a criticism which may prove to apply to the present study as well). The -reason why Hudson, _et al._ did not report most of the differences found -by me is not so apparent. Either the specimens studied by the former -workers showed a greater variation in these characters than did my -specimens or else those workers overlooked the differences. Probably -both factors are involved. It remains to be determined how many -specimens need to be studied in order to obtain a fairly accurate -picture of variation. - - -_Comparison with Other Studies of Innervation_ - -I accept the following concept of muscle-nerve relationship. All muscles -of the pelvic limb of birds have developed phylogenetically from either -the dorsal extensor muscle mass or the ventral flexor muscle mass. The -former was (at least originally) supplied by only the femoral and -peroneal nerves ("dorsal" nerves), the latter by only the obturator and -tibial nerves ("ventral" nerves). The best guide for determining which -muscles are phylogenetically dorsal and which are ventral seems to be -their embryogeny (as shown in the studies of Romer, 1927, and Wortham, -1948). In the phylogenetic changes undergone by the muscles under -consideration, the innervation may have changed in some instances, -although this is less likely to occur than changes in the attachment or -function of the muscles. If a change in innervation has occurred, it -would be more likely to be a change from one dorsal nerve to the other -or from one ventral nerve to the other rather than from a dorsal nerve -to a ventral one or _vice versa_. - -Thus, in my opinion, a report of a dorsal muscle supplied by a ventral -nerve, or _vice versa_, should be viewed with suspicion until it is -verified. I suspect that many previous workers have ignored this concept -of muscle-nerve relationship, or else do not accept it, since they -report, without comment, dorsal muscles (as determined embryologically) -innervated by ventral nerves, or _vice versa_. Owing to the intimate -association between the proximal parts of the tibial and peroneal -nerves, the true relationship may be difficult to determine. I suspect -that this relationship has been misinterpreted by a number of workers. I -found in _Tympanuchus_ and _Pedioecetes_ a branch of the tibial nerve -that is closely associated with, and distributed with, the peroneal -nerve and has been mistakenly considered a part of the peroneal nerve by -some workers. In the study here reported on, I have found no definite -exceptions to the expected innervation. The only possible exception is -an extra branch, which could not be traced to its origin, supplying M. -extensor iliofibularis in one leg. Thus my study of innervation agrees -with the embryological determination of the (phylogenetic) dorsal and -ventral muscles and lends strong support to the above-stated concept of -muscle-nerve relationship. - -I have compared my findings on the nerves with those of other workers, -who have studied the nerves with a varying degree of thoroughness. The -important differences in innervation between these studies and the -present one are discussed below. - -In neither of Gadow's works did he distinguish tibial and peroneal -components in the thigh. In his later work (1891), covering a wide -variety of birds, he found that M. piriformis sometimes has a femoral -innervation in addition to the constant sciatic one and that M. gluteus -profundus may or may not have a sciatic supply in addition to the -femoral one. A comparison of Gadow's terminology of the sciatic nerve -branches in the shank and foot (in both works) with mine shows that his -branch I represents my peroneal nerve plus my paraperoneal branch of the -tibial nerve (Ic); his branch II represents my medial division of the -tibial nerve; and his branch III represents my posterior (IIIa) and -lateral (IIIb) divisions of the tibial nerve. - -Gadow's study (1880) on the ratites included _Struthio_, _Rhea_, and -_Casuarius_. Only in _Casuarius_ did Gadow find a branch (IIe) of the -sciatic nerve supplying Mm. lumbricalis, adductor digiti II, and -abductor digiti II. The two former muscles are typically supplied (as in -_Rhea_) by the paraperoneal branch of the tibial nerve; Gadow's branch -IIe presumably represents a segregated branch of this nerve. More -surprising is his finding that M. abductor digiti II is innervated in -_Casuarius_ by both the deep peroneal nerve and branch IIe and in _Rhea_ -by branch Ic (paraperoneal branch of tibial nerve). The deep peroneal -innervation is typical. Also unexpected is his finding that the -posterior division of the femoral nerve gives minute twigs into M. -gastrocnemius pars interna in _Struthio_ and _Casuarius_. Since the -other terminal branches of this nerve in these birds are nonmuscular, -since this muscle is chiefly supplied by other nerves, and since the -innervation from the femoral nerve is apparently atypical for most -birds, the possibility should be considered that the femoral twigs are -sensory rather than motor. - -Sudilovskaya (1931), studying _Struthio_, _Rhea_, and _Dromaeus_ -(_Dromiceius_), used the same terminology as Gadow except that he -designates as branch III Gadow's branch Ic. Sudilovskaya's discussion of -the main branches of the sciatic nerve is confusing. He states that in -_Struthio_, branches I, II, and III all pass through the tendinous guide -loop for M. extensor iliofibularis; this is hard to believe. As near as -I can determine, he has mistakenly given the same designation (branch -III) to two separate branches (Gadow's Ic and III). There is no problem, -however, in determining to which of these two branches he is referring -when he is describing the innervation of a particular muscle, since one -supplies only muscles of the shank and the other only intrinsic foot -muscles. Sudilovskaya found M. abductor digiti II to be innervated by -branch III (Ic of Gadow); thus the innervation of this muscle -corresponds to that found in _Rhea_ by Gadow. Although M. adductor -digiti II had the expected innervation from branch III (paraperoneal -branch of tibial nerve) in _Dromaeus_, that muscle was found to be -supplied by branch II in _Rhea_. (Gadow, on the other hand, reports a -typical innervation for this muscle in _Rhea_.) Sudilovskaya found M. -peroneus brevis to be supplied by the deep peroneal branch (in contrast -to the superficial peroneal supply that I found in _Tympanuchus_ and -_Pedioecetes_). He found M. gastrocnemius pars interna to be supplied in -_Struthio_ by twigs of the femoral nerve in addition to its typical -innervation from branch II of the sciatic nerve; this agrees with -Gadow's findings in the same genus. Sudilovskaya reports that M. -gastrocnemius pars externa was innervated by branches II and III in -_Struthio_ and _Rhea_ and by branches I and III in _Dromaeus_. (Gadow -found only the typical innervation--branch III.) - -In the Whooping Crane, Fisher and Goodman (1955) found a peroneal, -rather than a femoral, nerve supply for pars postica of M. vastus -lateralis. They also report a peroneal nerve supply for M. flexor -ischiofemoralis (in contrast to the usual tibial nerve supply) and for -M. adductor superficialis (in addition to the usual supply from the -obturator nerve). The innervation was not given for the intrinsic foot -musculature. - -Fisher (1946), studying vultures, reports the following: tibial -branches, in addition to the main sciatic branch, supplying M. extensor -iliofibularis (typically supplied by the peroneal nerve); an obturator -supply, in addition to the usual tibial supply, to M. flexor cruris -medialis; a tibial supply, in addition to the typical obturator supply, -to M. obturator pars postica; a possible obturator supply, in addition -to the typical femoral supply, to M. ambiens; a possible peroneal -supply, in addition to the typical tibial supply, to M. flexor digitorum -longus; and a peroneal supply to Mm. abductor digiti IV, flexor hallucis -brevis, and adductor digiti II (which are typically supplied by the -paraperoneal branch of the tibial nerve). Fisher's postfibular branch of -the peroneal nerve, which supplies the latter three muscles, apparently -represents the paraperoneal branch of the tibial nerve. - -Carlsson (1884) did not find a femoral nerve supply for M. gluteus -profundus. He found an obturator supply, in addition to the usual -sciatic supply, to M. flexor ischiofemoralis in _Eudyptes chrysolopha_ -and _Mergulus alle_ but not in the other two forms studied. He reported -a peroneal supply, rather than the expected tibial (paraperoneal) -supply, to Mm. abductor digiti IV and adductor digiti IV. - -DeMan (1873) found a twig of the obturator nerve supplying M. flexor -ischiofemoralis, in addition to the typical innervation, in _Corvus -monedula_, but not in the few other forms studied. He did not -distinguish tibial and peroneal components in the thigh. - -Wilcox (1948), studying a loon, did not find any peroneal supply to M. -extensor iliotibialis lateralis or to M. gluteus profundus. He found a -femoral, rather than a peroneal, supply to M. piriformis. He found an -obturator, instead of a tibial, supply to M. flexor ischiofemoralis. (In -some of my specimens I found a tiny blood vessel, appearing much like a -nerve, emerging from the obturator foramen and entering M. flexor -ischiofemoralis.) Wilcox reports an innervation of M. caudofemoralis -pars caudifemoralis from the pudendal plexus, in addition to the usual -sciatic one. Wilcox did not distinguish tibial and peroneal components -in the thigh. In the shank and foot he misidentified the peroneal nerve -as the tibial nerve and therefore gave erroneous innervations for all -the muscles supplied by this nerve, except for M. adductor digiti IV, -which actually should be supplied by the tibial nerve. - -Howell (1938) studied only the hip and thigh musculature of the chicken. -He overlooked the femoral nerve supply for M. gluteus profundus. - -Romer (1927) studied only the hip and thigh muscles of the chick. He did -not distinguish tibial and peroneal components in the thigh. He did not -mention any sciatic supply for M. gluteus profundus. - -Appleton (1928), studied (in various birds) only those muscles of the -hip and thigh that are innervated by the tibial and peroneal nerves. He -terms the former "ischiadicus ventralis" and the latter "ischiadicus -dorsalis." His findings did not differ from mine. - -Many differences in the innervation of specific muscles are reported in -the literature, even in the same species (by different workers). Some of -these differences may be real; others are probably misinterpretations. -Consequently more work needs to be done before a complete understanding -can be obtained of the innervation of the leg muscles of birds. -Especially needed are studies of the tibial-peroneal nerve relationship, -perhaps approached by a method other than gross dissection. - - - - -SUMMARY - - -The muscles and nerves were dissected in eight legs of the Lesser -Prairie Chicken (_Tympanuchus pallidicinctus_), six legs of the Greater -Prairie Chicken (_T. cupido pinnatus_), three legs of Attwater's Prairie -Chicken (_T. c. attwateri_), and six legs of the Sharp-tailed Grouse -(_Pedioecetes phasianellus jamesi_) for the purpose of obtaining -information on individual variation as well as variation between these -closely related species. Relatively little information is available -regarding the nerves of the leg of birds and little is known about -individual variation and variation between closely related forms in the -muscles of the leg of birds. - -All osteological terms used in the present paper are defined and those -of the pelvis are illustrated. New terms were coined for some structures -for which no names could be found in the literature. Terms were also -coined for the major divisions of the femoral and sciatic nerves. With -three exceptions, my muscle terminology follows that of Fisher (1946) -and Fisher and Goodman (1955). Their term femoritibialis externus is not -used here; the muscle so named is considered to be a part of M. vastus -lateralis. Fisher's accessory head of M. flexor cruris lateralis is -considered to be a distinct muscle--M. femorocruralis. Usage of the term -obturator internus is avoided because the muscle so named is considered -not to be homologous with the mammalian muscle of the same name; the -entire obturator complex is called M. obturator, and is subdivided into -four parts. - -The typical (most common) condition of the nerves and muscles in -_Tympanuchus pallidicinctus_ is described in detail. Variations from -this condition among the other birds studied are then described. All -muscles of one leg of _T. pallidicinctus_ are illustrated. Several -variations in the muscles are also illustrated. The lumbosacral plexus -and nerves of the leg in several specimens that show variations are -illustrated. - -Considerable individual variation was found in both the muscles and the -nerves of the leg of the species studied. Certain muscles were more -variable than others. Mm. flexor digitorum longus, obturator, -caudofemoralis, and extensor hallucis longus showed the greatest number -of variations. Mm. vastus medialis, femoritibialis internus, flexor -perforatus digiti III, extensor brevis digiti III, and abductor digiti -IV did not exhibit any variations considered significant. Certain legs -showed a greater number of variations from the typical condition than -did others. - -Although most of the variations were minor, some were major. M. extensor -proprius digiti III was present in two legs of _Pedioecetes_ but absent -in the other legs studied. A fleshy muscle slip connected M. -caudofemoralis pars caudifemoralis with the tendinous raphe between Mm. -flexor cruris lateralis and femorocruralis in two legs, whereas in -others this connection was tendinous or even absent altogether. M. -flexor cruris lateralis had an accessory slip arising from the caudal -musculature in one leg. A vinculum connected the insertional tendons of -Mm. flexor perforans et perforatus digiti II and flexor perforatus -digiti II in one leg. - -In most specimens there was as much variation between the muscles of the -right and left legs of one individual as there was between individuals. -The same was true for the nerves, except for the lumbosacral plexus, in -which there was no significant variation between the right and left -sides of any individual. The peroneal and obturator nerves varied less -than the other nerves. - -No constant differences in the muscles or nerves was found between _T. -cupido pinnatus_ and _T. c. attwateri_. One constant difference was -found between _T. cupido_ and _T. pallidicinctus_: the fleshy origin of -M. extensor iliotibialis lateralis in _T. cupido_ was thicker -(associated with a thicker edge of the lateral iliac process). - -Although no constant differences in the nerves were found between -_Pedioecetes_ and _Tympanuchus_ (both species), 17 constant differences -in the muscles were found between these two genera. Study of additional -specimens possibly would show enough individual variation in some of -these differences to reduce the number of constant differences to fewer -than 17. Seven of these differences pertain to features of a single -muscle--M. flexor cruris medialis. Some of the other differences are -associated with the thinner and much less pronounced lateral iliac -process in _Pedioecetes_. The picture of the differences between -_Tympanuchus_ and _Pedioecetes_ that this study presents is radically -different from that presented by the study of Hudson, _et al._ (1959). - -The important differences in innervation between previous studies and -the present one are discussed. - -All of the muscles under consideration have been grouped as either -dorsal or ventral muscles, according to their embryonic origin, as -described by Romer (1927) and Wortham (1948). This grouping probably -represents accurately the phylogenetic origin of these muscles. The -dorsal muscles probably were originally supplied by dorsal nerves--the -femoral and peroneal--and the ventral muscles probably were originally -supplied by ventral nerves--the obturator and tibial. This primitive -muscle-nerve relationship has been relatively constant. - -Several previous workers have reported some dorsal muscles supplied by -ventral nerves and _vice versa_. Those findings should be viewed with -suspicion until verified, because the proximal parts of the tibial and -peroneal nerves are intimately associated and their relationship is -easily misinterpreted. I found a branch of the tibial nerve that is -closely associated with, and distributed with, the peroneal nerve. That -branch of the tibial nerve has been mistakenly considered a part of the -peroneal nerve by some workers. My study revealed no definite exceptions -to the expected innervation. - - -TABLE 1. SYNONYMY OF THE MUSCLES OF THE LEG OF BIRDS - - ===============+===============+============+==============+============== - | | Howell | Fisher & | - Gadow (1891) | Hudson (1937) | (1938) |Goodman (1955)| Holmes - ---------------+---------------+------------+--------------+-------------- - ilio-tibialis |ilio-tibialis |extensor |extensor |extensor - | | iliotibia- | ilio-tibia- | iliotibialis - | | lis latera-| lis | lateralis - | | lis | lateralis | - ---------------+---------------+------------+--------------+-------------- - ilio-tibialis |sartorius |extensor |extensor |extensor - internus s. | |iliotibialis| ilio-tibia- | iliotibialis - sartorius | |anterior | lis anterior| anticus - ---------------+---------------+------------+--------------+-------------- - ambiens |ambiens |ambiens |ambiens |ambiens - ---------------+---------------+------------+--------------+-------------- - femori-tibialis| | |femoritibialis|vastus - externus | | | externus | lateralis - | | | |(a) pars - | | | | postica - ---------------+ | +--------------+ - {|femori-tibialis|vastus |vastus |(b) pars - femori- {| externus | lateralis | lateralis | lateralis - tibialis {+---------------+------------+--------------+-------------- - medius {|femori-tibialis|} {|vastus |vastus - {| medius |} {| medialis | medialis - ---------------+---------------+}vastus {+--------------+-------------- - femori-tibialis|femori-tibialis|} medialis{|femoritibialis|femoritibialis - internus | internus |} {| internus | internus - ---------------+---------------+------------+--------------+-------------- - ilio-fibularis |biceps femoris |extensor |extensor |extensor - | | iliofibu- | ilio- | ilio- - | | laris | fibularis | fibularis - ---------------+---------------+------------+--------------+-------------- - ilio-femoralis |glutaeus medius|piriformis |piriformis |piriformis - externus | et minimus | | | - ---------------+---------------+------------+--------------+-------------- - ilio-trochante-|ilio-trochante-|gluteus |gluteus |gluteus - ricus | ricus | profundus | profundus | profundus - posterior | posterior | | | - ---------------+---------------+------------+--------------+-------------- - ilio-trochante-|ilio-trochante-|iliacus |iliacus |iliacus - ricus | ricus | | | - anterior | anterior | | | - ---------------+---------------+------------+--------------+-------------- - ilio-trochante-|ilio-trochante-| |ilio-trochan- |iliotrochante- - ricus medius | ricus medius | | tericus | ricus medius - | | | medius | - ---------------+---------------+------------+--------------+-------------- - ilio-trochante-|iliacus |psoas |psoas |psoas - ricus | | | | - internus | | | | - ---------------+---------------+------------+--------------+-------------- - caud-ilio- |semitendinosus |flexor |flexor cruris |flexor cruris - flexorius | | cruris | lateralis | lateralis - | | lateralis |(a) main head | - ---------------+---------------+------------+ +-------------- - accessorius |accessorius |femorocru- |(b) accessory |femorocruralis - semitendinosi| semitendinosi| ralis | heads | - ---------------+---------------+------------+--------------+-------------- - ischio- |semimembranosus|flexor |flexor cruris |flexor cruris - flexorius | | cruris | medialis | medialis - | | medialis | | - ---------------+---------------+------------+--------------+-------------- - caud-ilio- |piriformis | |caudofemoralis|caudofemoralis - femoralis | | | | - (a) pars |(a) pars |caudofemo- |(a) pars |(a) pars - caudi- | caudi- |ralis | caudi- | caudifemo- - femoralis | femoralis | | femoralis | ralis - | +------------+ | - (b) pars ilio- |(b) pars ilio- |flexor ilio-|(b) pars ilio-|(b) pars - femoralis | femoralis | femoralis | femoralis | iliofemo- - | | | | ralis - ---------------+---------------+------------+--------------+-------------- - ischio- |ischio- |flexor |flexor ischio-|flexor - femoralis | femoralis | ischiofe- | femoralis | ischiofemo- - | | moralis | | ralis - ---------------+---------------+------------+--------------+-------------- - {|adductor longus|adductor |adductor |adductor - {| et brevis | superfi- | superfici- | superficialis - {|(a) pars | cialis | alis | - pub-ischio- {| anterior | | | - femoralis {| +------------+--------------+-------------- - {|(b) pars |adductor |adductor |adductor - {| posterior | profundus | profundus | profundus - ---------------+---------------+------------+--------------+-------------- - obturator |obturator |} {|obturator |} - | internus |} {| internus |} - ---------------+---------------+} obturator{+--------------+} obturator - accessorii M. |obturator |} {|obturator |} - obturatoris | externus |} {| externus |} - ---------------+---------------+------------+--------------+-------------- - gastrocnemius |gastrocnemius | |gastrocnemius |gastrocnemius - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor perfo- |flexor perfo- - perforans et | perforans et | | rans et per-| rans et per- - perforatus | perforatus | | foratus | foratus - digiti II | digiti II | | digiti II | digiti II - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor perfo- |flexor perfo- - perforans et | perforans et | | rans et per-| rans et per- - perforatus | perforatus | | foratus | foratus - digiti III | digiti III | | digiti III | digiti III - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor |flexor perfo- - perforatus | perforatus | | perforatus | ratus digiti - digiti IV | digiti IV | | digiti IV | IV - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor |flexor perfo- - perforatus | perforatus | | perforatus | ratus - digiti III | digiti III | | digiti III | digiti III - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor |flexor perfo- - perforatus | perforatus | | perforatus | ratus digiti - digiti II | digiti II | | digiti II | II - ---------------+---------------+------------+--------------+-------------- - flexor hallucis|flexor hallucis| |flexor hallu- |flexor hallu- - longus | longus | | cis longus | cis longus - ---------------+---------------+------------+--------------+-------------- - plantaris |plantaris | |plantaris |plantaris - ---------------+---------------+------------+--------------+-------------- - flexor |flexor | |flexor digi- |flexor digito- - profundus | digitorum | | torum longus| rum longus - s. perforans | longus | | | - ---------------+---------------+------------+--------------+-------------- - popliteus |popliteus | |popliteus |popliteus - ---------------+---------------+------------+--------------+-------------- - peroneus |peronaeus | |peroneus |peroneus - superficialis| longus | | longus | longus - ---------------+---------------+------------+--------------+-------------- - tibialis |tibialis | |tibialis |tibialis - anticus | anterior | | anterior | anticus - ---------------+---------------+------------+--------------+-------------- - extensor |extensor | |extensor |extensor - digitorum | digitorum | | digitorum | digitorum - communis | longus | | longus | longus - ---------------+---------------+------------+--------------+-------------- - peroneus |peronaeus | |peroneus |peroneus - profundus | brevis | | brevis | brevis - ---------------+---------------+------------+--------------+-------------- - extensor |extensor | |extensor |extensor - hallucis | hallucis | | hallucis | hallucis - brevis | longus | | longus | longus - ---------------+---------------+------------+--------------+-------------- - abductor |abductor | |abductor |abductor - digiti II | digiti II | | digiti II | digiti II - ---------------+---------------+------------+--------------+-------------- - extensor brevis|} {| |extensor |extensor bre- - digiti III |} extensor {| | brevis | vis digiti - |} {| | digiti III | III - ---------------+} proprius {+------------+--------------+-------------- - extensor |} digiti {| |extensor |extensor - proprius |} III {| | proprius | proprius - digiti III |} {| | digiti III | digiti III - ---------------+---------------+------------+--------------+-------------- - extensor brevis|extensor brevis| |extensor |extensor bre- - digiti IV | digiti IV | | brevis | vis digiti - | | | digiti IV | IV - ---------------+---------------+------------+--------------+-------------- - flexor brevis |lumbricalis | | |lumbricalis - digiti III | | | | - ---------------+---------------+------------+--------------+-------------- - abductor |abductor | |abductor |abductor - digiti IV | digiti IV | | digiti IV | digiti IV - ---------------+---------------+------------+--------------+-------------- - flexor hallucis|flexor hallucis| |flexor |flexor hallu- - brevis | brevis | | hallucis | cis brevis - | | | brevis | - ---------------+---------------+------------+--------------+-------------- - adductor |adductor | |adductor | - digiti II | digiti II | | digiti II | - ---------------+---------------+------------+--------------+-------------- - adductor |adductor | | | - digiti IV | digiti IV | | | - ---------------+---------------+------------+--------------+-------------- - - -TABLE 2. RELATIVE SIZES (IN PERCENTAGES) OF SOME MUSCLES IN TYMPANUCHUS -AND PEDIOECETES - - ===========================+=======================+====================== - | _Tympanuchus_ | _Pedioecetes_ - Muscle +-----+---------+-------+------+--------+------ - | Ave.| Range | No.[1]| Ave. | Range |No.[1] - ---------------------------+-----+---------+-------+------+--------+------ - Iliacus: width of fleshy | | | | | | - origin (divided by length| | | | | | - of ilium) | .10 | .08-.11 | 13 | .19 | .17-.19| 6 - ---------------------------+-----+---------+-------+------+--------+------ - Flexor cruris lateralis: | | | | | | - maximum width of exposed | | | | | | - part (divided by length | | | | | | - of ilium) | .22 | .19-.27 | 13 | .31 | .27-.36| 6 - ---------------------------+-----+---------+-------+------+--------+------ - Flexor cruris medialis: | | | | | | - width of origin (divided | | | | | | - by length of ilium) | .11 | .08-.16 | 13 | .22 | .19-.23| 6 - ---------------------------+-----+---------+-------+------+--------+------ - Flexor cruris medialis: | | | | | | - width of insertion | | | | | | - (divided by length of | | | | | | - tibiotarsus) | .09 | .08-.13 | 13 | .17 | .15-.17| 4 - ---------------------------+-----+---------+-------+------+--------+------ - Adductor superficialis: | | | | | | - width of origin (divided | | | | | | - by length of ilium) | .20 | .17-.23 | 13 | .13 | .10-.16| 5 - ---------------------------+-----+---------+-------+------+--------+------ - Femorocruralis: distance of| | | | | | - proximal end of origin | | | | | | - from proximal end of | | | | | | - femur (divided by length | | | | | | - of femur) | .59 | .55-.63 | 13 | .40 | .38-.43| 6 - ---------------------------+-----+---------+-------+------+--------+------ - Extensor digitorum longus: | | | | | | - length of fleshy belly | | | | | | - (divided by length of | | | | | | - tibiotarsus) | .73 | .64-.83 | 13 | .59 | .50-.62| 4 - ---------------------------+-----+---------+-------+------+--------+------ - -FOOTNOTES: - -[Footnote 1: No. = number of legs.] - - -TABLE 3. OCCURRENCE OF INDIVIDUAL VARIATIONS IN MUSCLES - - ===========================+===============+===========+======+=========== - | T.p. | T.c.p. |T.c.a.| P.p. - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+- - |1|1|2|2|3|3|4|5|1|1|2|2|3|4|1|1|2 |1|1|2|3|3|4 - |L|R|L|R|L|R|L|R|L|R|L|R|L|L|L|R|L |L|R|L|L|R|L - ---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+- - Ambiens | | | | | | | | | | | | | | | | | | | | | | | - origin partly fleshy | | | | | | | | | | | | | | | |x| | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Vastus lateralis | | | | | | | | | | | | | | | | | | | | | | | - no vincula | | | | | | | | | | | |x| |x| | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Extensor iliofibularis | | | | | | | | | | | | | | | | | | | | | | | - insertional tendon double | | | | | | | | | |x| | | | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Piriformis | | | | | | | | | | | | | | | | | | | | | | | - posteroproximal corner | | | | | | | | | | | | | | | | | | | | | | | - tendinous | |x| | | | | | | | |x| | | |x|x| |x| | | | | - insertion fused to flexor | | | | | | | | | | | | | | | | | | | | | | | - ischiofemoralis | | | | | | | | | | | |x| | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Iliotrochantericus medius | | | | | | | | | | | | | | | | | | | | | | | - not notched | | | | |x|x| | | | | | | | |x| | | | | | | | - anterior part with fleshy | | | | | | | | | | | | | | | | | | | | | | | - origin | | | | | | | | | | | | | |x| | | |x| |x| | |x - insertion fused to gluteus| | | | | | | | | | | | | | | | | | | | | | | - profundus | | | | | | | | | | | | | | | |x| | | | | | | - muscle split | | | | | | | | | | | | | | | | | |x| | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor cruris lateralis | | | | | | | | | | | | | | | | | | | | | | | - accessory slip present | | | | | | | | | | | |x| | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor cruris medialis | | | | | | | | | | | | | | | | | | | | | | | - origin from pubis | | | | | | | | | | | | |x| | |x| | | | | | | - insertion partly fleshy | | | | | | | | | | | | | | | | | | |x|x| |x|x - insertional tendon split | | | | | | | | | | | | | | | | | | |x| | | | - | | | | | | | | | | | | | | | | | | | | | | | - Caudofemoralis | | | | | | | | | | | | | | | | | | | | | | | - accessory slip fleshy | |x|x| | | | | | | | | | | | | | | | | | | | - tendinous area in belly of| | | | | | | | | | | | | | | | | | | | | | | - pars caudifemoralis | | | | | | | | |x|x| | | |x| | | | | | | | | - origin from pubis | | | | | | | | | |x| | | | | | | | | | | | | - insertion entirely | | | | | | | | | | | | | | | | | | | | | | | - tendinous | | | | | | | | | | | | | | | | | | | | | |x| - | | | | | | | | | | | | | | | | | | | | | | | - Flexor ischiofemoralis | | | | | | | | | | | | | | | | | | | | | | | - insertion partly fleshy |x| | | | | |x| | | | | | | | | | | | |x| | | - | | | | | | | | | | | | | | | | | | | | | | | - Adductor superficialis | | | | | | | | | | | | | | | | | | | | | | | - groove for flexor cruris | | | | | | | | | | | | | | | | | | | | | | | - medialis present | | |x|x| |x| |x| | | | | | | | | | | | | | | - completely fused with | | | | | | | | | | | | | | | | | | | | | | | - adductor profundus | | | | | | | | | | | | | | | |x| | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Adductor profundus | | | | | | | | | | | | | | | | | | | | | | | - proximal part of insertion| | | | | | | | | | | | | | | | | | | | | | | - tendinous | | | | | | | | | | | | | | | |x| | | | | | | - distal end of insertion | | | | | | | | | | | | | | | | | | | | | | | - tendinous | | | | | | | | | | | |x| | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Obturator | | | | | | | | | | | | | | | | | | | | | | | - independent slip of pars | | | | | | | | | | | | | | | | | | | | | | | - antica present | | | |x| | | | | |x| | | | | | | | | | | | | - slip of pars antica fused | | | | | | | | | | | | | | | | | | | | | | | - to pars postica | | | | | | |x| | | | | | | | | | | | | |x| | - independent slip of pars | | | | | | | | | | | | | | | | | | | | | | | - dorsalis present | | | | | | | |x| | | | | | |x|x| | |x| | | | - pars dorsalis fused with | | | | | | | | | | | | | | | | | | | | | | | - pars antica | | | | | | | | | | | | | | | | | |x| | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Gastrocnemius | | | | | | | | | | | | | | | | | | | | | | | - pars interna overlaps | | | | | | | | | | | | | | | | | | | | | | | - peroneus longus | | | | | | | | | | | | | | |x| | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor perforans et | | | | | | | | | | | | | | | | | | | | | | | - perforatus digiti II | | | | | | | | | | | | | | | | | | | | | | | - anterior head entirely | | | | | | | | | | | | | | | | | | | | | | | - tendinous | | | | | | | |x| | | | | | | | | | | | | | | - vinculum joins flexor | | | | | | | | | | | | | | | | | | | | | | | - perforatus digiti II |x| | | | | | | | | | | | | | | | | | | | | | - origin from superficial | | | | | | | | | | | | | | | | | | | | | | | - surface of patellar | | | | | | | | | | | | | | | | | | | | | | | - tendon | | | | | | | | | | | | |x| | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor perforans et | | | | | | | | | | | | | | | | | | | | | | | - perforatus digiti III | | | | | | | | | | | | | | | | | | | | | | | - accessory head present | | | | |x|x| | | | | | | | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor perforatus digiti II| | | | | | | | | | | | | | | | | | | | | | | - roof of hypotarsal canal | | | | | | | | | | | | | | | | | | | | | | | - bony | | | | | | | | |x| | | | | | | | | | | |x|x| - | | | | | | | | | | | | | | | | | | | | | | | - Plantaris | | | | | | | | | | | | | | | | | | | | | | | - accessory head present | | | | |x| | | | | | | | | | | | | | | | | | - origin from medial | | | | | | | | | | | | | | | | | | | | | | | - collateral ligament | | | | | | | | | | | | | | | | |x | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Flexor digitorum longus | | | | | | | | | | | | | | | | | | | | | | | - notched for peroneal nerve| | |x|x| | |x|x| | | | | | | | | | | | | |x| - origin from tendon of | | | | | | | | | | | | | | | | | | | | | | | - extensor iliofibularis | | | | | |x| | | | | | | | | | | | | | | | | - third dorsal slip present | | | | | | | | | | | | | | | | | | | | | | | - in digit IV | | |x|x| | | | | | | | | | |x|x|x | |x|x|x|x| - third dorsal slip present | | | | | | | | | | | | | | | | | | | | | | | - in digit III | | |x|x|x| | | | | | | |x|x|x|x|x |x|x| | |x|x - second dorsal slip present| | | | | | | | | | | | | | | | | | | | | | | - in digit II | | |x|x|x| | | | | | |x| |x|x|x|x |x|x| | |x|x - vinculum joins flexor | | | | | | | | | | | | | | | | | | | | | | | - perforatus digiti IV | | | | | | | | | | | | | | | | | | | |x|x|x|x - | | | | | | | | | | | | | | | | | | | | | | | - Peroneus longus | | | | | | | | | | | | | | | | | | | | | | | - origin from patellar | | | | | | | | | | | | | | | | | | | | | | | - tendon |x|x| | |x|x| | | | | | | | | | | | | | | | |x - | | | | | | | | | | | | | | | | | | | | | | | - Tibialis anticus | | | | | | | | | | | | | | | | | | | | | | | - accessory insertion absent| | | | | | |x| | | | | | | | | | | | | | |x| - | | | | | | | | | | | | | | | | | | | | | | | - Extensor digitorum longus | | | | | | | | | | | | | | | | | | | | | | | - lateral branch of tendon | | | | | | | | | | | | | | | | | | | | | | | - not ossified |x| | | |x|x| |x| | | | | | | | | |x|x|x|x|x|x - origin from posterior | | | | | | | | | | | | | | | | | | | | | | | - surface of outer cnemial| | | | | | | | | | | | | | | | | | | | | | | - crest | | | | | | | | | | | | | | | | | |x| x | | |x - | | | | | | | | | | | | | | | | | | | | | | | - Extensor hallucis longus | | | | | | | | | | | | | | | | | | | | | | | - origin lateral to | | | | | | | | | | | | | | | | | | | | | | | - retinaculum | |x| | | | | | | | | | | | | | | |x| | | | | - distal fibers of distal | | | | | | | | | | | | | | | | | | | | | | | - head insert | | | | | | | | | | | | | | | | | | | | | | | - independently | | | | |x| | | | | | | | | | | | |x|x| |x| |x - accessory bundle present | | | | | | | | | | | | | | |x| | | | | | | | - entire distal head inserts| | | | | | | | | | | | | | | | | | | | | | | - independently | | | | | | | | | | | | | | | | | | | |x| | | - | | | | | | | | | | | | | | | | | | | | | | | - Abductor digiti II | | | | | | | | | | | | | | | | | | | | | | | - accessory insertion | | | | | | | | | | | | | | | | | | | | | | | - present | | | | | | | | | | | | |x| | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Extensor proprius digiti | | | | | | | | | | | | | | | | | | | | | | | - III present | | | | | | | | | | | | | | | | | |x| | | | |x - ---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+- - - -TABLE 4. NUMBER OF MUSCULAR VARIATIONS IN COMMON BETWEEN THE LEGS -STUDIED - - =========+========+===============++===========++======++===========+===== - | Other | T.p. || T.c.p. ||T.c.a.|| P.p. | - | leg +---------------++-----------++------++-----------+ No - Leg |of same |1|1|2|2|3|3|4|5||1|1|2|2|3|4||1|1|2 ||1|1|2|3|3|4|other - |specimen|L|R|L|R|L|R|L|R||L|R|L|R|L|L||L|R|L ||L|R|L|L|R|L| legs - ---------+--------+-+-+-+-+-+-+-+-++-+-+-+-+-+-++-+-+--++-+-+-+-+-+-+----- - T.p. 1L | 1 |-|-| | |2|2|1|1|| | | | | | || | | ||1|1|2|1|1|2| 1 - T.p. 2R | 6 | | |-|-|2|1|1|2|| |1| |1|1|2||3|3|3 ||2|3|1|1|4|2| 0 - T.p. 3L | 4 |2|1|2|2|-|-| |1|| | | |1|1|2||3|2|2 ||4|4|1|2|3|5| 1 - T.c.p. 1R| 1 | | | |1| | | | ||-|-| | | |1|| | | || | | | | | | 2 - T.c.p. 2R| 0 | |1|1|1|1| | | || | |-|-| |2||1| |1 ||1|1| | |1|1| 3 - T.c.a. 1R| 5 | |2|3|3|2| | |1|| | |1|1|2|2||-|1|3 ||3|4|1|1|3|2| 3 - P.p. 1L | 4 | | |2|2|3| |2| || | |1|1|1|3||3|-|2 ||-|-|3|2|3|7| 2 - P.p. 3R | 4 | | |4|4|2| | |1||1| | |1|1|2||3|3|3 ||3|5|4|-|-|5| 1 - ---------+--------+-+-+-+-+-+-+-+-++-+-+-+-+-+-++-+-+--++-+-+-+-+-+-+----- - - -TABLE 5. OCCURRENCE OF INDIVIDUAL VARIATIONS IN NERVES - - ===========================+===============+===========+======+=========== - | T.p. | T.c.p. |T.c.a.| P.p. - +---------------+-----------+------+----------- - |1|1|2|2|3|3|4|5|1|1|2|2|3|4|1|1|2 |1|1|2|3|3|4 - |L|R|L|R|L|R|L|R|L|R|L|R|L|L|L|R|L |L|R|L|L|R|L - ---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+- - Lumbosacral plexus | | | | | | | | | | | | | | | | | | | | | | | - two fureal nerves | | |x|x| | | | | | | | | | |x|x| | | | |x|x|x - S9 with three branches | | | | | | | |x| | | | | | | | | | | | | | | - prefixed | | | | | | | | | | | | |x| |x|x|x | | |x|x|x|x - sciatic nerve with six | | | | | | | | | | | | | | | | | | | | | | | - roots | | |x|x| | | | | | | | |x| |x|x|x | | |x|x|x|x - obturator nerve from S2 | | | | | | | | | | | | | | | | | | | | | | | - and S3 only | | | | | | | | | | | | | | | | |x | | | |x|x|x - femoral nerve mainly from | | | | | | | | | | | | | | | | | | | | | | | - S2-S4 | | | | | | | | | | | | |x| |x|x|x | | |x|x|x|x - | | | | | | | | | | | | | | | | | | | | | | | - Femoral nerve | | | | | | | | | | | | | | | | | | | | | | | - anterior division | | | | | | | | | | | | | | | | | | | | | | | - innervates | | | | | | | | | | | | | | | | | | | | | | | - extensor iliotibialis | | | | | | | | | | | | | | | | | | | | | | | - lateralis | | | | | | |x|x| |x|x| |x| | | | | | | | | | - dorsal division fused with| | | | | | | | | | | | | | | | | | | | | | | - anterior division |x| | | | | | | | | | | | | | | | | |x| |x| |x - dorsal division fused with| | | | | | | | | | | | | | | | | | | | | | | - middle division | | |x|x| |x| | | | | | | | |x| | | | |x|x| | - two branches to iliacus | | |x| | | | | | | | | | | | | | | | | |x| | - middle division anasto- | | | | | | | | | | | | | | | | | | | | | | | - moses with anterior | | | | | | | | | | | | | | | | | | | | | | | - division | | |x|x| | | | | | | | | |x|x|x| | | | | | | - anterodorsal division does| | | | | | | | | | | | | | | | | | | | | | | - not go through femoral | | | | | | | | | | | | | | | | | | | | | | | - notch | | | | |x|x| | | | | | | | | | | | | | | | | - branch of anterior divi- | | | | | | | | | | | | | | | | | | | | | | | - sion perforates iliacus | | | | | | | | | | | | | | | |x| | | | | | | - cutaneous branch perfo- | | | | | | | | | | | | | | | | | | | | | | | - rates extensor ilioti- | | | | | | | | | | | | | | | | | | | | | | | - bialis lateralis | | | | | | | | | | |x|x| | | | | | | | | | | - branch of middle division | | | | | | | | | | | | | | | | | | | | | | | - perforates vastus | | | | | | | | | | | | | | | | | | | | | | | - medialis | | | | | | | | | | | | | |x| | | | | | | | | - branch to vasti innervates| | | | | | | | | | | | | | | | | | | | | | | - extensor iliotibialis | | | | | | | | | | | | | | | | | | | | | | | - lateralis | | | | | | | | | | |x| | | | | | | | | | | | - anterior branch of ante- | | | | | | | | | | | | | | | | | | | | | | | - rior division cutaneous | | | | | | | | | | | | | | | | | |x|x| | | |x - | | | | | | | | | | | | | | | | | | | | | | | - Sciatic nerve | | | | | | | | | | | | | | | | | | | | | | | - twig to pars caudifemora- | | | | | | | | | | | | | | | | | | | | | | | - lis independent | | |x| | | | | | | | | | | | | | | | | | | | - branch to flexor cruris | | | | | | | | | | | | | | | | | | | | | | | - lateralis does not | | | | | | | | | | | | | | | | | | | | | | | - perforate caudofemoralis|x|x| |x| | | | |x|x|x|x|x| | | |x | | | | | | - paraperoneal nerve enters | | | | | | | | | | | | | | | | | | | | | | | - peroneal sheath |x| |x|x| | |x| | | | | | | | | | |x|x| | | | - cutaneous peroneal branch | | | | | | | | | | | | | | | | | | | | | | | - perforates gastrocnemius| | | | | | | | | | | | | | | | | | | | | | | - pars externa | | | | | | |x| | | | | | | | | | | | | | | | - cutaneous peroneal branch | | | | | | | | | | | | | | | | | | | | | | | - absent | | |x|x| | | |x| | | | | | | | | | | | | | | - distal cutaneous tibial | | | | | | | | | | | | | | | | | | | | | | | - branch absent | | | | | | | |x| | | | | | | | | | | | | | | - twig to tail present | | |x| | |x| |x| | | | | | | |x|x | |x| | |x| - nonmuscular peroneal twig | | | | | | | | | | | | | | | | | | | | | | | - deep to vastus lateralis| | | | | | | | | | | | | | | | | | | | | | | - pars postica | | |x|x| | | |x| | | | | | | | |x | | | | | | - branch to flexor cruris | | | | | | | | | | | | | | | | | | | | | | | - medialis from posterior | | | | | | | | | | | | | | | | | | | | | | | - tibial division | | | | | | | | | | | | |x| | | | |x|x| | | | - extra twigs join cutaneous| | | | | | | | | | | | | | | | | | | | | | | - tibial branches | | | | | | | | | | | | |x| | | | | | | | | | - branch to flexor cruris | | | | | | | | | | | | | | | | | | | | | | | - medialis an independent | | | | | | | | | | | | | | | | | | | | | | | - division | | | | | | | | | | | | | | | | | | | |x|x|x| - branch to flexor cruris | | | | | | | | | | | | | | | | | | | | | | | - medialis perforates | | | | | | | | | | | | | | | | | | | | | | | - flexor | | | | | | | | | | | | | | | | | | | | | | | - ischiofemoralis | | | | | | | | | | | | | | | | | | |x| | | | - two twigs to flexor | | | | | | | | | | | | | | | | | | | | | | | - ischiofemoralis | | | | | | | | | | | | | | | | | | |x|x|x|x|x - independent extra branch | | | | | | | | | | | | | | | | | | | | | | | - innervates extensor | | | | | | | | | | | | | | | | | | | | | | | - iliofibularis | | | | | | | | | | | | | | | | | | | | |x| | - branch to femorocruralis | | | | | | | | | | | | | | | | | | | | | | | - innervates gastrocnemius| | | | | | | | | | | | | | | | | | | | | | | - pars media | | | | | | | | | | | | | | | | | | | | | |x| - | | | | | | | | | | | | | | | | | | | | | | | - Peroneal nerve | | | | | | | | | | | | | | | | | | | | | | | - superficial and deep | | | | | | | | | | | | | | | | | | | | | | | - peroneal nerves do not | | | | | | | | | | | | | | | | | | | | | | | - join |x| | | |x| |x|x| | | | | | | | | | | | | | | - | | | | | | | | | | | | | | | | | | | | | | | - Tibial nerve | | | | | | | | | | | | | | | | | | | | | | | - independent extra branch | | | | | | | | | | | | | | | | | | | | | | | - innervates flexor | | | | | | | | | | | | | | | | | | | | | | | - perforatus digiti IV | | | | |x|x| | | | | | | | | | | | | | | | | - anastomosis involving | | | | | | | | | | | | | | | | | | | | | | | - posterior division | | | | |x|x| | | | | | | | | | | | | | | | | - branch to gastrocnemius | | | | | | | | | | | | | | | | | | | | | | | - pars externa an | | | | | | | | | | | | | | | | | | | | | | | - independent division | | | | | |x| | | | | | | | | | | | | | | | | - branch to gastrocnemius | | | | | | | | | | | | | | | | | | | | | | | - pars media innervates | | | | | | | | | | | | | | | | | | | | | | | - femorocruralis |x| | | | |x| | | | | | | | | | | | | | | | | - extra branch innervates | | | | | | | | | | | | | | | | | | | | | | | - flexor perforatus | | | | | | | | | | | | | | | | | | | | | | | - digiti III | | | | | | | | | | | | | | | |x| | | | | | | - branch to gastrocnemius | | | | | | | | | | | | | | | | | | | | | | | - pars interna perforates | | | | | | | | | | | | | | | | | | | | | | | - plantaris | | | | | | | | | | | | | | |x| | | | | | | | - branch to gastrocnemius | | | | | | | | | | | | | | | | | | | | | | | - pars interna innervates | | | | | | | | | | | | | | | | | | | | | | | - plantaris | | | | | | | | | | | | | | | | | | | | |x| | - ---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+- - - -TABLE 6. NUMBER OF NERVE VARIATIONS IN COMMON BETWEEN THE LEGS STUDIED - - =========+========+===============++===========++======++===========+===== - | Other | T.p. || T.c.p. ||T.c.a.|| P.p. | - | leg +---------------++-----------++------++-----------+ No - Leg |of same |1|1|2|2|3|3|4|5||1|1|2|2|3|4||1|1|2 ||1|1|2|3|3|4|other - |specimen|L|R|L|R|L|R|L|R||L|R|L|R|L|L||L|R|L ||L|R|L|L|R|L| legs - ---------+--------+-+-+-+-+-+-+-+-++-+-+-+-+-+-++-+-+--++-+-+-+-+-+-+----- - T.p. 1L | 1 |-|-|1|2|1|1|2|1||1|1|1|1|1| || | |1 ||1|2| |1| |1| 0 - T.p. 2L | 5 |1| |-|-| |2|1|3|| | | | | |1||2|2|2 ||1|2|1|2|1| | 1 - T.p. 3R | 3 |1| |2|1|-|-| |1|| | | | | | ||1|1|1 || |1|1|1|1| | 1 - T.c.p. 1R| 1 |1|1| |1| | |1|1||-|-|2|1|2| || | |1 || | | | | | | 0 - T.c.p. 2L| 2 |1|1| |1| | |1|1||1|2|-|-|2| || | |1 || | | | | | | 1 - T.c.a. 1R| 1 | | |2|1| |1| |1|| | | | | |1||-|-|1 || |1| | |1| | 2 - P.p. 1R | 3 |2| |2|1| |1|1|1|| | | | |1| || |1|1 ||-|-|1|2|2|3| 1 - P.p. 3L | 2 |1| |2|1| |1| | || | | | | | ||1| | || |2|3|-|-|2| 2 - ---------+--------+-+-+-+-+-+-+-+-++-+-+-+-+-+-++-+-+--++-+-+-+-+-+-+----- - - - - -LITERATURE CITED - - - APPLETON, A. B. - - 1928. The muscles and nerves of the post-axial region of the - tetrapod thigh. Parts I and II. Jour. Anat., 62(3,4):364-438. - - BERGER, A. J. - - 1952. The comparative functional morphology of the pelvic appendage - in three genera of Cuculidae. Amer. Midl. Nat., 47(3):513-605. - - BERGER, A. J. - - 1956. The appendicular myology of the Sandhill Crane, with - comparative remarks on the Whooping Crane. Wilson Bull., - 68(4):282-304. - - BOAS, J. E. V. - - 1933. Kreuzbein, Becken und Plexus Lumbosacralis der Vögel. Det - Kongelige Danske Videnskabernes Selskabs Skrifter. - Naturvidenskabelig og Mathematisk Afdeling. 9. række, 5(l):1-74, 15 - pls. - - CARLSSON, A. - - 1884. Beiträge zur Kenntniss der Anatomie der Schwimmvögel. Bihang - till K. Svenska Vetenskapsakad. Handlingar, 9(3):1-44, 5 pls. - - CHOMIAK, M. - - 1950. [Studies on the plexus lumbalis et sacralis in the domestic - hen.] Ann. Univ. Mariae Curie-Sklodowska, Lublin, Sect. DD-Vet. - Med., 5(3):29-45. - - FISHER, H. I. - - 1946. Adaptations and comparative anatomy of the locomotor - apparatus of new world vultures. Amer. Midi. Nat., 35(3):545-727, - 13 pls. - - FISHER, H. I., and GOODMAN, D. C. - - 1955. The myology of the Whooping Crane, _Grus americana_. Ill. - Biol. Mono., 24(2):viii + 1-127. - - GADOW, H. - - 1880. Zur vergleichenden Anatomie der Muskulatur des Beckens und - der hinteren Gliedmasse der Ratiten. Fischer, Jena, 56 pp., 5 pls. - - GADOW, H. (with E. Selenka). - - 1891. Vögel. I. Anatomischer Theil. _In_ Bronn's Klassen und - Ordnungen des Their-Reichs, 6(4):1-1008. Winter, Leipzig. - - HOLMES, E. B. - - 1962. The terminology of the short extensor muscles of the third - toe in birds. Auk, 79(3):485-488. - - HOWARD, H. - - 1929. The avifauna of Emeryville shellmound. Univ. Calif. Publ. - Zool., 32(2):301-394, 4 pls. - - HOWELL, A. B. - - 1938. Muscles of the avian hip and thigh. Auk, 55(1):71-81. - - HUDSON, G. E. - - 1937. Studies on the muscles of the pelvic appendage in birds. - Amer. Midl. Nat., 18(1):1-108, incl. 26 pls. - - HUDSON, G. E., _et al._ - - 1959. Muscles of the pelvic limb in galliform birds. Amer. Midl. - Nat., 61(1):1-67. - - JHERING (IHERING), H. V. - - 1878. Das peripherische Nervensystem der Wirbelthiere. Vogel, - Leipzig, xiv-238 pp., 5 pls. - - MAN, J. G. DE - - 1873. Vergelijkende myologische en neurologische Studien over - Amphibien en Vögels. van Doesburgh, Leiden, 148 pp., 4 pls. - - ROMER, A. S. - - 1927. The development of the thigh musculature of the chick. Jour. - Morph., 43(2):347-385. - - SUDILOVSKAYA, A. M. - - 1931. [Study on the comparative anatomy of the musculature and - innervation of the pelvic region and the hind appendages of the - Ratitae (_Struthio_, _Rhea_, _Dromaeus_).] Acad. Sci. U.S.S.R., - Leningrad, 84 pp. (In Russian.) - - TOIT, P. J. DU - - 1913. Untersuchungen über das Synsacrum und den Schwanz von _Gallus - domesticus_ nebst Beobachtungen über Schwanzlosigkeit bei - Kaulhühnern. Jenaische Zeitschr. Naturw., 49:149-312, 3 pls. - - WILCOX, H. H., JR. - - 1948. The pelvic musculature of the loon (_Gavia immer_). Univ. - Microfilms, Ann Arbor, 95 pp., 26 pls. - - WORTHAM, R. A. - - 1948. The development of the muscles and tendons in the lower leg - and foot of chick embryos. Jour. Morph., 83(1):105-148. - - YASUDA, M., _et al._ - - 1959. [Comparative and topographical anatomy of the fowl. XI. On - the nervous supply of the hind limb.] _In_ Proc. of 47th Meeting of - Jap. Soc. of Vet. Sci. Jap. Jour. Vet. Sci., 21(6):36. (Japanese - abstract.) - - _Transmitted October 30, 1962._ - - 29-5835 - - (Continued from inside of front cover) - - 18. Conspecificity of two pocket mice, Perognathus goldmani - and P. artus. By E. Raymond Hall and Marilyn Bailey - Ogilvie. Pp. 513-518, 1 map. January 14, 1960. - - 19. Records of harvest mice, Reithrodontomys, from Central - America, with description of a new subspecies from - Nicaragua. By Sydney Anderson and J. Knox Jones, Jr. - Pp. 519-529. January 14, 1960. - - 20. Small carnivores from San Josecito Cave (Pleistocene), - Nuevo León, México. By E. Raymond Hall. Pp. 531-538, - 1 figure in text. January 14, 1960. - - 21. Pleistocene pocket gophers from San Josecito Cave, Nuevo - León, México. By Robert J. Russell. Pp. 539-548, 1 figure - in text. January 14, 1960. - - 22. Review of the insectivores of Korea. By J. Knox Jones, - Jr., and David H. Johnson. Pp. 549-578, February 23, - 1960. - - 23. Speciation and evolution of the pygmy mice, genus Baimoys. - By Robert L. Packard. Pp. 579-670, 4 plates, 12 figures in - text. June 16, 1960. - - Index. Pp. 671-690 - - Vol. 10. 1. Studies of birds killed in nocturnal migration. By - Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44, 6 - figures in text, 2 tables. September 12, 1956. - - 2. Comparative breeding behavior of Ammospiza caudacuta and - A. maritima. By Glen E. Woolfenden. Pp. 45-75, 6 plates, - 1 figure. December 20, 1956. - - 3. The forest habitat of the University of Kansas Natural - History Reservation. By Henry S. Fitch and Ronald R. - McGregor. Pp. 77-127, 2 plates, 7 figures in text, 4 - tables. December 31, 1956. - - 4. Aspects of reproduction and development in the prairie - vole (Microtus ochrogaster). By Henry S. Fitch. Pp. - 129-161, 8 figures in text, 4 tables. December 19, 1957. - - 5. Birds found on the Arctic slope of northern Alaska. By - James W. Bee. Pp. 163-211, plates 9-10, 1 figure in text. - March 12, 1958. - - *6. The wood rats of Colorado: distribution and ecology. By - Robert B. Finley, Jr. Pp. 213-552, 34 plates, 8 figures - in text, 35 tables. November 7, 1958. - - 7. Home ranges and movements of the eastern cottontail in - Kansas. By Donald W. Janes. Pp. 553-572, 4 plates, 3 - figures in text. May 4, 1959. - - 8. Natural history of the salamander, Aneides hardyi. By - Richard F. Johnston and Gerhard A. Schad. Pp. 573-585. - October 8, 1959. - - 9. A new subspecies of lizard, Cnemidophorus sacki, from - Michoacán, México. By William E. Duellman. Pp. 587-598, - 2 figures in text. May 2, 1960. - - 10. A taxonomic study of the middle American snake, Pituophis - deppei. By William E. Duellman. Pp. 599-610, 1 plate, 1 - figure in text. May 2, 1960. - - Index. Pp. 611-626. - - Vol. 11. Nos. 1-10 and index. Pp. 1-703, 1958-1960. - - Vol. 12. 1. Functional morphology of three bats: Sumops, Myotis, - Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates, 24 - figures in text. July 8, 1959. - - *2. The ancestry of modern Amphibia: a review of the - evidence. By Theodore H. Eaton, Jr. Pp. 155-180, 10 - figures in text. July 10, 1959. - - 3. The baculum in microtine rodents. By Sydney Anderson. - Pp. 181-216, 49 figures in text. February 19, 1960. - - *4. A new order of fishlike Amphibia from the Pennsylvanian - of Kansas. By Theodore H. Eaton, Jr., and Peggy Lou - Stewart. Pp. 217-240, 12 figures in text. May 2, 1960. - - 5. Natural history of the bell vireo. By Jon C. Barlow. Pp. - 241-296, 6 figures in text. March 7, 1962. - - 6. Two new pelycosaurs from the lower Permian of Oklahoma. - By Richard C. Fox. Pp. 297-307, 6 figures in text. May - 21, 1962. - - 7. Vertebrates from the barrier island of Tamaulipas, - México. By Robert K. Selander, Richard F. Johnston, B. - J. Wilks, and Gerald G. Raun. Pp. 309-345, pls. 5-8. - June 18, 1962. - - 8. Teeth of Edestid sharks. By Theodore H. Eaton, Jr. Pp. - 347-362, 10 figures in text. October 1, 1962. - - 9. Variation in the muscles and nerves of the leg in two - genera of grouse (Tympanuchus and Pedioecetes). By E. - Bruce Holmes. Pp. 363-474, 20 figs. October 25, 1963. - - More numbers will appear in volume 12. - - Vol. 13. 1. Five natural hybrid combinations in minnows (Cyprinidae). - By Frank B. Cross and W. L. Minckley. Pp. 1-18. June 1, - 1960. - - 2. A distributional study of the amphibians of the Isthmus - of Tehuantepec, México. By William E. Duellman. Pp. - 19-72, pls. 1-8, 3 figures in text. August 16, 1960. - - 3. A new subspecies of the slider turtle (Pseudemys scripta) - from Coahulia, México. By John M. Legler. Pp. 73-84, pls. - 9-12, 3 figures in text. August 16, 1960. - - 4. Autecology of the copperhead. By Henry S. Fitch. Pp. - 85-288, pls. 13-20, 26 figures in text. November 30, 1960. - - 5. Occurrence of the garter snake, Thamnophis sirtalis, in - the Great Plains and Rocky Mountains. By Henry S. Fitch - and T. Paul Maslin. Pp. 289-308, 4 figures in text. - February 10, 1961. - - 6. Fishes of the Wakarusa river in Kansas. By James E. - Deacon and Artie L. Metcalf. Pp. 309-322, 1 figure in - text. February 10, 1961. - - 7. Geographic variation in the North American cyprinid fish, - Hybopsis gracilis. By Leonard J. Olund and Frank B. - Cross. Pp. 323-348, pls. 21-24, 2 figures in text. - February 10, 1961. - - (Continued on outside of back cover) - - (Continued from inside of back cover) - - 8. Decriptions of two species of frogs, genus Ptychohyla; - studies of American hylid frogs, V. By William E. - Duellman. Pp. 349-357, pl. 25, 2 figures in text. April - 27, 1961. - - 9. Fish populations, following a drought, in the Neosho and - Marais des Cygnes rivers of Kansas. By James Everett - Deacon. Pp. 359-427, pls. 26-30, 8 figs. August 11, 1961. - - 10. Recent soft-shelled turtles of North America (family - Trionychidae). By obert G. Webb. Pp. 429-611, pls. 31-54, - 24 figures in text. February 16, 1962. - - Index. Pp. 613-624. - - Vol. 14. 1. Neotropical bats, from western Mexico. By Sydney - Anderson. Pp. 1-8. October 24, 1960. - - 2. Geographic variation in the harvest mouse, - Reithrodontomys megalotis, on the central Great Plains - and in adjacent regions. By J. Knox Jones, Jr., and B. - Mursaloglu. Pp. 9-27, 1 figure in text. July 24, 1961. - - 3. Mammals of Mesa Verde National Park, Colorado. By - Sydney Anderson. Pp. 29-67, pls. 1 and 2, 3 figures in - text. July 24, 1961. - - 4. A new subspecies of the black myotis (bat) from eastern - Mexico. By E. Raymond Hall and Ticul Alvarez. Pp. 69-72, - 1 figure in text. December 29, 1961. - - 5. North American yellow bats, "Dasypterus," and a list of - the named kinds of the genus Lasiurus Gray. By E. Raymond - Hall and J. Knox Jones, Jr. Pp. 73-98, 4 figures in text. - December 29, 1961. - - 6. Natural history of the brush mouse (Peromyscus boylii) in - Kansas with - description of a new subspecies. By Charles A. Long. Pp. - 99-111, 1 figure in text. December 29, 1961. - - 7. Taxonomic status of some mice of the Peromyscus boylii - group in eastern Mexico, with description of a new - subspecies. By Ticul Alvarez. Pp. 113-120, 1 figure in - text. December 29, 1961. - - 8. A new subspecies of ground squirrel (Spermophilus - spilosoma) from Tamaulipas, Mexico. By Ticul Alvarez. Pp. - 121-124. March 7, 1962. - - 9. Taxonomic status of the free-tailed bat, Tadarida - yucatanica Miller. By J. Knox Jones, Jr., and Ticul - Alvarez. Pp. 125-133,1 figure in text. March 7, 1962. - - 10. A new doglike carnivore, genus Cynaretus, from the - Clarendonian Pliocene, of Texas. By E. Raymond Hall and - Walter W. Dalquest. Pp. 135-138, 2 figures in text. - April 30, 1962. - - 11. A new subspecies of wood rat (Neotoma) from northeastern - Mexico. By Ticul Alvarez. Pp. 139-143. April 30, 1962. - - 12. Noteworthy mammals from Sinaloa, Mexico. By J. Knox - Jones, Jr., Ticul Alvarez, and M. Raymond Lee. Pp. - 145-159, 1 figure in text. May 18, 1962. - - 13. A new bat (Myotis) from Mexico. By E. Raymond Hall. Pp. - 161-164, 1 figure in text. May 21, 1962. - - 14. The mammals of Veracruz. By E. Raymond Hall and Walter W. - Dalquest. Pp. 165-362, 2 figures. May 20, 1963. - - 15. The recent mammals of Tamaulipas, Mexico. By Ticul - Alvarez. Pp. 363-473, 5 figures in text. May 20, 1963. - - More numbers will appear in volume 14. - - Vol. 15. 1. The amphibians and reptiles of Michoacán, Mexico. By - William E. Duellman. Pp. 1-148, pls. 1-6, 11 figures in - text. December 20, 1961. - - 2. Some reptiles and amphibians from Korea. By Robert G. - Webb, J. Knox Jones, Jr., and George W. Byers. Pp. - 149-173. January 31, 1962. - - 3. A new species of frog (Genus Tomodactylus) from western - Mexico. By Robert G. Webb. Pp. 175-181, 1 figure in text. - March 7, 1962. - - 4. Type specimens of amphibians and reptiles in the Museum - of Natural History, the University of Kansas. By William - E. Duellman and Barbara Berg. Pp. 183-204. October 26, - 1962. - - 5. Amphibians and Reptiles of the Rainforests of Southern El - Petén, Guatemala. By William E. Duellman. Pp. 205-249, - pls. 7-10, 6 figures in text. October 4, 1963. - - 6. A revision of snakes of the genus Conophis (Family - Colubridae, from Middle America). By John Wellman. Pp. - 251-295, 9 figures in text. October 4, 1963. - - 7. A review of the Middle American tree frogs of the genus - Ptychohyla. By William E. Duellman. Pp. 297-349, pls. - 11-18, 7 figures in text. October 18, 1963. - - More numbers will appear in volume 15. - - - - - Transcriber's note: - List of Illustrations was added during transcription. - - - - - -End of the Project Gutenberg EBook of Variation in the Muscles and Nerves of -the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes), by E. 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