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diff --git a/41812-0.txt b/41812-0.txt new file mode 100644 index 0000000..e5ec95d --- /dev/null +++ b/41812-0.txt @@ -0,0 +1,5837 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 41812 *** + + 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. Bruce Holmes + +*** END OF THE PROJECT GUTENBERG EBOOK 41812 *** |