Part 16 (1/2)

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.

Wilc.o.x (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.) Wilc.o.x reports an innervation of M. caudofemoralis pars caudifemoralis from the pudendal plexus, in addition to the usual sciatic one. Wilc.o.x 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 relations.h.i.+p, 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 Att.w.a.ter's Prairie Chicken (_T. c. att.w.a.teri_), 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 ill.u.s.trated. 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 h.o.m.ologous with the mammalian muscle of the same name; the entire obturator complex is called M. obturator, and is subdivided into four parts.