Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes)

by E. Bruce Holmes

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).