Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes)Holmes, E. Bruce
Science
Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes)
Holmes, E. Bruce
Leg -- Innervation; Leg -- Muscles; Sharp-tailed grouse; Tympanuchus
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.
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