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
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.
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