The gracilis alone merits description.
Gracilis ([Fig. 87], 9; [Fig. 88], 6).—Designated in veterinary anatomy under the name of the short adductor of the leg, this muscle, expanded in width, occupies the greater part of the internal surface of the thigh, or flat of the thigh, as this region is also called. Let us imagine, in man, the internal surface of the thigh broader, and the internal rectus more expanded, and we shall have an idea of the same muscle as it exists in quadrupeds.
The gracilis arises from the ischio-pubic symphysis and from the neighbouring regions; thence it is directed towards the leg to be inserted into the superior part of the internal surface of the tibia, after being united to the tendons of the sartorius and semi-tendinosus. We find, accordingly, at this level, an arrangement which recalls the general appearance of what in man receives the name of the goose’s foot (pes anserinus).
It is between this muscle and the sartorius, at the superior part of the internal surface of the thigh, in the region which recalls the triangle of Scarpa, that we are able, especially in the cat and the dog, to see the adductor muscles of the thigh. We also partly see there, in these animals, the vastus internus and the rectus of the triceps (see [Fig. 87]). The gracilis is an adductor of the thigh.
Muscles of the Leg
We will divide the leg into three regions: anterior, external, and posterior. With regard to the internal region, there are no muscles which belong exclusively to it; for it is in great measure formed by the internal surface of the tibia, which, as in man, is subcutaneous.
Muscles of the Anterior Region
We first note that in the human species the tibialis anticus, extensor proprius pollicis, extensor longus digitorum and the peroneous tertius or anticus, form the subcutaneous layer of this region. We now proceed to study these muscles in quadrupeds.
