OCR Text |
Show 1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. 409 This muscle is similarly arranged in the Hare and Rabbit, but has the fascia which goes to the tendo Achillis relatively weaker than in the Crested Agouti and the Guinea-pig. Sartorius (fig. 4, Sa.). This muscle is very broad and fleshy. It is entirely different in its origin to that of M a n , and seems to have for its office the rotation of the limb inwards. Its position (at the origin) somewhat resembles that of the pectineus muscle in the hum a n subject. It arises from the ilio-pectineal eminence and the symphysis pubis, as far as its middle, a portion of the gracilis lying superficial to the posterior part of the origin of the sartorius. It is inserted by a tendinous fascia between the superior point of the elongated patella and the head of the tibia. This tendinous fascia is in close relation at its insertion with the semimembranosus. A very long superficial femoral artery (fig. 4, Art.) crosses this muscle about its middle. In the Guinea-pig this muscle has nearly the same position, relation, and attachments as in D. cristata. It differs considerably in the Rabbit and Hare. In the former of these two, besides having an origin from the ilio-pectineal eminence and slightly from the symphysis, it has another from the outer side of the anterior superior crest of the ilium, these different origins being connected by a strong fascia. In the Hare the main origin is from the anterior superior spine of the ilium, and but slightly from the ilio-pectineal eminence. The gracilis is very powerful, from its extensive insertion, although it is but a moderately thick muscle. It arises (fleshy) from fully the posterior half of the symphysis, and is inserted by a fascia from the head of the tibia as far down as the ankle, the sheet of fascia joining that of the semitendinosus. The two together spread out between the internal malleolus and the tuberosity of the os calcis (fig. 4, Gr.). This has a similar origin and insertion in the Rabbit, Hare, and Guinea-pig; but the fascia which proceeds down the leg is relatively weaker in the two first-mentioned. The pectineus arises from the ilio-pectineal eminence and the adjoining brim of the pelvis, covered by the sartorius ; its insertion is into the shaft of the femur, immediately beneath the insertion of the iliacus. In the Hare and Rabbit it can hardly be said to be covered by the sartorius, and it is scarcely so in the Guinea-pig. The vastus externus is very large, and with an origin from the upper half of the shaft of the femur as high as the rudimentary third trochanter; the insertion, which is by muscle, is on the outside of the patella, into the tendon common to the extensors of the thigh. The vastus internus is small, and has a similar origin and insertion to the preceding, but on the inner side of the shaft of the femur. It arises as high as the tibial trochanter (fig. 4, V. i.). The vasti are similar in the Guinea-pig and Hare. The rectus femoris is equal to the vasti muscles in thickness and bulk. It has the common origin by a double tendon, but a little muscular fibre extends beneath the lowest one ; insertion as usual. In the Guinea-pig there is no marked difference. PROC. ZOOL. Soc-1866, No. XXVII. |