lS6(j.] ON THE ANATOMY OF THE CRESTED AGOUTI. 411 



Gluteus medius. G. min. Gluteus minimus. //. Iliacus. Sc. Scansorius. 

 S.f. Keetus femoris. T.v.f.$ G. max. Conjoined tensor vaginas femoris 

 and gluteus maxiinus ; the tendinous part continuous with the lumbar fascia 

 is removed to exhibit the deeper muscles. B. Biceps. Q.f. Quadratus 

 femoris. S.f. Semitendinosus ; and lower down the same letters apply to its 

 fascia continued towards the ankle. T. q. e. Tendon of combined quadriceps 

 extensor going to patella. T. a. Tibialis anticus. P. /. Peroneus longus. 

 P. q. d. Peroneus quarti digiti. E. I. d. Extensor longus digitorum. E.p. h. 

 Extensor proprius hallucis. In. Interossei. So. Soleus. Ga. Gastrocnemius. 

 P. Plantaris. F. 1. d. Flexor longus digitorum. F. I. h. Flexor longus 

 hallucis. A. Anal opening. A. g. Anal gland. 



In the Hare and Rabbit the rectus is much less in size than the 

 vastus externus, but about equal to the vastus interims. 



The crureus covers the front of the femur as high as the surgical 

 neck. This muscle is very large and most unusually distinct in all 

 the four Rodents. 



What we take to be the adductor magnus, by reason of its inser- 

 tion, is a long and narrow muscle, in appearance not unlike an ad- 

 ductor longus as it exists in Man and some Quadrumana (fig. 4, 

 A. mag.*). It has origin by a narrow strongish tendon from the 

 ischium towards the posterior extremity of the pubic symphysis, and 

 has an insertion by tendon into the top of the lowest third of the 

 shaft of the femur at its back. 



The deep femoral artery passes over this muscle ; so that no Hun- 

 ter's canal exists, except what is formed by the fibres of the semi- 

 membranosus. 



The Guinea-pig agrees most nearly with the Agouti. In the 

 Rabbit and Hare the adductor magnus is broader and more fleshy, 

 it has also a larger insertion into the shaft of the femur. 



Adductor longus and brevis (fig. 4, A. I. fy br.). These, at their 

 origin from the symphysis pubis and brim of pelvis, form but one 

 mass, and so proceed to the femur. At their insertion into the back 

 of the bone, extending from its head to about the middle of the 

 shaft, there is a very slight interval, indicative of separation ; this 

 partial division is denoted by glistening tendinous fibres of the upper 

 and larger portion of the muscle. 



In the Hare and Rabbit these muscles are equally fused together ; 

 but, on the other hand, they are more separated in the Guinea-pig. 



Tibialis anticus. Instead of its having, as is so often the case, a 

 single origin and double insertion, this remarkable muscle has a 

 double origin and a single insertion. The greater part arises by 

 muscular fibres from the outer side of the upper fifth of the tibia 

 and the head of the fibula. The smaller division arises by a very 

 long and strong tendon from the front of the femur, on the outer con- 

 dyle, just outside the rotular surface. 



The two portions become intimately united a little below the middle 

 of the tibia, and are inserted by a quite single but exceedingly strong 

 tendon into the proximal end of the metacarpal bone of the index of 

 the foot, i. e. the inner toe (figs. 4 & 5, T. a.). 



It has the same peculiarities in the Guinea-pig*; but in the Hare 

 * In one specimen of the Guinea-pig this muscle had but a single head. 



