VIII.] 



THE MUSCLES. 



345 



and the crureus into even three, making with the rectus 

 femoris a sevenfold extensor muscle. 



The tendon of a muscle which seems to answer to the 

 rectus femoris may end by uniting with the plantaris, as in 

 the Alligator and in Birds, in which the plantaris is the 

 perforated flexor of the toes, as it is also in the Rabbit. 



FIG. 310. DEEPER MUSCLES OF INNER ASPECT OF RIGHT PELVIC LIMB OF 

 PARSON'S CHAMELEON. 



A, adductor; B, biceps; E l and E 2 , extensores metatarsorum ; EL, extensor 

 longus digitorum ; f 1 and F 2 , rectus femoris ; FD *, flexor longus digitorum ; 

 G, gracilis ; GE, gastrocnemius externus ; 67", gastrocnemius internus ; /, 

 iliacus ; IP,, ilio-peroneal ; .5", tibial adductor; ST, semi-tendinosus ; TA, 

 tibialis anticus; V 1 , vastus intemus. 



The vastus internus may be almost absent, as in the Three- 

 toed Sloth, and the rectus may be but imperfectly differen- 

 tiated from the deeper part of the extensor, as is the case in 

 Bats. The rectus may, on the contrary, be very large and 

 consist of two muscles with distinct origins, as in the Alligator, 

 Iguana, Menopoma, and Menobranchus. The vasti and cru- 

 reus may be absent, as in the two last-named genera. 



The gracilis in man is an exceptionally narrow and weak 



