488 THE RABBIT ^ CHAr. 



row is made up of three bones, the true first, together with 

 the corresponding digit (hallux), being absent as a distinct 

 bone. The second (apparent first) distal tarsal articulates 

 proximally with the centrale, and distally with the 

 innermost (preaxial) metatarsal : the third (apparent 

 second) with the astragalus and the corresponding meta- 

 tarsal : the fourth (apparent third), which corresponds to 

 the two outer (postaxial) tarsals fused together, with the 

 centrale and calcaneum and the remaining two digits. 



The foot or pes consists of four metatarsals with their 

 phalanges, of which there are three to each digit. The 

 rrietatarsal of the hallux, together with the corresponding 

 distal tarsal, is probably represented by a distinct ossification 

 which in the adult becomes fused with the second (apparent 

 first) metatarsal, and forms a process on that bone which 

 articulates with the centrale. The phalanges are similar to 

 those of the manus, and sesamoid hones are also present on 

 the under surface of the foot. 



Muscles and Body- wall. — It will be remembered that in 

 Amphioxus and the dogfish the muscles of the trunk arc 

 divided up into myomeres (pp. 404 and 418), while in the 

 adult frog the only indication of such a segmentation of the 

 muscles is seen in the recti of the abdomen (Fig. 16, ret. aid). 

 In the rabbit nearly all trace of a segmentation of the 

 muscles has also disappeared, and the muscular system, 

 although similar in its general arrangement to that of 

 the frog (compare Fig. 16), is more complicated and 

 highly differentiated. We shall have occasion to notice 

 certain of the muscles in the course of our examination 

 of other organs. 



Immediately beneath the skin, which consists of epiderm 

 and derm (p. 128), the whole ventral region of the trunk 



