t* 



290 SKELETON OF THE BABBIT 



4. The hand of the rabbit has five digits, as in man ; 

 the bones of each consist of a proximal metacarpal, 

 followed by the phalanges, the last of which is 

 conical, slightly curved, and supports the claw. 



The pollex, or preaxial digit, corresponding to 

 the thumb in man, is much shorter than the others, 

 and has only two phalanges, while each of the other 

 digits has three. 



Sesamoid bones are developed in the tendons of 

 the flexor muscles, opposite the metacarpo-phalangeal 

 and certain other articulations. 



C. The Pelvic Girdle, 



The pelvic girdle, which supports the hind-limb, consists of 

 two halves, which, though primitively nearly at right angles 

 to the vertebral column, are in the adult rabbit almost parallel 

 to it. They are firmly united to the sacrum in front, and with 

 each other in the ventral symphysis behind. 



Each half, or os innominatum, consists of three bones 

 ilium, ischium, and pubes and presents about the middle of 

 its outer surface a deep cup -shaped acetabular cavity for the 

 femur, in the formation of which all the three bones take part. 



i. The ilium is the anterior and dorsal member 

 of the girdle, corresponding to the scapula in 

 the pectoral girdle. It is expanded and blade- 

 like in front, and narrowed behind. On its 

 inner or sacral surface, a little way in front of 

 the acetabulum, is a roughened crescentic 

 surface for articulation with the sacrum ; 

 while its outer surface is divided by a longi- 

 tudinal ridge into ventral or iliac, and dorsal 

 or gluteal fossae. The ilium forms about 

 half of the acetabulum, the lines of boundary 

 between it and the ischium and pubes being 

 easily seen in the young skeleton. 



ii. The ischium forms the posterior and dorsal 

 portion of the os innominatum, and is sepa- 

 rated from the pubes by the large oval 



