330 THE SKELETON OF THE RABBIT. 



of the flexor muscles, opposite the metacarpo- 

 phalangeal and certain other joints. 



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 attached to the sacrum in 

 front, and to 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 longitudinal 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 

 separated from the pubes by the large oval 

 obturator foramen. It forms about a third 

 of the acetabulum, behind which it bears 

 on its inner surface the sharp, backwardly 

 directed ischial spine. Its posterior part is 

 flattened, the margin being thickened to 

 form the ischial tuberosity, which is raised 

 on its outer surface into a prominent hooked 



