CHAP. IV.] 



THE SKELETON. 



29 



resemblance to them. They consist, as stated above, of the 

 os innominatum, which forms the pelvic girdle connecting 

 the lower extremity with the trunk, of the thigh, the leg, 

 and the foot. The foot is separable into ankle, sole and 

 instep, and toes. 



The os innominatum, or nameless bone, so called from bear- 

 ing no resemblance to any known object, is a large irregular- 

 shaped bone, which, with its fellow of the opposite side, forms 

 the sides and front wall of the pelvic cavity. In young 



FIG. 20. BONES OF THE WRIST AND HAND, m, metacarpal bones ; 

 p, phalanges ; 3, bones of the wrist. 



subjects it consists of three separate parts, and although in 

 the adult these have become united, it is usual to describe 

 the bone as divisible into three portions, the ilium, the 

 ischium, and the pubes. The ilium, so called from its sup- 

 porting the flank, is the upper broad and expanded portion 

 which forms the prominence of the hip. The ischium is the 

 lower and strongest portion of the bone, while the pubes is 

 that portion which forms the front of the pelvis. Where 

 these three portions of the bone meet and finally ankylose is 

 a deep socket, called the acetabulum, into which the head of 



