234 



VERTEBRATES. 



The two component parts of this bone most easily recog- 

 nizable are the elongated second and third metacarpals ; 

 the second is stout and straight, the third is slender and 

 curved, and the two are fused only at their ends. The 

 short and stumpy phalanges of three rudimentary digits 

 are articulated with the carpo-metacarpus, one (the 

 thumb) at its anterior edge near its proximal end, the 

 other two toward its distal end. 



WING BONES OF SPARROW, slightly enlarged (ventral aspect of left wing) : 

 h, humerus ; r, radius ; u, ulna ; ol, olecranon process of the ulna ; c and c, 

 free carpal hones ; cmc, carpo-metacarpus ; 1, 2, and 3, phalanges. 



VI. The Pelvic Girdle. Study the pelvic girdle. Each 

 half of it is made up of the three usual bones, ilium, 

 ischium, and pubis, meeting around the acetabulum, 

 and solidly anchylosed together. The acetabulum is 

 but a rim of bone, its bottom being membranous. 



1. The ilium forms the front and upper walls, and a 

 great part of the hinder wall of the acetabulum. The two 

 ilia, together with the sacral vertebrae included between 

 them, form the entire roof of the pelvis. Each ilium is 

 attached along almost its entire length to the lateral pro- 

 cesses of the sacral vertebra. An obliquely transverse 

 line divides its dorsal surface into two parts, the anterior 

 one concave, the posterior one convex. A lateral process 

 from it overhangs the acetabulum, and articulates with a 

 process on the femur. 



2. The ischium forms a part of the hinder wall of the 

 acetabulum, and extends thence directly backward. It is 



