THE CAT 261 



tuberosity and the inner is the lesser tuberosity of the humerus. 

 Along the anterior side, near its upper end, is an elevation called 

 the deltoid ridge. Near the lower end is an opening in the bone, 

 the supracondyloid foramen; a deep depression, the olecranon 

 fossa, is present on the hinder side. 



The middle division of the leg is formed of the radius and the 

 ulna, which articulate with the distal end of the humerus. The 

 ulna is the hinder and the larger of the two bones and possesses at 

 its proximal end the large olecranon process, which articulates in 

 the olecranon fossa of the humerus and forms the elbow. The 

 articular surface of the ulna with the humerus is formed by the 

 semilunar notch, a deep depression just back of the olecranon 

 process. The radius is preaxial in position, being in front of the 

 ulna. Note carefully its relation to the ulna and to the bones with 

 which it articulates at both ends. 



The distal division of the foreleg is formed by the carpus, or 

 wrist, and the manus, or hand. The carpal bones are seven in 

 number, arranged in two rows, three being in the proximal and 

 four in the distal row. The hand is composed of the metacarpal 

 bones and the digits. The metacarpals are five in number, of 

 which the first is the shortest. The digits also number five, each 

 one being composed of a number of bones called phalanges. The 

 first digit, which corresponds to the thumb, is composed of two 

 phalanges ; the others have three apiece. 



Exercise 49. Make a drawing showing all the bones of the leg. Care- 

 fully label all. 



The posterior extremities are made up of the pelvic girdle, or 

 pelvis, and the hind legs. The pelvic girdle is formed by two 

 bones, the right and left innominate bones, which together form an 

 arch. This arch articulates dorsally with a portion of the spinal 

 column called the sacrum; ventrally the two innominate bones 

 meet and unite in the midventral line, this union being called 

 the symphysis pubis. In the middle of the lateral surface of each 

 innominate bone is a circular depression, called the acetabulum, 

 in which the femur articulates. A large hole, called the obturator 

 foramen, is present in the ventral half of the bone. The innom- 



