COMPARATIVE ANATOMY 29 



for the passage of a blood vessel and a nerve. Between the two 

 condyles is the smooth surface for articulation of the ulna and 

 radius. Above these on the posterior face is a depression, the 

 olecranon fossa, for reception of the olecranon process of the 

 ulna. 



4. Ulna. — This is the longer of the two bones of the fore- 

 arm. The notch into which the humerus fits is the greater 

 sigmoid cavity. Just distal to this is a smaller transverse con- 

 cavity, the lesser sigmoid cavity, for articulation with the radius. 

 The portion of the ulna proximal to the greater sigmoid cavity 

 is the olecranon -process. The projection at the distal end of the 

 ulna is the styloid process. 



5. Radius. — This is the shorter of the two bones of the fore- 

 arm. Proximally, by means of its head, it articulates with the 

 humerus and the ulna. A small projection toward the ulna, 

 slightly distal to the head, is the bicipital tubercle. As in the 

 ulna, the process at the distal end of the radius is the styloid 

 process. 



6. Carpus. — The seven bones in the wrist make up the 

 carpus. These are arranged in two rows. The three bones in 

 the proximal row, beginning on the medial side, are: scapholunar, 

 cuneiform, and pisiform. In kittens the scapholunar is repre- 

 sented by three bones; in man by two, the scaphoid and lunar. 

 The four bones of the distal row, beginning medially, are: 

 trapezium, trapezoid, magnum, and unciform. 



7. Metacarpus. — This consists of the five long bones of the 

 hand. For convenience they are numbered from i to 5, begin- 

 ning on the medial side. 



8. Phalanges. — The cat has five digits on the front foot, 

 each of which, with the exception of the thumb, contains three 

 phalanges; the thumb has two phalanges. The distal phalanx 

 of each digit has attached to it a retractile claw. 



Pelvic Girdle and Hind Limb of the Cat 



I. Innominate. — The pelvic girdle consists of two innomi- 

 nate bones, one on each side, the two joining in the mid-ventral 

 line to form the pubic sy7nphysis. Each innominate has near the 

 center of its lateral surface a depression, the acetabulum, for the 

 reception of the head of the femur. The acetabulum marks 



