564 



MAMMALIAN ANATOMY 



the part above the musculo-spiral groove gives origin to the external 

 head of the triceps muscle, and the larger part below the groove to the 

 internal head of the same muscle. 



The human humerus normally has no supracondyloid foramen. 



The lower extremity presents only a few differences. The capi- 

 tellum is more clearly defined from the trochlea ; the articular eminence 

 is not so deeply concave transversely ; the internal epicondyle is more 

 prominent. 



THE ULNA. 



General Description. The Ulna is about a seventh longer than 

 its companion the radius. It is the longest bone in the thoracic 

 extremity, and, with the exception of the tibia, is the longest bone in 

 the entire skeleton. It lies at the back of the forearm, on the inner 



PIG. 437. 



Vertebral Column. 



Hyoid. 



Clcmicle. 

 Sternum. 



Metatarsus. 

 Phalanges. 



THE SKELETON OF THE CAT. (LEFT SIDE ONLY.) 



side, and can be felt through the skin and muscles (Fig. 437). When 

 the palm of the hand is turned to face forward and inward, the radius 

 is on the outer side of the ulna and parallel with it ; but in the usual 

 position of the hand, with the palm partly on the ground and partly 

 facing backward, the radius is in front of the ulna, except for a small 

 distance at its upper end. The ulna articulates by its upper end with 

 the trochlea of the humerus, and by its lower end with two of the 

 bones of the wrist, the cuneiform and the pisiform. It articulates by 

 both ends with the contiguous ends of the radius. It is a narrow, 

 slender bone, whereof the long diameter is ten or eleven times greater 



