66 THE SKELETON OF THE CAT. 



surface is seen a broad groove, the sulcus intertubercularis or 

 bicipital groove (;/), which passes distad onto the surface of 

 the shaft. In the natural state it is converted into a canal by 

 overlying tendons and lodges the tendon of the biceps muscle. 



The shaft is nearly cylindrical at its middle, but its dorso- 

 ventral diameter is slightly greater than its mediolateral 

 diameter. Its proximal end is flattened mediolaterad, while its 

 distal end is flattened dorsoventrad. 



From the ventral margin of the greater tuberosity a ridge, 

 the pectoral ridge (e), is continued onto the surface of the shaft, 

 and from the dorsal margin another ridge, the deltoid ridge (_/"), 

 passes distad and ventrad so as to meet the pectoral ridge near 

 the middle of the ventral surface of the bone. On the medial 

 margin of the bone near the junction of the first and second 

 fourths is a roughened area (g) for the attachment of the ten- 

 dons of the latissimus dorsi and teres major muscles, and on the 

 same surface near the junction of the second and last thirds is 

 a nutrient foramen (//). 



The distal end of the bone presents a smooth saddle-shaped 

 articular surface, which, in well-marked bones, is divided, when 

 seen from the ventral surface, by a slight nearly median ridge 

 into two unequal portions, lateral and medial (i and /). The 

 lateral half is rounded and is called the capitulum (/). It is 

 broader ventrad than dorsad, and is not continued onto the 

 dorsal surface of the bone. It is for articulation with the 

 proximal end of the radius. 



The medial half of the surface, the trochlea (/), is concave 

 and passes directly into the capitular surface laterad, but is 

 limited mediad by a sharp ridge. It is continued onto the 

 dorsal surface of the bone, where it is limited also laterad by a 

 ridge. It articulates with the semilunar notch of the ulna. 



Proximad of the trochlea the dorsal surface presents a deep 

 fossa, the olecranon fossa, which receives the olecranon of the 

 ulna when the arm is straightened. On the ventral surface 

 (Fig. 47) are two shallower fossae separated by a longitudinal 

 ridge. The one over the trochlea receives the coronoid process 

 of the ulna when the arm is bent, and is called thence the 

 coronoid fossa (/). The one over the capitulum, the radial 



