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 (¢), 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 (Z). 
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 (¢ and 7). The 
lateral half is rounded and is called the capitulum (z). 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 (7), 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 fosse 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 
