296 SKELETON OF THE EABBIT 



cavity of the scapula, and at its distal end, by 

 the trochlea, with the bones of the forearm. , 



At the proximal end of the bone, in front 

 of the head, is the longitudinal bicipital 

 groove, for the tendon of the biceps muscle : 

 this is bounded on its inner side by the lesser 

 tuberosity ; and on its outer side by the greater 

 tuberosity, a large roughened projection con- 

 tinued as a ridge down the anterior surface of 

 the bone as far as its mid41e. 



The trochlea at the distal end of the bone 

 is an obhque pulley-like surface, divided in 

 front by a ridge, and articulating with the 

 radius and ulna to form the elbow-joint. 

 Immediately above the trochlea, in front and 

 behind, are the supra-trochlear fossae, which 

 communicate with each other through the 

 supra-trochlear foramen: the posterior or 

 olecranon fossa is much the larger of the two, 

 and lodges the olecranon process of the ulna 

 when the arm is extended. 



2. The forearm contains two bones, of about equal size, 

 immovably articulated, though not ankylosed, with 

 each other. 



i. The radius, or preaxial bone, Hes in front of 

 the ulna at the proximal end of the forearm, 

 but in the distal half lies along its inner or 

 preaxial side. 



It is an elongated bone, slightly convex 

 forwards. Its proximal end or head articulates 

 with both grooves of the trochlea of the 

 humerus, and also with the anterior surface 

 of the ulna : its distal and larger end articu- 

 lates with the bones of the wrist. 



ii. The ulna, or postaxial bone of the forearm, has 

 a greatly enlarged proximal end, on the 

 anterior surface of which is the sigmoid notch 



