202 ZOOTOMY. 



and its pre-axial border upwards ; in the manus the dorsal 

 surface looks upwards and the pre-axial border downwards 

 and forwards. 



95. The humerus, an elongated bone, consisting of a 

 cylindrical shaft and of two extremities : the proximal 

 extremity presents a rounded elevation or head for articula- 

 tion with the glenoid cavity, a triangular process, the greater 

 or radial tuberosityon the pre-axial side, and an irregular 

 elevation, the lesser or ulnar tuberosity on the post- 

 axial side : on the distal surface of the latter is a deep 

 excavation leading to the pneumatic foramen which 

 communicates with a large air- cavity in the shaft of the 

 bone. The distal end of the humerus has a pulley-like 

 surface or trochlea, with two raised articular surfaces, one 

 the radial tubercle pre-axial and set obliquely, the 

 other the ulnar tubercle post-axial and nearly at right 

 angles to the first : just external and proximal to the radial 

 tubercle is a small roughened elevation, the radial condyle ; 

 the ulnar condyle is similarly related to the ulnar 

 tubercle. 



96. The radius, a straight slender bone, articulating by 

 its discoid concave proximal extremity or head with the 

 radial tubercle of the humerus: its distal end bears an oblique, 

 elongated convexity for articulation with the carpus ; it is not 

 pneumatic. 



97. The ulna, a curved bone, having its concave side 

 towards the radius which it considerably exceeds in thick- 

 ness : its proximal end presents a concave surface, the 

 sigmoid cavity, set obliquely to the shaft for articulation 

 with the humerus, and is produced beyond this facet, post- 

 axially, into a short, blunt process, the olecranon ; a short 

 process is also given off from the dorsal and pre-axial region 

 which partly embraces the head of the radius. 



