THORAX AND RIBS. 35 



which, is articulated with the ulna. The condyles are separated by a 

 groove, which corresponds anteriorly with the radius for a small extent ; and 

 the rest of the articulating surface with the upper extremity of the ulna 

 (Plate XXT. Fig. 4). 



The length of the humerus is thirty-nine inches ; its greatest circum- 

 ference, thirty-nine inches and one eighth ; its smallest, eighteen inches. 



The fossa for the reception of the olecranon process lies between and 

 above the condyles. It is a very deep rounded indentation, passing gra- 

 dually into a fossa, which extends one-third up the bone, and differs from 

 that of the elephant in being pretty regularly continued from below upwards, 

 while in the elephant the upper part is distinctly separated from the lower. 



Fore-arm. — The bones of the fore-arm do not correspond in the Fore-arm. 

 direction of their perpendicular lines ; for the radius does not lie on the 

 outer edge of the limb, but is inclined across the ulna from without inward, 

 so that its inferior extremity forms the inner portion of the wrist-articu- 

 lation ; while the superior extremity corresponds in part with the outer 

 edge of the condyle of the humerus. About half of the radius lies on the 

 inside of the ulna, and the other half on its anterior surface : this position 

 represents the extremity in the human skeleton, when the hand is in its 

 utmost pronation. 



Eadius (Plate XXV.). — The radius lies on the anterior part of the Radius, 

 ulna above, and, crossing to the inner part of the limb, forms a large tube- 

 rosity below. Its head corresponds, by its superior articulating surface, 

 principally with the external condyle, as in man, but is situated on the 

 anterior part of the articulation ; the most external portion of which is 

 formed by the ulna, and not by the radius. The anterior part of this head 

 is flattened, and has nearly a triangular form. 



