190 bHUFELDT. 



maniDial habitually carries it3 limbs in this position, although the climbing 

 Galeopitheeus and the Sloths are not far from it. It is, however, very nearly 

 the normal position of some Reptiles, especially the Tortoises, although it is 

 ill adapted for anything but a very slow and clumsy mode of progression. 



In Cynocephalus the humerus makes the usual articulations with the 

 scapula proximalh', and the radius and ulna distally, that are seen among 

 mammals generally. These articulations are in all cases extensive and 

 the joints very perfect anatomically. 



The left humerus of the colugo (figure 15) offers the following points 

 for examination, some of which are better seen in the right humerus 

 (figure 16) from the same skeleton, this being diie to the different posi- 

 tions in which the bones were photogi'aphed. Its characters, including 

 its length and to some extent its size, vary somewhat in various in- 

 dividuals. It is considerably shorter than the ulna or the radius; in 

 man it is the longest bone of the arm. 



Viewed in its entirety, upon either its direct inner or outer aspect, 

 the humerus is seen to possess for its continuity the true "sigmoid curve." 

 This curve starts at the head and terminates with the trochlear extremity. 

 Ignoring the prominent ridges its shaft is for the most part subcylindrical 

 in form, the principal departure being at the distal end which is ex- 

 panded to support the trochlea for the bones of the antibrachium. It is 

 uniformly smooth, and pierced by an oblique, nutrient foramen situated 

 about 2 centimeters distad of the articular part of the head, on the 

 posterior aspect. 



The very conspicuously elevated deltoid ridge with its thickened edge 

 extends down the shaft, on its anterior aspect, for about one-third of its 

 length. It commences at the head and slopes away rather abruptly 

 distally. Its nearly straight free margin is almost parallel to the shaft's 

 long axis, its sides being smooth. On the other hand the supinator ridge 

 is low, sharp, and thin, extending from the external condyle almost to a 

 middle point of the shaft, following accurately the lower sigmoidal 

 curvature of the latter, where it is gi'adually lost. 



Among mammals we rarely meet with the humerus possessing a more 

 perfect head than it does in Cynocephalus, in which genus it is almost 

 a complete and entirely smooth hemisphere. For the most part its 

 articular surface is distinctly differentiated by its circular limiting line 

 and surrounding shallow groove or neck, the major part of which is seen 

 on posterior view. It reminds one of the humeral head of anthropotomy 

 and surmounts the shaft in a very similar manner (figure 15). Upon 

 either side of it the greater and lesser tuljerosities are well developed, the 

 comparatively deep bicipital groove passing the latter down the shaft and 

 the side of the deltoid ridge. 



At the distal extremity of the bone, posteriorly, the olecranon fossa 

 is very deep and markedly defined. Its osseous base is thin, and may 



