176 



been sufficiently described. Below, the radius and ulna together 

 articulate with the lunar, cuneiform, and a large bone which will 

 be described as the scapho-carpal, the radius taking the greatest 

 share in the formation of the joint. 



THE MANUS. 



The manus (PI. VIII., figs. 5 and 5a) is so distorted, and presents, 

 so many departures from the typical structure, that I cannot, with 

 my limited experience in comparative osteology, be quite certain 

 of the homologies of the different parts. Its features are best 

 seen from the palmar surface. Figure 5 represents that of the 

 left side enlarged to two and a half times, and, in order that the 

 details of the structure may be better shown, a large palmar sesam- 

 oid bone (tig. 5a) has been removed ; the relations of this 

 will be better understood when the other parts have been 

 described. The central tigure and most conspicuous feature of 

 the hand is a large irregular bone which extends almost 

 completely across the carpus, and which has its palmar surface 

 raised somewhat above the level of the remaining bones. It is 

 indicated in fig. 5 by sc, as well as by the two crosses nearest the 

 radial side ; a foramen pierces it from above downwards, the 

 position of which is indicated by the curved arrow. Articu- 

 lating with the radius on its extreme radial side, it occupies 

 the place of the scaphoid, but from its relation to the digits, 

 with all of which it articulates, it seems to represent also the 

 carpalia (I — Y), and I will therefore, for the sake of convenience 

 in description, term it provisionally the scapho-carpal. Lying 

 between it and the radius, and visible only from the dorsal side, 

 is a small bone, not shown in the figure, about the 

 size of a pin's head, which I take to be a diminutive lunar; 

 succeeding this on the ulnar side, and articulating with the 

 ulna, is a semilunar-shaped bone, which is doubtless the 

 cuneiform (cu). The scapho-carpal has on its inferior aspect, 

 and towards the palmar surface, a small concave facet, 

 which carries a metacarpal-like bone (fig. 5 r). This supports two 

 phalanges of the second digit, the more distal terminating in a long 

 narrow claw. To the same metacarpal, as well as to the base of 

 the proximal of its two phalanges, is attached, by ligamentous con- 

 nection, the slender representative of the pollex, which also is com- 

 posed of two segments, the terminal one ending in a claw. These 

 are the two digits which are, as has been described, folded over to- 

 wards the palmar surface of the manus, and form the inner of the 

 two rows which bound the palmar cleft. Immediately to 

 to the dorsal side of the facet for the bone described above as the 

 metacarpal (r) common to the second digit and pollex is anotlier for, 

 what appears obviously, the metacarpal of the third digit (s and s)', 



