PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 271 
On examining the other skeletal elements of the manus, in order to 
determine whether they show reversive modifications, one is at once 
struck by the form of the trapezoid (Fig. K, trzd.). Although of normal 
size, there is a remarkable change at its distal end ; instead of projecting 
as a wedge between metacarpals 11 and 11 (see normal manus, Fig. /, 
tred., p. 264), and presenting two distal facets nearly equal in size, 
scph. lun. cun. 
0S MAY. +. pes 
trzd, *<--- 
ies ore 
jm momecreececem |), 
II. 
III. IV. 
Fie. K, — Anterior view of left polydactyle manus of the pig, showing carpals and 
metacarpals. I-v, first to fifth metacarpals; cun., cuneiform; lwn., lunar; os mag., os 
magnum; pis., pisiform; scph., scaphoid; trz., trapezium; trzd., trapezoid; un., unciform. 
3 natural size. 
there is only one articular surface, which is slightly convex and occu- 
pied entirely by metacarpal 1. The trapezoid barely touches metacarpal 
111; its form and relations to the other skeletal parts thus approach those 
of the trapezoid of fossil swine (Fig. G, p. 265). 
In correspondence with these carpal variations, the metacarpals show 
some changes. The metacarpal of digit is slightly larger than nor- 
