PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 275 
Metacarpal 111 has scarcely any radial enlargement at its proximal end 
and does not articulate with the trapezoid. 
Turning now to the musculature of these cases in which the super- 
numerary digit is composed of three phalanges, we find that in every 
p--f-—cat, mt carp. ob. 
ext, mt'carp. Mag.-—-*--K---- 
----~ext, com. dq. %. 
III. IV. 
Fie. 0. — Anterior view of left polydactyle manus of the pig, showing extensor muscles. 
ext. com. dg. 1.,extensor communis digitorum internus; ext. m’carp. mag., extensor meta- 
carpi magnus; eat. mt’carp. ob., extensor metacarpi obliquus; ext. prp., extensor proprius 
pollicis et indicis; ext. prp. 7., extensor proprius internus. 3 natural size. 
case the extensor metacarpi obliquus (Fig. O, ext. mt’carp. ob.) has 
shifted its insertion from the second to the first metacarpal; the ex- 
tensor proprius pollicis et indicis (Fig. O, ext. prp.), which normally 
is extremely rudimentary, is in two cases inserted into the distal 
phalanges of digit 1. 
VOL. XL. — NO. 6 3 
