PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 275 



Metacarpal in 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 



ext. mfcarp. 



I— — cxt. prp. 



mt'carp. ob. 



com. dg. i. 



Fig. 0. — Anterior view of left polydactyle manus of the pig, showing extensor muscles. 

 ext. com. dg. t., extensor communis digitorum iuternus; ext. mt'carp. mag., extensor meta- 

 carpi magnus; ext. mt'carp. ob., extensor metacarpi obliquus; ext. prp., extensor proprius 

 poilicis et indicis; ext. pip. i., extensor proprius internus. iS natural size. 



case the extensor metacarpi obliquus (Fig. 0, ext. vit'carp. ob.) has 

 shifted its insertion from the second to the first metacarpal ; the ex- 

 tensor proprius poilicis et indicis (Fig. 0, ext. prp.), which normally 

 is extremely rudimentary, is in two cases inserted into the distal 

 phalanges of digit i. 



VOL. XL. — KO. 6 8 



