PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 279 
bears a large hoof, and the two hoofs are connected posteriorly by a cush- 
ion of horny tissue, as are the functional digits. The trapezium, which 
articulates with both extra digits, is very large, and shows evidence of 
duplication ; the scaphoid also is abnormally large and broad. The 
heves ext. mt’ carp. ob. 
Ginated ext. com. dg. 2. 
III. IV. 
Fic. R.— Anterior view of left polydactyle manus of the pig, showing extensor 
muscles. ext. com. dg. t., extensor communis digitorum internus; ext. mt’carp. mag., 
extensor metacarpi magnus; ext. mt’carp. ob., extensor metacarpi obliquus; ext. prp. é., 
extensor proprius internus; 1%, 1, supernumerary digits. % natural size. 
trapezoid is narrow, being flattened by the large trapezium ; the proxi- 
mal end of metacarpal 11 also suffers in this respect. 
When 1% and 1’ are so large as to be functional, the muscles of the 
manus show some important modifications. Extensor proprius internus 
(Fig. R, ext. prp. t.) sends a tendon to 1°; extensor metacarpi obliquus 
