PKENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 269 



respective digits divide, the larger of the resulting branches innervating 

 the lateral portions of the third and fourth digits. 



In pentadactyle animals (Carnivora and Primates) the median nerve 

 gives off a fifth branch radial to 2 of the pig's manus, which divides 

 and supplies the thumb and index. No remains of such a nerve branch 

 could be detected in dissections of the normal manus of the pig. 



n. m. 



IV. 



III. 



Fig. J. — Posterior view of the left normal manus of pig, showing innervation, n. m., 

 median nerve; 2-5, four branches of the median nerve supplying the corresponding digits. 

 § natural size. 



If the polydactyle manus of swine is due to reversion, we might ex- 

 pect to find reversive modifications in the muscles and nerves, as well as 

 in the skeletal parts. 



The extensor of the thumb and index might be fully developed and 

 its tendon inserted into the phalanges of digits i and ii, as in penta- 



