i6o 



EVOLUTION AND DISEASE. 



truly atavistic, and the leading features in the argument 

 are visually represented in the drawings (fig. 84). 



The museum of the Ecole Veterinaire de Lyons con- 

 tains a very remarkable specimen. It is the skeleton of 

 an equine manus with two functional digits (fig. 85), 

 on each side of the metacarpal bone a vestigial 

 metacarpal exists as in the normal manus. In the 

 specimen last considered we noted that the super- 

 numerary digit was articulated with the distal end of 

 the lateral metacarpal (fig. 85, B). In the Lyons speci- 



FIG. 84. A, the manus of Hipparion ', B, the 

 manus of a horse ( Equus} with the inner digit 

 functional (atavistic) ; C, the normal manus 

 of Equus, one toe functional, ii. and iv. 

 vestigial. 



men both digits articulate with the main metacarpal ; 

 and it is clear from even a cursory examination of the 

 preparation that we have to deal with an example of 

 dichotomy, or bifurcation of the terminal segments of 

 the functional digit. 



The museum of the Royal College of Surgeons, 

 England, contains a skeleton of an equine manus with a 

 supernumerary digit of this character, but it differs from 

 the Lyons specimen in that the third digit has dich- 



