EPIDERMIC PRODUCTS 261 



posterior ones. Indeed, if we suppose a digit taking its 

 origin at these points, it will be longer in front (the thumb) 

 than behind (the first toe). 



Hoofs of the Ox and the Pig. — The ox has four hoofs 

 on each foot — two which contain the third phalanges, and 

 two others, rudimentary, situated at the posterior aspect 

 of the limb, at the level of the inferior part of the canon ; 

 these latter bear the name of spurs. We will occupy our- 

 selves especially with the former (Fig. 105). 



Each of the hoofs presents three faces which, if we consider 

 them in relation to the median axis of the limb to which they 

 belong, are : external, internal, and inferior. The external 

 surface resembles the wall of the hoof of the horse. The 

 internal surface is slightly concave from before backwards, 

 so that the external and internal hoofs of the same foot are 

 not in contact with each other, except by the extremities 

 of this surface, and that an interval separates them between 

 these two points. The inferior surface, slightly depressed, 

 ends behind in a swelling produced by the plantar cushion, 

 which covers a thin lamina of horn. 



At the anterior part of the hoof these three surfaces unite 

 in forming a well-marked angle which, on account of the con- 

 cavity of the internal surface, is slightly curved towards the 

 axis of the foot. 



The pig has also four hoofs — two for the great digits and 

 two for the lateral digits. They recall those of the ox. 



