EPIDERMIC PRODUCTS 251 



are : the basilar process and the retrorsal process (Fig. 96) ; 

 by its posterior part, this border is continuous with a 

 structure known as the plantar cushion (see further on). 



The posterior border is directed obliquely upwards and 

 forwards. The superior border, which is convex or recti- 

 linear, is thin, and is separated from the posterior border by 

 an obtuse angle. Finally, the anterior border, which is 

 directed obliquely downwards and backwards, is united to 

 the ligamentous apparatus, which keeps the second and third 

 phalanges in contact. 



These fibro-cartilages, at their upper extremities, project 

 beyond the hoof, and therefore assist in the formation of 

 the lateral regions of the foot,* at the part which is 

 called the crown. They project less above the hoof in the 

 posterior limbs. 



Fig. 96. — Third Phalanx of the Horse : Left Anterior Limc, 



External Surface. 



I, Pyramidal eminence; 2, surface, for articulation with the inferior 

 extremity of the second phalanx ; 3, basilar process ; 4, retrorsal 

 process. 



The posterior and inferior borders of these cartilages 

 meet at an acute angle. The angle so formed, or cartila- 

 ginous bulb, constitutes the base of the region, which is 

 commonly called the heel — a part of the foot which, as 

 its name implies, is situated posteriorly, but which we 

 must not confound, as we might be led to do, with the 

 region occupied by the calcaneum. We know from our 



* Here, for the first time, apropos of the hoof, we use the word ' foot.' 

 As in osteology and in myology we have, for the sake of clearness of com- 

 parison, designated under this name the region limited above by the tarsus, 

 it is necessary to point out here that we employ the same word for a more 

 restricted region. This we did in conformity with the usage of veterinarians, 

 who so designate the region of the hoof. It is necessary to explain this 

 double employment of the word, and, further, to show the particular 

 meaning ascribed to it. 



