78 TOPOGEAPHICAL ANATOMY OF 



has taken on both a ligamentous structure and a ligamentous function 

 — a modification to be associated with the circumstance that the horse 

 walks on the tip of the third digit. 



The Hoof and its Contents. 



Seeing that, without considerable injury to soft structures, it is 

 well-nigh impossible to remove the hoof from a limb that has been 

 prepared for dissection as a whole, the dissector should obtain a special 

 specimen in which the hoof has already been removed. 



During the whole of his dissection the student should keep certain 

 facts clearly in view. The "foot," as the hoof and the structures 

 contained therein are commonly comprehensively named, is the distal 

 part of the digit, and all the component parts thereof have been 

 modified for two purposes. In the first place, the extremity of the 

 digit is protected from injury by a dense, horny covering — the hoof 

 — which is merely a specially thickened portion of the epidermis. 

 Secondly, the hoof and everything in it (except vessels and nerves) 

 are capable of absorbing and diminishing shock. 



The skeleton of the " foot " consists of part of the second phalanx, 

 the whole of the third phalanx with its cartilaginous appendages 

 (ungual cartilages), and the sesamoid bone of the third phalanx. 

 These, with the elastic digital torus, form a basis to which modified 

 skin is attached. The skin, here as elsewhere, consists of a highly 

 vascular corium or dermis and epidermis. The greatly thickened 

 epidermis forms the hoof or ungula, for which the corium provides 

 a matrix. 



Although the name matrix is applied to the corium in the foot, 

 this should not lead the student into the error of supposing that 

 it plays any part, except that of providing nourishment, in the forma- 

 tion and growth of the hoof. The hoof, being epidermis, grows from 

 its own deepest layer, or stratum germinativum, in the same manner 

 as the epidermis in any other region of the body. 



The dissector will do well to begin his examination with the 

 corium or matrix. 



The matrix (matrix ungulae i). — The highly vascular matrix of the 

 hoof differs from the corresponding stratum of ordinary skin in several 

 respects. It contains no sebaceous glands, and sweat glands are 

 comparatively few and of limited distribution. Its papillae are large, 

 and, in one region, modified so as to form ridges. Subcutaneous 



1 Matrix [L.], the womb, the form or mould in which something is shaped, from 

 'mater, mother. Unguis [L.l nail. 



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