THE MATRIX OF THE HOOF 769 



Usually it forms a distinct band somewhat less than an inch wide, except 

 at the heels, where it is much wider, and caps the angle of inflection of 

 the wall proper. The stratum vitreimi is a thin layer of horny scales which 

 gives the wall l)elow the periople its smooth, glossy appearance. The middle 

 or tubular layer forms the Ijulk of the wall, and is the densest part of the 

 hoof. Its horn tubes run in a straight direction from the coronary to the ground 

 border. In dark hoofs it is pigmented except in its deep part. The internal or 

 laminar layer consists of the primary and secondary laminae and is non-pigmented. 

 The laminae are narrow and thin at their origin at the lower margin of the coronary 

 groove, but become wider and thicker below. At the junction of the wall and sole 

 they are united by interlaminar horn to form the white line. Only the central 

 part of the laminae becomes fully keratinized. They are composed of non-tubular 

 horn in the normal state. 



The sole consists of tul)ular and intertubular horn. The tubes run parallel 

 with those of the wall and vary much in size. 



The frog is composed of relatively soft horn, which is much more elastic than 

 that of the Avall or sole, and is not fulh^ keratinized. The horn tubes in it are 

 slightly flexuous. 



The hoof is non-vascular and receives its nutrition from the matrix. It is 

 also destitute of nerves. 



The Matrix of the Hoof 

 The matrix of the hoof (Matrix ungukp) is the specially modified and highly 

 vascular part of the corium of the common integument which furnishes nutrition 

 to the hoof. It is convenient to divide it into five parts which nourish correspond- 

 ing parts of the hoof. 



1. The perioplic matrix or ring (Margo matricis ungula^) is a band 5 to 6 mm. 

 in width which lies in a groove between the periople and the coronary border of 

 the wall. It is continuous above with the corium of the skin, and is marked off by 

 a groove from the coronary matrix. At the heels it widens and blends with the 

 matrix of the frog. It bears very fine, short papillae which curve downward and 

 are received in depressions of the periople, to which it supplies nutrition. 



2. The coronary matrix or cushion (Corona matricis ungulae) is the thick part 

 of the corium which occupies the coronary groove, and furnishes nutrition to the 

 bulk of the wall. It diminishes in width and thickness posteriorly, and along the 

 upper border of the bar it is not very clearly defined from the matrix of the frog. 

 The convex superficial surface is thickly covered with papillae 4 to 6 mm. in length, 

 which are received into the funnel-like openings of the coronary groove. At 

 the heels and along the bars the papilla are arranged in rows, separated by fine 

 furrows. The deep surface is attached to the extensor tendon and the lateral 

 cartilages by an abundant subcutis which contains many elastic fibers and a rich 

 venous plexus. 



3. The laminar matrix (Latus matricis ungulae)— also termed the sensitive 

 laminae — bears primary and secondary laminae which are interleaved with the horny 

 laminae of the wall and bars in the natural state. It is attached to the wall surface 

 of the third phalanx by a modified periosteum (Stratum periosteale) which contains 

 a close-meshed network of vessels, and to the lower part of the lateral cartilages 

 by a subcutis which contains a rich venous plexus. The laminae are small at their 

 origin above, become wider below, and end in several papillae 4 to 5 mm. in length. 

 The sensitive laminae supply nutrition to the horny laminae and to the interlaminar 

 horn of the white line. 



4. The sole matrix (Latus volare matricis ungula^)— also termed the sensitive 

 sole — corresponds to the horny sole, to which it supplies nutrition. It is often 

 more or less pigmented and bears long papillae, which are specially large along the 



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