8fl TOPOGEAPHICAL ANATOMY OF 



and narrow groove only. In the form of a bulging band, this part 

 of the matrix encircles the digit almost completely. Broadest and 

 most convex at the middle line of the digit, it becomes narrower 

 and flatter as it is traced to the volar surface, where it ends indefinitely 

 by merging into the cuneate matrix. The whole surface of the coronary 

 matrix is beset with large papillae, 4 to 5 mm. long, which form a soft, 

 velvet-like pile. 



3. The lamina?' matrix (latus'^ matricis ungulse) is the most 

 modified part of the corium of the digit, and covers the dorsal surface 

 of the third phalanx and a small part of the ungual cartilages. It 

 is also continued on to the volar aspect of the digit in the form of 

 two elongated triangular areas. On the laminar matrix papillae are 

 replaced by a large number (about six hundred) of parallel ridges or 

 laminae which run from the coronary matrix to the edge of the digit, 

 where each ends in a number of papillae similar to those of the 

 adjoining solar matrix. The laminae are lowest close to the coronary 

 matrix, from which point they gradually increase in height until 

 a maximum is reached about the middle of their length. If the 

 laminae are examined microscopically, it will be seen that the surface 

 of each carries a considerable number of smaller ridges or secondary 

 laminffi. 



4. The sola7- (volar) jiiatrix (latus volare matricis ungulae) covers 

 the volar surface of the third phalanx, to which it is firmly attached. 

 Its surface is covered by large papilla3 some 4 or 5 mm. long. 



5. The cuneate matrix (cuneus matricis ungulae) is adherent to the 

 surface of the digital torus. It can be distinguished from the neigh- 

 bouring solar matrix by its paler colour and the smaller size (1-2 mm. 

 long) and closer packing of its papillae. 



The Hoof (ungula). — The hoof follows the general disposition of the 

 matrix, upon which it is closely moulded and to which it is firmly 

 adherent. For descriptive purposes the hoof is artificially divided into 

 three parts — the wall, the sole, and the " frog." 



1. The ivall (paries ungulae) is that part of the hoof which is visible 

 when the limb is in a state of rest, and has tapering continuations 

 (" bars ") inflected on to the volar aspect of the digit. For topographical 

 reasons it is convenient to divide the wall into " toe " (paries ungulae 

 dorsalis), "quarters'' (paries ungulse medialis: lateralis), and "heels" 

 (paries ungulae volaris s. plantaris); but this division has no morpho- 

 logical foundation. 



If the wall could be flattened out it would present a crescentic 

 outline, the horns of the crescent being represented by the abruptly 

 1 Latus [L.], tlie side (exposed part). 



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