84 TOPOGEAPHICAL ANATOMY OF 



eruro-parietales). The base of the cuneus is posterior and forms 

 two eminences separated from each other by a continuation of the 

 intercrural groove. 



The dissector should make sections of the hoof by means of a saw 

 in order that he may compare the thickness of the different parts. The 

 same method will permit him to determine the strata of the wall. 



Three layers can be distinguished in the wall. (1) The most super- 

 ficial is the thin, incomplete, glistening layer already described as 

 being present at the limbus ungulse. Because of its density and glassy 

 or varnish-like appearance it has been called the vitreous layer. 

 (2) The second layer forms the dense and hard portion of the wall, 

 which is only little affected by moisture and offers great resistance to 

 the knife. (3) The innermost layer is much softer and paler, and is 

 composed of the horny laminae that fit between the soft laminas of 

 the matrix. The ridges are low at the edge of the coronary groove, 

 but gradually increase in height as they proceed distalwards. They 

 terminate in the white line between the wall and the sole, where they 

 are mixed with horny tubules connected with the terminal papillfe of 

 the laminae of the matrix. 



The thickness of the wall varies considerably in different individuals, 

 and is not the same in all parts of the wall of the same hoof. The 

 difference in different regions has been expressed by saying that the 

 thickness of the wall at the " toe," " quarters," and " heels " is as 

 4:3:2 in the hoof of the thoracic limb, and as 3 : 2| : 2 in the hoof 

 of the pelvic limb. 



The thickness of the sole may range from 7 to 10 mm. ; while that 

 of the " frog " is from 10 to 15 mm. 



The relative density and rigidity of the hoof in different regions are 

 of moment from the physiological point of view. The oldest horn, 

 i.e. that at the extreme end of the " toe," is most rigid and least 

 yielding; whereas pliability, though nowhere very great, increases in 

 all parts of the wall as the coronary border is approached. The horn 

 of the sole is less rigid than that of the wall, and the "frog" is 

 composed of the softest and most pliable horn of the whole digit. The 

 presence of a layer of comparatively flexible horn at the junction of 

 the sole and the wall permits a certain amount of movement at this 

 place. 



The digital torus (torus digitalis).— The digital torus ^ is a 



pyramidal mass of fibrous and elastic tissue placed between the " frog " 



and the tendon of the deep flexor muscle. Each side of the base of 



the torus is intimately connected with one of the cartilages of the 



' Torus [L.], a bulge, protuberance, or prominence. 



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