PHYSIOLOGY OF THE FOOT. 261 



and held together by a glutinous horny exudation which is 

 removed, and the fibres separated by maceration. Inordi- 

 nate heat and dryness will partially do the same in the 

 living hoof, as we know by what are called sandcracks. 

 The wall of the hoof is divided into two layers, an external 

 and an internal. Taking up a black hoof which has been 

 freed from all its adherent parts, it will be found to be white 

 within ; and this white part will hkewise be found to be much 

 less hard than, and about a quarter the thickness of, the 

 coloured portion (see Plate X. Fig 2 . h). The hard black 

 external layer of horn is secreted by the coronet (see 

 Plate X. Fig I . k; Fig 4 . a) ; the internal white and soft 

 layer is secreted by the sensitive laminse, and it is thrown 

 into projections which exactly fitted into the folds of the 

 secreting surface (see Plate X. Fig 4 . b). The wall is 

 also divided into toe, heel, and quarters (see Plate X. 

 Fig 4 . €,f, g). The quarters are the lateral parts of the 

 walls ; the more forward and thickest portion of horn is 

 called the toe ; the more backward and thinnest, the heels 

 (Plate X. Fig^ . d). In the usual formation of feet, 

 the inner side of the hoof is observed to be weaker than 

 the outer ; and, as the inner side receives most weight, 

 this proves the care taken to secure elasticity in the horse's 

 movements. The horn yields to pressure, and the thinnest, 

 of course, yields most. The density of the hoof materially 

 decreases as it approaches the heels, evidently to favour 

 the descent of the elastic frog, which likewise favours elas- 

 ticity of motion. The superior marginal part of the hoof 

 is softer and thinner than the rest ; and if our eyes be 

 directed inward, we shall perceive an indentation called the 

 coronary ring, within which the coronary ligament once 

 reposed ; the thin and soft part is horn just secreted, and 

 in a single layer; whereas where the horn is thicker, the 

 coronary ligament is more bulky, for the horn is secreted 

 in several layers. 



To finish our description of the hoof, we must turn our 

 attention posteriorly ; where we shall find the laminse in- 

 flecting themselves abruptly inwards and downwards, form- 

 ing what are termed the bars ; which are nothing more than 

 continuations of the horn of the heels, stimulated and 

 thickened by pressure (see Plate X. Fig 3 . /) . So also 



