THE FOOT IN HEALTH AND DISEASE 105 



insensitive structures, the former being all parts enclosed 

 within the homy box, and the latter consisting of the wall 

 and the sole only, and being comparable to the finger-nail. 

 The wall is thickest at the toe, thinner at the quarters, 

 and thinnest of all at the heels. The outer surface of 

 the wall should be perfectly smooth, and it is covered by 

 a protective material known as the periople, which, in 

 reality, represents a natural varnish, and this is secreted 

 from the '' periopUc ring " at the upper border of the 

 hoof and beneath the coronary band. In the unshod foot 

 it forms a bluish bloom on the wall. In the shod foot it is 

 not often observed, as the farrier frequently, but un- 

 wittingly, removes it with his rasp, a thing which should 

 never be done. The inner surface of the wall consists of 

 a number of leaf-hke structures, arranged perpendicularly 

 with the upper and lower borders. These leaf -like struc- 

 tures are known as the horny or insensitive laminae, and 

 their use is to accommodate corresponding structures 

 covering the pedal-bones, and known as the sensitive 

 laminae. The two opposing structures are so dove-tailed 

 into one another as to constitute a very firm bond of union 

 between the two ; in fact, the weight of the horse is 

 mainly distributed through this channel. 



The horny sole joins the lower border of the wall at the 

 so-called white line, which is readily discernible when the 

 foot is pared. The lower border of the wall and its junction 

 with the sole at the white line constitute the chief weight- 

 bearing structures of the foot, therefore the shoe should 

 press upon these parts only. The ground surface of the 

 sole is, normally, concave, but as stated earlier on may, 

 through disease, become flattened, constituting the so- 

 called " dropped sole.'' Its inner surface is convex. 

 The sole is formed from papillae on the lower surface of 

 the pedal-bone exactly in the same manner as the horn of 

 the wall is secreted. The footpad, or the '* frog," con- 

 sists of a wedge-shaped piece of elastic tissue, with the 

 point of the wedge directed towards the toe. It is spoken 



