23 



THE HORNY SOLE AND ITS FUNCTIONS. 



The horny sole, the organized foundation, the chief weight- 

 'sustainer of the animal frame, constitutes the whole of the 

 plantar surface, not occupied by the edge of the wall, includ- 

 ing its inflections, the bars, and the external frog. Its line of 

 junction with its boundary wall may be traced by a white line 

 or zone, which Mr. Fleming, I believe, has been the first to 

 notice in print. 



A detached sole presents the remarkable peculiarity of a 

 deep indentation in the general form of an isosceles triangle,, 

 its base being placed posteriorly, and its apex extending fully 

 two-thirds of the distance from its base to the anterior margin 

 of the sole. 



Figure 4. — External View of the Horny Sole. 



Microscopic anatomists describe the horny sole as fibrous in 

 its inner substance, the fibres taking an oblique direction for- 

 wards and downwards, corresponding to that of the fibres of 

 the wall, and gradually changing into squamous incrustations, 

 somewhat similar to the epidermis of the skin as it approaches 

 its external limits. 



The horny sole is secreted by the vascular and sensitive sole, 

 and in the same manner as the wall is secreted by the coronary 

 band, by tufts or villi that penetrate the horny fibres. The 

 wall wastes by attrition when the animal is unshod ; the sole 

 and the frog, by exfoliation. 



