38 THE ANATOMY OF THE H0B8E. 



the hoof, is a stratum of soft protoplasmic epithelial cells by whose 

 growth and multiplication the hoof-horn is formed. This stratum of 

 cells represents the deepest cells of the rete mucosum in the skin, and 

 it is by its ready decomposition that the bond of connection between 

 the sensitive and insensitive structures is destroyed, permitting the 

 extremitj' of the digit to be extracted from its horny investment. 



Directions. — The student should next turn his attention to the ex- 

 tremity of the digit as exposed by the removal of the hoof, and he will 

 find it to present a configuration not unlike the exterior of the hoof itself 

 (Plate 10, figs. 1 and 5). And in the first place, let him examine that 

 jDart which he will easily recognise as having been separated from the 

 inner surface of the wall. This is traversed by a series of leaves which, 

 in contradistinction to those already seen on the inner surface of the 

 wall, are termed the sensitive laminse, and sometimes the podophyllous 

 tissue. 



The Sensitive Laminae. Each lamina is fixed by one of its borders to , 

 the periosteum of the os pedis, and extends in a vertical direction from 

 near the coronary cushion to the sharp edge of the bone, where it 

 terminates in five, or six long papillaj. In the natural state the sensitive 

 and the horny laminae are interleaved, and the former here represent 

 the corium, or true skin. The laminse, it will be noticed, become pro- 

 gressively shorter as they are traced backwards ; and at the end of the 

 series on each side, and adjacent to the plantar cushion, there is a number 

 of small leaves that were interleaved with the homy laminse of the bars. 

 The Coronary Cushion. This is a projecting, cornice-like structure, 

 - placed above the laminse and below the limits of the skin of the digit. 

 ; fits into the cutigeral groove at the upper border of the wall, and its 

 jurface is closely set with long papillse which were received into the 

 apertures found in that groove. These papillae give the coronary 

 cushion a velvety pile, which may be rendered very evident by immers- , 

 ing the foot in water. If the coronary cushion be traced backwards, it 

 will be seen to pass into the plantar cushion. Above the cushion is a/ 

 narrow groove separating it from the periopolic ring. Below the cushioiiv 

 there is a narrow smooth space which runs between the cushion and the 

 sensitive lamnise. The coronary cushion is a modified portion of thfe 

 cai^'am, and through the agency of the cells which cover the surface of 

 its papillae, the wall of the hoof is formed. 



The Pbrjoplic Eing. This ring is composed of papillse like those of 

 the coronary cushion, but smaller in size ; and it is by its agency that 

 the periople which covers the exterior of the wall is formed. 



The Plantar Cushion. This is a fibro-elastic pad interposed between 

 the homy frog and the terminal part of the perforans tendon. It 

 possesses two faces, two borders, a base, and an apex. The lower face 

 looks backwards as well as downwards when the foot rests on a flat 



