neath the navicular bone and perforans tendon, and protects these 

 structures from injurious pressure from below. Instantaneous photo- 

 graphs show that at speed the horse sets the heels to the ground before 

 other parts of the foot — conclusive proof that the function of this 

 tough, elastic structure is to dissipate and render harmless violent 

 impact of the foot with the ground. 



Pododerm (foot skin). — The horn-producing membrane, or "quick," 

 as it is commonly termed, is merely a downward prolongation of the 

 " derm," or true skin, and may be conveniently called the pododerm 

 (foot skin). The pododerm closely invests the coffin bone, lateral car- 

 tilages, and plantar cushion, much as a sock covers the human foot, 

 and is itself covered by the horny capsule, or hoof. It differs from the 

 external, or hair, skin in having no sweat or oil glands, but, like 

 it, is richly supplied with blood vessels and sensitive nerves. And, 

 just as the derm of the hair skin produces upon its outer surface layer 

 upon layer of horny cells (epiderm), which protect the sensitive and 

 vascular derm, so, likewise, in the foot the pododerm produces over 

 its entire surface soft cells, which, pushed away by more recent cells 

 forming beneath, lose moisture by evaporation and are rapidly trans- 

 formed into the corneous material which we call the hoof. It is proper 

 to regard the hoof as a greatly thickened epiderm, having many of 

 the qualities possessed by such epidermal structures as hair, feathers, 

 nails, claws, etc. 



The functions of the pododerm are to produce the hoof and to unite 

 it firmly to the foot. 



There are five parts of the pododerm, easily distinguishable when 

 the hoof has been removed, namely: (1) The perioplic baud, a narrow 

 ridge from one-sixteenth to one-eighth of an inch wide, running along 

 the edge of the hair from one heel around the toe to the other. This 

 band produces the perioplic horn, the thin varnish-like layer of glis- 

 tening horn, which forms the surface of the Avail, or "crust," and 

 whose purpose seems to be to retard evaporation of moisture from 

 the wall. (2) The coronary band, a prominent fleshy cornice encir- 

 cling the foot just below and parallel to the perioplic band. At the 

 heels it is reflected forward along the sides of the fleshy frog to 

 become lost near the apex of this latter structure. The coronet pro- 

 duces the middle layer of the wall, and the reflected portions produce 

 the "bars," which are, therefore, to be regarded merely as a turning- 

 forward of the wall. (3) The fleshy leaves, 500 to 600 in number, par- 

 allel to one another, running downward and forward from the lower 

 edge of the coronary band to the margin of the fleshy sole. They 

 produce the soft, light-colored horny leaves which form the deepest 

 layer of the wall, and serve as a strong bond of union between the 

 middle layer of the wall and the fleshy leaves with which they dovetail. 

 (4) The fleshy sole, which covers the entire under surface of the foot, 

 excepting the fleshy frog and bars. The horny sole is produced by 



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