554 BUKEAU OF AI^IMAL INJDUSTKY. 



buffer to disperye sbock when the foot i.s set to the ground. It 

 extends forward underneath the navicuhir bone and perforans tendon, 

 and protects these structures from injurious pressure from below. 

 Instantaneous photographs 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. 



The horn-producing rnemhrane^ or "quick," as it is commonly termed, 

 is merel}' a downward prolongation of the '"derm," or true skin, and 

 ma}" be conveniently called the 2^ododerm (foot skin). The pododerm 

 closely invests the coflSnbone, lateral cartilages, 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 skin, 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 laj'er upon layer of horny cells 

 (epiderm), wdiich 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 mois- 

 ture by evaporation and are rapidly transformed into the corneous 

 material which we call the hoof. It is proper to regard the hoof as 

 a greatly thickened epiderm having manv of the qualities possessed 

 b}' 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 

 tlje hoof has been removed, namely: (1) T\\q, pey^iopUc hand^ a narroAV 

 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 perloplic 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) Tie coronary hand^ 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 fleshj^ 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 mereh' as a turning 

 forward of the w^all. (3) TXiq fleshy leaves, 500 to 600 in number, par- 

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

 edge of the coronarj- 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, 



