104 DOMESTIC ANIMALS, DAIRYING, ETC. 



ossification, in which condition they are hard and unyielding. The 

 plantar cushion is a wedge-shaped mass of tough, elastic, fibro-fatty 

 tissue filling all the space between the lateral cartilages, forming the 

 fleshy heels and the fleshy frog, and serving as a buffer to disperse 

 shock when the foot is set to the ground. It extends forward under- 

 neath the navicular bone and perforans tendon, and protects these 

 structures from injurious pressure from below. Instantaneous pho- 

 tographs 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 podo- 

 derm (foot skin). The pododerm closely invests the coffinbone, 

 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, or hair, skin in having no sweat or oil 

 glands, but, like it, is richly supplied with blood vessels and sensi- 

 tive 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 tho 

 pododerm produces over its entire surface soft cells, which, pushed 

 away by more recent cells forming beneath, lose moisture by evapo- 

 ration and are rapidly transformed into the corneous material which 

 we call the hoof. It is proper to regard the hoof as a greatly thick- 

 ened epiderm, having many of the qualities possessed by such epi- 

 dermal 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 band, 

 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 glistening horn, which forms the surface of the wall, 

 or "crust," and whose purpose seems to be to retard evaporation of 

 moisture from the wall. (2) The coronary band, a prominent fleshy 

 cornice encircling 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 coro- 

 net produces 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, parallel 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 



