62 THE PROTECTIVE STRUCTURES OF THE FOOT. 



stratum corneurn. The deepest layer of the stratum mal- 

 pighii, that lying next to the corium, is a very active 

 layer, tlie elements are capable of dividing and giving origin 

 to otliers that go to take the place of those constantly 

 being shed. Moreover, from this layer any loss of epidermis, 

 as in a wound, is made good. Further, from the cells of this 

 layer all the epidermal appendages are derived, as we shall 

 presently explain. 



During the passage of the cells, derived from the actively grow- 

 ing cells of the stratum malpighii, to the surface, various changes 

 occur in them. Their substance is converted into a horny material, 

 they apparently lose their nuclei, they become flattened and more 

 or less dissociated. Eventually, they are lost as scurf. The 

 epidermis of the domestic animals generally is not so thick as 

 that of man, nor can it be shown to consist of so many well- 

 marked layers ; this masking is due to the amount of pigment 

 contained in the epithelial cells, and the finer differentiating 

 details are thereby lost. 



The corium is composed of a felted mass of connective tissue 

 (both white and yellow varieties are present, the former in 

 greater amount), and it contains blood-vessels, nerves, lym- 

 phatics, etc. A certain amount of fat, too, is present, occupying 

 the interstices of the connective tissue and mostly near the 

 blood-vessels, but fat is not abundant in the corium proper ; it 

 is below the corium in the subcutaneous tissues that the great 

 mass of adipose tissue seen in some animals, as the ass, is 

 <leposited. Here it forms the panniculus adiposus. 



The corium, from its structure, is elastic ; the suppleness and 

 the power of accommodation possessed by the skin is due 

 entirely to this feature. The blood-vessels are very numerous, 

 and the capillaries in the superficial parts of the corium are 

 extremely close set and complicated. Much blood is required in 

 this position owing to the non-vascularity of the epidermis, 

 which must draw its nourishment indirectly from the blood- 

 vessels of the corium. When we consider the rapidity of growth 

 of the epidermis, as evidenced by the constant call upon it for 

 the renewal of the hair, the renovation of the hoof, and the 

 amount of scurf lost daily, we must conclude that the supply 

 of nourishment required is great. Again, the corium possesses 

 nerves, and many of the nerves end here in special structures 



