i'8 FIRST PRINCIPLES. 



bodily heat by radiation, and thus protects the body to some 

 extent from chill. As a full supply of this oil is not secreted 

 in many diseased conditions, the presence of the gloss which 

 it gives to the coat is justly regarded as a valuable indication 

 of good health. The more blood is brought to the skin by 

 exercise and good grooming, the more plentiful will be the 

 secretion of this oil. 



5. To form epidermis, which is the general term for hair, 

 cuticle, and horn, all of which are varieties of the scaly 

 material (epithelium) formed by the true skin. Epidermis 

 acts mechanically in protecting the body from injury. The 

 short hair of the body of a horse is a protection against cold, 

 and to some extent against irritating objects, such as flies. 

 The duty of the long hairs of the tail, mane, and forelock is 

 chiefly defensive, especially against insects. The long hairs 

 of the muzzle serve almost entirely as feelers. 



Dandruff consists of loose scales of the outer skin (cuticle), 

 and of oil secreted by the skin. The cuticle and its dandruff 

 act like hair in protecting the skin against cold and against 

 irritation from external objects. Dandruff, on the other hand, 

 forms a comfortable nest for insects. 



CAUSES WHICH AFFECT EPIDERMAL GROWTH. 



Comparison between the winter and summer coats of horses 

 and other animals, proves that cold, which reduces the supply 

 of blood in the surface of the body, has a stimulating effect 

 on the growth of the epidermis. In seeking for an explana- 

 tion of this apparent anomaly, we must examine the manner 

 in which cold affects the respective processes of supply and 

 removal of this structure. Epidermis receives its nourish- 

 ment from lymph (fluid portion of the blood) supplied by the 

 blood vessels of the true skin. As it possesses no blood 

 vessels, its removal cannot be effected by means of the bloocl ; 

 but is accomplished by exfoliation, and by contact with 



