656 PHYSIOLOGY CF THE DOMESTIC ANIMALS. 



inorganic salts. Olein and palmatin are the principal representative 

 fatty bodies, phosphatic earths and chlorides, and salts. The wool of 

 the sheep contains a fatty potassium salt which is soluble in water, and 

 which constitutes at least one-third in weight of raw merino wool. 



The function of the sebaceous secretion is to act as a lubricant to 

 the skin and epidermal appendages. 



3. Cutaneous Absorption. — -When the body is plunged in a liquid 

 medium, as into a bath, a considerable amount of water is absorbed by 

 imbibition through the epithelium. Prom there it is able to pass by 

 absorption into the vessels which circulate through the superficial layers 

 of the derm, and from there into the general blood-current. This state- 

 ment may be demonstrated by the increase in weight which, as a general 

 rule, follows immersion in fluid. The result of such an immersion will, 

 however, vary according to the temperature of the fluid. When the 

 temperature of the bath is above that of the body, the increased secretion 

 from the skin will more than counterbalance the gain in absorption, and, 

 as a consequence, the weight of the body may be decreased. If, on the 

 other hand, the temperature of the bath is lower than that of the body, 

 the body may gain in weight through the absorption of water. The 

 epidermis is, nevertheless, not equally permeable by substances brought 

 into contact with it. And this interference with absorption is also 

 increased by the sebaceous secretion of the skin. Substances held in 

 solution in water are accordingly absorbed but to an extremel}' slight 

 extent, unless this immersion be so prolonged as to permit of softening 

 of the epidermis. 



Absorption through friction of the skin surface with different sub- 

 stances, especially when suspended in a fatty excipient, is to be explained 

 by the mechanical forcing of such substances into the sebaceous glands, 

 and, it may be, even into the interstices of the epidermal cells. Thus; 

 friction with tartar emetic suspended in oils may produce vomiting, 

 with mercury may produce salivation, and with belladonna dilatation 

 of the pupil. 



Abrasion of the skin leads to a marked increase in its facility for 

 absorption. 



4. Cutaneous Respiration. — The skin of man and animals in whom 

 the skin is bare offers a certain analogy to the lungs in that it is abunt 

 dantly supplied with blood-vessels which are nearly in contact with the 

 external atmosphere. It is, therefore, conceivable that through the skin 

 there may be an interchange between the gases of the atmosphere and 

 blood. Experiments show this to be a fact. If the body be inclosed in 

 an air-tight chamber extending to the neck, and after a time the air 

 within this chamber be analyzed, it will be found that it will have 

 decreased in the amount of oxygen and gained in carbonic acid. The 



