SKIN 585 



Adrenalin causes so powerful a contraction of the cutaneous 

 vessels that any stimulating action it may have upon the sweat 

 glands is masked. The action of heat seems also to be chiefly 

 peripheral, setting up an unstable condition of the gland cells so 

 that they respond more readily to stimulation. 



4 Chemistry of Sweat. — Sweat from the horse is a sherry- 

 coloured fluid, which, when pure, has a neutral or faintly 

 alkaline reaction. Its specific gravity is about 1020 in the 

 horse, and it contains about 5"5 per cent, of solids, of which 

 5 per cent, are inorganic and about 5 organic. When the 

 sweat dries on the coat a white deposit is left. Potassium is the 

 most abundant base. Chlorides are present in small amounts. 

 The chief organic substances present are proteins — some 

 globulin and some albumin. Fat is also present, probably 

 derived from the sebaceous secretions, and it combines with the 

 potassium to form a soap. 



B, Sebaceous Glands. 



The sebaceous glands are simple racemose glands which 

 open into the hair follicles, and their function is to supply 

 an oily material to lubricate the hairs. This secretion is pro- 

 duced by the shedding and breaking down of the cells formed 

 in the follicles of the glands. Those lining the basement mem- 

 brane are in a condition of active division, but the cells thrown 

 off into the lumen of the follicle disintegrate and become con- 

 verted into a semi-solid oily mass, which consists of free fatty 

 acids and of neutral glycerol and cholesterol fats. These 

 cholesterol fats are the lanolins, which differ from ordinary 

 fats in being partly soluble in water. Free cholesterol is also 

 present in the sebum. 



Grooming.— This is of great importance in the horse. It 

 removes salts of the sweat, shed epithelium, and loose hairs and 

 dirt. It prevents the development of mange and of lice, and it 

 acts as a form of massage to the skin and subjacent muscles. 



