THE SKIN. 75 



In the dog, the sweat-glands are very perfect and largely 

 developed, and, strange to say, in this animal the sweat 

 passes off constantly in the form of vapour, and is never 

 condensed in the liquid form of the sweat of horses, cattle, 

 and other animals. The secretion of the skin is increased 

 by heat, a dry atmosphere, certain electrical conditions of 

 the air, diminished atmospheric pressure, exertion, pain, and 

 efforts of all kinds, and is then called sweat or sensible per- 

 spiration. Painful and debilitating diseases are often cha- 

 racterised by sweating, whereas many acute affections are 

 associated with dry skin and checked perspiration. 



The sweat has been analysed by a number of chemists. 

 Thenard and Berzelius found in it water, acetic and lactic 

 acid, organic matter, chloride of potassium and sodium, 

 phosphate of lime, and traces of iron. Anselmino found that 

 the perspiration in man contained in 1000 parts: 

 Water ..... 99500 

 Animal matters with lime . . 10 



Sulphates and substances soluble in water 1 05 

 Chlorides of sodium and potassium, and 



spirit extract . . . .240 



Acetic acid, acetates, lactates, and alcohol 



extract . . . .1-45 



The only difference that Anselmino could detect between 

 the perspiratory secretion of man and that of the horse, was, 

 the excess of phosphate of lime and animal matter in the 

 equine sweat. 



This secretion is stated by all to be acid ; but Colin found 

 that when sweat is dropping off the surface of an animal in 

 abundance, it is alkaline. Carbonic acid gas is thrown off 

 in considerable quantities from the surface of the body in all 

 animals. 



Although, to all appearances, an animal in a quiet state 



