CH. XXXVIII. ] THE SWEAT 581 



when discharged they are smaller, granular, and their nucleus is 

 more central. 



The sweat, like the urine, must be regarded as an excretion, the 

 secreting cells eliminating substances formed elsewhere. 



Composition of the Sweat. Sweat may be obtained in abundant 

 quantities by placing the animal or man in a closed hot-air bath, or 

 from a limb by enclosing it in a vessel made air-tight with an elastic 

 bandage. Thus obtained, it, is mixed with epidermal scales and a 

 small quantity of fatty matter from the sebaceous glands. The con- 

 tinual shedding of epidermal scales is in reality an excretion. 

 Keratin, of which they are chiefly composed, is rich in sulphur, and, 

 consequently, this is one means by which sulphur is removed from 

 the body. 



The reaction of sweat is acid, and the acidity, as in the urine, is 

 due to acid sodium phosphate. In profuse sweating, however, the 

 secretion usually becomes alkaline or neutral. It has a peculiar 

 and characteristic odour, which varies in different parts of the body, 

 and is due to volatile fatty acids; its taste is saltish, its specific 

 gravity about 1005. 



In round numbers the percentage of solids is 1*2, of which 0'8 

 is inorganic matter. The following table is a compilation from 

 several analyses : 



Water . . 98*88 per cent 



Solids . .1-12 



Salts . .0-57 



NaCl . . 0-22 to 0-33 



Other salts .0-18 (alkaline sulphates, phosphates, 



lactates, and potassium 



chloride) 

 Fats . .0-41 (including fatty acids and 



isocholesterin) 



Epithelium . 0'17 



Urea . . 0'08 



The salts are in kind and relative quantity very like those of the 

 urine. Eunke was unable to find any urea, but most other observers 

 agree on the presence of a minute quantity. It appears to become 

 quickly transformed into ammonium carbonate. The proteid which 

 is present is probably derived from the epithelial cells of the 

 epidermis, sweat-glands, and sebaceous glands, which are suspended 

 in the excretion; but in the horse there is albumin actually in 

 solution in the sweat. 



Abnormal, Unusual, or Pathological Conditions of the Sweat. 



Drugs. Certain drugs (sudorifics) favour sweating, e.g., pilocarpine, 



Calabar bean, strychnine, picrotoxine, muscarine, nicotine, camphor, 



ammonia. Others diminish the secretion, e.g., atropine and morphine 



in large doses. 



