610 THE SKIN AND ITS APPENDAGES [CH. XL. 



thus unilateral perspiration is sometimes seen in cases of hemi- 

 plegia; degeneration of the anterior nerve-cells of the cord may 

 cause stoppage of the secretion. 



The changes that occur in the secreting cells have been investi- 

 gated by Eenaut in the horse. When charged they are clear 

 and swollen, the nucleus being situated near their attached ends; 

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

 urine ; sodium chloride is the most abundant salt. Funke 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 protein 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 albuminous matter 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. 



Large quantities of water, by raising the blood-pressure, increase 

 the perspiration. 



Some substances introduced into the body reappear in the sweat, 

 e.g., benzoic, tartaric, and succinic acids readily, quinine and iodine 



