PERSPIRATION AND SWEAT. 523 



2. A second portion was digested over oxide of lead, and the 

 digestion continued in an open vessel till all the liquid had been 

 driven off. The dry residue being moistened with sulphuric acid, 

 fumes of acetic acid were given out recognizable by the smell. 



3. Lime-water was added drop by drop to the third portion- 

 It became muddy, and carbonate of lime was deposited. From 

 these experiments Anselmino concluded that the matter of per- 

 spiration contains acetate of ammonia and carbonic acid. 



Collard de Martigny assures us that the skin not only gives 

 out carbonic acid gas, but also hydrogen gas and azotic gas, 

 though in very minute quantity.* But how far these statements 

 are correct we do not at present know. 



When the temperature of the body is increased either by ex- 

 posure to a hot atmosphere or by violent exercise, the matter of 

 perspiration not only increases in quantity, but even appears in 

 a liquid form. This is known by the name of sweat. This sweat 

 serves a very important purpose. No sooner is it thrown on the 

 surface of the skin than it begins to evaporate, absorbs heat, and 

 thus the temperature of the body is prevented from rising. This 

 is the reason that animals can endure a much higher tempera- 

 ture without injury than could have been supposed. The expe- 

 riments of Tillet, and the still more decisive experiments of For- 

 dyce and his associates, are well known. These gentlemen re- 

 mained for a considerable time in a room, the atmosphere of 

 which was hotter than boiling water. 



Sweat is a transparent and colourless liquid, having a saline 

 taste, and yielding, when evaporated, crystals of common salt. 

 According to Berzelius, it contains the same salts as those which 

 exist in the acid liquor obtained from animal muscle by expres- 

 sion ; namely, lactates of potash, soda, lime, and magnesia, to- 

 gether with common salt, sal-ammoniac, and traces of chloride 

 of potassium. It contains also traces of phosphate of soda and 

 phosphate of lime. It contains also a small quantity of animal 

 matter insoluble in alcohol. 



Anselmino examined a quantity of sweat collected by sponges 

 from the body of a man made to sweat abundantly in a hot stove. 

 The liquid thus obtained was muddy, probably from small por- 

 tions of the epidermis detached by the friction. It had a pecu- 

 liar smell, varying in intensity in different individuals. A por- 



* Berzelius, Traite de Chimie, vii. 325. 



