THE SWEAT. 345 



bonic acid and water, and in part, other matters which are 

 deposited on the skin, and mixed with the sebaceous secretion. 

 Thenard collected the perspiration in a flannel shirt which had 

 been washed in distilled water, and found in it chloride of 

 sodium, acetic acid, some phosphate of soda, traces of phos- 

 phate of lime, and oxide of iron, together with an animal sub- 

 stance. In sweat which had run from the forehead in drops, 

 Berzelius found lactic acid, chloride of sodium, and chloride 

 of ammonium. Anselmino placed his arm in a glass cylinder, 

 and closed the opening around it with oiled silk, taking care 

 that the arm touched the glass at no point. The cutaneous 

 exhalations collected on the interior of the glass, and ran 

 down as a fluid : on analyzing this, he found water, acetate of 

 ammonia, and carbonic acid ; and in the ashes of the dried 

 residue of sweat he found carbonate, sulphate, and phosphate 

 of soda, and some potash, with chloride of sodium, phosphate 

 and carbonate of lime, and traces of oxide of iron. Urea has 

 also been shown to be an ordinary constituent of the fluid of 

 perspiration. 



The ordinary constituents of perspiration, may, therefore, 

 according to Gorup-Besanez, be thus summed up : water, fat, 

 acetic, butyric and formic acid, urea, and salts. The princi- 

 pal salts are the chlorides of sodium and potassium, together 

 with, in small quantity, alkaline and earthy phosphates and 

 sulphates ; and, lastly, some oxide of iron. Of these several 

 substances, none, however, need particular consideration, ex- 

 cept the carbonic acid and water. 



The quantity of watery vapor excreted from the skin was 

 estimated very carefully by Lavoisier and Sequin. The latter 

 chemist inclosed his body in an air-tight bag, with a mouth- 

 piece. The bag being closed by a strong band above, and the 

 mouth-piece adjusted and gummed to the skin around the 

 mouth, he was weighed, and then remained quiet for several 

 hours, after which time he was again weighed. The differ- 

 ence in the two weights indicated the amount of loss by pul- 

 monary exhalation. Having taken off the air-tight dress, he 

 was immediately weighed again, and a fourth time after a cer- 

 tain interval. The difference between the two weights last 

 ascertained gave the amount of the cutaneous and pulmonary 

 exhalation together ; by subtracting from this the loss by pul- 

 monary exhalation alone, while he was in the air-tight dress, 

 he ascertained the amount of cutaneous transpiration. The 

 repetition of these experiments during a long period, showed 

 that, during a state of rest, the average loss by cutaneous and 

 pulmonary exhalation in a minute, is from seventeen to eigh- 

 teen grains, the minimum eleven grains, the maximum 



