822 THE POPULAR SCIENCE MONTHLY. 



The following passage from Lehmann's " Physiological Chemistry," 

 vol. ii, page 389, shows that the skin picks up plenty of nitrogen from 

 somewhere : " It has been shown by the experiments of Milly, Jurine, 

 Ingenhouss, Spallanzani, Abernethy, Barruel, and CoUard di Martigny, 

 that gases, and especially carbonic acid and nitrogen, are likewise 

 exhaled with the liquid secretion of the sudoriparous glands. Accord- 

 ing to the last-named experimentalist, the ratio between these two 

 gases is very variable ; thus, in the gas developed after vegetable 

 food, there is a preponderance of carbonic acid, and, after animal food, 

 there is an excess of nitrogen. Abernethy found that on an average 

 the collective gas contained rather more than two thirds of carbonic 

 acid and rather less than one third of nitrogen." But it appears that 

 less gas is exhaled when there is much liquid perspiration. 



Lehmann's summary of the experiments of Aberaethy, Brunner, 

 and Valentin (vol. ii, page 391), gives the amount of hourly exudation, 

 under ordinary circumstances, as 50 "71 grammes of water, 0*25 of a 

 gramme of carbon, and 092 of a gramme of nitrogen. This amounts 

 to twenty-one and a half grammes of nitrogen per day in the insensible 

 perspiration ; three quarters of an ounce avoirdupois, or as much ni- 

 trogen as is contained in four and a half ounces of dried muscle, or 

 more than one pound of natural living muscle. 



That the liquid perspiration contains compounds of nitrogen, and 

 just such compounds as would result from the degradation of nitroge- 

 nous tissue, is unquestionable. As Lehmann says (vol. ii, page 389), 

 " the sweat very easily decomposes, and gives rise to the secondary for- 

 mation of ammonia." Simon and Berzelius found salts of ammonia in 

 the sweat ; that the ammonia is combined both with hydrochloric acid 

 and with organic acids ; that it probably exists as carbonate of ammo- 

 nia in alkaline sweat. 



The existence of urea in sweat appears to be uncertain ; some 

 chemists assert its presence, others deny it. Favre and Schottin, for 

 example, who have both studied the subject very carefully, are at 

 direct variance. I suspect that both are right, as its presence or ab- 

 sence is variable, and appears to depend on the condition of the sub- 

 ject of the experiment. 



Favre describes a special nitrogenous acid which he discovered in 

 sweat, and names it hydrotic or sudoric acid. Its composition cor- 

 responds, according to his analysis, to the formula CjoHglSrOjj. 



I have summarized these facts, as they show clearly enough that 

 conclusions based on an examination of the quantity of nitrogen ex- 

 creted by the kidneys alone (and such is the sole basis of the modern 

 theories) are of little or no value in determining whether or not mus- 

 cular work is accompanied with degradation of muscular tissue. The 

 well-known fact that the total quantity of excretory work done by the 

 skin increases with muscular work, while that from the kidneys rather 

 diminishes, indicates in the plainest possible manner that an examina- 



