320 



EXCRETION 



Properties and Composition of the Sweat. An analysis of the sweat 

 was made by Favre in 1853. After taking every precaution to obtain 

 the secretion in a perfectly pure state, he collected a very large quan- 

 tity, nearly thirty pints (14 liters), the result of six transpirations from 

 one person, which he assumed to represent about the average in compo- 

 sition. The liquid was perfectly limpid, colorless, and of a feeble but 

 characteristic odor. Almost all observers have found the reaction of 

 the sweat to be acid ; but it readily becomes alkaline on being subjected 

 to evaporation, showing that it contains some of the volatile acids. 

 Favre found that the liquid collected during the first half-hour of the 

 observation was acid ; during the second half -hour it was neutral or 

 feebly alkaline ; and during the third half-hour, it was constantly alka- 

 line. The specific gravity of the sweat is 1003 to 1004. 



COMPOSITION OF THE SWEAT (FAVRE) 



Water . . /; . .; . ' . .. 



Urea . . . . '. . . . . . . 



Fatty matters '. . .' . . 



Alkaline lactates . . . . . . " L f'Y 



Alkaline sudorates 



Sodium chloride. 



Potassium chloride, 



Alkaline sulphates, \ soluble in water 



Alkaline phosphates, 



Alkaline albuminates, 



Alkaline earthy phosphates (soluble in acidulated water) 



Epidermic ddbris (insoluble) 



99 5573 

 0043 



014 

 0.317 



1 562 



2 230 



o 244 



0012 



a trace 



o 005 



a trace 



a trace 



The sweat is exhaled usually in the form of vapor, when it is known 

 as insensible perspiration. When from any cause it collects on the sur- 

 face, in the form of a liquid, it is called sensible perspiration. 



The peculiar constituents of the sweat are the following : The 

 neutral fats probably are derived in great part from the sebaceous 

 glands, although certain fats, palmitin and stearin, have been found in 

 the secretion of the palms of the hands, which contain no sebaceous 

 glands. The volatile fatty acids are formic, butyric, caproic, capric, 

 acetic etc., some of which exist also in milk. These give to the sweat 

 its peculiar odor. Urea is always present in small quantity, and its 

 proportion may be largely increased when there is a deficiency in 

 elimination by the kidneys. It is a matter, also, of common as well 

 as of scientific observation that the sweat is more abundant when 

 the kidneys are comparatively inactive, and vice versa. Usually, how- 



