SWEAT. 375 



as an acid which is peculiar to it, and is called sudoric acid 

 (Favre). The reaction of the sweat is, therefore, generally 

 acid, and becomes still more so when the fatty substances 

 which it contains are decomposed, and allow their acids to 

 be set free. It is these fatty and volatile acids which impart 

 to the blood its acid odor, which differs greatly in different 

 persons, and also in different races of men. The sweat 

 always contains a small quantity of fat ; thus there are no 

 sebaceous glands in the palm of the hand, but numerous 

 sudoriferous glands, the product of which always contains a 

 certain proportion of fatty matter. The perspiration of some 

 parts (the glands of the arm-pit, and especially the cerumi- 

 nous glands) contains a much larger proportion of fats. Finally, 

 some nitrogenous matters, urea, among others, are found in 

 the perspiration ; if the decomposition of these products ex- 

 ceeds that of the fats, ammonia is produced, and the perspi- 

 ration becomes alkaline. The elimination of the urea, and, in 

 general, that of the products of combustion of the albumi- 

 noids is of sufficient importance to render the skin an emunc- 

 tory similar to the kidney, and which may supply its place in 

 some cases. We shall find that, in the normal state, two- 

 thirds of the nitrogen introduced into the organism is 

 eliminated by the urine ; the other third probably escapes, 

 partly by the lung, with the fecal matters, or through the 

 skin. 



The sudoriferous secretion was formerly supposed to be 

 only the evaporation of the fluid parts of the blood while 

 passing through the epidermis. The discovery of the sweat 

 glands has shown where this secretion is produced : in order 

 to understand the interior mechanism of the secretion of 

 these glands, the ceruminous glands must first be studied ; 

 we find that their thick and fatty product, cerumen, is pro- 

 duced by the imperfect melting of the globules of the gland ; 

 the perspiration of the armpit also is remarkable for the pro- 

 portion of solid matter, evidently arising from vegetation and 

 decay of the epithelium. We are thus led to believe that 

 the secretion of ordinary perspiration takes place in the same 

 manner, only by means of a far more perfect melting, and 

 borrowing a much larger quantity of water from the blood ; 

 thus, when the blood is unable to furnish a sufficient supply 

 of water, as in cholera, in which disease the water becomes 

 extremely thick, the perspiration itself becomes viscous, and 

 is known as the sticky sweat of cholera patients. 



This cellular moulting, or secretion, is chiefly produced by 



