ix THE SKIN AND CUTANEOUS GLANDS 495 



perfectly with Schierbeck's results. The subject of experiment 

 was enclosed in a metal box, so that only the head was outside. 

 The cutaneous transpiration of the rest of the body was deter- 

 mined at a temperature of 12-34 C. by estimating the content 

 of water and carbonic acid in the air that circulated through the 

 apparatus, and was entirely renewed every five minutes, the 

 quantity being measured by gasometers, before and after its 

 passage through the box. He found that when the body was 

 completely at rest the elimination of water increased slowly, and 

 in proportion with the temperature of the external air, which rose 

 from 12 C. to the point at which perspiration broke out, which 

 occurs between 30 and 33 C. 



The elimination of carbonic acid by the skin at a temperature 

 fluctuating between 20 and 33 C. is unaltered, provided the body 

 is completely at rest, and amounts to 7-8 grins, in 24 hours. But 

 when the temperature rises to the point at which sweat breaks out 

 (i.e. 33 C.) a rapid three- or four-fold rise in the discharge of C0 2 

 appears suddenly. 



The molecular concentration of human sweat was first studied 

 by Ardin-Delteil (1900) with the cryoscopic method. He found 

 that the freezing-point of sweat was always higher than that of 

 blood, on an average A = 0'237 0. It varies considerably with 

 the individual and the time of year : in the summer, when the 

 sudoriferous glands secrete much water for the purpose of regulat- 

 ing the temperature, the molecular concentration of the sweat falls 

 to A = 0'08 ; its maximum, on the contrary, may be A = - 46. 

 These oscillations are principally due to the varying content of 

 sodium chloride. The fact that sweat has a lower molecular con- 

 centration than the blood was also confirmed by Strauss (1901) 

 for the sweat collected from sick people and that obtained by 

 hot-air baths. The normal hypotonia of the secretion of the 

 sudoriferous glands, as compared with the normal hypertonia of 

 the renal secretion, witnesses to the different functions of the two 

 secretory processes, the former being mainly concerned with 

 excretion of water, the latter with excretion of the solid products 

 of metabolism. 



Experiments have been made to determine whether the sweat 

 has any toxic properties (Eohrig, Queirolo, Capitan and Gley, 

 Cabitto, Arloing, Charrin and Mavrojannis, Mairet and Ardin- 

 Delteil), but have not led to any consensus of results. Some 

 authors assert that there is a toxic action, but the majority 

 entirely deny the toxicity of normal sweat. 



IV. When the secretory activity of the sudoriferous glands 

 rises to the point at which it is manifested in the sensible form 

 of sweat, it is usually accompanied (as occurs with many other 

 secretions) by dilatation of the cutaneous vessels. The thermo- 

 regulatory function of the skin depends fundamentally on this 



