some Experiments in Climatological Physiology, 327 



realized in the experiments so far as the measurement of 

 dryness is concerned. 



In considering the phenomena of losses of weight through 

 evaporation from the skin, and losses of water and carbon 

 through the respiratory apparatus, the following conception 

 will be of service : — 



The human body is, within certain limits, a fairly well and 

 automatically regulated thermostat. In general it is immersed 

 in air of a lower, very rarely of a higher temperature. On 

 the principle of transfer of heat without change of state, 

 therefore, it would tend, if other factors did not operate, to 

 fall slightly below a certain critical value, say J£ c , in air of 

 lower temperature than the body, and to rise above this tem- 

 perature in air of higher temperature. The value of 3£ c is 

 peculiar to the individual and can be taken as having a 

 definite value only as the mean of a large number of 

 individuals. % c is thus somewhere about 37° C, or 98° to 

 99° F. 



In the mechanical and chemico-physical arrangements of 

 the human thermostat, however, actions supervene after about 

 say 30° 0. (S6° F.) is reached, which disturb those conditions 

 of thermogenesis and thermolysis which are necessary for the 

 thermostasis of the organism ; that is to say, the whole con- 

 dition tends thermostatically to become more or less labile. 



Within the limits of thermostatic stability the mechanism, 

 for the purposes of physical representation, may be regarded 

 thus : — 



Heat is generated within the organism, mainly by com- 

 bination of carbon with oxygen brought by the blood. This 

 carbon is eliminated chiefly by the means of the respiratory 

 apparatus. Water is also given out, in the form of vapour, 

 by the respiratory system. These two may be called the 

 chief elements of the respiratory losses. Besides these are 

 minor anthropotexic products which, from the merely quanti- 

 tative point of view, may be regarded as negligible. 



Besides these losses, there is loss, chiefly of water, through 

 the skin. For the purpose of representing this loss, we may 

 regard the skin as a porous wall backed by capillary vessels 

 by means of which the moisture is supplied. These capil- 

 laries, however, are profoundly affected both by physical 

 conditions without (e. g. by cold, produced by wind-cooling 

 or otherwise), and by physiological conditions within. 



The elimination of heat-energy from the body is effected, 

 where the surrounding air is cooler, by radiation, by con- 

 nection losses (since the film of air next the body is heated 

 and distributed by convection), and by the conversion of 



Z2 



