602 



JOHN K. MUKLIN 



2.5 to 3.5. In the case of the leech, the same factor, between 10 and 24, 

 is from 2.4 to 3.0 (Putter, A.). 



In living things the range within which any such law applies is neces- 

 sarily very narrow as compared with its range in inorganic reactions ; and 

 the factor (Qi ) varies, according to the best determinations which have 

 yet been made, very widely. Nevertheless, it may be said that the law 

 that the rate of chemical change (metabolism) varies with the temperature 

 of the living substance is a universal law for all animals and plants. As 

 applied to the production of heat in living things, this law would result 

 in a vicious circle (the temperature increasing the oxidation and the oxida- 

 tion increasing the temperature) which would rapidly destroy the living 

 substance itself, if special mechanisms did not exist for the removal of 

 the heat. Where these mechanisms break down, as in fevers, the heat 

 must be removed by artificial means. 



DuBois(fr) has recently shown that the metabolism of men in fevers in- 

 creases from" 30 to 60 per cent for a rise of three degrees (from 37 to 40 

 C.) and the value of Q 10 therefore is about 2.3. In other words the 

 metabolism in fevers obeys Van't Hoff's law. 



b. In Warm-blooded Animals.^ In warm-blooded animals with the 

 development of the capacity to regulate the body temperature indepen- 

 dently of the surrounding medium, Van't Hoff's law is apparently re- 

 versed, so that the lower the external temperature becomes the greater 

 is the heat production. This is necessarily the case if the body tempera- 

 ture is to be maintained. Confirming the original observation of Lavoisier 

 that more heat is produced in the human subject when the external tem- 

 perature is low, C. Voit(e) exposed a man in light clothing in his respira- 

 tion apparatus to different temperatures and found that, as the temperature 

 fell, the metabolism increased independently of any muscular motions. 

 Eubner(^) carried this line of investigation much farther, using dogs and 

 guinea pigs, and formulated his laws of the chemical and physical regula- 

 tion of the body temperature. In brief, these laws are : (1) That, from 

 a temperature of about 30 C. downward, the body temperature is regu- 

 lated chiefly by varying the heat production (chemical regulation). Heat 

 loss is regulated, to some extent, by decreasing the amount of blood brought 

 to the surface. (2) From 30 C. upward the body temperature is regu- 

 lated chiefly by varying the amount of water evaporated from the surface 

 (sweating) and again by decreasing the amount of blood brought, to the 

 surface (physical regulation). 



The conclusions of Voit and Rubner with regard to the effect of cold 

 as such have frequently been called in question, the contention being that 

 even if visible shivering and increased tonus of the muscles are avoided 

 no more heat is produced at low temperature. Lusk(&) found that a man 

 immersed for a few minutes in a cold bath at 8 C. would, immediately 

 thereafter, shiver enough to increase his metabolism 180 per cent above the 



