INTERNAL WORK. 353 
simply for the sake of the heat produced is still an unsettled ques- 
tion and one which, for our present purpose, we need not pause 
to consider. As to the fact of the increase there is no question. 
CriticaL TEMPERATURE.—In early writings upon this subject 
the influence of external temperature in increasing or diminishing 
the heat production of the body was frequently spoken of as if it 
were of unlimited application, and the same idea has passed more 
or less fully into the popular literature of the subject. But little 
reflection is necessary, however, to show that this cannot be the 
case. Common observation teaches us that neither our own metab- 
olism nor that of our domestic animals, as roughly measured by 
the consumption of food, is affected, for example, by the difference 
between winter and summer to any such extent as would correspond 
to the difference in average temperature. Moreover, if every rise 
in external temperature diminished the heat production, there 
would be a temperature at which no heat production at all would 
occur and at which, therefore, life could exist without metabolism, 
which is a contradiction in terms. This extreme case renders clear 
the fundamental error of this view, viz., that of regarding the heat 
production as an end in itself and not as, substantially, an incident 
of the general metabolism. 
Carl Voit * was the first to demonstrate by exact scientific 
experiments the limits within which the influence of temperature 
upon metabolism (the so-called chemical regulation) is confined. 
His experiments were a continuation of those of Theodor (p. 351), 
and were made upon a man weighing about 70 kgs. and wearing 
ordinary clothing. After exposure for some time to the tempera- 
ture to be tested he passed six hours in the chamber of the respira- 
tion apparatus, fasting and in complete rest. During the six hours 
the excretion of carbon dioxide and nitrogen was as follows: 
Temperature.} Sogo, | Nitrogen ||Temperature| 2092 | Nitroged, 
eg. C. Grms. Grms. CBs Grms. Grms. 
4.4 210.7 4,23 23.7 164.8 3.40 
6.5 206.0 4.05 24.2 166.5 3.34 
9.0 192.0 4.20 26.7 160.0 3.97 
14.3 155.1 3.81 30.0 170.6 jee 
16.2 158.3 4.00 
* Zeit. f. Biol., 14, 57. 
