196 



ARON. 



temperature. The whole lieat regulation consists therefore of a balance 

 between the production of heat by the chemical process of combustion 

 (the cliemical heat regulation) and the loss of heat by physical means 

 (the physical heat regulation). 



It lias been known for a long time that in a cold climate there is an 

 increased combustion of food stuffs, and an accelerated metabolism in 

 general. This increase of combustion which corresponds to the burning 

 of more coal in the furnace on a cold day, can be demostrated by estimat- 

 ing the amount of carbon-dioxide expired by an animal under the same 

 conditions at different temperatures. Kubner obtained the following 

 values in such an exjieriment on a guinea pig: 



Tempera- 

 ture of air. 



CDs in 1 

 hour, per 

 kilogram 

 of animal. 



°C. 



Grams. 



11 



2.15 



21 



1.77 



26 



1.54 



30 



1.32 



35 



1,27 



40 



1.45 



While these results are unquestionably correct, it would be wrong to 

 apply them to man for the following reason : A person living in an 

 atmospheric temperature below 30° to 35° C, by suitable clothing 

 protects the surface of the body against the loss of heat by conduction 

 or radiation. Since air is a very- bad conductor of heat, a layer of 

 stationary air protects the body against loss of heat, even if the sur- 

 rounding atmosphere has a lower temperature. Eubner has shown this 

 very clearly by an experiment performed on a dog. The animal with its 

 normal coat of hair was first kept at different temperatures and its heat 

 production estimated, then it was shaved and the heat production again 

 determined by the same method. 



The heat production calculated per kilogram of body weight was as 

 follows : 



Tempera- 

 ture of air. 



Dog with 



normal 



coat of 



hair. 



Dog 

 shaved. 



°C. 



Calories. 



Calories. 



20 



55. 9 



82.3 



25 



.51.2 



61.2 



30 



56.2 



52.0 



