6 RESPIRATORY MECHANISMS 



groups, is shown in Fig. 1. In several cases the increase in 

 metabolism with temperature is even larger than expressed 

 by this curve. 



When studied at increasing temperature the metabolism 

 will be found to increase according to the individual curve 



25' 



Fig. 1. The relation between temperature and resting metabolism in a 

 frog, toad, goldfish, mosquito and a young dog. Ordinate in arbitrary units. 

 (Krogh.) 



only up to a certain point. Beyond that there is usually only 

 a slight further increase and then a definite irreversible drop, 

 indicating that the high temperature is harmful and rapidly 

 fatal. 



The influence of activity. The effects on the call for oxygen 

 so far discussed are from the point of view of the efficiency of 

 respiratory organs of secondary importance only, because they 

 affect the minimum requirements, and the respiratory organs 

 must be able to meet the maximum requirements during 

 activity. These requirements are not known, even approxi- 

 mately, except in a small number of cases. 



We can state generally that the possible rate of sustained 

 activity stands in some relation to the body temperature. 

 This is common knowledge as regards, for instance, flies or 



