Respiration and Metabolism 



24B 



reflecting an intrinsic activity or nutritive cycle, has been claimed for the 

 catfish— measured, although not necessarily maintained, under conditions of 

 total darkness and constant temperature and water flow. A consistently higher 

 oxygen consumption (about 50 per cent) was demonstrated in the afternoon 

 and evening, compared with that of the forenoon.'"^ Depressions in the oxygen 

 consumption correlated with both temperature changes and food shortage have 

 been pointed out in various warm-blooded animals. The chicken, for instance, 

 has a metabolic maximum in the morning (78° F., air tem^ierature) and a low 



.28 



1 .24 



E 

 E 



.20 



.16 



Q. 



2 



(A .12 



z 



O 

 O 



.08 - 



.04- 



MELANOTUS 



.010 



.008 



.006 - 



.004 



.002 



TALORCHESTIA 



30 400 300 



BODY WEIGHT (mgmt.) 



200 



100 



Fig. 54. Oxygen consumption in click beetles, Melanotus, and beach fleas, Talorchestia, 

 of different weights, showing the greater response of the smaller individuals to tempera- 

 ture change. After Edwards.^'^^ 



at evening (61° F.).-° Koskimies-"-* has recently shown that under conditions 

 of partial starvation swifts (Micropiis a. apus) become poikilothermic— the body 

 temperature drops in the early morning hours to within 2-3° C. of the external 

 temperature, respiratory breathing rate falls from about 40 to 10 per minute, 

 and the oxygen consumption decreases proportionately. The sloth '^*^ too tends 

 toward poikilothermy as a respiratory increase accompanies a temperature rise 

 from 33° to 37° C. All things considered, it becomes increasingly evident that 

 many mammals and birds show marked changes in internal temperature and 



