HEAT REGULATION IN ANIMALS. 929 



The Action of the External Temperature also stands in close relation 

 to muscular work, namely to the question as to whether the chemical 

 heat regulation is independent of the muscular activity. .The heat 

 regulation, as is well known, is of two kinds, namely the chemical heat 

 regulation, which consists in a change in the metabolism and which man- 

 ifests itself as an increased heat production due to the increased metabo- 

 lism at low temperatures, and the physical heat regulation, which occurs 

 generally at higher temperatures and is caused by changes in the con- 

 ditions in the heat elimination of the thermal equilibrium. 



In regard to the chemical heat regulation, which will only be discussed 

 here, we must differentiate between cold-blooded and warm-blooded 

 animals. In the first the metabolism rises with an increase in the surround- 

 ing temperature, while in the second group the conditions are different. 

 The experiments of SPECK, LOEWY and JOHANSSON 1 on human beings 

 have shown that the lowering of the external temperature is without 

 influence upon the extent of metabolism (measured by the gas exchange) 

 only as long as all natural and non- voluntary movements of the muscles 

 are excluded; otherwise the metabolism is raised. A chemical heat regu- 

 lation, i.e., a rise in metabolism without noticeable movements of the 

 muscles, is not accepted in man, or at least it has not been proven. The 

 heat regulation, in man, at lower temperatures seems to be brought about 

 by the natural or reflex production of muscle action, nor has a chemical 

 heat regulation in the reverse sense, namely, a fall in the catabolism by 

 raising the external temperature, been shown in man. The investigations 

 of EYKMAN 2 upon inhabitants of the tropics also show the same result, 

 namely, that in human beings no appreciable chemical heat regulation 

 occurs. 



In animals the conditions are different so far as that a chemical heat 

 regulation in the true sense has been positively shown. The investiga- 

 tions of RuBNER 3 on various animals have shown that the reduction 

 of the external temperature with these, causes a considerable chemical 

 heat regulation by increasing the metabolism without any chill or shiver 

 movements. On sufficient cooling the temperature of the body may fall 

 irrespective of the increased metabolism, and at a certain limit of body 

 temperature the exchange of material becomes still lower with decreasing 

 temperature. According to RUBNER many animals can bear a temperature 

 of C. for days in absolute rest. If the natural muscular activity is 

 eliminated by poisoning with curare or by section of the spinal cord, then, 

 as shown by PFLUGER 4 and his pupils, the warm-blooded animal behaves 



1 Speck, 1. c.; Loewy, Pfluger's Arch., 46; Johansson, Skand. Arch. f. Physiol., 7. 



2 Virchow's Arch., 133, and Pfluger's Arch., 64. 



8 Arch. f. Hyg., 37, and Handbuch d. Hyg., Bd. 1, Leipzig, 1911. 

 4 See footnote 2, page 591. 



