136 A BIOMETRIC STUDY OF BASAL METABOLISM IN MAN. 



are subject to widely different laws, and the difficulty of disentangling 

 their effects and subjecting them to calculation is often one of the most 

 serious obstacles in the experimental investigation of heat under the 

 controlled conditions of the physical laboratory. 



If one assumes the applicability of Newton's law to living organisms 

 it is evident that it might under special conditions reduce to a surface 

 law. Thus in 1898 Richet 29 wrote: 



"Supposons, en effet, qu'il s'agisse d'un corps inerte; sa radiation sera, 

 conforme*ment a la loi de Newton, e"gale a la difference des deux temperatures, 

 multiplied par sa surface S (t ') En supposant t t' constant, ou peu vari- 

 able, il s'ensuit que la radiation calorique est proportionnelle a la surface. Or 

 j'ai pu prouver que les chiffres calorime'triques expe"rimentalement obtenus 

 sont tels que 1' unite" de surface de*gage tou jours a peu pres la meme quantite" 

 de calories." 



In modern discussions of the body-surface law the question of the 

 nature of the integument is generally ignored. Yet in the earlier writ- 

 ings the nature of the surface received detailed consideration. 



This subject is discussed in detail by Richet, 30 who not merely 

 treats it from the comparative side but records experiments with 

 animals in normal condition, with shaved animals, and with those 

 whose fur had been smoothed down by a coating of oil or varnish. He 

 even gives the results of experiments with animals having white, gray, 

 and black coats, and claims differences in their heat loss. 31 



Since Newton's law is really a law of the rate of cooling due to 

 differences in temperature, it should be evident that its validity when 

 applied to organisms could be tested only by having all basal-metab- 

 olism determinations made under comparable conditions of internal 

 and external temperature. Certainly this can not be assumed of the 

 series of determinations on diverse organisms which are brought 

 together for comparison in substantiation of the body-surface law. 



Among the earlier physiologists who had not yet lost sight of the 

 true significance of Newton's law, studies of metabolism at varying 

 temperatures were seriously considered. When the influence of en- 

 vironmental temperature was studied, difficulties were immediately 

 encountered. In discussing the fact that certain animals show abnor- 

 mal relationships between the environmental temperature and their 

 body temperature, d'Arsonval 32 introduces the following significant 

 sentence : 



Cela tient eVidemment a ce que la surface rayonnante physiologique de 

 1'animal n'est pas constante comme sa surface physique. Aux basses tempe'ra- 

 tures, le phe'nom&ne se complique d'une constriction vasculaire pe'riphe'rique, 

 qui restreint conside*rablement le pouvoir rayonnant de 1'animal a egalite" de 



i9 Richet, Dictionnaire de Physiologic, Paris, 1898, 3, p. 130. 



80 Richet, La Chaleur Animale, Paris, 1889; see especially Chapter XI. 



31 Richet, loc. cit., p. 237. 



32 d'Areonval, Mem. Soc. de Biol., 1884, 8 ser., 1, p. 723. 



