A CRITIQUE OF THE BODY-SURFACE LAW. 133 



consumption is proportional not to the body-surface but to the area 

 of the lung-surface. 



A careful study of the large mass of literature on metabolism subse- 

 quent to 1883 will show that there has been at no time a fixed inter- 

 pretation of the relationship between body-surface and heat-production. 

 Even the most ardent advocates of the body-surface law have at times 

 called attention to noticeable abnormalities. But attempts were made 

 to explain these discrepancies by the nature of the integument, the 

 density of the fur and hair coverings, and variations in the amount of 

 body-surface exposed. 17 



To attempt to review in any detail the extensive discussions of the 

 earlier writers would be a useless task. 



Unfortunately many modern authors are not so conservative in 

 their expressions as to the cause of this relationship between body- 

 surface and heat-production as were earlier students. The attitude 

 maintained in more recent times may be illustrated by the following 

 quotations. In his deservedly oft-cited contribution on respiration in 

 Schaefer's Physiology, Pembrey says : 1S 



"Now, small mammals and birds have a temperature equal to or even 

 higher than that of large animals of the same classes; and, on account of the 

 relatively greater surface which they expose for the loss of heat, they must 

 have a relatively far greater production of heat than the large animals, for 

 there is generally no marked difference in the protective coat of fur orfeathers." 



While Minot 19 does not explicitly state that heat-loss and heat- 

 generation are determined by body-surface, his comparison and dis- 

 cussions would seem to have this implication. 



The range of applicability over which Rubner himself would con- 

 sider the surface law valid is perhaps indicated by a quotation from a 

 paper of 1908, 20 in which he discusses the metabolism of various 

 mammals after birth. Referring to the values used, he says : 



"Wenn es auch nicht immer Neugeborene waren, die der Stoffwechsel- 

 untersuchung unterzogen sind, so wissen wir auf Grund des von mir enviesenen 

 Oberflachengesetzes, dass bei den Saugern ihr Stoffwechsel nicht des Masse, 

 aber genau der Oberflache proportional verlauft. Man kann daher die 

 gewiinschten Grossen des Energieverbrauchs fur jede beliebige Kleinheit der 

 Thiere, also auch fur die Neugeborenen, durch Rechnung finden." 



Lefevre specifically states that the application of the law of Newton 

 to living animals is illusory, 21 but in his discussion of the production 

 of heat per unit of surface the following statement appears : 22 



17 For example, we frequently find in the text of the earlier writers such statements as the 



following: " Warmeabgebende Flache und Hautfluche sind zwei sehr verschiedene 

 Dinge." Rubner, Beitrage zur Ernahrung im Knabenaiter mit besonderer Beriicksicht- 

 igung der Fettsucht, Berlin, 1902, p. 40. 



18 Pembrey, Schaefer's Text-Book of Physiology, London, 1893, 1, p. 720. 



19 Minot, The Problem of Age, Growth, and Death, New York, 1908, pp. 18-20. 



:o Rubner, Sitzungsb. d. Kgl. Preuss. Akad. d. Wissensch., phys.-math. Kl., 1908, p. 36. 



21 Lefevre, Chaleur Animale et Bioenergetique, Paris, 1911, p. 379. 



22 Lefevre, loc. cit., p. 500. 



