612 JOHN R. MURLIN 



who had metabolic rates beyond the normal limits established by DuBois 

 which could not be accounted for by the presence of a definite pathologic 

 condition." 



This truly phenomenal uniformity of heat production, quite equal to the 

 uniformity of body temperature in normal subjects, has been explained in 

 various ways. Rubner following Bergman and Regnault and Reiset at- 

 tempted to bring the heat production into causal relationship with heat 

 loss as we have seen (p. 599). This attempted explanation has not been 

 wholly satisfactory for the reason that, as Lefevre has shown, physiological 

 adjustments can be made by the skin which greatly modify the applica- 

 tion of Newton's law of cooling. Rubner himself, therefore, is obliged to 

 postulate "similar physiological conditions" (page 599) and to assume that 

 the minimal metabolism (basal) cannot undergo rapid changes but is 

 adapted to the usual conditions regarding loss of heat which the animal has 

 to meet. V. Hoesslin(&) has subjected the hypothesis of Rubner to a se- 

 vere test by keeping two exactly similar- young dogs for a long time under 

 widely different temperatures and determining their resting metabolism at 

 the end. The rate of heat loss must have been continuously very different 

 for the coats of hair at the* beginning were the same. Later it became 

 thicker on one dog and thinner on the other in very obvious response to the 

 conditions of heat loss to which they were subjected. But the basal 

 metabolism was not altered. 



V. Hoesslin himself considers that the metabolism of a tissue depends 

 upon the supply of oxygen, that the circulation (and consequently the oxy- 

 gen supply) must for anatomical reasons be proportional to the two-thirds 

 power of the weight (i. e., to surface) and that the correlation of energy 

 exchange with surface finds its explanation in these purely mechanical 

 conditions. Dreyer, Ray and Walker have given some plausibility to this 

 view by the discovery that in both mammals and birds the blood volume, 

 the sectional area of the aorta and of the trachea in animals of different 

 size are proportional to the two-thirds power of the weight. The trend 

 of this view is wholly away from the teleological view outlined at p. 602 

 in connection with the subject of heat loss, and probably more correctly 

 reflects the attitude of the modern mechanistic physiology. 



Dreyer has more recently attempted the application of a more general 

 formula to the normal basal metabolism and has compared the results 

 found with those obtained by the more elaborate prediction formula of Har- 



W n 



ris and Benedict. His formula is K = where W is the 



^ X A 



weight, n approximately 0.5, C is calories of basal metabolism, and A the 

 age in years. Table 22 shows that he gets a somewhat more concordant 

 result than is obtainable with the prediction formula. 



2. Influence of Age on Basal Metabolism. DuBois (a) first assembled 

 the data for the influence of time of life from birth to old age upon the 



