BIOMETRIC STANDARDS IN HUMAN NUTRITION 395 



where h total heat production in calories per twenty-four 

 hours, h ]c = calories per kilogram of body weight, h== calories 

 per square meter of body surface, as estimated by the Du Bois 

 height-weight chart. These lines are represented in the three 

 diagrams of Fig. 5. While the actual mean heat productions are 

 distributed about these lines with very great irregularity be 

 cause of the small number of individuals (considered from the 

 statistical, not from the physiological, side) it is doubtful 

 whether equations other than those for straight lines could be 

 advantageously employed. 



These equations show that in men the daily heat production 

 decreases about 7.15, while in women it decreases about 2.29 

 calories per year. Women are smaller than men and have a 

 lower heat production. When the decrease in metabolism with 

 age is expressed in calories per kilogram of body weight or in 

 calories per square meter of body surface, the results for the 

 two sexes are more nearly identical. The linear nature of the 

 change in metabolism with age during the period of adult life 

 fully substantiates the conclusions of biological writers concern 

 ing the greater continuity of senescence in the vertebrates as 

 compared with lower organisms. It also shows that during 

 adult life senescent changes take place at a sensibly uniform 

 rate. 



Throughout the entire history of the investigation of the 

 metabolism of the warm-blooded animals, the question of the 

 relationship between the body surface area of the organism and 

 its heat production has been a center of interest. Even before 

 the development of adequate experimental methods of investi 

 gating the energy transformation which takes place in the body 

 of the vertebrate organism, the possible relationship of body 

 surface area to heat production was a subject of speculation. 

 Physiologists recognized that a whale or an auk in the arctic 

 exposes relatively far less surface for the loss of heat than a 

 flying fish or a humming bird in the tropics. Attempts were 

 consequently made to explain the relatively higher food require 

 ments of small as compared with large animals by the relatively 

 larger surface exposed for heat loss in small organisms. 



Newton s law of cooling made a strong appeal to the imag 

 ination of earlier physiological writers. It is not surprising 

 that, impressed as they were by the relative constancy of body 

 temperature in the warm-blooded animals, they conceived of 

 heat production as proportional to heat loss as a means of main 

 taining constant body temperature, and came to look upon heat 

 loss as determined by body surface area, and to consider heat 

 loss as determining in its turn heat production. 



