966 



NUTRITION AND HEAT REGULATION. 



deduced from the study of the energy given off in the oxidation of 

 the foodstuffs of the daily diet. They show that the adult when fast- 

 ing (basal metabolism) gives off heat from his body to the amount of 

 about 24 Calories per kilogram of weight during twenty-four hours, 

 that is, about 1 Calorie per hour per kilogram of body weight,* or, 

 expressed in another unit, about 40 Calories per hour per square 

 meter of skin surface. This amount is increased greatly under 

 conditions demanding much muscular work. This loss of heat is, 

 of course, made good by the production of an equal amount within 

 the body by the oxidation of the food material, f Actual experi- 

 ments upon different animals show that small animals produce more 



CAL 



YRS. 10 



Fig. 3016. Du Bois's figure to show the variation of basal metabolism with age. The 

 results are expressed in terms of calories per square meter of body surface per hour; the age is 



f'ven along the abscissa and the calories per square meter per hour along the ordinates. (From 

 .F. Du Bois, "American Journal of the Med. Sciences," June, 1916.) 



heat in proportion to their weight than larger animals of the same 

 species, owing to their relatively larger surface, and, therefore, 

 greater loss of heat. This fact has been expressed by Rubner in 

 what he calls his surface area law. According to this law the metab- 

 olism is proportional to the surface area, or for the same amount 

 of surface area there will be the same production of heat. He esti- 

 mates that in man there is produced in twenty-four hours for each 

 square meter of surface 1042 Calories. This important generaliza- 

 tion has been investigated with care by E. F. and D. Du Bois.J 



* Du Bois and Gephart and Du Bois, "Archives of Internal Medicine," 

 17, 887, 902, 1916; Benedict, et. al., "Journal of Biological Chemistry," 18, 

 139, 1914. 



fSee Rubner, "Zeitschrift f. Biologie," 19, 535, 1883; and "Gesetze des 

 Energieverbrauchs," 1902. 



t Du Bois, D. and E. F., "Archives of Internal Medicine," 15, 868, 1915, 

 and 17, 863, 1916. 



