816 



SCIENCE 



[N. S. Vol. XLII. No. 1093 



THE CALORIMETER AS TEE INTERPRETER 

 OF THE LIFE PROCESSES^ 



Shortly after the outbreak of the pres- 

 ent war a scientific commission in Berlin 

 reported that the quantity of energy units 

 required during a year by 68,000,000 in- 

 habitants in Germany amounted to about 

 57 thousand million calories, and that 

 under changed conditions of dietary hab- 

 its 81 thousand million calories would be 

 available. In accordance with the require- 

 ments of the crisis the habits of the people 

 were changed. 



Our own Commission for Relief in Bel- 

 gium forwarded food on the basis of the 

 knowledge that 1,000 calories in cornmeal 

 cost 11 mills, in wheat 14 mills, in rice 18 

 mills, in wheat flour 20 mills, in beans 29 

 mills, and in pork "fat backs" 28 mills. 



All this was the world's recognition of 

 the need of fuel for the life processes in 

 human beings. 



Rubner's work has made it possible to 

 picture the energy liberated in various 

 forms of living things. Thus Rubner esti- 

 mates that a horse requires 11 calories per 

 kilogram per day in order to maintain the 

 normal life processes and for the fulfilment 

 of the same necessities a man requires 30 

 calories per kilogram of body weight, a 

 newborn mouse weighing one gram requires 

 654 calories per kilogram while a yeast 

 cell weighing 0.000.000,000,5 gr. produces 

 1,743 calories per kilogram of substance, 

 this also being the heat produced by a kilo- 

 gram of diphtheria bacilli. The energy 

 production in these lower forms of life was 

 measured by determining the rise in tem- 

 perature of the medium in which they lived 

 when this was confined within the limits of 

 a Dewar flask. The heat production of a 

 kilogram of yeast thus measured was three 

 fold that found for the same unit of mass 



1 Read at the New York meeting of the Na- 

 tional Academy of Sciences, November 16, 1915. 



in a newborn mouse, 58 times that of a man 

 and 157 times that of a horse. 



Although these values appear to be ex- 

 tremely variable, there is one unit of meas- 

 urement which in mammalia is quite con- 

 stant and that is the heat production per 

 square meter of surface. Bergmann, in 

 1848, was the first to advance this hypoth- 

 esis and a year later the French observers 

 Regnault and Rieset stated that the heat 

 production of sparrows per unit of weight 

 was ten fold that of fowls, a phenomenon 

 which they asserted was due to the fact 

 that the smaller animals present a rela- 

 tively larger surface to the surrounding 

 air and thereby experience a considerable 

 chilling, with the consequent generation of 

 sufficient heat to maintain the normal bodj' 

 temperature. In 1883, Rubner published 

 calculations which showed that the heat 

 production of mammalia of various shapes 

 and sizes was the same per square meter of 

 surface. Figures are given such as 1,042 

 calories for man, 1,039 for the dog and 

 1,122 calories for the new-born mouse per 

 square meter of surface during periods of 

 24 hours when the temperature of the envi- 

 ronment is 15° C. and when moderate 

 voluntary movements are permitted. 



Further analysis showed Rubner that 

 this evenness of heat production per unit 

 of body surface was not due to any rela- 

 tion between the area of bod.v surface and 

 the area of cell surface within the organ- 

 ism. There are in one kilogram of body 

 weight of man 150.2 square meters of such 

 surface and each square meter of cell sur- 

 face produces 0.2 calories per day. In the 

 new-born mouse each square meter of cell 

 surface produces eleven times this amount 

 or 2.2 calories. It is of interest, also, to 

 note that a kilogram of yeast cells presents 

 a surface area of 600 square meters and 

 at a temperature of 38°, or that at which 

 mammalian cells exist, 1.25 calories per 



