RUBNER'S LAWS OF GROWTH 525 



laboratory that the growth of pigs runs parallel with the 

 value in calories of the ingested food ; and analogous results 

 were obtained by Eost in case of young, growing dogs of the 

 same litter, fed on meat, fat and bone-ash. 23 Eubner has 

 succeeded by his careful and systematic studies in formulat- 

 ing certain rules characterizing the energetics of growth. 

 First, the law of constant consumption of energy, an 

 expression of the observation that the number of calories 

 necessary to double the weight of a newly born individual 

 (horse, cow, sheep, pig, dog, cat, rabbit), in spite of the 

 enormous difference in time consumed in attaining the 

 doubled weight, is practically the same for all species, 

 reckoned upon the unit of weight. The building up of one 

 kilogram of body substance requires about 4800 calories. An 

 exception is met in the case of man, in whom about six times 

 this amount is required. Man is exceptional in that, while 

 in the animals enumerated, of one hundred net calories in- 

 troduced about thirty-four are fixed (quotient of growth = 

 34), human beings are able to retain only about five. From 

 the law of constant consumption of energy it follows that the 

 shorter the period of development, the more actively must 

 the energy-metabolism take place. As, however, the amount 

 of the latter is, in accordance with Eubner 's views, to be re- 

 garded as a function of the surface area, we arrive at the 

 conclusion that the smaller the animals the more rapidly 

 must they grow. Eubner has, however, also attempted to de- 

 duce a rule covering the length of life. He calculated the 

 amount of energy which is consumed in a kilogram of living 

 protoplasm from the stage of full development to death, and 

 found this again constant for all domestic animals under in- 

 vestigation. But here, too, man occupies an exceptional posi- 

 tion, as human protoplasm is said to possess the capacity of 



23 C. Opppenheimer, Zeitschr. f . Biol., 42, 158, 1901 ; M. B. Wilson, Amer. 

 Jour, of Physiol., 8, 197, 1902; E. Host, Arb. a. d. kaiserl. Gesundheitsamt, 

 18, 206, 1902. 



