496 ON INCREASE IN SIZE [pt. iii 



Averaging the whole of development, Rubner divided each of these 

 figures by 2, and, taking the duration of appreciable development at 

 six-tenths of the whole (the first four-tenths being a negligible 

 quantity), he multiplied each by six-tenths of the total gestation time 

 in days, thus: 



Thus I kilo of an imaginary animal (it would be very like a horse), 

 which weighed 50 kilos at birth, would eliminate 2631 Calories 

 during its whole gestation period, while i kilo of an imaginary 

 animal which weighed 6-25 kilos at birth would eliminate 2470 

 Calories, its relatively more intense heat output being compensated 

 for by its shorter gestation period. Rubner called this relation the 

 "fundamental law of intra-uterine developmental energy". 



In the above discussion, we were dealing with imaginary examples, 

 but Rubner calculated out the figures for actual animals, as follows : 



Average ... 2240 



Now if we assess the calorific value of the formed kilogram 

 of finished embryo at 1504 Calories, 2480 plus 1504 Calories, i.e. 

 3984 Calories, are required for the formation of i kilo of embryo 

 during intra-uterine life in the higher mammals. Rubner spoke of 

 a "growth-quotient" in this connection, defined as follows: 



Energy stored in the tissues x 100 

 Energy stored plus energy given off as heat * 



In the case of pre-natal life, it was 1500/4000, i.e. about 38 per cent. 

 There is a certain contradiction here between this efficiency datum 



