970 ENERGETICS AND ENERGY-SOURCES [pt. iii 



which, multiplied by loo, is the percentage efficiency. This they 

 termed the "rendement energetique brut", or "apparent energetic 

 efficiency" (A.E.E.). They proceeded to point out, however, that 

 this A.E.E, involves a fallacy, for it does not take into account the 

 basal metabolism — and only if this is done can the "rendement 

 energetique reel" be computed. Tangl's Ea., as has been pointed out, 

 is only a measure of the total embryonic catabolism. In just the same 

 way the "rendement energetique brut" fails to allow for the fact 

 that some of the energy absorbed by the embryo is expended in basal 

 metabolism, maintenance energy, "energie d'entretien", etc., to 

 which the embryo is committed by the mere circumstance of being 

 aHve at all. Thus of the energy in the material combusted only a 

 certain fraction ought really to be included in the calculation of the 

 efficiency, for the rest is earmarked for the upkeep of that part of 

 the building already constructed. The "rendement energetique brut" 

 does not take into account the fact that every cell embarks upon a 

 basal metabohsm as soon as it is completed. A calculation of the 

 true growth energy must therefore allow for this, according to the 

 following formula : 



Energy laid up in the organism 

 /Energy in the raw ) - ( Energy in the raw materials ^ Energy of V 

 ^materials at zero hour/ \at the end of development maintenance/ 



U' 



U-{Ur+Ue) 



The denominator is now the energy absorbed for growth and non- 

 basal metabolism only. Armsby also advocated taking the basal 

 metabolism into account. Some doubt may naturally be raised as to 

 whether the usual notions of basal metabohsm can be applied to a 

 system so rapidly changing as the embryo. Basal metabolism is that 

 amount of energy given off in the maintenance of a steady state, 

 but can the embryo be considered to be in a steady state even over a 

 short period? However, from another point of view, the embryo 

 has a certain amount of surface, and the minimum production of 

 heat by its cells would be expected to be sufficient to fit in with this; 

 or conversely, it possesses a certain surface corresponding to the 

 minimum heat production of its cells. In either case some approxima- 

 tion to the basal metabohsm might perhaps be obtained by calculating 

 what the surface would require. Terroine & Wurmser, in the case 

 of the mould Aspergillus niger were enabled to alter its growth-rate 



