SECT. 7] OF EMBRYONIC DEVELOPMENT 981 



interesting in view of the efficiencies found by other workers on the 

 early post-natal life of mammals, thus : 



Armsby stated that in later post-natal life the efficiencies were higher 

 still, but though he calculated them from Kern & Wattenberg's data 

 on the sheep, Tschirwinski's data on the pig, and Armsby & Fries' 

 data on the cow, he did not give any actual values. From a general 

 point of view, therefore, it is probable that as more data come to 

 light it will be found that the efficiency of the organism considered 

 as a machine for storing energy rises from fertilisation to death. 

 Nothing is known about the rapidity with which the adult level of 

 efficiency is reached, but Armsby & Fries considered that this would 

 probably occur not long after weaning (see also Brody). 



A comparison may be made between the embryo and other engines. 

 Its business is to store as much energy as is given it with as little 

 loss as possible. The object of the steam engine is to produce as much 

 mechanical work from the energy given it with as little loss as possible. 

 The efficiency of this process is not great; in the locomotive engine, 

 which is notoriously wasteful, it may not exceed 1 5 per cent. Wimperis 

 and Bird give 25 per cent, for the gas engine with suction producer, 

 and the best recorded efficiency for a Diesel engine with high maxi- 

 mum pressure is 40 per cent. But a much better comparison is 

 between the embryo and the electric accumulator, for this does not 

 alter the form of the energy passing through it. Cooper's average 

 estimate is that an electric accumulator will give back 74 per cent, 

 of the energy put into it, and another figure (Davidge & Hutchinson) 

 is 70 per cent. It is interesting that the average A.E.E. of developing 

 embryos should be of the same order. 



7*6. Synthetic Energetic Efficiency 



Now Terroine & Wurmser's formula for calculating the R.E.E. was 



Energy stored in the embryo 

 /Energy in raw materials \ _ /Energy in unused , Energy in solid burned \' 

 \at zero hour / \raw materials for basal metabolism ) 



or, in their notation : ^ r, 



U-iUr^+U^) 



