984 ENERGETICS AND ENERGY-SOURCES [pt. iii 



An amount of yolk and white, therefore, equivalent to the finished embryo has 34-4 Cal. 

 as against its 37-5 Cal. But from this 34-4 Gal. must be subtracted a correction for the 

 skeletal system of the finished chick, which contains very little energy. 



The 37-5 Cal. is the heat contained in, not 6-oo gm. dry weight but 4-5 gm. dry weight, 

 for the bones weigh 1-5 gm. dry weight (Tangl), i.e. 75 % of 34-4 Cal. will give the energy 

 of an amount of yolk and white equivalent to the finished embryo =25-7 Cal. 



Then 37-5 -25-7 = 1 1-8 =energy stored in embryo by the endothermic components 

 of coupled reactions, i.e. increase of chemical potential. 



This gives for the S.E.E. : 



U' — X 37-5 — 25-7 



jT- — — - or -— — — ^^^^T^ ^^-^-7 TT '^ 100 = 27- 1 5 per cent. 



U-{Un + Ue) 86-85 - (26-4 + 17 (say)) ' ^ ^ 



But this calculation is only of illustrative significance, for the data 

 are taken from various different sets of material. It is evident, never- 

 theless, that the S.E.E. will always work out at a very low level, 

 certainly under 30 per cent. 



Wurmser, independently following a like train of thought, found 

 26 per cent., instead of Terroine & Wurmser's 70 per cent., for the 

 growth oi Aspergillus nigra. Rapkine suggests that it might be possible 

 to discover what these coupled reactions are which store extra energy 

 in the embryo and provide most of the O.E., by placing various 

 hydrogen donators in the presence of embryonic tissues at different 

 stages of development and following electrometrically their dehydro- 

 genation. Cahn gives the following argument to show that they do 

 not interfere much in the formation of the protein part of the embryo : 



I gm. of the total proteins of the whole egg on the gth day has a 

 calorific value of 4-91 Cal. and therefore for 5-846 gm. ... 28-700 Cal. 



I gm. of the proteins of the remainder of the egg on the 21st day 

 has a calorific value of 4-72 Cal. and therefore for 2-36 gm. 1 1-150 Cal. 



1 gm. of the proteins of the embryo on the 2 ist day has a calorific 

 value of 5-28 Cal. and therefore for 3-22 gm. ... ... 17-000 Cal. 



28-150 Cal. 



(The figures are Cahn's.) So there is a difference of 550 cal. and as, 

 judging from Fridericia's uric acid figures (which are probably too 

 high), about 135 mgm. of protein are combusted and therefore 

 500 cal. liberated, the balance was regarded by Cahn as exact enough 

 to allow of the conclusion that there was no measurable O.E. in 

 this case. 



Attention may be drawn to the similarity shown in Fig. 259 

 between the fraction of energy contributed to the embryo by syn- 

 thetic processes and the O.E. Both of these are, of course, quite 



