7o6 THE RESPIRATION AND [pt. iii 



merits will appear in the section on Energetics and Energy Sources 

 of the embryo. For hourly radiation the correspondence was equally 

 good, being 506-8 gm. cal. observed and 504-72 calculated. Thus 

 there was no energy unaccounted for, none held back for the pur- 

 pose of maintaining the embryo in physico-chemical equilibrium, 

 or as "Entwicklungsarbeit". "Wahrend der Entwicklung des Em- 

 bryos", as Bohr & Hasselbalch put it, "in bedeutenden Mengen 



Table 83. Heat-production of chick embryo in gram calories per hour produced. 



Averages 



umgesetzten chemischen Energie auf neugebildete Gewebe nichts 

 iibergefiihrt wird, dass dieselbe dagegen in ihrer Gesammtheit das 

 Ei als Warme verlasst." Tangl's earlier papers were appearing at 

 this time, and they naturally found in his estimations of the calorific 

 value of the egg-substance at different times during development 

 confirmation of their view that fatty acids were the exclusive source 

 of energy by combustion. It is only fair to add that they did take 

 into account the possibility of combustion of proteins, but their 

 arguments against it were extremely poor. From their figures for 

 heat-production, Bohr & Hasselbalch did not calculate the metabolic 

 rate by referring them to i gm. of embryonic body- weight, probably 

 because they were doubtful about how much the membranes might 

 be producing. The results of such a calculation^ are shown in Fig. 146, 



^ Leaving the membranes out of accoimt. 



