SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 651 



oxygen", and various workers had obtained the theoretical values 

 for it, as follows : 



Zuntz Rubner Pfliiger Average 



For protein 314 3-0 3-3 -3-24 3-2 



For fat 3-28 3-27 3-29 33 



For carbohydrate ... 3-54 — 3"53-3'40 35 



The differences are very small, and this probably accounts for the 

 fact that less is heard of calorific than of respiratory quotients in 

 the general literature. Nevertheless, in cases where the estimation 

 of carbon dioxide output is difficult, such as eggs whose alkali reserve 

 is unknown, the calorific quotient is very valuable. Meyerhof 

 estimated it for normally developing eggs — leaving out of account 

 eggs without membranes, etc. — as 2-75, 2-88, 2-675, 2-7, 2-675, 

 2-85, and 2-7; these were his seven quite satisfactory experiments. 

 Roughly speaking, it wavered between 2-55 and 2-9, a value obviously 

 much underneath the theoretical for any of the three main classes 

 of energy source, although, as the lowest theoretical number was for 

 protein, they lay nearer that than any of the others. These relation- 

 ships are shown diagrammatically in Fig. 117. There was apparently 

 no variation at all in the calorific quotient during development, as 

 the following table shows: 



Calorific quotient 

 Unfertilised eggs ... ... 2-8, 2-525 



I- to 2-cell stages ... ... 2-75, 2-775, 2-675 



Morula stages ... ... 2-7,2-55 



Swimming larvae ... ... 2-675 



Blastulae 2-8 



Some explanation was evidently required to deal with the marked 

 lowness of all the figures. What made the situation still more per- 

 plexing was that these figures were uncorrected for the heat of solu- 

 tion of carbon dioxide in sea water and for other phenomena con- 

 sequent upon the carbon dioxide output of the eggs. Meyerhof did 

 not estimate the carbon dioxide directly, but calculated its effects 

 from the few estimations which had already been done by Warburg, 

 and, when this correction was made, the average calorific quotient 

 sank to 2-6. 



Meyerhof also found that, just as phenylurethane had been found 

 by Warburg to inhibit cleavage while leaving respiration untouched, 

 so it had no effect on the heat production, and, therefore, none on 

 the calorific quotient. The calorific quotient of eggs in phenyl- 

 urethane solutions was 2-65 to 2-75, a finding which conclusively 



