654 THE RESPIRATION AND [pt. hi 



question would be, does the calorific value of the eggs decrease or 

 increase, and, in either case, what relation does it bear to the wet 

 and dry weights of the eggs. Evidently, the only way to ascertain 

 what these relations were was to investigate the eggs during their 

 development with the aid of a bomb calorimeter, and Meyerhof 

 promised a study on these lines. But perhaps because of the great 

 difficulties such a continuation of his work, which would have been 

 extremely interesting, was never published. 



To the three possible explanations of Meyerhof's low calorific 

 quotients, however, a fourth might have been added, namely, the 

 suggestion that, in spite of all his precautions, a consistent leakage 

 of heat was going on in his apparatus. The great advances which 

 have been made in recent years as regards the measurement of the 

 heat-production of muscle tissue have shown how difficult it is to 

 be sure of registering all the heat eliminated. Impressed with such 

 considerations as these, Shearer in 1922 determined to re-investigate 

 the matter. He criticised Meyerhof's technique on various grounds, 

 e.g. use of too crowded cell-suspensions, insufficient aeration, reliance 

 upon the Winkler method instead of on manometric methods. Shearer 

 had already shown in the case of bacteria that the cytolysis of the 

 cells was accompanied by a greatly increased oxygen intake and 

 heat-production, so in this work he took special precautions against it. 



His differential microcalorimeter was substantially the same as 

 that elaborated by A. V. Hill for muscle, consisting of two vacuum 

 flasks, a copper-constantan thermocouple, and a very sensitive 

 galvanometer. Elaborate precautions were taken to prevent errors 

 and to find the total amount of heat produced. Shearer felt that the 

 most important result of Meyerhof's experiments was that whether 

 he took the unfertilised egg, the fertilised egg, or the fertilised egg 

 treated with phenylurethane, so that no cell formation was going 

 on, although the egg was fully alive, he found that the value of the 

 calorific quotient was always the same. Yet if any of the chemical 

 energy liberated in the egg as the result of the increased oxygen 

 consumption on fertilisation were utilised in producing the visible 

 morphological structure of the embryo, the calorific quotient could 

 not have been the same in all the instances. 



Fig. 118 gives a graph showing one of Shearer's experiments. 

 The calorimeter contained an amount of eggs corresponding to 58-4 

 mgm. nitrogen. In the ist hour after fertilisation the eggs liberated 



