SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 653 



he got values at all resembling the theoretical ones. He was not able 

 to devise a satisfactory explanation for this. Hypertonic sea water, 

 which had a great effect on the heat-production rate, just as it had 

 on the respiratory rate, made very little difference to the calorific 

 quotient. In a sodium chloride solution of 4-3 per cent, it was 2-6, in one 

 of 3-5 percent, it was 2-85, in one of 2-3 per cent, it was 2-9 (unfertilised) 

 and 2-85 (fertilised). The calorific quotient of spermatozoa was found 

 to be between 3-05 and 3-1, from which Meyerhof concluded that 

 perhaps they were making use of protein as a source of energy. 



Indeed, the question of the interpretation of the low calorific 

 quotient was the main point of interest to Meyerhof. He examined 

 the Strongylocentrotus eggs for glycogen and free glucose, and could find 

 no trace of either^. Nor could he detect any nitrogenous breakdown- 

 products in the sea water surrounding the eggs (Nessler's reagent). 

 But by the use of the Kumagawa-Suto method, he did succeed in 

 revealing the presence of fatty substances in the unfertilised eggs, 

 obtaining for an amount of egg-mass equivalent to 140 mgm. nitrogen, 

 1-905 gm. ash-free dry substance, a total ether extract of 0-323 gm., 

 which contained 0-282 gm. of saponifiable fatty acids. This would 

 correspond to 14-8 per cent, of fatty acid and 2-15 per cent, of lipoids 

 and sterols (dry weight) . This material might then be used to supply 

 the necessary energy. Meyerhof supposed that there were three 

 possibilities: (i) That the oxygen was all being used for the oxidation 

 of the fatty acids, but that at the same time certain strongly endo- 

 thermic processes were going on which accounted for the missing 

 25 per cent, of the heat. In certain conditions, e.g. sea water contain- 

 ing ammonia, these endothermic processes would be considered to be 

 abohshed, and the full amount of heat permitted to escape, giving 

 a reasonable calorific quotient. (2) The oxygen consumed might not 

 all be used for the combustion of the fat, but might partly be employed 

 in synthetic processes without accompanying heat-production. We have 

 already met with this idea in Rapkine's work. Lastly (3), the source 

 of energy might not be exclusively fatty acids, but other substances, 

 burning in exothermic manner, and sharing the total oxygen. In 

 the two last-named cases the energy-content or calorific value of 

 the eggs would decrease during development, even if some of the 

 products of combustion were retained inside the cells, but, in the 

 first alternative, this would not occur. Put in another way, the 



^ But see on this, Section 811. 



