SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 717 



was inclined to regard the oxygen curve as the more reUable, for 

 much the same reasons as have already been brought forward in 

 the case of echinoderm work. The uncertainty of alkali reserve, and 

 the known utilisation of carbon dioxide in the transport of calcium 

 from shell to bones, obviously introduce doubtful factors. The total 

 oxygen consumption for the first 19 days estimated by graphical 

 integration came to 2988 c.c, which, on the basis that fat only is 

 burned, leads to the conclusion that 1-48 gm. of dry substance is 

 oxidised during that period. 

 If only protein and carbo- 

 hydrate were burned, it would 

 require over 3-28 gm. to use 

 the observed amount of oxy- 

 gen. Chemical analyses, to be 

 discussed later, show, how- 

 ever, that approximately 1-62 

 gm. of solid substance is burnt 

 during the first 19 days, a 

 figure which can be accounted 

 for on the assumption that 

 92 per cent, of the catabolism 

 is oxidation of fat, and the rest 

 of protein and carbohydrate. 

 Murray's work on carbon 

 dioxide output had led him 

 to assess the amount of fat 

 burned as 98 per cent, of the 

 total food-stuff catabolised, 



1 1 r> • -1 Fig- 150- 



but that figure is certainly too 



high. In direct bearing upon these questions was his calculation of the 

 respiratory quotient. According to him, it varies during the period 

 under discussion from 0-82 to o-6o. Curiously enough, his lowest 

 value, o-6o, he obtained on the 6th day, i.e. the very time when a 

 particularly high one would have been expected. However, if his 

 oxygen consumption on that day was in error on the high side, as 

 has already been surmised, then the true respiratory quotient for 

 that moment would be much higher. 



Apart from the work of Warburg and his collaborators, which will 

 be treated as a whole below. Shearer is the only investigator who has 



6 17 18 19 20 



