ioi6 CARBOHYDRATE METABOLISM [pt. iii 



It is important to remember that he was dealing with the egg as a 

 whole, so that any diminution in a substance or fraction means its 

 absolute disappearance; as regards ovomucoid glucose, this strongly 

 substantiates the conclusions drawn above^. 



Sakuragi considered that protein played no part as an energy 

 source in the metabolism of the chick embryo. "It seems to be very 

 interesting", he said, "that a small quantity of sugar is always kept 

 undecomposed and moreover towards the end of foetal life some 

 glycogen appears. The significance of this phenomenon may be inter- 

 preted as the necessity to convert the fat into sugar before it can be 

 utilised as energy. . . . This is the reason why the egg contains a rela- 

 tively high amount of sugar initially, sufficient to maintain the sugar 

 balance until the organ capable of transferring fat into glucose has 

 had time to develop." 



However the kinematics of the inter-carbohydrate transformations 

 may run, it is likely from Fig. 269 that the carbohydrate of the egg 

 as a whole receives some reinforcement between the 8th and nth 

 days. This increase amounts to about 90 mgm., so protein is at once 

 ruled out as a source, because during the whole of development only 

 68 mgm. are lost, and most of this must be due to true protein cata- 

 bolism. It is true that the peak in protein catabolism occurs at just 

 the same time as the gain of carbohydrate, but as between the 8th and 

 gth days the egg only loses i mgm. of protein while it gains 47 mgm. 

 of carbohydrate this correlation is probably but a coincidence. We may 

 safely conclude that the protein which is broken down is used for the 

 production of energy, and being burnt away does not go to form 

 that extra carbohydrate which appears in the middle of develop- 

 ment. 



The other possible source is fat, and here the position is a good 

 deal more hopeful. As will be shown in Section ii-i, between the 

 7th and the 14th days there is a discrepancy between the fat lost 

 as determined by the averaged chemical analyses and that deter- 

 mined by the carbon dioxide output on the supposition that all of 

 it was due to fat, which is not true. More is lost than can be ac- 

 counted for even on this assumption. "The figures of Bohr & Hassel- 

 balch", I said in 1927, "would give an even worse divergence than 

 those of Murray for they were lower than his. The explanation for 

 this missing fat must be that during that period it is used for other 



1 See also Sagara. 



