ioi8 CARBOHYDRATE METABOLISM [pt. iii 



free from criticism. In the present case, moreover, it is true that a 

 passage through the form of cyclose might account for the fall and 

 the rise in Fig. 269, but no stress can be laid on the high absolute 

 values for the inositol in White Leghorn eggs, and further, if the car- 

 bohydrate goal is abandoned some other objective must be found for 

 the missing fat. As evidence for the possibility of the fat-carbohydrate 

 route in vivo these arguments give support to the experiments of 

 Furusawa and of Calvocriado. Furusawa considered that the liver is 

 the organ responsible for converting fat into carbohydrate, and, if 

 this is so, it is interesting to note that the liver-cells of the developing 

 chick can make carbohydrate from fat before they can store carbo- 

 hydrate when it is made. 



We must now examine this property of storing carbohydrate, and 

 to do so the metabolism of glycogen in the embryo must be dealt 

 with more fully. 



8-5. The Metabolism of Glycogen and the Transitory Liver 



The increase of glycogen in the embryo has already been men- 

 tioned. But we also possess figures for the glycogen in the whole egg 

 owing to the investigations of Idzumi and Sakuragi, arid, as they 

 are quite concordant, confidence may be placed in them. They are 

 depicted graphically in Fig. 270. By subtracting the glycogen in the 

 embryo from the glycogen in the whole egg, we obtain that in the 

 remainder, the figures for which appear as a dotted line in Fig. 270. 

 By the end of development the glycogen in the embryo has only 

 attained about a quarter of the total sugar in the embryo. It is in- 

 teresting that Idzumi; Sakuragi; and Shaw all observed a great 

 decrease of embryo glycogen during the process of hatching^, Idzumi 

 to 10 and Sakuragi to 25 mgm. per embryo. They consider that this 

 is related to the vigorous muscular movements which the embryo then 

 makes for the first time, including the lung movements, which come 

 into play as the animal lays aside its allantois. As may be seen from 

 Fig. 270, the glycogen is at its highest outside the embryo about the 

 13th day; after that time it rapidly falls, and is, indeed, more or less 

 the reciprocal of the glycogen inside. Evidently after the 13th day the 

 glycogenic function is shifted from somewhere outside the embryo to 

 somewhere inside. 



1 Confirmed by Vladimirov & Danilina. 



