SECT. 8] 



CARBOHYDRATE METABOLISM 



1029 



The transitory liver may be regarded as an excellent instance of 

 those special functions of embryonic life which will be discussed in 

 the Epilegomena. 



8-6. Free Glucose, Glycogen and Insulin in the Embryonic 

 Body 



It will be convenient now, before proceeding further, to ask what 

 happens to the free carbohydrate of the embryonic body, for so far 

 this important fraction has not been discussed at all. Only one 

 set of measurements exists, ^ 

 those of Needham, but these 

 were done on a very large 

 number of embryos with the 

 Hagedorn-Jensen method, and 

 some reliance may be placed 

 on them. The curve for ab- 

 solute milligrams of free glu- 

 cose per embryo, after having 

 been suitably corrected for the 

 presence of creatinine on the 

 basis of the factor introduced 

 by Holmes & Holmes (that 

 8 mgm. of creatinine affect 

 the Hagedorn-Jensen reagents 

 to the same extent as i mgm. 

 of glucose), naturally rose, 

 keeping pace with the growth 

 in size of the embryo. It is shown in Fig. 281 . It will be remembered 

 that the total glucose in the embryo also rose steadily with the 

 increasing size, as is shown by Fig. 264, but, if the two are compared, 

 it will be seen that the shape of the curve is not exactly the same in the 

 two cases, so that, when the two are related by expressing the free 

 glucose in percentage of the total glucose, a peaked curve emerges 

 (see Fig. 284). 



For the moment, however, attention may be directed to the rela- 

 tion between free and total glucose and wet and dry weight, as 

 shown in Fig. 282 and Fig. 283. 



We see that 100 gm. of embryo (wet weight) contain on the 5th 

 day of development 160 mgm. of total carbohydrate and 8 of free 



10111213I41516I7I813 20 

 Days 



Fig. 281. 



