PT. Ill, SECT. 8] CARBOHYDRATE METABOLISM 



8-2. Total Carbohydrate, Free Glucose and Glycogen 



The first question which presents itself is naturally what happens 

 to the total carbohydrate in the 

 hen's egg during development, 

 and how it is transferred to the 

 embryo. The impossibility of 

 estimating glucose by copper 

 reduction methods in the pre- 

 sence of amino-acids as in pro- 

 tein hydrolysates makes the 

 figures of Sakuragi for total 

 carbohydrate uncertain, and 

 the only available ones are those 

 of Needham, who used the Hage- 

 dorn-Jensen method, after pre- 

 cipitating the hydrolysate with 

 phosphotungstic acid. Hydro- 

 lysis was carried out with 5 per Days ^5 



cent, hydrochloric acid for 5 pig. 264. The inset shows the early ' 



hours. In this way the amount portion of the curve enlarged. 



of total carbohydrate, i.e. free carbohydrate plus carbohydrate com- 

 bined with proteins plus glycogen, was determined each day during 

 development (a) for the embryo 

 and (b) for the rest of the egg. 

 Fig. 264 shows the former 

 values ; they rise as the embryo 

 grows very regularly from 

 i/ioth mgm. on the 3rd day to 

 70 mgm. at hatching. Similar- 

 ly, Fig. 265 shows the behaviour 

 of the total carbohydrate out- 

 side the embryo ; it first of all 

 falls, then rises again some- 

 what, after which it falls again 

 till the end of incubation. 



§200 



o Single experiments 

 • Averages 



Days 



Fig. 265. 



Evidently by adding the data of Fig. 264 and Fig. 265 together, 

 we obtain the amount of total carbohydrate in the whole egg on each 

 day of development. This is shown in Fig. 266, from which it appears 



64-2 



