1030 



CARBOHYDRATE METABOLISM 



[PT. Ill 



Fig. 282. 



carbohydrate. The former falls to a level of about 100 and subsequently 

 rises to over 300, the latter rises all the time in an S-shaped curve to 

 about 48 mgm. This would seem to indicate that the carbohydrate 

 present in the embryo on the 

 4th and 5th days, at which time 

 there is more in proportion 

 than at any subsequent period, 

 is not in the form of free glu- 

 cose, and as it cannot be glyco- 

 gen it must be sugar in some 

 unidentified combined form. 



The dry weight data bear 

 out this view even better. On 

 the 5th day 100 gm. of dry 

 embryo contain 3000 mgm. of total carbohydrate, about 100 mgm. 

 of free carbohydrate, and about the same amount of glycogen. After 

 that point the total carbohydrate continuously falls, reaching a value 

 of 1750 on the i6th day, while the free carbohydrate continuously 

 rises, its highest point being 

 reached on the 1 1 th day with a ^''°°° 

 value of 360 mgm., after which i 

 it falls, but not below 220 mgm. e^°°° 

 The fact that the total glucose | 

 falls, while the free glucose "5,2000 

 rises, is of some interest. The 2 

 presence of such a large pro- 0,000 

 portion of glucose not free and 5 ^ 

 not in the form of glycogen a 

 may be correlated with certain 

 histological facts which have 

 been known for some time, and which have already been referred 

 to (see p. 566). 



What happens to the concentration of the various carbohydrate 

 fractions in the water of the embryonic body? It was pointed out 

 above that when total protein, total carbohydrate and total fat were 

 expressed as grams per 100 gm. of water in the embryonic body, the 

 protein and the fat start at a very low level (owing to the great 

 wetness of the earhest stages) and rise steadily, while the carbo- 

 hydrate begins fairly high, falls to a minimum on the 8th day, and 



ays 



10 



Fig. 283. 



