1040 



CARBOHYDRATE METABOLISM 



[PT. Ill 



Fig. 288). The blood sugar, however, is not a large enough factor to 

 affect to any great extent the free glucose of the embryo as a whole, 

 as a rough calculation demonstrates. Assuming 230 mgm. per cent, 

 for the 20th day, the amount of blood in the embryo would be 



1-54 gm. (from the formula of Dreyer & Ray, i.e. 5 = -^, takmg 



the mouse value (6-7) for K as the mammal nearest in weight to 

 the hatching chick). This would give 3-53 mgm. of blood sugar, 

 which, although a high estimate, is only 15 to 20 per cent, of all the 

 free sugar in the embryo. 



The results which have been obtained on mammalian embryos 

 are sHghtly more coherent. 



Aron investigated the blood 99nU oChick.viadimirov^Schr 

 sugar of embryos of the 

 guinea-pig, rabbit, dog, cow 

 and pig, using the Fontes- 

 Thivolle method and accu- 

 mulating the results shown 

 graphically in Fig. 289. Al- 

 though the points arrange 

 themselves roughly along de- 

 finite curves, Aron did not 

 treat them as if this was so, 

 but simply averaged out the 

 data, and concluded that for 

 each species of embryo there was a characteristic blood sugar level 

 which did not change appreciably throughout intra-uterine Hfe. The 

 values thus calculated were as follows : 



220 

 210 

 200 



190 



'180 



Hanans lowest O 

 Normal adult level (ScheunertS^,Pelchrzim) 



Fig. 288. 



Blood sugar in mgm. % 



Thus in some cases the glucose concentration in the foetal blood was 

 higher, in other cases it was lower, than in the maternal blood. For 

 comparison, the following values of other observers may be advan- 

 tageously placed here. 



