I034 CARBOHYDRATE METABOLISM [pt. iii 



Langerhans islets, the relation holds, for the change occurred at the 

 beginning of the 4th month of gestation, and from the work of Livini 

 we know that no appreciable quantity of glycogen can be shown to be 

 present in the hver before that time. Gierke and Lubarsch both made 

 similar statements about the liver in early pig embryos. Thus the biliary 

 always appears in ontogeny before the glycogenic function of the liver. 



In 1928 Aron extended these conceptions to the amphibian 

 embryo and larva. Glycogen was determined by histochemical 

 methods in the livers of Rana temporaria, Rana esculenta and Bufo 

 vulgaris. Aron found, just as Claude Bernard had found long before, 

 that none is present before the appearance of the hind limb buds, 

 i.e. before the disappearance of the yolk. Complete ablation of the 

 pancreas in early stages altogether prevented the appearance of the 

 glycogenic function, so Aron naturally concluded that the mechanism 

 of its control in amphibia was similar to that in mammals. This would 

 mean that the chemical regulation of the embryonic and yolk-sac 

 period in the frog is carried on without the aid of insulin. Aron has 

 suggested various further mechanisms of control involving the action 

 of the thyroid, but these are not at present very certain. 



Judging from the work of Goldfederova, the increase in liver 

 glycogen, when it does come, must be very sudden, for she obtained 

 the following figures : 



Stage 

 Hind limb buds visible 

 Mobile hind limbs and tails 

 Front limb buds visible 

 Resorption of tail 

 Completely metamorphosed 



Claude Bernard himself went further afield than to the amphibia, 

 for in studying the embryos of molluscs, especially the common 

 oyster, he observed that the cushion or disc which carries their ciHa 

 and makes them mobile was very rich in glycogen (histochemically) . 

 As the disc subsequently falls off when the embryos become sessile, 

 Bernard felt justified in seeing in it an analogy with the placenta 

 of mammals as regards glycogen storage. 



In other researches Aron, Stiilz & Simon carried out the experi- 

 ment of Carlson & Drennan at various stages of gestation in the 

 dog, i.e. they depancreatised the mother, and observed whether 

 there was any evidence of protection from hyperglycaemia due to 



