I026 CARBOHYDRATE METABOLISM [pt. m 



month. For this last value, Higuchi got a lower figure — 0-032. 

 Again, Loveland & Maurer found 1 00 mgm. of glycogen in rabbit 

 placentas of 22 days' gestation and less than 25 mgm. at 32 days, 

 and their histological checking fits in down to the last detail with 

 what has been said above. Correspondingly Snyder & Hoskins re- 

 ported that the glycogen of the rabbit foetal liver rose from a trace 

 to 40 mgm. per gram — as much as the adult possesses — while the 

 glycogen of the foetal body increased fivefold. 



Interesting experiments have also been made by Huggett who has 

 given attention to the factors which modify the amount of placental 

 glycogen. These turned out to be few, for the percentage of glycogen 

 in the placenta of the rabbit was unchanged by starvation, by carbo- 

 hydrate feeding, by injections of carbohydrates, or by injections of 

 hormones (adrenalin, thyroxin). Repeated injections of large doses 

 of insulin did succeed in slightly lowering the percentage, and as 

 phloridzin had already been shown by Lochhead & Cramer to have 

 a similar effect, Huggett concluded that the only influences having 

 any marked action on the glycogen of the maternal placenta were the 

 profound disturbances of metabolism induced by massive insulin doses, 

 phloridzin, and semi-pathological changes such as those induced by 

 ether, amytal, and tetrahydro-j3-naphthylamine^. Wertheimer has also 

 made similar observations. All the glycogen of the maternal organism 

 can be mobilised in the rat or guinea-pig by the action of cold and ad- 

 renalin, but the glycogen in the foetus remains untouched. This im- 

 munity persists for some time after birth, newborn animals requiring 

 huge doses of adrenalin to shift any glycogen. It was significant that 

 neoplasms also remained uninfluenced by treatment affecting the 

 carbohydrate stores of the rest of the animal, and Wertheimer in other 

 experiments (see Appendix 11) found that amphibian ovarial eggs 

 possessed a like independence. 



We may now return to the development of the chick embryo, and 

 unravel the mechanism of its carbohydrate metabolism further. 

 Fig. 270 shows that the nth day of incubation may be fixed on 

 as being the point in ontogeny at which the glycogen storage in 

 the embryonic body begins to become notable, when considered in 

 absolute terms, or at which it is increasing more rapidly, if con- 

 sidered in terms of per cent, dry weight (see Fig. 280 taken from 



^ Conversely, placental glycogen cannot be increased by alimentary hyperglycaemia 

 (Runge & Hartmann; Kessler). 



