FCETAL NUTRITION: THE PLACENTA 463 



exists in the mother. Under similar conditions glucose passes into 

 the urine and liquor amnii in man, but it does not pass normally.^ 

 Hence it has not been proved that the sugar of the maternal blood is 

 'diffused unchanged through the trophoblast. It is more probable 

 that the transference of sugar is not effected by a purely physical 

 process, since the serum of the foetal rabbit contains Isevulose, while 

 the serum of the mother has none (Paton, Kerr, and Watson ^). 



Between the glycogen metabolism and the growth of the foetus 

 there is a distinct relationship, which probably depends directly on 

 the uses to which glycogen is put. Part of it is accounted for by the 

 intense carbohydrate metabolism which proceeds in the foetus (Bohr ^). 

 The glycogen, which is thus katabohsed, furnishes thereby the energy 

 necessary for the formation of new tissues, the " Entwicldungsarbeit " 

 of Tangl.* The question arises whether glycogen also, performs 

 anabolic functions in the development of the foetus. " The absence 

 of glycogen from some of the growing foetal tissues, and the fact that 

 many of the tissues in which it is present do not contain even as 

 much as the adult pnes, leave little doubt that a definite formative 

 power cannot be attributed to glycogen as such. On the other hand, 

 the scarcity of glycogen in embryonic tissues does not' necessarily 

 justify the conclusion that glycogen does not take part in the buildiag 

 up of the tissues. It is well known that embryonic tissues are rich 

 in mucin, which contains a large amount of a carbohydrate group in 

 its molecule. Although glycogen as such has no formative power, it 

 may yield one of the ' Bausteine ' for the building up of the main 

 protein body of foetal tissues. In this connection it is interesting to 

 consider the conditions in the hen's egg, which contains in itself the 

 material of which the embryo is built up.^ In the ovum carbohydrate 

 as such is practically absent. At the same time all the protein 

 substances of the white of egg are distinguished by the presence of a 

 large amount of glucosamine in their molecule. Here the carbohydrate 

 group has entered into the protein molecule, and correspondingly 

 there is a scarcity of free carbohydrate." ** 



1 Even in the hyperglycsemia of diabetes the figures do not support the 

 theory of the mere diffusion of glucose. Offergeld found 0'8 per cent, of sugar 

 in the maternal blood, and 2-2 per cent, in the foetal blood in diabetic coma 

 (" Ueber das Vorkommen von Kohlehydraten im Fruchtwasser bei Diabetes," 

 Zeit. f. Oeb. u. Gynak, vol. li.). 



2 Paton, Kerr, and Watson (B. P.), " On the Source of the Amniotic and 

 Allantoic Fluids in Mammals," Trans. Roy. Soc. Edin., vol. xlvi., 1907. 



3 Bohr, " Die respiratorische Stoffwechsel des Saugetierembryos," Skand. 

 ArcLf. Physiol., vol. x., 1900. See also vol. xv., 1904. 



* Tangl, " Beitrage zur Energetik der Ontogenese," PflUger's Arch., vol. xciii., 

 190.3. 



5 Compare Emrys-Eoberts, " A Further Note on the Nutrition of the Early 

 Embryo, with Special Eeference to the Chick," Proc. Roy. Soc. Lmidon, B., -vol. 

 Ixxx., 1908. 



^ Lochhead and Cramer, loa. cit. 



