282 Drs. Lochhead and Cramer. Gilycogenic Changes [Jan. 1, 
the function of storing glycogen for the foetus has not yet been acquired by 
the liver and is, in the meantime, fulfilled by the placenta.* 
The glycogen metabolism of the placenta and the foetus differs in some 
essential points from that of the adult organism. In the latter case the 
glycogen deposited in the tissues represents a store dependent upon external 
conditions and showing irregular fluctuations. The placenta and the fcetus, 
on the contrary, are characterised by the absence of individual variations 
in the amount of glycogen they contain at a given period of gestation. 
The glycogen metabolism of these organs shows a regular succession of 
changes which proceed almost regardless of external conditions, and which 
are independent to a great extent even of the glycogen metabolism of the 
mother. 
These facts point to the conclusion that in the development of the fcetus 
glycogen fulfils a definite function and is not merely an accessory source of 
nutritive energy as it is in the adult organism. Part of the glycogen which 
is absorbed from the placenta may be accounted for by the intense 
carbohydrate metabolism, which, according to Bohr’st experiments on the 
gaseous metabolism, proceeds in the foetal rabbit. Bohr’s results are not in 
agreement with those of Cohnheim and Zuntz.t But since the latter 
observers worked with sheep, which, in view of our observations, may have 
a different metabolism of pregnancy, and since Bohr’s figures show that 
his method entailed very little interference with the foetus, his observations 
may be taken as representing the normal condition in rabbits. The glycogen 
which is thus catabolised furnishes thereby the energy necessary for the 
formation of new tissues, the “ Entwicklungsarbeit ” of Tangl.§ 
The question arises whether glycogen performs also anabolic functions in 
the development of the foetus. : 
The absence of glycogen from some of the growing fcetal tissues, and the 
fact that the tissues where it is present do not contain even as much as the 
adult ones, leave little doubt that a definite formative power cannot be 
attributed to glycogen as such. On the other hand, the scarcity of glycogen 
* In order to account for the behaviour of the hepatic glycogen during development on 
‘purely anatomical grounds it would be necessary to assume that at the beginning of the 
last week of pregnancy the vascular supply of the liver undergoes a complete change, so 
that after that date the foetal liver is freely supplied with blood from the placenta, while 
before that date very little blood from the placenta reaches the liver. We are not aware, 
however, that such a relation between vascular changes and the storing of glycogen can 
‘be established. 
_ + Bohr, ‘Skandinavisches Archiv fiir Physiologie,’ vol. 10, 1900, p. 413 ; vol. 15, 1904, 
p. 23. 
{ Cohnheim and Zuntz, ‘ Pfliger’s Archiv,’ vol. 34, 1884, p. 173. 
§ Tangl, ‘ Pfliiger’s Archiv,’ vol. 93, 1903, p. 327. 
