1908.] a the Placenta and Fetus of the Pregnant Rabbit. 283 
in embryonic tissues does not necessarily justify the conclusion that glycogen 
does not take part in the building 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 ben’s egg, which must necessarily contain 
in itself the material of which the embryo is built up. In the egg, 
carbohydrate as such, in the form of either glycogen or glucose, is almost 
absent. At the same time all the protein substances of the white of egg are 
distinguished by containing a large amount of glucosamine in their molecule. 
In the egg, therefore, the carbohydrate group has already entered into 
the protein molecule, and correspondingly there is a scarcity of free 
carbohydrate. 
Summary. 
In an age-series of pregnant rabbits from the 14th day of gestation to 
the end of pregnancy, quantitative estimations were made of the glycogen 
present in the placenta, in the liver of the foetus, and in the rest of the 
fcetal body. ‘The mechanical separation of the placenta into the maternal 
and the foetal part made it possible to determine the amount of glycogen in 
the peninsule of the maternal placenta, which are most intimately associated 
with the foetal placenta, apart from the glycogen in the rest of the maternal 
placenta. 
A marked feature of the results is the absence of individual variations in 
the glycogen contents of the various organs. Instead, there is an orderly 
sequence of changes, which allows of a graphical expression. 
Glycerine extracts of both the maternal and the fetal parts of the rabbit’s 
placenta contain an active glycogen-splitting enzyme. No evidence was 
obtained for the presence in these extracts of a proteolytic or lipolytic 
enzyme. 
Comparative observations on the placenta of the sheep show that the 
paucity of glycogen in the placenta of this animal is associated with the 
presence of a very weak glycogen-splitting enzyme in the glycerine extracts 
from this organ. The glycogen store of the rabbit’s placenta is not increased 
by feeding the mother animals on a diet rich in carbohydrates. Nor has such 
a diet any effect in increasing the hepatic glycogen reserve of the foetus either 
in the earlier or in the later stages of pregnancy. On the other hand, the 
placenta does not give up readily its store of glycogen to the mother organism 
when the hepatic reserve of the mother is exhausted by conditions such as 
injections of phloridzin. Neither during gestation nor at birth does the 
