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in this way empty spaces here and there are formed in this tissue. 

 The encroachment of the glycogenic trophoblast cotnmences in the 

 centre, and thence spreads upwards and outwards; but the cells 

 which are situated peripherally also cooperate in the process, 

 penetrating the overlying layer of niegalokaryocytes, and invading 

 the thin layer of maternal tissue outside. 



The histolytic and histogenic changes of the placenta are now 

 completed; the glycogen is gradually used up, and at parturition 

 the placenta breaks away across this region, and a very little 

 glycogen remaius adhering to the afterbirth. The traces of em- 

 bryonic tissue remaining behind in the uterus are exceedingly slight. 



The view which I have here put forward, that the changes 

 taking place on the maternal side of the placenta consist essen- 

 tially in the disintegration of a maternal glycogen-producing 

 tissue, and in its gradual replacement by a mass of cells contain- 

 ing the same substance, but derived from a totally different 

 source, is one which I have only adopted after a careful consider- 

 ation of the evidence. On this evidence I have already laid em- 

 phasis as occasion arose, but I may perhaps be allowed here to 

 summarize the facts which have led me to prefer this iuter- 

 pretation. 



I have shown that in the earlier phases of pregnancy, before 

 the allantois has reached the trophoblast, and before therefore a 

 placenta, in the proper sense of the word, can be said to be 

 established, there is a rapid proliferation of subepithelial cells 

 which results in the formation of a glycogenic tissue, the glycogen 

 secreting cells of which may be distingnished, by certain well 

 marked characters, from all other maternal or embryonic cells 

 whatever; that the tissue itself is, sharply delimited from the tro- 

 phoblast by a layer of flattened cells; and that it is at the height 

 of its development at a comparatively early period, before any 

 secretion of glycogen has set in the trophoblast, but that thence 

 onwards it shows unmistakeable signs of disruption, the cslls 

 separating from one another, and breaking down until finally 

 nothing remains but the blood vessels, the supporting cells, and 



