RELATION OF VESICULAR MOLE TO CHORION CARCINOMA 139 
This represents the view of most English and Continental observers. 
Cullen refers to it as follows : ' It is doubtful whether Langhans' layer 
in reality consists of epithelial cells, some believing that it probably represents 
nothing more than the outlying stroma cells, which have of necessity assumed a 
marginal arrangement.' 
Roberts follows Eden in saying that Langhans' layer is a ' specialized 
stratum of the connective tissue corpuscles ot the stroma.' 
There are, however, several observers whose opinion must carry great 
weight who differ very widely from the foregoing. Among these are Minot, 
Katschenko, Kuppfer, Spee, Webster, and Peters, who all believe not only in a 
common foetal origin for both syncytium and ' zellschicht', but also that both layers 
are derived from the foetal ectoderm. It is of interest that, after careful microscopic 
study of the young ovum previously reterred to, I had independently arrived at the 
same conclusion. 
Turning now, for a moment, to the consideration of the origin of the syncytium, 
we find that a still greater diversity of opinion exists. 
Many believe it to be an entirely maternal product. 
Turner believes the whole covering of the villi to be derived from the uterine 
epithelium. 
Ercolani derives it from the connective tissue of the uterus, i.e., from the 
decidual cells. 
Winkler agrees that the covering has two layers, but derives the inner from 
the foetal epithelium, and the outer from the endothelium of maternal blood sinuses. 
Minot, Kuppfer, Spee, Hart, Gulland, Merrtens, and Fothergill, all 
believe that the syncytium is derived from the foetal ectoderm. 
Webster says, ' the foetal origin of the syncytium cannot now be denied. It 
has been clearly pointed out in different manuals by Van Beneden, Hubrecht, and 
Dewal. The importance of the labour of these authorities in the investigation of this 
matter cannot be too highly emphasized. Among recent German workers, their work 
has received scant attention. The maternal origin of the syncytium was advocated 
in the days when there was no such careful technique in microtomy as is found now- 
a-days, and it is hard to break away from traditional views.' 
Katschenko believes in a common ectodermal origin for the zellschicht and 
syncytium, and Ulesco-Stroganowa says, ' One can undoubtedly see an intimate 
connexion between the cellular elements and the syncytium,' and firmly believes in 
the same ' genetic identity ' for both layers. 
Minot has shown very clearly, in his elaborate description of the human 
chorion, that both epithelial layers of the villus are already formed before the con- 
nective tissue core has penetrated to its tip. ' They are at first clumsy cylinders, 
which may grow to a millimetre in length before they begin branching. They arise, 
