MESOLEPIDOMAS : THEIE PROPERTIES 323 



from organs of mesothelial origin are more liable to pass back, 

 and to assume characters approaching those of the primitive 

 mesenchyme and mesoblast, than are growths from hypoblastic 

 and epiblastic organs to revert to what we might term the morula 

 stage. And if it be correct to regard the endothelium as a still 

 later development from the mesenchyme, then we can understand 

 how it is that Endotheliomata are peculiarly liable to take on 

 the characters of the primitive pulp tissue from which endothelium 

 became differentiated. 



Israel 1 recognizes fully this same dependence of the characters 

 of the endotheliomata upon the embryogeny of the mother 

 tissues, for he remarks (the italics are mine) : " Diese (endotheliale) 

 Deckzellen haben sich nicht unter alien Umstanden in ihren 

 Eigenschaften von diejenigen ihrer Intercellularmasse bildenden 

 Stammesgenossen so weit entfernt, dass nicht auch sie gelegentlich 

 wieder befahigt wurden, Intercellularmasse hervorzubringen, 

 deren Qualitat von den ererbten Eigenthumlichkeiten abhangig 

 ist. . . . Gelegenliche Vorkommnisse in den Endothelgeschwiil- 

 sten und auch bei gewissen entziindlichen Neubildungen zeigen, 

 dass die Fahigkeit Intercellularsubstanzen zu produciren, manchen 

 in Tumoren gewachsenen Endotheldescendenten, nicht unwieder- 

 bringlich verloren gegangen ist, wie den Epithelien. Das ist aber 

 auch der fur die Diagnose praktische bedeutsamste Unterschied 

 endothelialer Krebse gegeniiber den epithelialen, und er macht 

 von alien die tJbergangsformen vom Endotheliom zum Sarkom 

 verstaudlich." 



I am far from saying that this is the one and sufficing cause 

 why certain orders of the Mesolepidomata have this marked 

 tendency to assume more sarcomatous characters. I do not 

 think that this is everything ; nevertheless it does, I think, 

 materially aid us to understand why this peculiarity in the 

 progressive development of these tumours manifests itself ; it 

 is one factor. Indeed, it is not all the Mesolepidomata which 

 present these same tendencies. To give one example : we 

 never, to my knowledge, find that carcinomata of the uterus, 

 either in their more rapidly growing parts or in their metastases, 

 show other than well-developed cancerous structure. In fact, 

 there is singularly little distinction to be drawn between the 

 characters of cancers originating from the uterine mucosa and 

 1 Israel, O., loc. cit. p. 668. 



