THE
CANCER PROBLEM 111
of
an embryo would stay its growth just as the formation of the sexual generation
ends the growth of a shoot of a flowering plant. How does “the embryo” bring
about this result? It does not devour the trophoblast, but it must produce
something which, as was pointed out two years ago,* brings the
degeneration to pass. Only in ordinary chorio-epithelioma is the malignant
neoplasm a persisting portion and derivative of the trophoblast of the
immediately previous gestation. Any ordinary cancer or sarcoma is a new
development of trophoblast, due to the attempt of a germ-cell to start the
cycle anew. Except in mode of nutrition, this irresponsible trophoblast does
not resemble normal trophoblast, but it often mimics the structure in which it
lies or it is like no other organ or tissue in the body. In any and every
higher mammalian (Eutherian) development there is the potentiality of a
malignant tumour,** chorio-epithelioma, and this danger exists until the
degeneration of the trophoblast is an assured but not completed fact. As
researches made some years ago, but never published, demonstrated,
* The Lancet, June 21, 1902, p. 1758.
** So far as is at present known, chorio-epithelioma does
not occur in any mammal except man. The multiplicity of embryos in most other
cases is against its happening. In almost every gestation in the pig, and often
in the rabbit, there are abortive embryos, from the trophoblast of which a
malignant tumour might arise but for the presence and influence of the other
embryos. In the course of the discussion the case of a full-time anencephalic
(headless) human foetus was cited as against the validity of the conclusions
advanced. In this the entire alimentary canal and pancreas were absent. A
little cross-examination elicited the information that nothing was known as to
its foetal membranes, and that it was one of twins. The latter point is
decisive in explaining how this monster had escaped the weeding-out of the
critical period. Had it been a single embryo, not a twin, it would undoubtedly
have been aborted at the critical period, and, moreover, hydatid mole or
chorio-epithelioma would very possibly have followed.