THE INTERLUDE OF CANCER 131
its way through uterus and other organs, finally blocking the lungs and brain of the mother. This is chorio-epithelioma, recognized to be a form of cancer by Professor F. Marchand in 1895. This is without doubt the most deadly form of cancer. Here the sexual generation being unable to suppress the asexual one or trophoblast, the latter exhibits the characteristics of asexual generations, the powers of indefinite growth and increase. Pathologists at present distinguish wrongly between two forms of chorio-epithelioma, a malignant one and a benign one. The latter has no real existence, for in it the trophoblast cells are all dead and undergoing the characteristic degeneration due to the action of pancreatic ferments. A “benign “ chorio-epithelioma, as Professor Schmorl found, may happen in any gestation, for the trophoblast cells of the pre-critical periods, which have invaded the maternal organs—even the lungs—are normally also brought to commencing degeneration at the critical period.
In 1902 the conclusion was reached that cancer was asexual generation or irresponsible trophoblast, and in these words for the first time in human history the nature of cancer was laid bare.
Its origin was not at first so clear, but by the year 1904 it was recognized that the problems of like or identical twins, upon which the writer was then and since engaged, threw light upon its origin. Owing to their extra-embryonic origin aberrant germ-cells are quite common, and they may be met with anywhere in the embryonic body. The ordinary aberrant germ~cel1s, which usually degenerate, were much too abundant a source to furnish the origin of a cancer. Entia non sunt multiplicanda. The etiology of double monsters and of malignant tumours was traceable to the phenomena of