110 THE ENZYME TREATMENT OF CANCER
certain microscopical preparations of transient ganglion cells, parts of the asexual generation of a dogfish. These may be taken to typify the trophoblast of a mammal or the cells of a malignant tumour. The preparations show:
(a) cells in full functional activity prior to the critical period, and (b) cells which, with the passing of the critical phase, have entered upon their long, slow course of degeneration by simple atrophy. It would have been preferable to exhibit preparations of trophoblast, but those made after this method some years ago are now faded. The facts in the two cases, the mammal (sheep, pig, and others) and the fish (Scyllium, Raja, and others), are, however, quite similar. There is, indeed, only one mode of development in vertebrate animals. Freshly made preparations of human trophoblast of, say, the fifth and ninth weeks of gestation would display the like bloom on the one side of the critical period and the same decay on the other. Such figures of mammalian trophoblast have, indeed, been published already in the writings of my friend Dr. J. P. Hill.
The question which I wish to discuss is one which interested me exceedingly some years ago, long before its significant hearings upon the cancer problem were obvious. In a nutshell it is this: Why do these and certain other cells of a fish development, like those of the mammalian trophoblast, go on flourishing for a certain definite portion of the early development, whilst the parts of the sexual generation, “the embryo,” are unfolding, and then with an almost tragic suddenness commence to degenerate and die? What brings this remarkable change to pass, one which in human development is lacking, if “the embryo” be absent or very abnormal?
Cancer is an irresponsible trophoblast. The unfolding