ASPECTS AND ETIOLOGY OF CARCINOMA 65
developmental cycle. The embryologist and pathologist may ignore and neglect the plain and palpable fact, but on no theory of direct development—a thing only existing for the higher animals in the human imagination—can any explanation whatever of the nature of carcinoma be advanced. This would have been recognized clearly long ago had some embryologist taken the trouble, as the writer has done since 1888, to trace out in full the details of the life-cycle of one of the higher animals from egg to egg. The idea of direct development, accepted without examination of the evidences, and the erroneous belief in the somatic (body) origin of germ-cells, have retarded the advance of knowledge to an extent difficult to estimate.
The nature of the argument employed in the present writing may be summarized as follows Granted the facts of the origin, migrations, and history of the germ-cells of vertebrates, and assuming the course of the life-cycle to be that previously indicated, by hypothesis cancer is derived from vagrant primary germ-cells, which, instead of forming a more or less complete embryo or embryoma, skip this, and give rise to an asexual generation of indefinite unrestricted powers of growth. This is, of course, purely hypothetical, but it becomes the true explanation by the following facts: On the one hand, as my researches have shown, the hypothetical verirrte Keime, or “lost germs,” of pathologists not only exist, but they are numerously represented, and by things capable of abnormal development—the vagrant primary germ-cells. On the other hand, the carcinomatous nature of such an abnormal growth of an asexual generation has been demonstrated abundantly by Marchand for the instances of the pernicious growth of the chorion,chorio-epithelioina. If such a chorion, or trophoblast, the representative more