THE EMBRYOLOGY AND ETIOLOGY OF TUMOURS 79
with degeneration of some of their products, they leave as the basis of a tumour a greater or less number of cells, endowed with more or fewer potentialities. As so derived, they are not parts of the organism, but are its sisters or brothers, identical with it in ultimate characters,
As indicating the amount of agreement between my conclusions and those of Wilms, and the extent to which I have adopted his views, except in so far as these are embryological, the following passage from his latest work (1903) may be cited: “The groups of tumours are of equal value in their etiology; they differ among themselves only in that the one group arises from cells of the earliest period of development—the time of the cleavage; the other, from cells of somewhat later time—the period of the formation of the germinal layers” (p. 270). This I would amend as follows:” In their etiology the tumours are of equal value, and they are the results of pathological bizarre attempts at development on the part of aberrant primary germ-cells, originally identical in characters, and, in fine, in all respects, with that primary germ-cell, by whose unfolding the individual harbouring such a tumour arose. As the offspring of primary germ-cells, they may be referred to cells of the cleavage, but not to such appertaining to the embryo. They never arise from cells of the period of embryo-formation (Zeit der Keimblattbildung).
The comparison sufficiently emphasizes the divergences, and, be it added, the existence of ovarial and testicular embryomata is decisive against their derivation from cleavage-cells in the sense of Wilms and Bonnet for none such appertaining to the embryo can find their way into these organs, but instead thereof there are germ-cells, which originally go back to the cleavage. In passing, Wilms’s denial of the possible origin of an embry-