THE EMBRYOLOGY AND ETIOLOGY OP TUMOIJRS 71
adrenal, ovary, or spleen. In no embryological sense can such be considered to represent the missing hypothetical rests. Such structures have not been known to give rise to tumours.
Perhaps the theory of embryonic rests has undergone its most important and most scientific alterations at the hands of Wilms,* of whose views—to some extent, at least—Borst** is also an exponent. Of Wilms’s researches on tumours, and especially of the facts laid bare by them, it is not too much to say that they are epoch-making. But of his embryological conclusions it must be added that they are necessarily false, because based on the premisses of an impossible embryology.
The lost germs or rests of Remak-Cohnheim are replaced by Wilms by what he terms “germinal shuntings” (Keimausschaltungen). Essentially, Wilms’s theory is almost as simple as that to be here advocated, and, like the latter, the hypothesis of germ-shuntings will readily explain many tumours. The germ-shuntings of Wilms are conceived of as follows: At various periods of the development, from the earliest to undefined later ones, prior to the completion of the parts of the embryo, there are single cells or little groups of such, set apart to furnish some structure of the embryo. These are often serially repeated (metameric segmentation) in great numbers. Some one or more of these may be shunted out of the normal connection (? by what) at almost any period of the development. According to Wilms, this shunting is not to be regarded as a displacement, for the thing shunted actually remains in the organ to which it really
* Wilms, Max: “Die Mischgeschwülste,” Leipzic, 1899-1903, 3 Hefte.
** Borst, Max: “Die Lehre von den Geschwülsten,” Wiesbaden. 1902, 2 vols.