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.