THE EMBRYOLOGY AND ETIOLOGY OF
TUMOURS 73
somites
may be shunted, actually or but physiologically, from the normal connection is
purely hypothetical, and nothing of the kind has ever been witnessed. Rudimentary
somites occur even in the trunk region in some animals, but these are
rudimentary, and probably always disappear.
Wilms
regards his germs as things destined in reality to form parts of “the embryo,”
and therefore as belonging to this.* Under his views cases of five embryomata
in one ovary require the shunting into this of five blastomeres during the
early development; that is to say, in this instance the original fertilized egg
must have been divided up in some way or other into at least six portions, one
of which formed a normal embryo, while the remaining five retained at least the
potentialities of each becoming an abnormal embryo or embryoma. It is open to
doubt whether any upholder of epigenesis will admit the possibility of the
course of events happening in this way. As it would seem, a new hypothesis is
needed to account for each of the five embryomata, with an additional one to
explain the continued normal character of the development after such a shaking
and shunting.
Equally
formidable difficulties are furnished by the well-known instances of multiple
tumours, of various kinds, in one individual. Indeed, the doctrine of epigenesis
as the mode of the development labours under quite sufficient insuperable
intrinsic difficulties without having to bear the burdens imposed upon it by
such
* As decisive against the origin of
tumours from cells, or tissues, of the individual in which they develop, may be
cited the facts that very many of them are encapsulated from the surroundings—thus,
tumours of the kidneys, breast, and parotid; and that various observers—thus,
Wilms and Borst—deny any passage or transition of normal tissues into them. The
encapsulation of many tumours is of embryological interest, because many of
the aberrant germ-cells exhibit this feature.