THE INTERLUDE OF CANCER 133
ologist. They recall to him other similar phenomena in
embryology. Reductions in numbers of units (cells), formerly of importance, but
which now persist, not because they are really required, but because their
existence and persistence are parts of an old scheme of the cycle of animal
life.
The
writer has had abundant opportunities of noting the liability of identical
twins to cancer, but to state the matter in this way is misleading. Those
individuals who develop malignant growths are as liable to such as are
identical twins, and for the same reasons. Without doubt cancer is hereditary.
This is abundantly borne out by clinical histories in my possession. There are
records where both parents died of it, where even one or other grandparent
developed cancer, and it is only too commonly told the writer that in some
particular case the father or the mother was a victim of cancer. The most
remarkable example known to me at present is in the family of a
master-carpenter in Edinburgh. His mother died of uterine cancer, and he has
lost all his brothers and sisters, seven in number, by some form or other of
malignant disease. Embryologically regarded, persons suffer from cancer because
they are at the basis members of a group of identical twins or triplets. It is,
therefore, not from any and every aberrant germ-cell that a cancer takes its
start, but from one or other of some few germ-cells, embryonic in destiny,
cells which should have given rise to twins, triplets, etc., identical with the
embryo, which arose in any particular gestation.
(continued from p 132) But if the
number of young here arising at every gestation were much reduced, while all
the preliminaries were retained, what a rich harvest of tumours might be the
result! In a case of identical triplets, cited by Professor H. H. Wilder, at
least two of the sisters died of cancer.