THE EMBRYOLOGY AND ETIOLOGY OF TUMOURS 83
each and every primary germ-cell (those of the ovary and testis, of course, included) possesses the faculty of that primary germ-cell, which unfolded as an embryo, of doing likewise.
Of great significance with reference to the question of the germ-cell origin of tumours are the comparatively frequent instances of tumours arising in multiple centres. Some of the recorded cases may be cited from Borst (loc. cit., p. 57, A, et seq.). In the same individual, tumours have been found in liver, uterus, ovary, kidney, skin, etc.; or, again, in the paired organs of the two sides. Babesiu found in the uterus, in the middle of a myoma, a columnar epithelial cancer, and Niebergall recorded a complicated uterine tumour of myoma, polypes, sarcoma, and cancer. Equally important and significant to the embryologist are the facts relating to the occasional presence of different tumours at the same time in different parts of the body. Borst (loc. cit., p. 58) gives the following instances:
1. Cancer of the stomach with ovarial cystoma and fibroma of uterus.
2. Cancer of skin and of rectum.
3. A teratoid of the cranial cavity and an ovarian embryoma.
4. Uterine myoma, lipoma of kidney, enchondroma of lung.
5. Cancer of the thyroid, and multiple fibromata of kidney and uterus, with large papillomata of skin.
Borst looks upon all these and other recorded cases as accidental! They are interesting, however, in the light of—(1) the hypothetical germ-shuntings; (2) the various places in which vagrant germ-cells may be found, and (3) the probable necessity of a certain physiological condition or nidus for the development and growth of a tumour of a certain character.