THE EMBRYOLOGY AND ETIOLOGY OF TUMOURS 81
relinquished it, because in one instance he found not less than five embryomata in a single ovary, and, of course, this number of polar bodies has been met with nowhere in the animal kingdom. Even two embryomata, a teratoid in the cranial cavity and an ovarian embryoma—a condition recorded—suffice to negative the possibility; for it has been pointed out to me that nowadays it would appear to be the rule in mammals that only one polar body should be formed.*
Wilms (loc. cit., p. 250) sums up his ideas pretty clearly in the following: “In other words, double monstrosities, foetal inclusions, and embryomata are all, indeed, to be referred back to an over-production (!) in the early development, but only in the double formations (Bildungen) do the cleavage-cells (Furchungskugeln) and the formation proceeding from them develop at the same time; in the other cases the one of the two only attains development at a later period.”
Before treating of the comparative embryology of the tumours at length, one or two other things call for notice. Marchand, and finally Wilms, consider all the teratomata as of equal value morphologically. With this I would express cordial agreement. A vagrant germ-cell, developing pathologically in pericardium, abdomen, sacral region, or elsewhere, to form a more or less rudimentary embryo, in doing this is giving rise to something exactly comparable to an embryoma of ovary or testis. On p. 251 of “Die Mischgeschwulste,” Wilms writes: “A series of sacral teratomata is remarkably completely developed. An embryo en miniature in the most exquisite fashion may be developed.” He goes on to say that he himself possesses
* This was written in 1903, but now (1911) more recent researches of Sobotta, Burckhard, van der Stricht, Lams, Doorme, and J. P. Hill, have shown that in certain mammals the first polar body is formed in the ovary, and afterwards disappears.