Page:Popular Science Monthly Volume 84.djvu/31

Rh the basis of embryonic malformations. It is very probable that many embryomata especially those of the ovaries and testicles owe their origin to the parthenogenetic development (development without previous fertilization) of a germ cell, a suggestion made more probable through the discovery of Jacques Loeb that in various classes oi invertebrates ova can be induced by artificial means to develop without previous fertilization. And yet the majority of pathologists believe with Bonnet and Marchand that such embryomata just as other mixed tumors of childhood are due to embryonic aberrations, to a separation of early cells which are formed in the course of the early division of the previously fertilized ovum or to the abnormal fertilization of a little cell separated normally from the egg previous to the entrance of the spermatozoon.

However, this hypothesis can not be easily reconciled with the fact that the majority of embryomata appear in the germinal.glands (ovaries and testicles), an observation which can be readily explained, if we assume that these embryomata are due to the parthenogenetic development of ova in the ovarian follicles. This is the more probable as I found that in about 10 per cent, of the ovaries of young guinea-pigs formations occur which can not very well otherwise be explained than as embryonal structures, placental as well as embryonic in the stricter sense, developing abnormally from ova in the ovarian follicles and gradually being destroyed by the surrounding tissues. A previous fertilization could be excluded in these cases.

Moreover in the ovaries of various mammals one can not rarely observe ova in athretic (degenerating) follicles which show the first, somewhat irregular segmentations, and in the armadillo as many as eight cells may, according to H. H. Newman, be seen.

While these observations explain satisfactorily the relatively frequent occurrence of embryomata in the germinal glands, they may also explain the embryomata found at other places, inasmuch as it is known that the germ cells migrate in various directions in the developing embryo, before they reach the germinal gland. In some cases however blastomeres (cells formed in the course of the early segmentation of the egg) may form the matrix of the tumors, inasmuch as it has been shown in certain