The germ-cells. Q']\ 



brane. The teeth were of the milk-dentition with permanent teeth. 

 They corresponded in form and size with the age of the child." 

 Sloman and Wilms regard the structure as a parasitic formation. Out 

 of what it arose they do not attempt to explain. 



Other and similar instances will be found in other parts of Wilms' 

 memoir, that is to say, in sections other than those treating of the 

 ovarial dermoids. 



He does not consider any of those tumours to be of the same 

 nature as the latter. The only apparent difference between many of 

 them and the embryomas is in position, the structure being more or less 

 identical. Some of them are set down as "Doppelbildungen" or "In- 

 clusiones foetus in foetu". What, it may be asked, are these but more or 

 less complete and abnormal embryos, that is to say, embryomas? 



Wilms also speaks of the origin of some of them from "Keim- 

 verirrungen". It cannot be supposed, that under this term he under- 

 stands their formation by vagrant germ-cells. What are referred to 

 are the "lost germs" of the pathologists. These are hypothetical 

 things, which are supposed to have lost their connection with some 

 organ or organs, of which they were destined to be the builders in 

 whole, or only in part. Of the actual existence of "germs" of this 

 sort there is no embryological evidence whatever. Of the occurrence 

 of vagrant or lost germ-cells there is now plenty of proof, at any 

 rate, in certain fishes. 



The complicated dermoids, wherever they occur in the body, must 

 be the products of such vagrant germ-cells, or, if in ovary and testis, 

 of persistent primary germ cells. From Wilms' work and my own 

 there is no other possibility. 



Whether or not all "dermoids" be the products of such is an- 

 other question 1). Each case must stand on its own merits. To 

 my mind there is abundant evidence to show, that the embryomas 

 may and do occur in places other than the sexual organs. It is quite 

 natural, that they should be more numerous in these than in other 

 places. Wilms' attempt to restrict their occurrence to the ovary and 

 testis seems to me to have been induced by the absence of any record 

 of the presence of true germ-cells in various parts of the body other 

 than ovary and testis during embryonic life. 



The formation of an embryoma in the neck or head may appear 

 to be a very strange and inexplicable thing, but it loses much of its 



1) How, it may be asked, shall one limit the possible reduction 

 of an embryoma? Where shall the line be drawn? 



