492 



taken the following remarks 1 ) by the late C. Giacomini seriously to 

 heart, instead of ignoring them : "Das Chorion ist von allen Bildungen 

 des Eies diejenige, welche vor jeder anderen entsteht, sich bald von 

 den anderen Teilen unabhängig macht, und indem es frühzeitig seine 

 Zellen entwickelt, in den Stand gesetzt wird, zu leben und sich zu 

 entwickeln, auch wenn alle anderen Teile des Eies durch 

 irgend welchen Umstand aufgehört haben, zu exi- 

 stieren". In recent years the writer has again and again urged, that 

 in researches upon animal dovelopment two things must be kept 

 sharply separate, the embryo or sexual form, and the asexual foundation, 

 in human development the chorion or trophoblast, upon which it arises. 

 What is there to prevent, as Pick suggests, the total disappearance 

 of all parts of an ovarian or testicular embryoma except the (patho- 

 logical) chorion or trophoblast? The persistence and further growth 

 would but, and do, result in carcinoma! As the chorion 2 ) is 

 always present before an embryo, nothing in the abnormal development 

 of a vagrant or aberrant primary germ- cell would appear to forbid 

 the arrest of this prior to the appearance of any trace of an "embryoma" 

 — with the natural sequel, a carcinoma! 



But, surely now, the etiology of cancer is as clear as that of the 

 tumours in general? 



Since the date of reading the foregoing paper, a little further 

 light has been obtained in another direction. It is a natural question 

 to ask, "can any and every primary germ-cell undergo abnormal de- 

 velopment, or is this power limited to certain of them?" A full reply 

 to this query would entail very prolonged investigation into the de- 

 velopmental problems of identical twins, triplets, etc. For some time 

 this matter has engaged the writer's attention, but, though some land- 

 marks can be recognised, the end is not yet in sight. The whole 

 doctrine of the tumours centres in, so far as I can see, the 

 problems of identical twins, triplets, etc., in fine, in 



1) C. Giacomini, Probleme aus Entwickelungsanomalien des mensch- 

 lichen Embryo. Ergebn. Anat. u. Entwickelungsgesch., Bd. 4, 1894, 

 p. 615—649, loc. cit. p. 640. 



2)' According to the orthodox embryology of the textbooks apart 

 of the embryo! — Although it is invariably present before any part 

 of an embryo, may persist after the complete disappearance of the 

 embryo, is never formed from or by an embryo, and ultimately never 

 makes any part of the embryonic body! 



Logically, how can it be maintained, that a structure, which arises 

 before an embryo and out of no part of it, and which never goes to 

 form any part of any organ of the body, is embryonic or foetal in nature ? 



