1 62 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
that the many cases described as ' Deciduoma Malignum ' really do belong to that 
class, especially when the microscopic findings, as shewn by photo-micrographs, 
etc., shew structures which are obviously of foetal origin. 
One observer alone suggested that the tumour arises from foetal connective 
tissue. 
Gottschalk, in recording a case where the disease developed after an abortion 
at the sixth week, described the condition as a sarcoma of the stroma of chorionic 
villi. The plasmodial layers, although seen to be in an active state of prolifera- 
tion, budding not only into surrounding tissues but also into neighbouring blood 
vessels, he regards as unaltered by disease, and maintains that the malignant 
change affects the connective tissue of the stroma only. 
In the light of our present knowledge, this explanation falls to the ground, 
since a malignant growth of the stroma could not give rise to proliferation and 
metastasis of the syncytium. 
Marchand believes this condition to be a carcinoma of structures arising from 
the foetal ectoderm, and Whitridge Williams, although leaving the origin of the 
polymorphous cells an open question, regards the syncytial masses found in his 
specimen as arising from chorionic villi, and, therefore, of foetal origin. 
In conclusion, I may add that Virchow made an invaluable discovery when 
he found that every tumour had a physiological prototype, a statement that may 
well be applied to the disease we have described, since chorionic elements are found 
normally during the period of pregnancy in close connexion with the maternal 
tissue, and have been shewn by recent observers to have the power of reaching 
distant parts of the body, without producing any untoward results. 
