As is well known Dold (1) discovered, in the salt-solution extract of viscera, a poisonous property, which can be neutralized by blood serum. This so-called “Organgift” still remains a problem attracting the attention of observers. As to the nature and properties of the poison we have a number of other investigations (Dold and Ogata (2), Ascoli (3), Isar and Patane (4), Ichikawa (5), Aronson (6), Dold and Kodama (7), Yoshimura, Goto and Ishikawa), the results of which diverge from one another. It would seem probable that the toxin above mentioned is contained also in the placenta, which may be considered as one of the viscera. The placenta is, in fact, a viscus which is present in the female sex only during a certain period of life and which is often placed anatomically in the category of tumor; it extends its villi into the maternal blood in which they are bathed so long as they exist, thus standing in a relation to the maternal body that is quite peculiar to itself.