introduction of substances out of harmony with the blood plasma, ferments appeared which are capable of transforming these products, and of depriving them thus of their specific character. These facts established beyond doubt one means of defence possessed by the animal organism against the invasion of disharmonious substances.
My thoughts then turned at once to the relation of these facts to immunity, and especially also to anaphylaxy, and I undertook experiments to decide the question as to whether the animal organism develops any ferments of a specific nature against substances produced by micro-organisms. And I was particularly interested in the question whether the stages that arise, in any given case, during the decomposition of a particular substrate vary with the species of the invading cell, and whether this may not give us the explanation of many phenomena that appear in the course of certain infections. Finally, I was able to demonstrate that, during pregnancy also, the organism defends itself, by means of ferments, against certain constituents which are passed into the blood, most probably from the cells of the chorionic villi, and which, though in harmony with the species, are out of harmony with the plasma. This observation renders possible a diagnosis of pregnancy.
The above statements have a bearing on a great
