The theory of phagocytosis, which was first advanced to explain certain phenomena in zoölogy, was applied to pathology, and at the present time its sphere is being extended to the explanation of certain problems in immunity by its strongest supporters, namely, Metchnikoff and his pupils. Heretofore the phagocytic phenomena observed in pathology have always been more or less closely connected with microbic infection; of late the reactions of phagocytes to purely toxic chemic substances are receiving attention.
In a recent communication Besredka1 records the results of his observations upon the action of leucocytes on a very toxic combination of sulphur with arsenic (tri sulfure d' arsenic). This substance is of a clear beautiful yellow color, quite insoluble or nearly so, and is therefore readily recognized in the tissues. The experiments were made on the guinea-pig, the arsenic compound being injected into the abdominal cavity in an aqueous suspension. After