The test for malignancy which is the subject of the present paper was first described in 1926.1 It has been the object of considerable attention in Europe since that time and has served as the basis for a number of immunologic investigations by its author and others. Clinical studies have been reported on more than 1,000 cases, with an accuracy of about 90 per cent. There appears to have been no work done on it in the United States.
Fuchs observed that washed fibrin from one species of animal was not digested by serum from the same species but was digested by serum from other species. This reaction appeared to be so specific that different breeds of the same animal, e. g., rabbits,2 could be distinguished from each other by means of it. He then investigated the reactions of pathologic blood and found that blood from patients suffering