therapeutics and serum-diagnosis and by the extension of the idea of preventive inoculation. As may readily be seen, the fundamental observations of Pasteur, of Behring and of Pfeiffer had been elaborated into some of the most serviceable principles, acknowledged at the moment, in the science and practise of medicine. Nor is this influence a matter of the past. In our own day has been established the theory of specific precipitation of foreign proteins (Uhlenhuth, 1901). This has led to the elaboration of a specific test for the differentiation of both vegetable and animal proteins, a method which has been adopted for the determination of species, not only in bacteriology, but also as a medico-legal test for determining the origin of blood stains and as a general biological procedure.
So also, through the work of Denys and later of A. E. Wright, a body has been recognized in the serum which had the power to prepare bacteria for ingestion and digestion by the leucocyte. To this body the name of opsonin or tropin has been given. You will remember that Metchnikoff discovered the fact that the white cells of the blood have the power to engulf bacteria, Wright supplemented this conception of demonstrating that a substance in the serum could so affect bacteria that they would be taken up more readily and in greater numbers; also he demonstrated that this opsonic power of the serum could be increased, and as the results of his teachings a definite opsonic therapy has developed. This treatment depends on the principle of vaccination with bacterial products. Before Wright, with the exception of Pasteur's treatment for hydrophobia, vaccination was used as a preventive measure only, but the studies which his observations have stimulated have led to very satisfactory results in the treatment of certain local infections as those due to the pus cocci and colon bacillus. Also, these studies have extended the practise of immunizing vaccination, as a prophylactic measure with, it has been claimed, most favorable results in the prevention of typhoid fever. For example the sanitary record of the maneuver division of the United States Army recently stationed on the Mexican border shows that in a body of 8,097 enlisted men, careful sanitation and antityphoid inoculation prevented almost entirely the occurrence of typhoid fever; only one case of typhoid fever was observed, and it was not fatal; while at the same time in the near-by city of San Antonio 49 cases were reported. Comparing the record of the maneuver division with that of a division of the Seventh Army Corps stationed at Jacksonville, under quite similar circumstances in 1898, we have one case of typhoid among the 8,097 men of the former and 2,693 undoubted cases among the 10,759 men of the latter division. It must be admitted in regard to this record of the maneuver division, that it is difficult to say to what extent the excellent showing was due to careful sanitation and to what extent to the antityphoid inoculation,
