IMMUNITY AND SUSCEPTIBILITY. 77 encased produce an inflammatory transndate which may have properties very different from those of the normal juices. How much of the immunity which animals enjoy de- pends upon the antibactericidal action of their body- juices must remain an open question. In some cases the germicidal action of the blood seems to be unquestion- able. Buchner has shown that the blood-serum of ani- mals only possesses this germicidal power when freshly drawn, and that exposure of the serum to sunlight, its mixture with the serum from another species of animal, its mixture with distilled water or with dissolved cor- puscles, and heating" it to 55° C., check the bactericidal power. Buchner also points out that the bactericidal and globulicidal actions of the blood are simultaneously extinguished. Meltzer and Morris1 found that lymph taken from the thoracic duct of the dog possessed marked bactericidal powers upon the typhoid bacillus. The experiments of Pfeiffer seem to add additional support to the humoral theory of immunity. He found that when guinea-pigs were given experimental choleraic peritonitis, they could be saved from death from the affec- tion by intraperitoneal injection of serum from an immunized animal. He also showed that when the cul- ture of cholera, or a culture