34 STUDIES IN IMMUNITY. 



method is particularly to be recommended for preparations of 

 exudates or any body fluids containing albumin. The eosin used 

 is an alcoholic solution (0.5 grams of eosin to 100 c.c. of 60 per 

 cent alcohol) and the methylene blue is in saturated aqueous 

 solution. 



In general, it is best to leave the inoculated drop of exudate in the 

 incubator for about 4 hours. By this time the bacteria will not 

 have increased to an unreasonable extent, but phagocytosis and the 

 changes caused in the bacteria by the secretion of leucocytes are 

 already quite manifest. It may be noted that in a quarter of an 

 hour, at a temperature of 35 degrees, or in even less time, leucocytes 

 may show a very distinct phagocytic activity. 



The exudate employed was obtained from guinea-pigs that 

 had never received an injection of bacteria, but had simply been 

 given bouillon. A list of the bacteria subjected to the action of 

 leucocytes, with the resulting phenomena that we have noted, 

 follows : 



V. cholerce (culture from Eastern Prussia). Polynuclear leu- 

 cocytes have taken up a large number of the vibrios. The micro- 

 organisms outside the cells have retained intact their form and their 

 reaction to dyes. Within the phagocytes there are vibrios of 

 normal appearance colored a good blue, and also numerous organisms 

 that show distinct granulations. These granulations take different 

 shades of blue, light pink and deep pink. They are quite like those 

 granules that Pfeiffer noted in the peritoneal cavity of immunized 

 animals after injecting a culture of vibrios. These oval or rounded 

 granulations are simply vibrios that have contracted in response 

 to the harmful secretion from the leucocytes. The fact that none 

 of these granulations are found outside the cells shows very clearly 

 the superior bactericidal power of the protoplasm of the phagocytes 

 over that of the surrounding fluid. We shall later consider these 

 granulations more carefully and also the influences that produce 

 them. 



Some of the vibrios within the leucocytes, whether transformed 

 into granules or not, show marked changes in reaction to dyes. 

 Instead of staining with methylene blue, the basic color, they stain 

 with eosin. Metchnikoff has already observed vibrios taken up in 

 the animal body that stain with eosin; he also noted the same fact 



