74 STUDIES IN IMMUNITY. 



the organism only after death and during life usually remains in the 

 intestine; that is to say its culture medium is the intestinal secretion. 

 It is important, therefore, to consider the properties of this secretion. 

 Metchnikoff, as we know, succeeded in producing true intestinal 

 cholera in young rodents. His method consists in introducing the 

 cholera vibrio accompanied by certain bacteria that facilitate their 

 development, into the stomach of these animals. Under these 

 conditions cholera is regularly produced. When one autopsies 

 young rabbits treated in this way the intestine is found filled with 

 a rather clear fluid swarming with vibrios. Metchnikoff has further 

 determined that this intestinal cholera may be produced in animals 

 that have received large injections of a strong preventive serum 

 quite as well as in animals which have had no previous treatment. 

 In such animals the vibrio increases in the intestine, and remains 

 motile and unmodified. It may be easily shown that intestinal 

 secretion plus our preventive serum causes no metamorphosis of 

 the vibrio. The same negative result is obtained if normal serum 

 be added to the intestinal fluid from a young rabbit killed by cholera. 

 This animal, however, had received a previous dose of cholera serum 

 and its blood was strongly bactericidal for the vibrio. An intes- 

 tinal secretion of this sort contains no leucocytes ; it does contain, 

 however, epithelial cells which apparently give the fluid no distinct 

 activity. 



Does the cholera vibrio become accustomed to bactericidal sera? 

 Can we by repeated passage through bactericidal fluids adapt it so 

 that it no longer feels the bactericidal effect with the same intensity 

 and fails to give granular transformation? 



If we inoculate a rather large quantity of the cholera vibrio (East- 

 ern Prussia) in a mixture of fresh guinea-pig serum and immunized 

 goat serum the metamorphosis takes place rapidly. But if the 

 amount inoculated is sufficient the vibrio will eventually grow and 

 after 24 hours a considerable number of normal organisms will be 

 found. 



A few drops of this growth may then be inoculated in a mixture 

 similar to the first and when this culture has grown out a new 

 transfer made. If this transfer is repeated twenty times we find 

 that after each inoculation a rapid metamorphosis of the vibrio 

 occurs, and even after two days, when the culture has finally grown 



