Immunity 507 



live: The organism should liquefy 10 per cent, gelatin and 

 should not coagulate milk. (4) Metabolic: Indol reaction 

 should be marked. (5) Immunity reactions: The organism 

 when injected into guinea-pigs in ascending doses should 

 occasion immunity against the typical cholera organism, 

 and the serum of the immunized guinea-pig, when intro- 

 duced into a new guinea-pig, should protect it from infection 

 and produce Pfeiffer's phenomenon. The blood-serum of 

 animals immunized against the cholera organism should 

 agglutinate the doubtful organism in approximately the 

 same dilution, and that of animals immunized to the doubtful 

 organism should agglutinate the cholera organism recipro- 

 cally. Both organisms should have equal capacity for 

 absorbing complements and amboceptors from blood-serum. 

 (6) The true cholera organism should not be hemolytic. 

 Too much reliance must not be placed upon the agglu- 

 tination tests alone, as will be made clear by a perusal of 

 the paper upon Bacteriological Diagnosis of Cholera by 

 Ruffer.* 



Immunity. Gruber and Wiener, f Haffkine.J Pawlow- 

 sky, and Pfeiffer || have immunized animals against toxic 

 substances from cholera cultures or against living cultures. 

 There seems, according to the researches of Pfeiffer, to 

 be no doubt that a protective substance exists in the blood 

 of immunized animals. In the peritoneal infection of 

 guinea-pigs the spirilla grow vigorously in the peritoneal 

 cavity, and can be found in immense numbers after from 

 twelve to twenty-four hours. If, however, together with 

 the culture used for inoculation, a few drops of the serum 

 from an immunized animal be introduced, Pfeiffer found 

 that, instead of multiplying, the organisms underwent a 

 peculiar granular degeneration and disappeared, the unpro- 

 tected animal dying, the protected animal remaining well. 

 This bacteriolytic change takes place as well in the test- 

 tube as in the peritoneal cavity. 



For a long time this bacterial destruction, known as 

 " Pfeiffer's phenomenon," could not be explained. If the 



* "British Medical Journal," March 30, 1907, I, p. 735. 

 t "Centralbl. f. Bakt.," etc., 1892, xiv, p. 76. 



J"Le Bull, med.," 1892, p. 1113, and "Brit. Med. Jour.," 1893, 

 p. 278. 



"Deutsche med. Wochenschrift," 1893, No. 22. 

 || "Zeitschrift fur Hygiene," Bd. xvm and xx. 



