CHOLERA. 433 



fected by thorough washings with jets of boiling water 

 thrown upon them through hose. Baggage can be steril- 

 ized by superheated steam. 



It often becomes a matter of importance to detect the 

 presence of cholera in drinking-water, and, as the dilu- 

 tion in which the bacteria exist in such a liquid may be 

 very great, much difficulty is experienced in finding them 

 by ordinary methods. One of the most expeditious meth- 

 ods that have been recommended is that of Loffler, who 

 adds 200 c.cm. of the water to be examined to 10 c.cm. 

 of bouillon, allows the mixture to stand in an incubator 

 for twelve to twenty-four hours, and then makes plate- 

 cultures from the superficial layer of the liquid, where, 

 if present, the development of the spirilla will be most 

 rapid because of the presence of air. A similar method 

 can be used to detect the spirilla when their presence is 

 suspected in feces. 



Gruber and Wiener, Haff kine, Pawlowsky, and Pfeiffer 

 have all succeeded in immunizing animals against the 

 toxic substances removed from cholera cultures or against 

 living cultures properly injected. There seems, accord- 

 ing to the researches of Pfeiffer, to be no doubt that in 

 the blood of the protected animals a protective substance 

 is present. In the peritoneal infection of guinea-pigs 

 the spirilla grow vigorously in the peritoneal cavity, and 

 can be found in immense numbers after twelve to twenty- 

 four hours. If, however, together with the culture used 

 for inoculation, a few drops of the protective serum be in- 

 troduced, Pfeiffer found that instead of multiplying the 

 organisms underwent a peculiar granular degeneration 

 and disappeared, the unprotected animal dying, the pro- 

 tected animal remaining well. 



Pfeiffer and Vogedes l have suggested the application 

 of this " immunity-reaction " for the positive differentia- 

 tion of cholera spirilla in cultures. A hanging-drop of 

 a 1 : 50 mixture of powerful anti-cholera serum and a 

 particle of cholera culture is made and examined under 



1 Centralbl. fur Bakt. und Parasitenk., March 21, 1896, Bd. xix., No. II. 



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