ASIATIC CHOLERA. 187 



were repeatedly demonstrated in the water-supply through 

 conduits, in the water of improperly situated irrigation-fields 

 (Nietleben), in the water of streams, and in the bilge-water of 

 ships. The waters in question all bore some close relation to 

 cholera-foci, having been contaminated by the dejections of 

 the first cases of the disease introduced, so that in this way 

 they were capable of constituting the source for the further 

 spread of the disease. These facts demonstrate that the 

 cholera-bacillus may pass a saprophytic existence. Forms 

 of comma-bacilli have, further, been cultivated from the 

 Spree, the Elbe, the Danube, and the Seine, that, in their 

 microscopic and cultural appearances, closely agreed with 

 the vibrio of Koch, but whose relation to existing cases of 

 cholera was not so easily demonstrable. These water- 

 vibrios are in part to be distinguished from the bacillus of 

 Koch by the absence of pathogenicity ; others, however, 

 are toxic for animals. Thus, virulent vibrios were found 

 almost regularly in the contents of Paris sewers in the 

 summer of 1892, although at the time there was not a sin- 

 gle case of cholera in Paris. All of these bacteria, however, 

 exhibit differences as compared with the vibrio of Koch, 

 even though they are often slight and difficult of dem- 

 onstration. A bacterium absolutely identical with the 

 cholera-bacillus, but in its source without any relation to 

 cholera, has never been found. 



There are two methods of making with certainty the 

 differential diagnosis between the true exciting agent of 

 cholera and the vibrios resembling it. These are the reac- 

 tions of Pfeiffer and Gruber (pp. 62 and 63). In the per- 

 formance of Pfeiffer' s test the blood-serum of guinea-pigs 

 or of other animals that have been highly immunized to 

 cholera is diluted with ordinary bouillon in the proportion of 

 I : 100. To one cubic centimeter of this mixture are added 

 about two milligrams of the vibrios to be examined, caught 

 up with a platinum loop, and the whole is injected into the 

 abdominal cavity of a young guinea-pig weighing about 

 200 grams. By means of delicate capillary glass tubes 

 specimens of the peritoneal exudate that at once forms are 

 removed at intervals of five minutes and examined, both 

 stained and unstained. If the suspected organisms are true 

 cholera-vibrios, the bacilli are shortly seen to become 

 immobile, later collected in small spherules, and finally, 

 within twenty minutes, completely dissolved. If, however, 



