Immunity 521 



The opinion expressed is that "the only trustworthy 

 difference between many of these varieties and the true 

 cholera spirillum is the specific reaction with serum from 

 animals immune against cholera, or by Pfeiffer's method of 

 intraperitoneal testing in such animals. " 



In discussing these spirilla of the Philadelphia waters 

 Bergey * says : 



' ' The most important point with regard to the occurrence 

 of these organisms in the river water around Philadelphia 

 is the fact that similar organisms have been found in the 

 surface waters of the European cities in which there had 

 recently been an epidemic of Asiatic cholera, notably at 

 Hamburg and Altona. . . . The foremost bacteriolo- 

 gists of Europe have been inclined to the opinion that the 

 organisms which they found in the surface waters of the 

 European cities were the remains of the true cholera organ- 

 ism, and that the deviations in the morphologic and biologic 

 characters from those of the cholera organism were brought 

 about by their prolonged existence in water. No such 

 explanation of the occurrence of the organisms in Phila- 

 delphia waters can be given." 



A number of interesting spirilla, more or less closely 

 resembling that of Asiatic cholera, have been described 

 from time to time. Their variation from the true cholera 

 organism can best be determined by an examination of the 

 following table, though for precise information the student 

 will do well to look up the original descriptions, references 

 to which are given in each case. 



* "Jour. Amer. Med. Assoc.," Oct. 23, 1897. 



