202 ACTIVE IMMUNIZATION 



fection of the human being with the organism in question can only 

 take place by way of the intestinal canal, Ferron injected living 

 organisms subcutaneously, using eight drops of a broth culture for 

 the first and 0.5 c.c. for the second and third, the inoculations being 

 made six to eight days apart. His statistics and experiments on 

 guinea-pigs, which formed the basis of his work on the human being, 

 have been adversely criticised by a number of subsequent investi- 

 gators; but the fact remains that he was the first to attempt anti- 

 cholera vaccination in the human being, that he injected a large 

 number of people (200,000, according to his statements) with living 

 cultures, and that his method is essentially the same as that which 

 Haffkine subsequently used in India, and which unquestionably can 

 afford protection. We also know that as a consequence of such in- 

 jections bactericidal substances appear in the serum in large amounts, 

 and that attempts in this direction hence have a proper theoretical 

 basis. 



The essential difference between Ferron and Haffkine is that the 

 latter uses an attenuated culture (vaccine I) for his first injection, 

 and then follows this with one that has been brought to a high degree 

 of virulence by animal passage, and which, in conformity with Pas- 

 teur's nomenclature, he speaks of as virus fixe (vaccine II). Later 

 investigations have shown, as a matter of fact, that a high degree of 

 virulence is essential to effect successful immunization. But, like 

 Ferron, Haffkine thought it imperative to use living cultures. That 

 this is unnecessary, however, was subsequently shown by Kolle, 

 and the results which have thus far been obtained with the latter's 

 method, both in the human being and in the animal experiment, 

 seem to render future work with living cultures unnecessary and 

 perhaps even undesirable. 



Kolle's Method. The vaccine is prepared by emulsifying twenty- 

 four-hour-old cultures of a virulent strain (increased by passage 

 through guinea-pigs) of the cholera vibrio in normal salt solution, 

 such that 1 c.c. shall contain 1 oese ( = 2 mg.) of organisms. 

 These are then killed by exposure to 60 C. for one-half hour, when 

 carbolic acid is added, to the extent of 0.5 per cent., as preservative. 

 Two injections are given hypodermically about a week apart, 1 c.c. 

 the first tune and 2 c.c. the second time. Care should be taken not 

 to inject at a place where the skin is bound tightly down. Suitable 

 districts are the area over the triceps and the loin. 



