196 ACTIVE IMMUNIZATION 



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 mgrms.) 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 time and 2 c.c. the second time. Care should be taken 

 not to inject at a place where the skin is bound tightly down. Suit- 

 able districts are the area over the triceps and the loin. 



Symptoms following the Inoculation. As in the case of the anti- 

 typhoid injections, the symptoms vary in different people. Locally 

 there is more or less pain which begins after five to six hours, with 



