﻿REPORT ON CHOLERA IN MANILA. 433 



in vitro, the binding power of the organism for amboceptors in a cholera 

 immune serum is independent of the virulence of the organism. In 

 some instances they found that a virulent cholera culture was able to 

 bind more amboceptors than an avirulent one, but in many instances 

 the reverse was the case. 



Their experiments referring to the relation between virulence and 

 immunizing power are not numerous. This seems to me to be un- 

 fortunate, for by means of their method of examination and the large 

 number of cultures which they studied, they were in a position to solve 

 this problem conclusively. In fact, in the small number of experiments 

 they record, only one instance is given in their table of results in which 

 they found that 1/10 oese of a killed avirulent organism, when injected 

 intravenously into a single rabbit, furnished a serum with a bactericidal 

 value of 1 : 1,000, while 1/10 oese of a killed, highly virulent strain in 

 another animal produced a bactericidal value of only 1 : 200. However, 

 while the results of those experiments suggest that immunizing power 

 is independent of virulence, nevertheless, in the inoculation with such 

 small amounts of the organism, the individual variation in the immunity 

 of an animal plays such an important role that it would not be prudent 

 to draw any general conclusions from this single result. For example 

 in this same series of experiments three other rabbits were inoculated 

 with 1/10 oese of the cholera strain (number 74) ; one of these gave a 

 serum of a bactericidal value of 1 : 2,000, one of 1 : 1,000, and one of 

 1 : 400. Therefore, it would seem that further experiments are neces- 

 sary before we can reach a final conclusion on this subject. This ques- 

 tion in particular is not settled in regard to the inoculation of the living 

 organisms of different virulence, and of the relative immunity produced. 

 1 32 recently performed some experiments with living plague bacilli 

 of different virulence and found that the more virulent organism fur- 

 nished the greater immunity. However, as I worked with but three 

 strains of this bacillus my experiments also can not be considered as en- 

 tirely conclusive for other strains of the plague organism. It seems 

 possible that the coefficient of growth of the spirillum may play some 

 part in the degree of cholera immunity produced; that is, the virulent 

 organism may multiply more rapidly after inoculation than the less 

 virulent one, as Gotsclich and Wiegand found in cultures; this need 

 not necessarily imply that a greater volume of growth is obtained with 

 the virulent organism, in fact the individual spirilla may be smaller 

 in size than in the case of the avirulent culture. The larger forms of 

 the spirillum, it has been observed, are much more common in cultures 

 of the avirulent strains than they are in those of virulent ones. It must 

 be recalled that Haffkine in connection with the question of virulence 



""-This Journal, Sec. B., Med. Sci. (1907), 2, IS?. 



