On Preventive Inoculation. 



257 



the tissues, becomes innocuous. Immunity against morbid symptoms 

 generated by the products of microbes does not seem to imply neces- 

 sarily the ridding of the system of such microbes. It is known now, 

 since the discoveries of Behring and Kitasato, that such a resistance 

 to these products can be originated artificially, by gradually treating 

 the system with increasing quantities of toxines. The system reacts by 

 developing anti-toxines tending to neutralise the effect of the toxines. 



On the other hand, Gamaleia first drew attention to the fact that it 

 is possible to create in an animal resistance to lethal doses of virulent 

 microbes without that animal acquiring any resistance to a dose of the 

 products prepared from the same microbes in the laboratory. 



One seems justified therefore in considering separately two kinds of 

 immunity : One against the living microbe, which would prevent it 

 from entering the system and causing an attack ; and another against 

 the fatality of the symptoms of the disease caused by the products of 

 the microbe when the latter overcomes the initial resistance and does 

 invade the system. 



In the inoculation against cholera, which is done with the bodies of 

 microbes, the first result alone is obtained. 



These considerations were confirmed by a set of laboratory experi- 

 ments by PfeifTer and Kolle, intended to verify our Indian results, 

 and in the course of which they detected in the serum of men inocu- 

 lated with only one dose of cholera vaccine an extremely high pro- 

 tective power, equal to that which, in goats for instance, could be 

 created only after a very prolonged treatment, extending over five 

 or six months, and including injections with gigantic doses of cholera 

 vaccine. 



On analysing, however, in detail the properties of that serum they 

 found that it possessed an intense power of destroying the cholera 

 microbes, but exhibited no antitoxic properties capable of neutralising 

 the effect of the products of those microbes. 



The Plan of A nti-plague Inoculation. 



When, in 1896, I was confronted with the problem of working out a 

 prophylactic treatment against the plague, I determined to put to test 

 the ideas originated by the observations on our cholera patients, and to 

 attempt, in the new preventive inoculation, to obtain at once a lower- 

 ing of the susceptibility to the disease, and a reduction of the case 

 mortality. 



This I resolved to obtain by treating the system with a combination 

 of the actual bodies of microbes and of the concentrated products of 

 their activity. 



In presenting the above considerations, I beg that they may be con 

 sidered as provisional, subject to modification or to complete refutation. 



