Serum Therapy and Prophylaxis 459 



into guinea-pigs continues in some cases as long as four and 

 a half months, but the power of their serum to confer 

 immunity is lost much sooner. 



Serum Therapy and Prophylaxis. Of the numerous 

 attempts to produce immunity against cholera in man or 

 to cure cholera when once established in the human organ- 

 ism, nothing very favorable can be said. Experiments in 

 this field are not new. As early as 1885 Ferran, in Spain, 

 administered hypodermic injections of pure virulent cul- 

 tures of the cholera spirillum, in the hope of bringing 

 about immunity. The work of Haffkine,* however, is the 

 chief important contribution, and his method seems to be 

 followed by a positive diminution of mortality in protected 

 individuals. Haffkine uses two vaccines one mild, the 

 other so powerful that it would bring about extensive tissue- 

 necrosis and perhaps death if used alone. His studies 

 embrace more than 40,000 inoculations performed in India. 

 The following extract will show results obtained in 1895: 



" 1. In all those instances where cholera has made a large number 

 of victims, that is to say, where it has spread sufficiently to make 

 it probable that the whole population, inoculated and uninoculated, 

 were equally exposed to the infection, in all these places the results 

 appeared favorable to inoculation. 



"2. The treatment applied after an epidemic actually breaks out 

 tends to reduce the mortality even during the time which is claimed 

 for producing the full effect of the operation. In the Goya Garl, 

 where weak doses of a relatively weak vaccine had been applied, this 

 reduction was to half the number of deaths ; in the coolies of the Assam- 

 Burmah survey party, where, as far as I can gather from my pre- 

 liminary information, strong doses have been applied, the number 

 of deaths was reduced to one-seventh. This fact would justify the 

 application of the method independently of the question as to the 

 exact length of time during which the effect of this vaccination lasts. 



"3. In Lucknow, where the experiment was made on small doses 

 of weak vaccines, a difference in cases and deaths was still noticeable 

 in favor of the inoculated fourteen to fifteen months after vaccination 

 in an epidemic of exceptional virulence. This makes it probable 

 that a protective effect could be obtained even for long periods of 

 time if larger doses of a stronger vaccine were used. 



"4. The best results seem to be obtained from application of middle 

 doses of both anticholera vaccines, the second one being kept at the 

 highest possible degree of virulence obtainable. 



"5. The most prolonged observations on the effect of middle doses 

 were made in Calcutta, where the mortality from the eleventh up to 

 the four hundred and fifty-ninth day after vaccination was, among 

 the inoculated, 17.24 times smaller, and the number of cases 19.27 

 times smaller than among the not inoculated." 



*"Le Bull, med.," 1892, p. 1113; "Indian Med. Gazette," 1893, 

 p. 97; "Brit. Med. Jour.," 1893, p. 278. 



