Serum Therapy and Prophylaxis 579 



The immunity produced by the injection of the spirilla into 

 guinea-pigs continues in some cases as long as four and a half months, 

 but the power of the 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 organism, 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 cultures 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 virulent that it would 

 bring about extensive tissue-necrosis and perhaps death if used 

 alone. His studies embrace more than 40,000 inoculations per- 

 formed in India. The following extract will show results obtained 

 in 1895: 



" i. 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 preliminary 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 excep- 

 tional 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." 



Pawlowsky and others have found the dog susceptible to cholera, 

 and have utilized it in the preparation of an antitoxic serum. 

 The dogs were first immunized against attenuated cultures, then 

 against more and more virulent cultures, until a serum was ob- 

 tained whose value was estimated at 1:130,000 upon experimental 

 animals. 



Freymuthf and others have endeavored to secure favorable 



* "Le Bull, med.," 1892, p. 1113; "Indian Med. Gazette," 1893, p. 97; "Brit. 

 Med. Jour.," 1893, p. 278. 



t "Deutsche med. Wochenschrift," 1893, No. 43. 



