VACCINES ROGER. 463 



immunity by introducing into the organism either sterilized cul- 

 tures, liquids of the culture free from microbes, or extracts of the 

 bacteria. Each of these different methods has to its credit a certain 

 number of experimental successes and admits of practical application. 



The prophylaxis of typhoid fever has attracted special attention 

 and incited numerous researches. After the first attempts of Chan- 

 temesse and Widal, it was established through the work of Wright 

 that cultures sterilized by heating can be used. It is only necessary 

 to take care not to exceed a temperature between 53° and 56°. Even 

 within these limits heating has the drawback of weakening the 

 ability to render immune. It has also been proposed to sterilize the 

 cultures by the antiseptics phenol, chloroform, ether, and iodine. 

 And for some time there have been used in practice the autolysats of 

 microbes. It is known that the protoplasm of bacteria, as all living 

 protoplasm, contains digestive ferments. Left to themselves under 

 unfavorable conditions the cells are digested — ^that is, liquefied by 

 the ferments which they contain. This autodigestion is given the 

 name autolysis. On this principle is based the vaccine of M. Vin- 

 cent. But as among the higher plants innumerable varieties of a 

 single species are known (it will be recalled what the horticulturists 

 have obtained in growing roses or chrysanthemums), so in each 

 microbe species we should distinguish the varieties or races which 

 close study permits us to differentiate. That is why, in the prepara- 

 tion of vaccines, bacilli from different sources have been used. The 

 polyvalent vaccine of Val de Grace is prepared with 10 different 

 specimens. They are sprinkled on a liquid solidified by agar-agar, 

 and after 48 hours in the incubator the cultures are taken out and 

 their surface scraped. The bacilli thus collected are put in salt 

 water to be macerated. The liquid is agitated at different intervals, 

 then at the end of 36 to 40 hours it is submitted to electric centrif- 

 ugalization to be clarified, and finally it is sterilized with ether. 

 Four injections with this vaccine must be made at intervals of eight 

 hours to confer absolute immunity against typhoid fever. 



The different antityphoid vaccines give excellent results. The 

 trials made in the Army have demonstrated their efficacy and their 

 harmlessness. The only effects observed during the time following 

 their application are a slight discomfort and a small rise of tem- 

 perature. But these manifestations are light and passing. So it is. 

 with good reason that compulsory antityphoid vaccination has been 

 decreed for the whole French Army. This measure is the more 

 important since in time of war the rate of siclmess and death from 

 typhoid fever is extremely high. Even with the precautions taken 

 there is a large number of cases, but these occur only among those 

 not vaccinated or insufficiently vaccinated. However, even among 

 Shose who have received the necessary inoculations, infections simi- 



