PROPHYLACTIC VACCINATION 275 



rapid development of immunity against rabies. In the only experiment 

 reported at this time it was shown that some protection was afforded 

 by the mixture, although the inoculated animal finally succumbed to 

 rabies. Lorenz in 1892 made similar observations in swine erysipelas. 

 Since this time numerous workers have used the method. The most 

 important advance was made when Besredka suggested the removal 

 of the excess of serum by centrifugally washing the sensitized bacteria. 

 Subsequent work has been carried on with killed bacteria treated with 

 their immune sera, washed and suspended in a suitable menstruum. 

 The ordinary non-sensitized bacterial vaccines injected into an animal 

 during the incubation period of a disease are likely to hasten the death 

 of the animal, or if the infection is already acquired, the injection of 

 the vaccine appears to lower the natural resistance. Besredka and 

 Metchnikoff believe that sensitized bacterial vaccines produce no nega- 

 tive phase, but only slight local and general reactions and facilitate the 

 production of antibodies. Kakechi has shown that the toxicity of 

 sensitized bacterial vaccines is less than that of the non-sensitized. 

 Sensitized bacterial vaccines have been employed in numerous infec- 

 tious diseases such as typhoid fever, asiatic cholera and bubonic plague 

 with varying degrees of success. 



Killed Bacterial Vaccines. These are suspensions of bacteria usu- 

 ally in salt solution but sometimes in other mentsrua such as neutral 

 oil. The organisms are usually killed after the suspension has been 

 made, but in making oil suspensions the organisms are killed before 

 the final suspension. Heat is usually employed for killing the bacteria 

 and the action is further supplemented by the addition of a bactericidal 

 preservative to the suspension. Under certain circumstances chemicals 

 such as formaldehyde or phenol may be employed both for killing and 

 preserving the vaccine. Autogenous vaccines are bacterial vaccines 

 prepared from bacteria which have been freshly isolated from the 

 individual patient. At times it is very difficult to isolate the organism as 

 for instance in gonorrhea. In these cases stock vaccines are usually 

 employed. Stock vaccines are made from strains of bacteria isolated 

 at some previous time and kept in the laboratory stock. Stock vaccines 

 are used extensively in prophylactic vaccinations. Mixed vaccines are 

 composed of various kinds of bacteria. Their value is questionable 

 and their use unscientific, except on the basis of non-specific therapy. 

 Many efforts have been made to produce the bacterial antigen in a pure 

 form so as to obtain a minimum of local and general reaction, and to 

 immunize in the shortest space of time possible. Such vaccines have 

 been made from nucleoproteins, autolyzed bacteria, digested bacteria 

 and detoxicated organisms. It appears that some of these methods are 

 promising, especially for the production of antigens from spore- 

 bearing bacteria. 



Preparation of a Bacterial Vaccine. Under strict asepsis an emulsion of 

 the organism in question is prepared by adding 5 to 10 c.c. of physiological salt 

 solution to a twenty-four-hour agar slant culture. This is allowed to stand ten 

 minutes and then rotated actively in order to make a suspension of the organisms. 

 The suspension is now filtered through sterilized filter paper in a funnel into a 



