SENSITIZED BACTERIA 3! 



To this class of experimental work belong also the attempts of Fried- 

 mann to immunize against human tuberculosis by the use of the tubercle 

 bacilli of cold-blooded animals, and those of Wassermann, Ostertag and 

 the author, to inoculate against hog cholera with living cultures of mouse 

 typhoid. 



Besides the preceding mode of virus attenuation by passage through 



animals, there are other methods employed for the diminu- 



Other tion of the toxicity of the virus. Growing the bacteria at 



Methods of too high a temperature, or exposing bacterial emulsions to 



Vaccine light, disinfectants or moderate heating, accomplishes the 



Preparation. same purpose . 



The mixture of bacteria with their specific serum (i.e., serum 

 obtained from animals that have been inoculated with these bacteria), 

 also diminishes the virulence of the bacteria. Such bacteria are des- 

 ignated by Bordet as " sensitized." In this mixture, the bacteria 

 attach their specific antibodies; after 'centrifugalization, the added 

 specific serum now devoid of its specific antibodies is removed, and 

 the sensitized bacteria can be used as vaccines. Inoculations of the latter 

 rarely produce any infiltration. The same object can be accomplished 

 by injecting bacteria and at the same time also their specific serum. This 

 is technically simpler and is known as the "Simultaneous Method." It 

 has shown itself of great value in Lorenze's prophylactic inoculations 

 against swine erysipelas. 



2. Immunization with Dead Bacteria. Immunization with dead 

 bacteria was first undertaken by Toussaint, Salmon and Smith, and 

 Chamberland and Roux. 



This method is to be distinctly separated from those already discussed. Bail 

 claims that the immunization with living bacteria as well as by aggressins (to be 

 mentioned later) is an immunization against the infectious disease; while the immuniza- 

 tion with dead bacteria is an immunization against the bacterial bodies. While this 

 holds true for some bacteria, it is, to say the least, questionable whether it can be 

 considered a general rule. 



Whenever a real immunity is desired that is, protection against 

 disease, a vaccine either in the form of living or attenuated bacteria should 

 be given the preference. Up to a certain degree, the extracts of living bac- 

 teria, and the natural and artificial aggressins can be similarly employed. 

 If, however, no real immunity, but just a serum containing a great number 

 of antibodies is wanted, as in serum diagnosis, for agglutination, bacteri- 

 olysis, complement fixation, etc., then immunization by dead bacteria 

 is just as, if not more so, efficient. 



Recently, the question has been raised whether the antibodies pro- 

 duced by immunization with heated antigens are identical with those ob- 

 tained with unheated antigens. The experiments of Obermeyer and Pick, 



