30 ACTIVE IMMUNIZATION. 



can also be accomplished by injecting bacteria and at the same time also 

 their specific serum. This is technically simple and is known as the "Simul- 

 taneous Method" It has shown itself to be of great value in Lorenze's pro- 

 phylactic inoculations against swine erysipelas. 



2. Immunization with Dead Bacteria. Immunization with dead bac- 

 teria was first performed by Toussaint, Salmon and Smith, and Chamber- 

 land 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 immunization 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 as 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 bacteria, 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, bacteriolysis, complement 

 fixat on, etc., then immunization by dead bacteria is just as, if not more so, 

 efficient. 



Recently, the question has been raised whether the antibodies produced 

 by immunization with heated antigens are identical with those obtained 

 with unheated antigens. The experiments of Obermeyer and Pick which 

 will be referred to under proteid immunization, seem to prove that they 

 are not alike. For laboratory work it is advisable to use living cultures 

 only in cases of absolute necessity. 



In heating bacteria to destroy their virulence and thus be suitable for 

 inoculation, we must be very careful not to raise the temper- 

 Death of ature to such a degree where not only the toxicity but also the 

 Bacteria immunization power is destroyed. It is best to employ the 

 by Heat, minimum amount of heat which will kill the respective bacteria. 

 For most of these as Typhoid, Paratyphoid, Colon, and Dysen- 

 tery bacilli, Cholera Vibrios, Meningo-, Staphylo-, Strepto- and Pneumo- 

 coccis, one hour at 60 C. is sufficient. 



The bacteria are grown upon agar cultures and the required amount 

 is removed and suspended in sterile physiological salt solution or bouillon. 

 This suspension is then placed into a hot water bath or thermostat regulated 

 at 60, for one hour. 



If the bacteria employed are highly infectious, one must be sure that all 

 bacteria have been killed. This must especially be noted when giving 

 prophylactic inoculations in man. Several drops of the emulsion are there- 



