164 ATLAS OF BACTERIOLOGY. 



(2) Extinct cultures of the micro-organism in ques- 

 tion; or 



(3) The blood serum or tissue juices of an animal 

 immunized by the plans mentioned under (1) and (2). 

 After (1) and (2) there develops an active immunity , 

 after (3) a passive immunity. 



According to the most widely entertained opinion 

 specific immunity depends upon the presence of 

 specific " antisubstances" (Behring) in the blood and 

 tissues of the immunized animal. According to 

 Buchner the "antisubstances" are derived from the 

 injected bacteria cultures and are much more resis- 

 tant than alexins to noxious influences. Thus 

 tetanus antitoxin tolerates a temperature of 70-80 

 and the action of sunlight and putrefaction without 

 decomposing. Brieger and Ehrlich have extracted 

 diphtheria antitoxin in a solid form from the milk of 

 goats which were rendered immune against diph- 

 theria. Whether it is an albuminoid or adheres to al- 

 buminoids, is not yet known. The antitoxins are best 

 extracted (Brieger and Boer: Z. H., XXI., 266) by 

 means of zinc chloride, but we have not yet succeeded 

 in freeing them from the last traces of zinc. Accord- 

 ing to Emmerich the " antisubstances," which he calls 

 "immune proteidins," are combinations of a sub- 

 stance furnished by the bacteria with body albumin 

 from the immunized animal. 



In some cases the character of immunity, the action 

 of the "antisubstances," is purely antitoxic, a true 

 antidote. The notion, first advanced by Behring and 

 Kitasato, that toxin and antitoxin neutralize one an- 

 other chemically (somewhat like an acid and its base) 

 has not been corroborated. We have to deal rather 



