ISOLATION OF TOXIN 451 



Isolation of toxin. In 1888, Roux and Yersin showed that the 

 diphtheria bacillus produces a toxin. Roux had realized that 

 the germs might secrete a deadly toxin which he attempted to 

 separate from the germs. He grew the bacilli on broth and used 

 a porcelain filter that held back the germs, but permitted the 

 soluble material to pass through. The filtered liquid was then 

 inoculated into guinea pigs which developed the symptoms of 

 diphtheria. Thus Roux showed that the diphtheria bacilli kill 

 through a toxin rather than by the spread of the germs. Earl'er 

 investigators of this disease were unsuccessful because they did 

 not realize that the germs stayed in the throat and sent out 

 toxins (exotoxins) which affected the body. The healthy people 

 who had diphtheria germs were probably diphtheria carriers and 

 the sick people who did not have the bacilli in their throats 

 probably did not have diphtheria. 



The discovery of antitoxin. The toxic effects of the diphtheria 

 bacillus led Von Behring to believe that blood contained certain 

 chemical substances which would kill invading microbes without 

 injuring the person or animal. After a series of experiments, 

 he finally inoculated diphtheria toxins under the skin of guinea 

 pigs that had recovered from diphtheria. 

 They were not affected by the toxins, but 

 when he inoculated toxins under the skin 

 of guinea pigs that had not had diph- 

 theria, they became ill. 



Von Behring obtained blood from guinea 

 pigs that had recovered from diphtheria, 

 separated the serum, and mixed it with 



^ 



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V S* * * ' ^"* ' i 



diphtheria toxin. He injected this mix- The be aded appearance, 

 ture of serum and toxin into healthy ^SyffS&f^ 

 guinea pigs and they were not injured by carefull y p^pared culture, 

 it. But, when he mixed blood serum from guinea pigs that had 

 never had diphtheria with diphtheria toxin, and inoculated the 



