TWENTY-FIVE YEARS OF BACTERIOLOGY 121 



obtained by precipitation in, it is true, an impure state 

 but one in which its poisonous action was preserved. In- 

 deed, so appalling- did its poisonous effect prove to be that 

 these investigators could not imagine any other non-living 

 substance than an enzyme which could exhibit such active 

 properties. 



The isolation of the diphtheria toxin, quickly to be fol- 

 lowed by the similar isolation of the tetanus toxin, was 

 an event of capital importance and reacted at once vigor- 

 ously on the chemical aspects of bacteriology just strug- 

 gling into the light. The immediate effect of the study of 

 the new poisons, called toxalbumins, was to discredit a 

 whole series of pure, crystalline basic substances obtained 

 not long before from a wide variety of bacteria, to which 

 the name of ptomaines had been given. Many of the 

 ptomaines were possessed of poisonous properties ; but 

 what was disconcerting- was that very diverse bacteria 

 might yield identical chemical compounds which, there- 

 fore, lacked the property of specificity, an essential qual- 

 ity of bacterial activity. The toxalbumins, on the other 

 hand, which even to this day have not been secured in a 

 chemically pure state, exhibit in perfect degree the prop- 

 erty of specificity and display all the power for evil ancj 

 all the potential possibilities for good which their original 

 and respective bacilli possess ; and although no method of 

 chemical identification of their special nature is available, 

 yet their pathological effects and immunological activities 

 serve readily and accurately to distinguish one from the 

 other and to indicate their origin. 



The rendering of animals immune to diphtheria, on the 

 one hand and to tetanus on the other, proved a difficult 

 but not impossible task. The method adopted was to 

 admix disinfectant chemicals, of which the one finally 

 selected was iodin trichlorid, with the bacilli to be injected 

 under the skin of animals, or with the contents of the 

 culture flasks at the end of the incubation period. Ob- 

 viously, the intent was to moderate the poisonous action 



