210 . TEXT-BOOK OF BACTERIOLOGY. 



reported experiments in which he thinks he has nearly accomplished 

 this; but his results are not sufficiently certain and indubitable to 

 warrant a final decision as to the nature of the anthrax virus. 

 More recent experiments have made it at least extremely probable 

 that, in the case of the anthrax bacilli and other pathogenic bac- 

 teria, not only cry stallizable substances of a basic character, but also 

 some peculiar derivatives of the albuminoid substances, the so- 

 called toxalbumins, play an important part in the pathogenic action. 



We have special reasons for the opinion that the excretions are 

 of decisive importance. We have already considered at some 

 length the fact that it is possible by certain measures of an injuri- 

 ous nature to attenuate anthrax bacilli and rob them of their infec- 

 tious qualities. The best means for this purpose is heat the breed- 

 ing of the bacilli at an unusually high temperature. 



Toussaint, for instance, was able to render blood from splenic 

 fever harmless by keeping- it for ten minutes at 55 C.; Pasteur 

 made use of low temperatures; Koch, Gaffky, and Loffler showed 

 that a high temperature of about 42.6 is the most suitable for 

 depriving the anthrax bacillus of its virulent properties. 



One must, it is true, cultivate it for a considerable time at that 

 temperature, and it is not fully harmless till the end of about 

 twenty-four days. One takes a number of Erlemneyer's flasks with 

 food bouillon, inoculates them with bacteria in possession of their 

 full virulence, and lets them stand about three weeks in the incuba- 

 tor at 42- C. Cultures which before the end of this period are 

 brought back into natural circumstances show at least a partial 

 attenuation, and it is possible to pruserve in a continuous series the 

 intermediate degrees of virulence. For instance, one takes the first 

 flask out of the incubator at ten days, finds by experiment on an 

 animal that the virulence has diminished, and transfers at once to a 

 culture medium which remains at ordinary temperature, in order 

 to breed this variety of attenuated virus. 



Behring has found that the attenuated bacilli form different 

 excretions than the virulent ones. With the imperfect means at 

 our command we have only been able to absolutely fix this differ- 

 ence in one point. We have found that the virulent rod-cells 

 develop large quantities of acid, while the attenuated ones excrete 

 substances rather alkaline than acid. The latter, too, have a power 

 of raising the temperature which is wanting in the former. WhiJe 

 the heat of an infected animal's body will rise several degrees 

 when infected with the attenuated anthrax bacilli, the inoculation 

 with virulent ones produces no such result, and shortly before death 

 we even notice a very considerable decrease of temperature. 



