240 BACILLI PATHOGENIC IN MAN. 



which the means used for the attenuation are employed 

 depends apparently the answer to the question whether 

 and within what time the hacilli can regain their viru- 

 lence on subsequent continued cultivation under favour- 

 able normal conditions. The degree of attenuation can 

 he modified with precision to any desired extent by the 

 method described by Koch. The inoculation of suffi- 

 ciently attenuated bacilli sets up in the case of sheep, 

 cattle, &c., a mild disease ending in recovery, after which 

 the animals in question are immune for a considerable 

 time against the virulent anthrax bacilli (Pasteur's 

 protective vaccination) . 



Buchner's According to Buchner the anthrax bacilli are extremely 



experiments, variable in morphological and biological characters, and by 

 variations in the cultivations can be transformed, after pass- 

 ing through a series of intermediate stages, into the closely 

 allied hay bacilli (Bacillus subtilis), and in like manner the 

 latter can be converted by suitable cultivations into true- 

 anthrax bacilli. Buchner in the first place cultivated the 

 anthrax bacilli for many generations in a nutritive solution 

 containing extract of meat, peptone and sugar ; after a short- 

 time these cultivations were only virulent in large doses, but 

 the bacilli again regained their full virulence in the animal 

 body ; ultimately they entirely lost their pathogenic pro- 

 perties, but grew and behaved exactly like hay bacilli. Koch 

 has shown in the most convincing manner that this supposed 

 transformation can only have been due to contamination and 

 the gradual displacement of the anthrax bacilli by the hay 

 bacilli. Had it been a case of gradual loss of pathogenic- 

 properties, there must have been, in the first place, just as in 

 the case of the anthrax bacilli cultivated at high tempera- 

 tures, a less severe and no longer fatal disease ; in Buchner's 

 experiments there was no effect after small doses, while after 

 large doses there was the complete fatal action ; this circum- 

 stance, as well as the increase of virulence after passage 

 through the animal experimented on, corresponds entirely 

 with the behaviour of impure nutritive substrata containing 

 only a few infective organisms from which by the culti- 

 vation in the body the pathogenic organism is again isolated 

 .and cultivated pure. Buchner tried to carry out the trans- 

 formation of the hay bacilli into anthrax bacilli by cultivating 

 the former in the first place in white of egg with a little meat 

 infusion, and then in fresh rabbit's blood which was con- 

 stantly shaken up with air but not sterilised. From such 

 blood cultivations further cultures were made in meat in- 



