70 JOHNE'S DISEASE 



Considering again the apparent close relationship 

 between the tubercle bacillus and the bacillus of 

 pseudo-tuberculous enteritis, and the fact that both 

 these bacilli live in the bodies of bovines, we judged it 

 probable that they would require the same chemical 

 substances for building up their protoplasm, certain of 

 which substances could be elaborated from artificial 

 media by the tubercle bacillus but not by the bacillus 

 of pseudo-tuberculous enteritis — in other words, that 

 the latter bacillus has lived a pathogenic existence from 

 such remote ages that it has lost the original power of 

 its wild ancestor — whatever bacillus that may have 

 been — and can no longer build up all its necessary 

 foodstuffs outside the animal body. 



It was thought probable that if these substances 

 could be obtained ready formed, and were added to 

 some good artificial medium (Dorset's egg medium) the 

 bacillus would grow, and, further, that these substances 

 might be elaborated by allied micro-organisms such as 

 the tubercle bacillus, and even stored up as reserves in 

 their envelopes. On this reasoning, which led to a 

 partially successful cultivation of the lepra bacillus of 

 man, we decided to prepare media containing these 

 allied bacilli, which had been killed by heat. 



We had, at the time, in our possession about three 

 hundred strains of tubercle bacilli, mostly isolated from 

 human tuberculous material on Dorset's egg medium. 

 Some of these cultures were taken, and after the 

 necessary subcultures had been made, they were killed 

 by steam. The growth was then scraped off, care being 

 taken to avoid any admixture of the medium which 

 might contain the waste products of bacillary growth 

 and be toxic to the bacillus of pseudo-tuberculous 

 enteritis ; more recently we have found this precaution 

 to be unnecessary. The growth of tubercle bacilli thus 



