CULTIVATION OF THE BACILLUS 79 



cultural characters were also the same. More recently 

 we have isolated Johne's bacillus on media containing 

 some of the other acid-fast bacilli mentioned above 

 — i.e.^ Nos. I, 2, 5, 6, and 7. 



From these experiments it is clear that Johne's 

 bacillus will grow on media containing the dead 

 timothy-grass bacillus, or bacilli Nos. i, 2, 5, 6, or 7, 

 not only after it has been cultivated in the laboratory 

 for a considerable period, but also when taken direct 

 from the diseased gut of cattle. 



Having determined the various acid-fast bacilli most 

 suitable for the growth of Johne's bacillus, we at- 

 tempted to extract the " essential substance " (the 

 substance necessary for the growth of Johne's bacillus) 

 from certain of these bacilli. The timothy - grass 

 bacillus was chosen, chiefly because it gave the best 

 results in the experiments with the whole bacilli, also 

 because it is harmless to man, and grows quickly on 

 simple media, thus enabling a large quantity to be 

 obtained in a short time. 



For this purpose Dr. W. Bulloch kindly gave us a 

 quantity of this bacillus, besides various dead and 

 dried tubercle bacilli, which had been given to him 

 by Professor Bang about eight years previously. 

 Many of these had already been extracted by Bulloch 

 and Macleod when investigating the acid-fast proper- 

 ties of the tubercle bacillus. In a preliminary series 

 of experiments the different bacillary powders were 

 made up into media, the tubercle bacillus of our 

 original medium being replaced by one or other in 

 quantities of J per cent. Tubes of each were inocu- 

 lated with a fresh culture of Johne's bacillus, and the 

 results may be summarized as follows : 



Dried timothy-grass bacillus {B. phlei) gave very 

 good results. 



