96 JOHNE^S DISEASE 



otherwise of the essential substance, and the same 

 rule holds good for other acid-fast bacilli, including 

 the bovine type of tubercle bacillus. 



Reasoning now on the same lines that first induced 

 us to try the addition of other acid-fast bacilli to a 

 medium for growing Johne's bacillus, we thought 

 that as the essential substance was necessary for 

 the growth of Johne's bacillus, so, too, the material 

 from which such organisms as the B. phlei formed 

 the essential substance, would be more or less neces- 

 sary for the growth of B. phlei, for the simple reason 

 that the essential substance, or an allied substance, 

 or one of a number of allied substances, must be 

 formed by B. phlei before that micro-organism can 

 grow. 



Now, it is well known that fatty substances play an 

 important part in the metabolism of the acid-fast group 

 of bacilli, and also that certain alcohols, such as glycer- 

 ine and mannite, greatly improve the media on which 

 the bacilli can be grown. These and allied substances, 

 then, were the first to receive attention. They were 

 added to ordinary peptone-beef broth, a number of 

 other fluid media being prepared as controls. On 

 each of the media B, phlei was tested, not only as 

 regards growth, but also as regards the formation of 

 the essential substance. The following are the most 

 important of the media that were tested : 



Naegeli's fluid + 4 per cent, glycerine. 



Naegeli's fluid + 4 per cent, glycerine + i per cent, peptone. 



Watery extract of hay. 



Watery extract of carrot. 



Gordon's lemco medium. 



Gordon's lemco medium -|- 4 per cent, glycerine. 



Watery extract of fish + i per cent, peptone. 



Watery extract of brain -f- 1 per cent, peptone. 



Watery extract of mammary gland of cow -f i per cent, peptone. 



Watery extract of beef + i per cent, peptone. 



