CULTIVATION OF THE BACILLUS 91 



opinion necessarily represent an important bio- 

 logical difference : it is probably physiological in 

 nature, and may be due to the presence or absence 

 of some reserve food material existing, or other- 

 wise, outside the strictly vital portion of the 

 bacillus, or it may be due to some fat, wax, or 

 other covering material preventing this substance 

 from being utilized by Johne's bacillus. In the 

 light of some recent experiments the latter possi- 

 bility seems improbable, as we have been unable 

 to extract any substance suitable for the growth 

 of Johne's bacillus. These experiments are being 

 continued. 



"While in this paper we cannot enter into the 

 controversy concerning the relationship between 

 the human and bovine types of tubercle bacilli, 

 yet, incidentally, we venture to remark that, 

 in spite of all that has been written in this 

 country, we are not yet convinced that the human 

 and bovine types are only slightly different varieties 

 of one and the same micro-organism. In this con- 

 nection the difference between the two bacilli 

 described above may be worthy of note and 

 further investigation ;" 



In the same paper we wrote : 



" We have not tested man}^ strains of the bovine 

 bacillus, and it is possible that Johne's bacillus will 

 grow on some bovine strains, or on those strains 

 which have been described as occupying an inter- 

 mediate position between the typical human and 

 typical bovine bacilli." 



In describing the results obtained by M'Fadyean, 

 Sheather, and Edwards, and the results obtained by 



