450 APPLICATION OF METHODS OF BACTERIOLOGY 



terium tuberculosis, by retaining the stain to a greater or 

 less extent when treated with decolorizers, and by being 

 in many instances strikingly like bacterium tuberculosis 

 in their morphology. The members of this group seem 

 to be distributed pretty widely in nature. They have been 

 detected in non-tuberculous sputum, in gangrene of the 

 lung, in the normal intestinal contents of man and domes- 

 tic animals, in certain of the cold-blooded species, in the 

 soil, in fodder i. e., grass, hay and seed in manure, 

 and in butter. They are not regularly found under any 

 of these conditions, and they are rarely present in very 

 large numbers. Inasmuch as they are occasionally en- 

 countered under circumstances that might lead one to 

 look for true tubercle bacilli, and since they possess certain 

 peculiarities similar to those by which it has been the cus- 

 tom to identify bacillus tuberculosis i. e., retention of the 

 stain when acted upon by acids or alcohol, and a more 

 or less delicate, beaded form the possibility of their being 

 confounded with that organism is obvious. In consequence 

 they received a great deal of attention for a time. 



Space does not permit of a description of the twenty 

 odd species (?) that have been described by different in- 

 vestigators. It will suffice to say, from personal study of 

 the group, that in all probability not more than three, per- 

 haps only two, species are really represented, and that the 

 remainder may fairly be regarded as varieties. As said, 

 the characteristic common to all the members of this group 

 is that they are to greater or less extent acid-proof i. e., 

 when once stained by the Koch-Ehrlich or Ziehl process 

 the color is not in all cases removed by the ordinary acid 

 decolorizers. In this particular, however, there is such a 

 striking difference between the degree of their resistance to 



