424 APPLICATION OF METHODS OF BACTERIOLOGY 



used in staining bacterium tuberculosis. It has no patho- 

 genic power. It is said to have been artificially cultivated 

 upon coagulated hydrocele fluid and in milk. 



The Acid-proof Bacteria. — In addition to the species 

 mentioned, quite a group of other "acid-proof" bacteria, 

 as they are called, have been described by different inves- 

 tigators. They are characterized by staining, as does bac- 

 terium tuberculosis, by retaining the stain to a greater or 

 less extent when treated with acids and alcohol, and by 

 being in many instances strikingly like bacterium tuber- 

 culosis 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 have received a great deal of attention during the 

 past few years. 



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- 



