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. y 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- 



