I "7 'A peared as more intensely stained spots bulging from the main 

 diameter of the bacillus. Wherry recalled that such varieties 

 usually turned up in old tuberculous lesions, like lung cavi- 

 ties. Here infection is generally of the "mixed" variety, in 

 other words, the tubercle bacilli grow in conjunction with 

 other microorganisms. Wherry repeated this state of affairs in 

 test tubes by growing his tubercle bacillus in double. "Spores" 

 appeared regularly when the Bacillus coli was house guest. 



The effects of the latter upon the culture medium furnished 

 the tubercle bacillus a something necessary for the production 

 by it of the fat-like substance characteristic of the "spores," 

 Wherry believed. What this might be, was an alcohol, he 

 thought. Wherefore he prepared a series of soups of exact com- 

 position for culture of the organism. They consisted of salts 

 dissolved in water with a bit of ammonia added (as a source 

 of nitrogen) and then an alcohol of some sort. In all of them 

 there was luxuriant growth. Any alcohol did the organism 

 good but some were better than others. Best of all for the pro- 

 duction of "spores" was propyl alcohol. Thus another "varia- 

 tion" in morphology was proved to be dependent upon the 

 kind of food furnished the organism in its environment. 



These studies showed Wherry that the presence of certain 

 food substances improved not only the opportunities for the 

 development of "spores" but for the development of "acid- 

 fastness" by the organism in general. The term is statement 

 for a characteristic of the bacillus of tuberculosis not common 

 to the general run of microorganisms. Back in the seventies 

 of the eighteen-hundreds, observers with their microscopes 

 found that by pouring the newly discovered aniline dyes over 

 their bacteria or the slices of tissue they had prepared for 

 microscopic examination, certain parts (like the bacteria or 

 the nuclei of cells) took up the dye, thus to expose themselves 

 as more strongly differentiated figures against a less defined 

 background. By this method the great Robert Koch had first 

 made visible the rod shaped organisms which, buried in tissue, 

 he held to be the cause of tuberculosis. But all organisms could 

 be "stained" by such method. What Koch now brought 

 out was that the tubercle bacillus, once so stained, resisted 

 destaining if bathed in acid. All other organisms, after such 

 ablution, yielded up their cosmetics, the tubercle bacillus alone 



