MYCOBACTERIUM TUBERCULOSIS. 413 



Potato. If potato is inclosed in an air-proof (i. e., 

 protected from evaporation) reagent glass, there slowly 

 develops small, crumbly, yellowish, friable masses, devoid 

 of coherence, much elevated above the surface of the 

 potato, dull or with a faint luster (61, in). The culture 

 is well developed after about three weeks. (See Pawlow- 

 sky, C. B. iv, 340). The growth is better if air can enter 

 and other precautions are taken to prevent drying of the 

 potato. 



Fluid Nutrient Media. If glycerin (up to about 4%) 

 is added to the nutrient fluids, the T. B. will grow very 

 well upon most various mixtures; for example, bouillon, 

 potato water, and artificial non-albuminous nutrient 

 media. As an example of such a medium we may men- 

 tion: Mannite, 0.6; citrate of magnesium, 0.25; sulphate 

 of ammonium, 0.2; glycerin, 1.5; diphosphate of potas- 

 sium, 0.5. See Proskauer and Beck (C. B. xvi, 974). 



According to Rabinowitsch, the T. B. forms a thick film 

 upon all liquid nutrient media and gives off an odor of 

 flowers. Formation of endogenous spores does not occur, 

 and whether a form of arthrospore is produced is at least 

 very doubtful. (See p. 411 regarding chlamydospores. ) 



Resisting Powers Against : 



(a) Light : Pure cultures are very susceptible to direct 

 sunlight; are also injured by pale, diffuse daylight (accord- 

 ing to Koch, cultures on a window die in five to seven 

 days). 



(6) Drying: According to Sawitzky (C. B. xi, 153), 

 human phthisical sputum retains its virulence, when 

 dried at room temperature, for two and one-half months; 

 also sunlight does not here produce injury. Obici (C. B. 

 xix, 314) obtained a series of similar results. On the 

 contrary, Migneco found them dead in the sun after 

 twenty-four to thirty hours if the dried sputum was not in 

 too thick a layer (A. H. xxv, 361). Tubercule bacilli 

 dried on cigars die in ten days; on the contrary, on paper 

 they may live as long as four weeks. 



(c) Moist heat: 50 does not kill in twelve hours, 55 

 kills in four hours, 60 in forty-five to sixty minutes, 70 

 in ten minutes, 80 and 90 in about five minutes, 95 in 

 one minute (Forster, H. R. n, p. 869). 



