TUBERCULOSIS. 179 



liquid, its use for the purpose is disadvantageous rather 

 than useful. 



Pawlowski was able to cultivate the bacillus upon 

 potato, but Sander, who found that it could be readily 

 grown upon various vegetable compounds, especially 

 upon acid potato mixed with glycerin, also found that 

 upon such compounds its virulence was constantly lost. 



It has also been shown that the continued cultivation 

 of the tubercle bacillus upon such culture-media as 

 are appropriate so lessens its parasitic nature that in the 

 course of time it can be induced to grow feebly upon the 

 ordinary agar-agar. 



It is really surprising to note the extremely simple 

 compounds in which the tubercle bacillus can be grown. 

 Instead of requiring the most concentrated albuminous 

 media, as was once supposed, Proskauer and Beck have 

 shown that the organism can grow in non-albuminous 

 media containing asparagin, and that it can even be in- 

 duced to grow upon a mixture of commercial ammonium 

 carbonate, 0.35 per cent.; primary potassium phosphate, 

 0.15 per cent; magnesium sulphate, 0.25 per cent.; 

 glycerin, 1.5 per cent. It was even found that tuberculin 

 was produced in this inorganic mixture. 



The tubercle bacillus seems to require a considerable 

 amount of oxygen for its development. It is also pecu- 

 liarly sensitive to temperatures, not growing at a tem- 

 perature below 29 C. or above 42 C. Temperatures 

 above 75 C. kill it after a short exposure. 



The tubercle bacillus does not develop well in the 

 light, and when its virulence is to be maintained should 

 always be kept in the dark. Sunlight kills it in from 

 a few minutes to several hours, according to the thick- 

 ness of the mass exposed to its influence. 



The widespread character of tuberculosis at one time 

 suggested the idea that tubercle bacilli were ubiquitous 

 in the atmosphere, that we all inhaled them, and that it 

 was only our vital resistance that prevented us all from 

 becoming its victims. 



