BACILLUS OF TUBERCULOSIS. 269 



ous bacilli have been distributed over the surface of 

 the culture medium, a rather uniform, thick, white 

 layer, which subsequently requires a slightly yellowish 

 tint, is developed; when the bacilli sown are few in 

 number, or are associated in scattered groups, separate 

 colonies are developed, which acquire considerable 

 thickness and have more or less irregular outlines. 



Growth on Peptonized Veal or Beef Broth Containing 

 5 per cent, of Glycerin. On these media the tubercle 

 bacillus also grows readily if a very fresh thin film of 

 growth from the glycerin agar is floated on the surface. 

 The latter of these media is used for the development of 

 tuberculin. The small piece of pellicle removed from 

 the previous culture continues to enlarge while it floats 

 on the surface of the liquid, and in the course of three 

 to six weeks covers it wholly as a single film, which on 

 agitation is easily broken up and then settles on the 

 bottom of the flask, where it ceases to develop further. 

 The liquid remains clear, containing in solution the 

 products formed by the growth of the bacillus, and is 

 really a dilute crude tuberculin. A practical point of 

 importance, if a quick growth is desired, is to remove 

 for the new cultures a portion of the pellicle of a grow- 

 ing bouillon culture, which is very thin and actively 

 increasing. 



The Obtaining of Cultures of the Tubercle Bacillus from 

 Sputa and Infected Materials for Diagnostic Purposes. 

 As this is a matter of great and increasing importance, 

 we will consider in detail the methods which have 

 been successfully employed. Pure cultures can be ob- 

 tained directly from tuberculous material ; but as 

 it is so difficult to get rid of the other bacteria 

 which are almost always present, and which grow 



