116 TUBERCULOSIS. 



Nocard, 8 per cent, glycerin-bouillon. In this bouillon, kept 

 at a temperature of 37 C., at the end of from twelve to 

 fourteen days it forms a small pellicle on the surface. 



In slant cultures of glycerin-agar and blood-serum it grows 

 over the surface of the medium as a dried-up, scaly-looking 

 mass. According to some authorities, it is a spore-bearing 

 bacterium ; others fail to find the existence of spores in it. 

 It is non-motile, though occasionally slight movements have 

 been detected in it. It appears to have no flagella. It is 

 usually killed by exposure to 70 C., but in the dried state 

 may be preserved alive for a considerable time even at a tem- 

 perature approaching 100 C. 



Staining. It is difficult to stain by the usual staining 

 methods, and requires the use of special staining technic. 

 Koch's method of staining it consists in adding liquor potassse 

 to the alkaline anilin dyes. 



Ehrlich's modification of Koch's method, which consists in 

 preparing anilin water and adding this to the solution of an 

 anilin dye, is perhaps the best method of bringing out the 

 tubercle bacillus. 



The mode of procedure for the staining of bacilli in secre- 

 tions, especially in sputum, has been described in the chapter 

 on staining, as the Koch-Ehrlich method, or'the Ziehl carbol- 

 fuchsin method, or, better still, as Gabbett's modification of 

 Ziehl's method. 



In tissue the bacillus is stained best by an application of 

 either method, which will also be found described in the chap- 

 ter on staining. 



When so stained, the bacillus shows a number of unstained 

 places in the cell-body, somewhat resembling spores. They 

 have given rise to the opinion that the bacilli are spore-form- 

 ing, but the fact that when the usual method for staining 

 spores is applied these spots remain unstained seems to prove 

 that they are not spores, but are due possibly to some degen- 

 eration in the protoplasm of the bacillus. 



Nature and Occurrence. As mentioned, the tubercle bacillus 

 is a strict parasite, and is found only in tuberculous tissues 

 and in the secretions from tuberculous patients, especially the 



