METHODS OF STAINING TUBERCLE BACILLI. 43 



fluous stain with distilled water, and then transfer to a watch-glass 

 half filled with alcohol, to which has been added a couple of drops 



Fig. io. — Pair of spring forceps with platinum points. These are 

 so constructed that a cover-glass is held between the points when 

 no pressure is exerted. The other end is simply a pair of ordinary 

 forceps. 



of nitric acid ; allow it to remain here for about a quarter of a 

 minute ; again wash in distilled water ; dry, and mount in balsam. 

 Here of course only the bacilli are stained, but a contrast stain may 

 be used, if it is thought necessary. 



29. Kaatzer's method. — A capital method is that recommended by 

 Kaatzer, who, after staining the prepared film on the cover-glasses 

 with aniline water, lo c.c, and saturated alcoholic gentian violet 

 solution fifteen drops, warmed to about 80° C. for a few minutes, and 

 removing the superfluous staining fluid with clean blotting-paper, 

 immerses them for about a half to one minute in a solution made up 

 as follows : — 



Alcohol, ninety per cent. . . . 150 parts. 



Distilled water, . . . . 30 parts. 



Hydrochloric acid, ... i part. 



Wash thoroughly in ninety per cent, alcohol (one to two minutes) 

 until the whole of the colouring matter disappears from the film; 

 allow to dry, and then drop on the prepared surface a few drops of a 

 concentrated watery solution of vesuvin. At the end of a coufde of 

 minutes again wash in distilled water, dry, and mount in balsam. 

 This method gives exceedingly good, and, according to the author, 

 very lasting results. 



Heneage abbes' modification may also be used, especially where 



