166 BACTERIOLOGY. 



watery solutions of the three common basic aniline dyes 

 — fuchsin, gentian-violet, and methylene-blue — or, what 

 is better, the alkaline methylene-blue solution of Loef- 

 fler may be employed for general use. 



Some of the acid aniline dyes, as well as some of the 

 vegetable coloring matters, are essentially nuclear stains, 

 and are not applicable to the staining of bacteria. 



Into a watch-glass containing either of the stainiug- 

 solutions mentioned the sections are to be placed after 

 having been in water for about one minute. They re- 

 main in the staining-solutions for from five to eight 

 minutes. They are then removed, rinsed in water, and 

 partly decolorized in 0. 1 per cent, solution of acetic acid 

 for only a few seconds; again washed out in water, then 

 in absolute alcohol for a few seconds, and from this again 

 into absolute alcohol for the same time, and finally into 

 cedar oil or xylol. Here they remain for from one-half 

 to three-fourths of a minute. They are now to be care- 

 fully spread out upon a spatula, which is held in the 

 fluid under them, and, without draining off the fluid, are 

 transferred to a clean glass slide. This must be done 

 carefully to avoid tearing. The easiest way to do this 

 is to hold the spatula on which the section floats in one 

 hand, with its point just touching the surface of the 

 glass slide, and then with a needle pull the section 

 gently off upon the slide. The fluid comes with it, and 

 the floating section may be easily spread out into a flat 

 surface. The excess of fluid is taken up with blot- 

 ting-paper, after which a drop of xylol-balsam is placed 

 upon the centre of the section, and is then covered with 

 a thin, clean cover-slip. It is now ready for examina- 

 tion. 



Each step in the above process has its definite object. 



