STAINING THE SECTIONS. 187 



Staining the SEt'TioNS. — The sections when cut 

 may be stained in a variety of ways. The ordinary 

 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 Loffler, 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 staining- 

 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 ^vashed 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 evenly 

 spread upon a spatula, which is held under them in 

 the fluid, and, without draining oif 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 gently pull the 

 section 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, which is then covered with 

 a thin clean cover-slip. ' It is now ready for examination. 



