PREPARATION AND STAINING OF TISSUE SECTIONS. 57 



the aniline-gentian-violet solution quite freshly 

 prepared, and the following useful method is 

 invariably used by the author : Place four or five 

 drops of pure aniline in a test-tube, fill it three- 

 quarters full with distilled water, close the mouth 

 of the tube with the thumb and shake it up 

 thoroughly. Filter the emulsion twice, and pour 

 the filtrate into a watch-glass or glass capsule. To 

 the perfectly clear aniline water thus obtained add 

 drop by drop a concentrated alcoholic solution of 

 gentian-violet till precipitation commences. Stain 

 sections in this solution from ten minutes to half 

 an hour, then transfer to iodine-potassic-iodide 

 solution, and decolorise in alcohol. The process 

 of decolorisation may be hastened by placing the 

 section in clove-oil and returning it to alcohol, and 

 again to clove-oil. If examined, after it has been 

 finally treated with clove-oil and mounted in 

 Canada balsam, the tissue appears colourless or 

 tinged faintly yellow, while micro-organisms, e.g., 

 bacilli and micrococci, are stained blue or blue- 

 black. Double staining is obtained by transferring 

 the sections after decolorisation to a solution of 

 eosin, bismarck brown, or vesuvin, again rinsing 

 in alcohol, clearing in clove-oil, and mounting in 

 balsam. Another instructive method is to place 

 the decolorised sections in picro-carminate of 

 ammonia for three or four minutes, and then treat 

 with alcohol, oil of cloves, and balsam. In this way 

 the nuclei are well stained. A somewhat similar 



