*Nissl’s aniline method.*--This method is complementary to Golgi’s method. The latter impregnates the cell rendering it opaque and shewing its form with great definiteness. Nissl’s method stains the protoplasm without greatly reducing its transparency and allows us to study details of cell structure. Small portions of tissue, _removed as soon as possible after death_, are hardened in alcohol. Sections are then cut, preferably in gum, as celloidin is inconvenient owing to its staining so deeply with aniline dyes. Sections are transferred from alcohol to a one-half per cent. aqueous solution of methylene blue, which is heated in a watch glass till it steams freely, but short of the boiling point. Stain for about a quarter of an hour and allow to cool. Transfer the sections to a mixture containing one part of aniline oil and ten of absolute alcohol, and move them about till no more colour comes away. Transfer the section to a slide with a section lifter, drain, and dry well by pressing folded filter paper carefully on the section. Allow some origanum oil to flow over the section and remove excess of this by pressure with blotting paper. Moisten with benzine,[1] and add a drop of colophonium resin dissolved in benzine. The slide is warmed cautiously till the benzine is driven off and the colophonium liquefied by heat alone, and then the cover-glass is applied. [1] The student will bear in mind the danger of working with benzine near a naked light. Magenta and other aniline dyes may also be employed in a similar manner. CHAPTER VII. SPECIAL METHODS FOR STAINING MICRO-ORGANISMS AND BLOOD. It is impossible, within the limits of this work, to attempt any adequate description of the modern methods of bacteriological investigation. Some of these are very lengthy and complicated, and require much skill and practice before good results can be relied on. But those who do not desire to make a special study of bacteriology may often require to examine for the presence of organisms in sections, or in various excretions, and it is hoped that they may find the following short description of special methods sufficient for their purpose. For more elaborate work they must consult one of the many excellent textbooks on the subject. The student should provide himself with the following dyes in powder:-- *Methylene blue.* *Gentian violet.* *Methyl violet.* *Fuchsine.* *Bismarck brown.* The following solutions of these dyes are used:-- 1. Saturated alcoholic solutions which may be kept in stoppered bottles. 2. One per cent. aqueous solutions. These must be freshly made each time of using. In filtering either alcoholic or aqueous solutions it is well to moisten the filter paper beforehand with alcohol or water as the case may be. The following special solutions will also be wanted:-- *Löffler’s methylene blue.*--In this solution a weak solution of caustic potash is employed as a mordant:--