If a solution of methyl green be allowed to fall drop by drop into a solution of an acid dye, for instance orange g., a coarse precipitate first results, which dissolves completely on the further addition of the orange. No more orange should be added than is necessary for complete solution. This is the type of a simple neutral staining fluid. Chemically the above-mentioned example may be thus explained; in this mixture all three basic groups of the methyl green are united with the acid dye, so that we have produced a triacid compound of methyl green. Simple neutral mixtures, which have one constituent in common, may be combined together straight away. This is very important for triple staining, which can only be attained by mixing together two simple neutral mixtures, each consisting of two components. A chemical decomposition need not be feared. We thus get mixtures containing three and more colours. Theoretically there are two possibilities for such combinations: 1. Staining mixtures of 1 acid and 2 basic dyes, _e.g._ orange--amethyst--methyl green; narcein--pyronin--methyl green; narcein--pyronin--methylene blue. 2. Staining mixtures of 2 acids and 1 base, in particular the mixture to be described later in detail of orange g.--acid fuchsin--methyl green. Further narcein--acid fuchsin--methyl green, and the corresponding combinations with methylene blue, and amethyst violet may be mentioned. The importance of these neutral staining solutions lies in the fact that they pick out definite substances, which would not be demonstrated by the individual components, and which we therefore call =neutrophil=. Elements which have an affinity for basic dyes, such as nuclear substances, stain in these neutral mixtures purely in the colour of the basic dye; acidophil elements in that of one of the two acid dyes; whilst those portions of tissue which from their constitution have an equal affinity for acid and basic dyes, attract the neutral compound, as such, and therefore stain in the mixed colour. * * * * *