486 APPENDIX III. 



Magenta. See Fuchsin. 



Magnesia sulphate. Used in Knop's culture fluid for Algae ; Cohn's normal 

 solution and Pasteur's Fluid. 



Marjoram, Oil of. Clearing reagent, before mounting in dammar or Canada 

 balsam. 



Methyl-blue (Loffler's), 100 c.cm. potash of strength 1 : 1000, and 30 c.cm. 

 concentrated alcoholic solution of methyl-blue. This solution can 

 be preserved for years in a well-closed bottle. For staining bacteria 

 in the tissues, see p. 274. 



(Methylene-blue). Watery solution. Preparations washed, 

 after staining, in water, show the cell-wall coloured, and not the 

 protoplasm. Sections of alcohol material must be washed in water- 

 before staining. Is also taken up by the tannins. 



green. Alcoholic solution, used for material in absolute alcohol. 

 Stain for five to thirty minutes, wash in distilled water, and mount 

 in glycerine. Stains nuclei only. 



Acetic. See Aniline-green, Acetic. 



violet. A concentrated alcoholic solution should be kept. For use, 

 it can be added drop by drop to a little distilled water till this is 

 deeply coloured. This fluid is specially used for stain ing the pellicle 

 (zoogloea) of bacteria. A portion of the pellicle is placed on an 

 object-slide, and a drop or two of the methyl- violet placed thereon 

 and allowed to remain till the stain appears sufficiently deep. A 

 little experience is needed here to judge the strength of the fluid and 

 depth of the staining. If this is too deep, the jelly in which the 

 bacteria are embedded is also stained. After staining, wash the 

 preparation with water, or, better, with a 10 per cent, solution of 

 acetate of potash. After lying for half an hour in the air, the 

 preparation can be mounted in Canada balsam ; not in glycerine, as 

 that dissolves out the colour. Or it can be mounted in a watery 

 (10 per cent.) solution of acetate of potash. 



Watery solution. Used as stain for chromatophores, 53 ; also as 

 a stain for the protoplasmic connections in sieve-tubes, the colour 

 being removed from the walls by lying for a few days in glycerine. 



Millon's reagent. Dissolve metallic mercury in its weight of concentrated 

 nitric acid, and dilute with an equal volume of distilled water. 

 Plugge recommends dissolving 1 part by weight of metallic mercury 

 in 2 parts of nitric acid of sp. gr. 1'42, and then diluting with twice 

 its volume of water. This reagent ought to be prepared fresh, but 

 is said to be restored to a useful state by a few drops of a solution of 

 potassium nitrate. Swells cell-walls, and displays their lamination. 

 Protein substances are disorganised, but, after standing for a while, 

 take a characteristic brick-red colour ; slightly warming hastens 

 this. (This reaction appears to fail sometimes. The crystalloids 

 of Ricinus retain their form even when heated nearly to boiling 

 point.) 



