(1) Eosin and Methylene-blue.--In many instances this stain will give all the information desired. It is especially useful in studying the red corpuscles. Nuclei, basophilic granules, and all blood parasites are blue; erythrocytes are red or pink; eosinophilic granules, bright red. Neutrophilic granules and blood-plaques are not stained. * * * * * (1) Fix the film by heat or chemicals. (2) Stain about five minutes with 0.5 per cent. alcoholic solution of eosin, diluted one-half with water. (3) Rinse in water, and dry between filter-papers. (4) Stain one-half to one minute with saturated aqueous solution of methylene-blue. (5) Rinse well, dry, and mount. Films upon slides may be examined with an oil-immersion objective without a cover-glass. * * * * * (2) Ehrlich's Triple Stain.--This has been the standard blood-stain for many years, and is still widely used. It is probably the best for neutrophilic granules. It is difficult to make, and should be purchased ready prepared from a reliable dealer. Nuclei are stained blue or greenish-blue; erythrocytes, orange; neutrophilic granules, violet; and eosinophilic granules, copper red. {173} Basophilic granules and blood-plaques are not stained (see Fig. 85). Success in staining depends largely upon proper fixation. The film must be carefully fixed by heat: underheating causes the erythrocytes to stain red; overheating, pale yellow. The staining fluid is applied for five to fifteen minutes, and the preparation is rinsed quickly in water, dried, and mounted. Subsequent application of Löffler's methylene-blue for one-half to one second will bring out the basophilic granules, and improve the nuclear staining, but there is considerable danger of overstaining. (3) Wright's Stain.--Recently the polychrome methylene-blue-eosin stains, dissolved in methyl-alcohol, have largely displaced other blood-stains for clinical purposes. They combine the fixing with the staining process, and stain differentially every normal and abnormal structure in the blood. Numerous methods of preparing and applying these stains have been devised. Wright's stain is one of the best, and is the most widely used in this country. Directions for preparing it are given in most of the newer large text-books upon clinical diagnosis. The practitioner will find it best to purchase the stain ready prepared. Most microscopic supply houses keep it in stock. The method of application is as follows: * * * * * (1) Without previous fixation, cover the blood film with the stain, and let stand one minute. (2) Add water, drop by drop, until a delicate metallic scum forms upon the surface. Let this mixture remain on the preparation for two or three minutes. (3) Wash in water until the better spread portions of the film have a pinkish tint. (4) Dry between filter-papers and mount. * * * * *