3. Mix 1 and 2, allow the mixture to stand forty-eight hours, then filter. 4. Add Glycerine 85.0 c.c. Acetic acid, glacial 10.0 c.c. 5. Allow the stain to stand for one month exposed to light; then filter again ready for use. ~Hæmatin~ (Mayer's).-- A. Weigh out Hæmatin 1.0 gramme and dissolve in Alcohol 90 per cent. (warmed to 37°C.) 50 c.c. B. Weigh out Potash alum 50 grammes and dissolve in Distilled water 100 c.c. Prepare these two solutions in separate flasks. Take a clean flask of 250 c.c. capacity and insert a large funnel in its neck. Pour the solutions A and B simultaneously and slowly into the funnel to mix thoroughly. Store for future use. NOTE.--If acid hæmatin is required, introduce glacial acetic acid (3 c.c.) into the mixing flask before adding the solutions A and B. ~Alum Carmine~ (Mayer).-- Weigh out Alum 2.5 grammes Carmine 1.0 gramme and place in a glass beaker. Measure out in a measuring cylinder, Distilled water 100.0 c.c. Place the beaker on a sand-bath, add the water in successive small quantities, and keep the mixture boiling for twenty minutes. Measure the solution and make up to 100 c.c. by the addition of distilled water. Filter. ~Lithium Carmine~ (Orth).-- Weigh out Carmine 2.5 grammes and dissolve in Lithium carbonate, cold saturated solution 100.0 c.c. Filter. ~Picrocarmine.~-- Weigh out Picrocarmine 2.0 grammes and dissolve in Distilled water 100.0 c.c. BLOOD STAINS When watery solutions of medicinal methylene blue and water soluble eosins are mixed a precipitate is formed which is soluble only in alcohol, and solutions of this precipitate impart a peculiar reddish-purple colour to chromatin. This compound was first used by Romanowsky to demonstrate malarial parasites, but various modifications are now employed for staining blood films generally, and also for bacteria and protozoa. The best modifications of the original Romanowsky are those of Jenner and Leishman--Jenner being most suitable for the histological study of the blood, and Leishman for the demonstration of protozoa. ~Jenner's Stain.~-- A. Weigh out: Eosin aqueous yellow 6.0 grammes Dissolve in Distilled water (non-alkaline) 250 c.c. This will make a thick solution. B. Weigh out: Methylene blue (medicinally pure) Hoechst 5.0 grammes Dissolve in Distilled water (non-alkaline) 250 c.c. 1. Add B to A very slowly, stirring all the time. A viscous precipitate forms which frequently loses its viscosity when heat is applied. (This explains the necessity of mixing slowly). 2. Evaporate slowly in a porcelain basin, stirring occasionally, on a water bath at 55° C. When a paste begins to form scrape and break up occasionally. (On no account must the paste be allowed to fuse.)