In placing specimen on the block be careful that the specimen lies conveniently for cutting the sections in the right direction. As soon as the surface has hardened a little, add a few drops of thick celloidin, and repeat until there is a good body of celloidin. Allow to stand until the tissues are quite firmly fastened to the block, but not long enough to permit shrinking. Then place in 80 per cent. alcohol until the specimen is perfectly firm, 12 or more hours, before cutting. All tissues, cut sections, and mounted blocks are to be placed in 80 per cent. alcohol. As containers for this purpose shell vials will be most handy. Cut the sections with the microtome as thin as possible, the thinner the better. The following process of staining will make the nucleus blue and the cytoplasm reddish. 1. Float section in a tumbler of tap water. 2. Place section on slide, and immerse in hematoxylon for five to ten minutes. 3. Immerse in acid alcohol from two to five seconds. 5. Place on slide, and immerse in eosin from one-half to three minutes. 6. Wash thoroughly in alcohol. 7. Clarify in oil of cloves, oil of cedar, or beechwood creosote, ten minutes. 8. Mount in balsam. 9. Label and study. Delafield’s hematoxylon is prepared as follows: Hematoxylon crystals 4 grams Alcohol, 95 per cent 25 c.c. Saturated aqueous solution of ammonia alum 400 c.c. Add the hematoxylon dissolved in the alcohol to the alum solution, and expose in an unstoppered bottle to the light and air for three or four days. Filter and add: Glycerin 100 c.c. Alcohol, 95 per cent. 100 c.c. Allow the solution to stand in the light until the color is sufficiently dark; then filter, and keep in a tightly stoppered bottle. The solution keeps well and is extremely powerful. So long as it is good the solution has a purplish tinge. If time permits, it would be wise to combine the alum, the hematoxylin, and the water, and to ripen the solution for two or three weeks before adding the other ingredients, which have a tendency to prevent oxidation. The acid alcohol is made as follows: Absolute alcohol 70 c.c. Distilled water 30 c.c. Mix. Above solution 99 c.c. Hydrochloric acid 1 c.c. Eosin is sold in two forms, that soluble in water and that soluble in alcohol. The eosin soluble in water is preferred, because with it a greater degree of diffusion in stain can be obtained.