Dissolve 1 grm. of hæmatoxylin in 100 cc. of 96 per cent alcohol. Allow to ripen several days, but this solution should not be kept longer than six months. Make a second solution of 4 cc. of liq. ferri. sesquichlor. (German Pharmak. IV, sp. gr. 1,124), 1 cc. of concentrated hydrochloric acid and 100 cc. of water. Mix equal parts of each solution just before staining. The mixture stains well for 5-8 days, so that a quantity of stain sufficient for this time only should be made up. The two stock solutions are easily made and keep well. The nuclei stain quickly and deeply, and differentiation and long washing are unnecessary when hydrochloric acid is included in the second solution, as given above. After-staining with eosin, picric acid or the Van Gieson’s mixture gives better results with Wiegert’s iron-hæmatoxylin than with any other hæmatoxylin. Method of Staining with Haematoxylin. 1. Stain 1-15 minutes, controlling progress of stain by examination of section in water, on slide, using low-power. 2. If sections are over-stained, differentiate in ½-1 per cent potassium-alum or in acid alcohol. 3. Wash thoroughly in tap water, until a good blue is obtained. Exposure to ammonia vapor or washing for a few seconds in lithium-carbonate solution will hasten the development of the blue color. If these reagents are used the section should afterwards be thoroughly washed in water. (Stain with a plasma stain, if contrast is desired.) 4. Dehydrate in 80 and 95 per cent alcohols. 5. Clear in carbol-xylol. 6. Mount in balsam. Over-ripened hæmatoxylins may stain reddish or even brownish, and too diffusely. In such cases the celloidin will be deeply stained. The addition of alum-water to the stain may counteract the fault. Alum-hæmatoxylins must always be filtered before using, as precipitates are constantly formed as the result of oxidation. 2. =Carmine.= Carmine is the coloring matter of cochineal, the dried bodies of the female _coccus cacti_, and is obtained chiefly from Honduras. The coloring principle is carminic acid (C_{2}H_{22}O_{12}). When combined with alum, borax, lithium, etc., carmine gives a good, permanent nuclear stain, varying from reddish violet to deep scarlet. It is used chiefly in pathology to give a contrasting nuclear stain to the various pigments, and when specific blue stains have been used for fibrin, mucin, bacteria, elastic tissue, etc., or when a blue injection-mass has been used. Alum-carmine is the most precise nuclear stain. Differentiation with acid-alcohol is necessary after staining with borax- or lithium-carmine. Lithium-carmine is on the whole the best of the three for use as a contrast-color to the various pigments. a. =Alum Carmine.= Carmine ½-1 grm., 1-5 per cent alum solution 100 cc.; boil 20 minutes; cool; filter. Add crystal of thymol as preservative. 1. Stain 15 minutes to several hours.