If desired its staining action may be complemented by dehydrating it in an alcoholic solution, either of eosine (1 in 1500) or of picric acid, and then clearing up in oil of cloves, and mounting in Canada balsam. By itself it gives a stain very like that of hæmatoxyline, only warmer. It picks out the nuclei and axis cylinders of nerves, stains cell protoplasm slightly, and the fibrous elements scarcely at all. It may be used for the same purposes as hæmatoxyline. The colour is less attractive, and not so deep as that of the latter, but as it does not overstain sections, even when left in it for a week, it is a very convenient stain for general purposes. It is particularly useful as a contrast stain for sections of brain and spinal cord, after the Weigert-Pal hæmatoxylin process (p. 88). *Ammonia-picrocarmine* was formerly very largely used as a staining reagent. Its place has now to a large extent been taken by lithio-picrocarmine. In its preparation the best carmine must be used. It is made as follows:-- Carmine 1 part. Liq. ammon. fort. 3 parts. Distilled water 3 parts. Dissolve with gentle heat, and add Cold saturated aqueous solution of picric acid 200 parts. Bring the mixture to the boiling point, and then place in a shallow vessel, covered with a glass plate, and leave it in full sunlight for a month or more. Filter, bottle, and add six drops of carbolic acid to each ounce of the mixture. It will keep indefinitely and improves with age. It requires filtering from time to time, as a gelatinous crimson mud tends to deposit from the solution. *Lithio-picrocarmine.*--Prepared as follows:-- Carmine 2·5 grms. 10 grs. Saturated solution lithium carbonate 100 c.c. 1 oz. Dissolve, and add Saturated solution picric acid 250 c.c. 2-1/2 oz. Add a few drops of carbolic acid to each ounce. It should stand a day or two in sunlight and then be filtered. It improves by keeping. It should be kept in a stoppered bottle with a glass rod fused into the stopper. When sections are to be stained they are to be floated out on a clean glass slide as described on page 55. The slide should then be tilted to allow the water to drain off, and superfluous moisture round the section removed by a soft rag, or blotting paper. A drop or two of the stain should then be transferred to the slide, which should be left lying quite flat for about ten minutes. Unless the room is very warm it is advisable to heat the slide very gently over a spirit lamp, as this causes the tissues to stain more brightly and more rapidly.