206 THE MICROSCOPE AND ITS REVELATIONS. 



some time, the perfectly clear supernatant fluid may be poured off and kept for 

 use. If, after long keeping, a little of the carmine should be deposited through 

 the escape of the Ammonia, the addition of a drop or two of Liquor Ammonise 

 will redissolve it. Prof. Rutherford recommends that, for slow but more certain 

 staining, the liquid should at once be put into a stoppered bottle, so as not to 

 allow the ammonia to evaporate, and should be diluted by the addition of from 

 two to seven volumes of water. Carmine is used as a general stain in ' double 

 staining ' ( 203); a-nd a suitable fluid for this purpose is made by mixing 30 grains 

 of carmine with 2 drachms of borax, and 4 fl. oz. of water, and pouring off the 

 clear supernatant fluid. To fix the stain of carmine, the section should be 

 immersed for a few minutes in a mixture of five drops of glacial Acetic acid and 

 1 oz. of water. 



b. Picro-Carminate of Ammonia, known as Pier o-Car mine, is a very excellent 

 staining material, which is applicable to a great variety of purposes. Being 

 somewhat difficult to prepare, it is best purchased ready for use (from Martin- 

 dale, New Cavendish Street). About ten drops should be filtered into a watch- 

 glass, and diluted with distilled water; the sections should remain in the solution 

 for from 20 to 30 minutes; and if at the end of that time they should not be suf- 

 ficiently stained, a little more picro-carmine should be added. This dye, used 

 alone, produces a double staining; nuclei fixing upon the carmine, while other 

 tissues are colored yellow by the picric acid. If the sections be placed in methy- 

 lated spirit, they may be kept without loss of color, and may be afterwards 

 subjected to other processes. If placed in water, the picric acid stain is removed, 

 while the carmine is left. 



c. Hcematoxylin, or Extract of Logwood, is now employed more generally 

 than carmine (which it much resembles in action), its violet color being more 

 pleasant to the eye. The following is given by Kleinenberg as the best mode of 

 preparing it: Make a saturated solution of crystallized chloride of calcium in 70 

 per cent alcohol; mix one volume of this solution with from 6 to 8 volumes of a 

 saturated solution of alum in 70 per cent alcohol; and having half -filled a watch- 

 glass with this mixture, pour into it as many drops of a concentrated solution of 

 Haematoxylin in absolute alcohol as will serve to give the required intensity of 

 color. The object must remain in the dye for a period varying from a few 

 minutes to six hours, according to its size and the nature of the tissues composing 

 it, and is then to be washed in water. If it should be stained throughout, and it 

 be desired that only tissues to be specially distinguished should retain their color, 

 the diffused stain may be removed by immersion in rectified or methylated spirit, 

 or in a 1-half per cent solution of alum. The following is another formula given 

 by Dr. Gibbes: Mix 6 grammes of Extract of Logwood (as obtainable from Martin- 

 dale, New Cavendish Street) with 18 grammes of alum, and add 28 cub. centim. 

 of distilled water. Filter, and add to the filtrate 1 drachm of spirit. Keep in a 

 stoppered bottle a week before using. If what remains on the filter be mixed 

 with 14 cub. centim. of distilled water, and, after soaking for an hour or two, be 

 filtered, and drachm of spirit be then added, a second solution will be made as 

 strong as the first. From 7 to 10 drops of this solution are to be diluted with a 

 watch-glassful of distilled water; the best degree of dilution being only to be 

 found by trial. All staining fluids of this kind are liable to change by keeping; 

 a portion of the coloring matter passing out of solution, and being deposited on 

 the sides and bottom of the Vessel containing it. A deposit of the same kind is 

 liable to occur on the specimen during the staining, especially if the process be 

 prolonged; and it is better in such cases at once to transfer the specimen to a 

 fresh solution. When sufficiently stained, the specimens may be treated with 

 methylated spirit, which will fix the color; whilst, if the staining has been 

 carried too far, the excess of color may be removed by the Acetic acid mixture 

 which is used to fix carmine. If the substance to be stained with Logwood 

 should have been previously hardened with chromic acid, it should be previously 

 steeped in a weak solution of bicarbonate of soda. 



d. Magenta has nearly the same selective staining property as carmine; and ia 

 useful in the examination of specimens for which rapid action and sharp definition 

 are required. But, like other Aniline dyes, it is liable to fade; and should, there- 

 fore, not be employed for permanent preparations. Ordinary magenta fluid may 

 be prepared by dissolving 1^ grains of magenta crystals in 7 fl. oz. of distilled 

 water, an(J adding fl. oz. of rectified spirit. The color of a section stained with 

 this may be preserved for some time, by immersing it in a l-3d per cent watery 

 solution of corrosive sublimate. 



e. Eosin, which dyes the tissues generally of a beautiful garnet-red color, 



