38 THE AMERICAN MONTHLY [Febinary, 



stains well, though those left too long in chromic acid solutions may 

 prove refractory, unless very strong solutions are used. Of the many 

 diflerent haematoxylin dyes, none have given me such uniformly good 

 results as the one made by adding Merck's haematoxylin, a few^ grains 

 at a time, to a hot saturated aqueous solution of common alum, con- 

 tained in a porcelain capsule, boiling slowly for fifteen minutes, add- 

 ing sufficient water to make up for evaporation, exposing to the air 

 for a few days in a wide-mouth bottle in which has been placed 30 

 grains of camphor, and filtering each time before using. The quan- 

 tity of hcematoxylin added may be varied according to the strength of 

 dye desired, or a strong solution may be made, and weakened as 

 required by adding a saturated solution of alum. 



Like haematoxylin, the aniline dyes stain well, irrespective of the 

 hardening methods employed, but carmine acts best with tissues which 

 have been hardened in alcohol, corrosive sublimate, or osmic acid solu- 

 tions ; though alum carmine acts much as the alum haematoxylin fluids 

 do, and so stains well tissues hardened in the bichromate and kindred 

 fluids. With it most satisfactory purple stains may be obtained, but 

 the bright reds, given by other carmine stains, are often difficult to at- 

 tain in sufficient density when a bichromate or chromic acid fluid has 

 been used for hardening. 



IL Use ordinary tap and not distilled water for washing tissues 

 stained with haematoxylin. 



Ordinary tap water is slightly alkaline, and changes the color into a 

 deep, bluish purple, while distilled water leaves the sections with a 

 rather disagreeable reddish tinge. Also any trace of acid in any of the 

 fluids tlu'ough which the sections have to pass after staining will pro 

 duce the same reddish color, so that it is well to make them faintly 

 alkaline by the addition of a small quantity of sodium bicarbonate. 



IIL Never pass tissues stained by an alum stain (e. g.^ alum haema- 

 toxylin or alum carmine solutions) through turpentine. 



Turpentine in some manner destroys all alum stains, generally 

 slowly, the turpentine still acting even after the section has been 

 mounted in balsam. 



If tissues are stained in mass with an alum stain, and are afterward 

 passed through turpentine before imbedding, the sections will be 

 fomid to be partially decolorized and the brilliancy of the stain entirely 

 destroyed. For this reason it is with such staining that turpentine has 

 to be avoided and chloroform resorted to, and when sections are stained 

 on the slide in alum dyes they should not be cleared with turpentine, 

 but with oil of cloves. As this agent attacks collodion, and so may 

 loosen sections from the slide if cemented with it, the oil of cloves 

 must be allowed to act but as short a time as possible, or an albumen 

 cement must be used. In this connection it, is well to remark that 

 balsam should never be thinned with tui'pentine, but with chloroform 

 or benzole, as these latter have no ill effects on stains. 



Mounting. — I. Do not use balsam exclusively as a mountant. 



The high refractive power of balsam is in many cases a disadvantage 

 in histological and pathological work, as fluids of lower refractive index 

 allow some of the more transparent parts to be more easily seen and 

 certain delicate tissue connections to be more readily made out. It 

 does not follow that because a section is cut very thin by the celloidin 



