AND HOW TO USE IT. 187 



ammonice and sufficient distilled water to make 8 drachms of solu- 

 tion. The fluid must now be exposed to the air for two days to 

 get rid of superfluous ammonia, when 7 drachms of distilled water 

 are to be added to it. Many recommend the carmine solution to 

 be made with borax instead of ammonia. It is not in our opinion 

 nearly so good as that mentioned above, as it not unfrequently 

 spots the stained sections with an apparently crystalline deposit, 

 which utterly ruins them. This never occurs when ammonia 

 ' carmine is employed ; that is, if the solution used be fresh. To 

 prepare the green dye, take 3 grains of aniline green, and by 

 means of heat dissolve it in 2 drachms of distilled water ; then 

 filter this solution into 6 drachms of absolute alcohol. If wood 

 sections, without any previous preparation, were to be stained with 

 these agents, we should find that when, in order to mount them in 

 balsam, the sections being passed through alcohol in the usual 

 manner, a great part, or the whole of the colour due to the action 

 of the aniline green would be discharged by the alcohol. In 

 order, therefore, to render the staining permanent, it is advisable 

 to use some kind of mordant to fix the aniline stain, and for this 

 purpose we have found tannic acid extremely useful. It is 

 employed in the form of solution made by dissolving i drachm of 

 the acid in 2 ounces of methylated spirit, and then filtering the 

 product. 



The sections to be stained, having been bleached and washed 

 in the manner already described, must, after a short preliminary 

 soaking in alcohol, be placed in the tannic fluid for about one 

 minute, and thence transferred to the green dye for three minutes, 

 upon the expiration of which time they are to be rapidly washed 

 in distilled water, and immediately passed into the carmine fluid, 

 there to remain for from three to four minutes, then rinsed in 

 dilute acetic acid (5 drops of glacial acetic acid to i ounce of 

 distilled water), again rapidly washed in distilled water, and finally 

 transferred to clean methylated spirit. Let them remain in this 

 for five minutes, pour off the alcohol, and replace by fresh spirit ; 

 allow the sections to remain in this another five minutes, and 

 afterwards transfer to oil of cajuput. In ten minutes pour off the 

 oil of cajuput, and replace by turpentine, in which they should be 



