STAINING AGENTS. 
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he kept in a solution of alcohol and glycerin, or oil of 
bergamot or a mixture of xylol and paraffin. When 
the material is to be examined it should be removed 
to 85 per cent, alcohol for from six to twenty-four hours, 
then to 95 per cent, alcohol and absolute alcohol suc- 
cessively for the same length of time. Of the other 
dehydrating agents the most important are anhydrous 
glycerin, pure carbolic acid, and anhydrous sulphuric 
acid, the latter being used in a desiccator and not 
applied directly to the specimen. 
Clearing Agents. — Most dehydrating agents are also 
clearing agents because of the fact that the air and 
water in the specimen are replaced by a medium having- 
greater refractive properties. Some clearing agents act 
chemically on the tissues and cell-contents. Among 
the clearing agents most frequently employed are : 
Chloral in saturated aqueous solution, and chloral- 
glycerin solution, a solution of equal parts of glyc- 
erin and water saturated with chloral. Essential oils, 
as clove, turpentine, cedar, marjoram, etc., are also use- 
ful for this purpose, particularly when the specimen is 
to be mounted in Canada balsam. 
Staining Agents are those that produce more or less 
definitely colored compounds with the cell-contents or 
walls. The}' may be divided into two classes: (1) the 
Aniline Dyes and (2) Non-aniline Stains. 
The aniline stains may be used in aqueous solutions, 
weak alcoholic solutions or strong alcoholic solutions, 
in which from 1 to 3 per cent, of the dye is dissolved. 
The following are the aniline stains most frequently 
employed: Aniline blue, Bismarck brown, fuchsin, gen- 
tian violet, methylene blue, methyl violet and safranin. 
In addition to these, aniline hydrochloride or sulphate 
is used in what is known as “ Wiesner’s Reagent,” which 
is a 25 per cent, solution of alcohol containing 5 per 
