REAGENTS AND PROCESSES 559 



stained with these stains are to be mounted in glycerine. The sections before 

 staining are placed in a 20 per cent, solution of powdered tannin in cold water. 

 After washing well in distilled water, they are placed for 24 hours in a 2 per cent, 

 solution of antimonium-potassium tartrate. After washing again in distilled 

 water, they are transferred to the stain. From the stain the sections are washed 

 quickly in distilled water and placed in strong alcohol, where the color is washed 

 out until the desired degree of intensity is reached. They are now ready for mount- 

 ing in glycerine, or, if desired, they may be placed in xylol and then mounted in 

 balsam. If the sections are so deeply stained that they cannot be sufficiently 

 washed out in alcohol, they should be placed for a time in a 2.5 per cent, solution 

 of tannin. 



Turpentine. This may be used to dissolve paraffin from sections which have 

 been cut from material imbedded in paraffin. See also under Carbolic Acid. 



Venetian Turpentine. To prepare a mounting medium from Venetian turpen- 

 tine the product as it comes from the apothecary is diluted with an equal volume 

 of strong alcohol, and after the mixture has become clear by long standing or by 

 filtering after being well shaken, it is thickened somewhat on the water-bath. 

 Objects may be mounted directly from strong alcohol into Venetian turpentine 

 as above prepared. Objects which are found to shrink by this treatment may be 

 transferred from strong alcohol to a mixture of 10 parts of the turpentine with 100 

 parts of alcohol. The alcohol is then to be withdrawn from this mixture by placing 

 the latter, together with a dish of calcium chloride, under a bell-jar. In order to 

 keep the mixture of turpentine and alcohol from mounting the sides of the vessel 

 which contains it, the rim of the vessel should be coated over with hot paraffin. 

 The turpentine hardens quite slowly, and in order quickly to fasten a cover-glass 

 to the slide when the turpentine is being used for a permanent mount, a wire which 

 has been heated in a flame should be quickly drawn around the edge of the cover- 

 glass. 



Xylol. This is used as a solvent for paraffin, either in removing paraffin from 

 sections or in preparing a dilute solution of paraffin to be used in the gradual 

 infiltration of tissues with this substance. Used also as a solvent of Canada balsam. 



Ziel's Carbol -fuchsia. This solution is prepared by adding 15 mils of a con- 

 centrated alcoholic solution of fuchsin to 100 mils of water containing 5 Gm. 

 of carbolic acid. 



