32 MOUNTING MEDIA. 



Although not absolutely necessary to seal the cover glass of 

 balsam mounts, it is, nevertheless, a good precaution, as the cover 

 may crack away from the medium and the section be displaced. 

 The balsam should always be kept in a glass-stoppered bottle, and 

 applied to the slide from a pointed glass rod. 



Carbolic Acid. 



Carbolic acid in a 1 per cent, aqueous solution is used as a 

 mounting medium, also carbolic acid crystals in glycerin, for some 

 of the firmer tissues. These ageiits have a tendency, to make the 

 sections clear or faded. 



Calcic Chloride. 



About one part of this salt to two parts of water is a good 

 mounting medium for many tissues. A little camphor should be 

 added to the solution to preserve it. 



Glycerin Jelly. 



This is extensively used as a mounting medium for small and 

 delicate objects, which might be injured by clearing for balsam. 

 Glycerin jelly mounts will, after a time, become transparent, unless 

 they have previously been stained with a permanent stain. Care 

 should be taken in mounting sections to prevent air bubbles 

 getting under the cover glass, since they do not disappear as in 

 balsam mounts. Glycerin jelly mounts should be sealed as soon 

 as cold. 



Many formulae for the preparation of this mounting medium 

 are in use, several of which seem to be equally good. Kaiser's jelly 

 is easily made and keeps well. It is prepared by soaking oue pare 

 by weight of best French gelatine in six parts of distilled water for 

 two hours ; 7 parts of glycerin are then added, and 1 drop of con- 

 centrated carbolic acid for every gram of the mixture. Warm 10-15 

 minutes, with constant stirring, until the mixture becomes clear, 

 and then filter while warm though wet glass wool in a hot water 

 filter. The jelly will require warming before use. The mixture 

 keeps well for years and is a very convenient mounting medium. 



Glycerin. 



Glycerin is often used as a permanent mounting medium and, 

 with proper precautions, gives satisfactory results. To prevent 



