MOUNTING 33 



manent, the cover-slip should be fixed to the slide by applying 

 a coating of gold size, Brunswick black, or Canada balsam dis- 

 solved in benzol, round its edge with a brush. If a circular 

 cover-slip be used, a turn-table will be found to save much 

 time in this process. Care should be taken that no glycerine 

 is on the slide outside the cover-slip ; if any is there it should 

 be removed by means of blotting-paper before applying the 

 varnish. 



Glycerine Jelly. Objects which may be mounted in glycerine 

 may equally well be mounted in glycerine jelly, in which case 

 since the jelly sets firmly, it is unnecessary to use any cement 

 or varnish. The sections should be previously soaked for 

 one or two days in glycerine so as to remove water or alcohol 

 from them. A trace of carbolic acid should be added to the 

 glycerine jelly in order to prevent the growth of Fungi. 



Canada Balsam. This is a highly refractive medium, and is 

 thus well adapted for lending transparency to objects. It is 

 specially suited to sections stained with hamiatoxylin. Water 

 must be completely extracted from the objects before mounting, 

 by treatment with absolute alcohol, or strong methylated spirit ; 

 they are then to be transferred to oil of cloves, or a mixture 

 of turpentine and creosote, or cedarwood oil, and finally 

 mounted in Balsam. 



The stain produced by aniline colours is apt to fade, so that 

 they are not to be recommended for preparations which are to 

 be kept for a long time. The staining of hsematoxylin also 

 fades, but more slowly. In order to prevent fading, the 

 preparations should be kept in the dark. 



