18 APPARATUS AND METHODS. 



16. Permanent Glycerine Mounts. Preparations mounted 

 in water or in iodine or aniline sulphate solution are purely tem- 

 porary, since these liquids quickly evaporate. Mounts made in 

 glycerine or chlor-zinc-iodine do not evaporate. A glycerine mount 

 may be made permanent by (1) sealing, or (2) transference to 

 glycerine jelly. 



To seal a glycerine mount, either unstained or after staining 

 (see 17), place the specimen in 10 per cent, glycerine in a watch- 

 glass or on a slide (without cover-glass), and put the preparation 

 in a covered dish, to let the water evaporate from the glycerine 

 gradually in a place as free as possible from dust. When the 

 glycerine has become about as thick as pure glycerine, cover the 

 preparation, taking care to have just enough glycerine to come to 

 the edge of the cover-glass if any comes beyond the edge carefully 

 wipe it away. Then seal the mount, and with a brush paint around 

 the edge of the cover-glass a ring of Canada balsam, gold size, or other 

 cement. Gold size answers well ; apply it with a camel-hair or sable 

 brush ; a turn-table may be used with advantage ; on three or four 

 successive days, or at shorter intervals, apply the size again as the 

 previous portion sets, so as to have a fairly thick ring not thick 

 enough to be in the way in using the high power objective ; if the 

 size gets too thick, thin it with turpentine if it is too thin, leave 

 the cork out of the bottle till it thickens. 



An excellent method, devised by Prof. Lagerheim : Take equal 

 parts of hard paraffin wax (melting-point 55 to 60 C. ) and mastic ; 

 powder the mastic and heat it in a porcelain dish (on a tripod over 

 a Bunsen or spirit-lamp) until melted ; then add the paraffin in small 

 pieces, stir the mixture till free from lumps and quite homogeneous ; 

 then pour it into a fiat dish which can be covered (a Petri dish 

 answers well), and let it cool ; to apply the wax, fix into a wooden 

 handle the long arm of a L-shaped piece of thick copper wire, the 

 short arm of which is just under 1 inch long (i.e. a little longer 

 than the length of the square cover-glass used ; heat in a spirit or 

 Bunsen flame, dip into the wax, and apply the wax-covered wire 

 along each edge of the cover-glass in turn the melted wax solidifies 

 at once on contact with the glass, forming a strong join ; then paint 

 a thin coating of gold size over the wax. 



If carefully sealed a glycerine mount is fairly permanent, but it 

 is a useful plan to transfer the specimen from glycerine to glycerine 

 jelly, especially if the object is of such thickness that the glycerine 

 oozes out beyond the cover and thus makes it difficult to seal the 

 preparation. Place the specimen in 10 per cent, glycerine, let this 

 evaporate and become thick, then put the glycerine-jelly bottle into 

 hot water until the jelly melts, put a drop of melted jelly on a 

 warmed slide (using a glass rod, which may be passed through a 

 hole in the cork of the jelly bottle), and transfer to it the specimen ; 

 cover, and set aside to cool. It is as well to seal jelly mounts, in 

 the same way as glycerine mounts. A simpler method is to put a 

 bit of the cold jelly on a slide, heat the slide till the jelly melts, 



