ON MOUNTING MICROSCOPICAL OBJECTS. xxxiii 



XI. ON MOUNTING MICROSCOPICAL OBJECTS. 



The most convenient slide for microscopical objects is a 

 slip of glass three inches long and one inch wide, or for large 

 series of sections the slide may be 1^ inch wide. The glass 

 should be free from air-spaces and other flaws, and the edges 

 should be ground. 



Cover-glasses must be very thin (No. 1) and free from flaws. 

 For single objects square covers ( to inch) are best, and for 

 series of sections oblong covers, which should not come within 

 -jJg- inch of the edge of the slide. Space should also be left at one 

 end for a label. 



' Cells ' are required to protect thick objects from the pres- 

 sure of the cover-glass. Thin flat rings of tin are good, and 

 should be cemented to the slide with gold size or ' brown 

 cement ' ; or a ring of the cement painted on with a brush and 

 allowed to dry may be used as a cell for thinner objects. No 

 cell is required for sections. Copper, brass, and vulcanite cells 

 are to be avoided. 



An object may be mounted dry by fixing it to the slide in 

 the centre of a cell with a very small quantity of collodion or 

 gum-water, or of solution of shellac in creosote or alcohol. 

 When the cement is dry, a cover of the same diameter as the 

 cell is to be laid over it, and secured by varnishing at the edge 

 with any of the cements sold for the purpose. 



More usually it is advisable to mount an object in a liquid 

 or solid medium. Such are glycerin, which is liquid ; Farrant's 

 medium, and Canada balsam, which are liquids becoming solid ; 

 and glycerin-jelly, which is solid when cold. 



An object, stained or otherwise, to be mounted in glycerin or 

 Farrant's medium may be transferred to it direct from water, 

 great care being taken to avoid introducing air. The drop 

 of glycerin, &c, used should be just large enough to spread out 

 to the edge of the cover. When glycerin is used, the cover must 

 be fixed by means of gold size or other cement applied round 

 the edge with a small paint-brush. 



To mount in glycerin-jelly the object is first soaked in 

 glycerin and then in melted glycerin-jelly {see Appendix) ; it 



C 



