TRANSFERENCE OF SECTIONS. 149 



strument even very thin arid fragile sections may be 

 readily lifted from one vessel to another without 

 injury. The staining fluid, which should always be 

 freshly filtered, and not be used for too many sec- 

 tions, may be in a watch-glass, which should be 

 covered over by another watch-glass inverted, but 

 the other fluids which are constantly in use it is 

 better to keep in covered glass or china pots, for 

 they especially the oil of cloves may be used for 

 a considerable number of sections without detriment. 

 The process of preparation may be arrested at any 

 stage and completed at another time, if the sections 

 are left in spirit or in oil of cloves. 



In transferring sections* from one fluid to another, 

 and especially when they are put in the staining 

 fluid, care should be taken that they are actually 

 immersed, and do not merely float on the surface. 



Instead of the ordinary logwood solution Kleinen- 

 berg's fluid (see post) may with advantage be used 

 for staining sections that are to be mounted in bal- 

 sam or dammar. In this case the sections can be 

 placed from spirit into the staining fluid, and from 

 the latter directly into the spirit again without the 

 necessity for placing them in water at all. 



The sections then being in oil of cloves, and the 

 clearing up satisfactorily effected, all that remains 

 is to mount them permanently. For this purpose 

 either dammar varnish or a solution of Canada bal- 

 sam in chloroform the same liquid that was em- 

 ployed for cementing the cover-glass of the glycerine 

 preparations is employed. 1 These solutions, al- 

 though perfectly limpid even in the cold, readily 

 dry when exposed to the air, and thus become hard 



1 The Canada balsam used, must be heated over a sandbath 

 until it is quite hard when cold ; it is then dissolved in an equal 

 volume of chloroform. Dammar varnish is made by dissolving one 

 part of gum dammar in two parts of oil of turpentine, and one part 

 of gum mastic in two parts of chloroform ; mixing the solutions 

 and filtering. The mixture is apt to become opalescent on keep- 

 ing, but this disappears permanently on boiling the fluid. 



13* ' 



