114 CHAPTER VIII. 



^either floated on to the surface of warm water or warm 

 alcohol contained in a watch glass or suitable dish, which 

 causes them to flatten out perfectly, and are then transferred 

 to a slide, by floating them into position, or otherwise. Or 

 the slide has a layer of water spread over it, the sections 

 are laid on the water, and the slide is heated (to somewhat 

 below the melting-point of the paraffin) until the sections 

 flatten out, which happens in a few seconds. The method 

 can be made available for fixing series of sections to the 

 slide ; the further details necessary for the successful ac- 

 complishment of this are given in the chapter on " Serial 

 Section Mounting " (the Water Method). 



A special water-bath for flattening sections is described by NOWAK in 

 -Zeit.f. wiss. Mile., xii, 4, 1896, p. 447). 



VAN WALSEM (Zeit.f. wiss. Mik., si, 2, 1894, p. 228) describes a plan 

 according to which the sections are arranged on a strip of parchment-paper 

 which is moistened and passed over a warmed cylinder revolving in water on 

 the principle of a postage-stamp datupener (see abstract with illustration in 

 Journ. Roy, Mic. Soc., 1895, p. 121). 



139. Clearing and Mounting. The sections having been 

 duly smoothed by one of these processes, and duly fixed to 

 the slide (see " Serial Section Mounting ") (unless it is 

 desired to keep them loose) all that now remains is to get 

 rid of the paraffin and mount or stain as the case may be. 

 Many solvents of paraffin have been recommended for free- 

 ing sections from the paraffin with which they are infil- 

 trated : Turpentine, warm turpentine, a mixture of 4 parts 

 of essence of turpentine with 1 of creasote, creasote, a 

 mixture of turpentine and oil of cloves, benzin, toluol, xylol, 

 thin solution of Canada balsam in xylol (only applicable to 

 very thin sections), hot absolute alcohol, naphtha, or any 

 other paraffin oil of low boiling-point. Of these xylol, toluol, 

 benzol, and chloroform are generally in most respects the 

 best. 



If the slide be warmed to the melting-point of the paraffin, 

 a few seconds will suffice (with thin sections) to remove the 

 paraffin if the slide be plunged into a tube of xylol or toluol. 

 The sections may be mounted direct from the xylol or the 

 slide may be brought into a tube of alcohol to remove the 

 solvent for staining. 



