112 SERIAL SECTION MOUNTING. 



certain brilliant transparent look that is easily recognisable. As 

 soon as chy the paraffin may be removed, and they may be further 

 treated as desired. To remove the paraffin all that is requisite is to 

 put the slide into a tube of xylol or other good solvent, which in a 

 few seconds, or minutes at most, removes the paraffin perfectly. 

 Most workers first melt the paraffin, but I find this is not necessary. 



(6) For series of numerous small sections. Clean a slide perfectly, 

 so that water will spread on it without any tendency to run into 

 drops (see below). Breathe on it, and with a brush draw on it a 

 streak of water as wide as the sections and a little longer than the 

 first row of sections that it is intended to mount. With a dry 

 brush arrange the first row of sections (which may be either loose 

 ones or a length of a ribbon) on this streak. Breathe on the slide 

 again, draw on it another streak of water under the first one and 

 arrange the next row of sections on it, and so on until the slide is 

 full. Then breathe on the slide again, and with the brush add a 

 drop of water at each end of each row of sections, so as to enable 

 them to expand freely ; then warm the slide so as to flatten out the 

 sections, taking care not to melt the paraffin. Some persons do this 

 by holding it over a small flame for a few seconds. I prefer to lay 

 it on a slab of thick glass, warmed, watching the flattening of the 

 sections through a lens if necessary. As soon as they are perfectly 

 flat, draw off the excess of water from one corner of the mount with 

 a dry brush, and put aside to dry as before (a). 



In order to succeed in this method it is absolutely essential that 

 the sections be perfectly expanded and come into close contact with 

 the slide at all points. And to ensure this it is necessary that the 

 slide should be perfectly free from grease, so that the water may wet 

 it equally everywhere. The test for this is, firstly, to breathe on 

 the slide ; the moisture from the breath should condense on it 

 evenly all over, and disappear evenly. Secondly, streaks of water 

 drawn on it with a brush should not run. To obtain a slide that 

 will fulfil these conditions, clean it well in the usual way, place a drop 

 of water on it and rub it in thoroughly with a damp cloth and try 

 the tests. If this does not suffice, take a turn of a corner of the cloth 

 round a finger and rub it with a piece of chalk, then damp the cloth 

 and rub the slide with it, finishing up with a clean part of the cloth 

 and clean water (DE GROOT, loc. cit., supra). If after performing 

 this operation twice the slide still refuses to take the water thoroughly 

 it should be rejected as incorrigible ; for there are apparently some 

 sorts of glass that can never be got to wet properly. Mayer finds 

 carbonate of magnesia or soda useful. 



