120 CHAPTER X. 



performed in a stove or on a water-batli at a temperature a 

 few degrees below the melting-point of tlie paraflSn (best not 

 above 40° C), in which case fixation will be much more rapid^ 

 large thin sections being often sufficiently fixed in an hour, 

 though thick ones will require half a dozen hours or more. 

 The paraffin must not he allowed to melt before the sections are 

 'perfectly dry, the sections are sure to become detached if it 

 does. Perfectly dry sections have a certain brilliant trans- 

 parent look that is easily recognisable. As soon as dry 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 sei'ies 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 

 parafjin. Some persons do this by holding it over a small 

 flame for a few seconds. I jjrefer 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 ofl: 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 necessai-y 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 



