xxxiv INTRODUCTION. 



is then transferred to a drop of the melted glycerin- jelly upon 

 the slide, and the warm cover, previously wetted with the 

 melted jelly to aid in excluding air, is immediately placed 

 upon it and held in position till the jelly solidifies. Avoid 

 heating more than is necessary. The edges of the cover may 

 be cemented as above, but this is not absolutely necessary. 



To mount an object in Canada balsam, it must, after 

 staining, be dehydrated by soaking in absolute alcohol ; then 

 soaked in oil of cedar- wood or xylol, till the alcohol is removed ; 

 and, lastly, placed in the drop of balsam upon the slide and 

 covered. 



Mounting sections cut in paraffin. Take a clean, dry slide 

 and spread evenly over it with the finger a very thin layer of 

 glycerin and albumen (see Appendix), so that the slide appears 

 to be only slightly greasy. An excess of glycerin and albumen 

 must be avoided, otherwise the sections will be cloudy. Place 

 the sections perfectly flat upon the slide, and press them down 

 gently with the finger. Warm gently in an oven or over a 

 flame till the paraffin is just melted, and immerse the slide in 

 xylol for two or three minutes to dissolve out the paraffin from 

 the sections. Lift the slide out of the xylol, drain and remove 

 the excess of xylol with a duster, place a drop of balsam over 

 the sections while still moist with xylol, and cover. In the 

 case of sections stained with hematoxylin it is advisable, 

 after removing the excess of xylol, as described above, to run 

 oil of cedar-wood over the sections in order to completely 

 remove the xylol, which tends to oxidise and decolorise 

 hsematoxylin, and thus destroys the stain. 



In some cases it is necessary to stain sections on the slide. 

 The following is a convenient method : Fix the section with 

 glycerin and albumen, and remove the paraffin by warming 

 the slide and placing it in xylol as described above. When 

 the paraffin is all dissolved out, place the slide in absolute 

 alcohol for a few minutes to remove the xylol. Then pass the 

 slide gradually through 90 per cent., 70 per cent., 50 per cent, 

 alcohol. If an alcoholic stain (e.g. borax carmine, alcoholic 

 safranin, &c.) is to be used, the slide is now placed in stain. 

 If an aqueous stain (e.g. heemalum, &c.) is to be used, the 



