428 MICROSCOPICAL TECHNIQUE. 



tion of commercial Canada balsam in a shallow tin pan over a low 

 flame, until the point is reached of wax-like consistence on cooling 

 as tested on drops removed and tested from time to time. About 

 a quarter of a pound of the hardest commercial paraffin, melting 

 point above 45*^ C, is heated over a low flame to the melting point, 

 a piece of balsam-cement (size of a nut) is then added, and the 

 mass digested with frequent stirring for about an hour, until all the 

 paraffin has a slight yellowish tinge. The stock is preserved in a 

 shallow porcelain capsule, so that when required it can be readily 

 warmed up. A cell made with this paraffin-balsam is ready for 

 use directly after it is spun. 



Mounting Sections in Canada Balsam.— The most satisfactory 

 method of mounting specimens permanently in Canada balsam is 

 undoubtedly that originated by Cole some years ago. It is cleanly, 

 the various operations may be performed deliberately, and there is 

 practically no risk of spoiling a preparation durmg the process of 

 mounting. The process as described in Cross and Cole's Modern 

 Microscopy^ just published, has been somewhat modified since 

 originally published, and is now simplified and improved. After 

 the section has been properly cut and stained, it is directed to be 

 cleared by floating in oil of cloves for about five minutes, and then 

 transferred to turpentine. The Canada balsam should have been 

 previously prepared by dissolving three ounces of the dried balsam 

 in three fluid ounces of pure benzol and filtering. A glass slide 

 having been breathed upon, a clean cover-glass is applied to the 

 moistened surface so as to adhere to it. A little benzole-balsam 

 is then placed on the exposed side of the cover, and the section 

 immersed in it. The diff'erence in the result may be very slight or 

 even nothing, but it is just possible that by first spreading the 

 section on the cover and then covering it with the medium, it may 

 be left closer to the cover in the finished slide, and so be more 

 advantageously placed for examination with high-angled objectives, 

 which have correspondingly short working distances. The risk of 

 air-bubbles in either case is extremely slight. The slide is after- 

 wards covered with a bell-glass, or otherwise protected from dust, 

 and left for twelve hours for the benzol to evaporate. A drop of 

 fresh benzol-balsam is then added to that enclosing the section, 



