1G0 SUMMARY OF CURRENT RESEARCHES RELATING TO 



least, so inclined that the slide lies wholly ahove the ether. The saturation 

 df the sections will be sufficiently complete in about half a minute. 



(c) The slide is next to be warmed in the water-bath in order to 

 evaporate the ether. The paraffin is then removed, and the mounting 

 completed in the usual manner. 



It is best to use balsam dissolved in turpentine or benzole rather 

 than in chloroform, as the latter softens the shellac, and thus often 

 loosens the sections. 



One great advantage of this method of using shellac is that it permits 

 of arranging and flattening the sections on the slide. Ordinarily 

 sections are placed while the adhesive coating is soft, and must then lie 

 as they fall. 



With reference to collodion, Dr. Mayer remarks that it depends 

 entirely upon the quality of the gun-cotton employed whether the 

 sections bear well treatment with alcohol and aqueous fluids. When 

 sections are to be stained on the slide, the albumen-fixative is preferred 

 to collodion. The mixture is prepared as follows: — White of egg, 

 50 grm. ; glycerin, 50 grm. ; sodium salicylate, 1 grm. These in- 

 gredients are mixed and thoroughly shaken together, then filtered and 

 kept in a well-cleaned bottle. Dr. Mayer has kept this mixture three 

 years in a good condition. Other antiseptics have proved far less 

 efficient than salicylate of sodium. 



Substitute for Clearing.* — Dr. G. A. Piersol says that clearing 

 with oil of cloves or other oil can be omitted where the sections are thin, 

 especially when numerous and fixed to the slide or cover. If the sections 

 be thoroughly dehydrated in strong or absolute alcohol, they may be 

 mounted directly in balsam. The slide with the dehydrated section is 

 removed from the absolute alcohol, hastily drained, a drop of balsam 

 added, and the clean cover which is for a moment held over the flame is 

 applied, when the slide is gently wanned over the lamp. There may be 

 cloudiness at first towards the edges of the cover, but in a few minutes 

 (with large sections somewhat longer) this all disappears. After a night 

 in the oven at 40° C. these slides come out with covers so firmly fixed, 

 that oil-immersions may be used and the covers cleaned with little fear 

 of shifting. 



Mounting in Canada Balsam by the Exposure Method.f — It has 

 been a matter of surprise to Mr. G. H. Bryan that amongst the various 

 methods of preparing microscopical slides, the so-called " exposure " 

 method (due to Mr. A. C. Cole) of mounting in Canada balsam or other 

 gum-resins, in which the balsam is partially dried before the cover is 

 finally placed on the slide, has received so little notice, and he therefore 

 desires to call attention to the advantages of this process for mounting 

 almost all classes of objects, and also to describe a slight modification of 

 it, by which means such arranged objects as sections in series, the various 

 parts of an insect or other groups of objects may be mounted in balsam 

 without difficulty. 



The following is a brief outline of the exposure method : — Breathe 

 thoroughly on a glass slip, and on it drop three clean covers, which will 

 thus adhere temporarily to the slip, or, if preferable, each may be let fall 



* Amer. Mon. Micr. Journ., viii. (1887) p. 155. 

 1 Scieutif. Enquirer, ii. (1887) pp. 184-6. 



