224 American Quarterly Microscopical Journal. 



sample of Canada balsam is evaporated, either in a water bath 

 by artificial heat, or better, by placing it in a shallow dish, and 

 exposing it to the heat of the sun until it becomes hard and 

 brittle throughout when cold, and until all odor of turpentine 

 has disappeared when warm. This resinous balsam is then dis- 

 solved in warm, absolute alcohol to the consistency of thin 

 syrup, and filtered through flannel. If, by accident, the balsam 

 has become brown during evaporation, the alcoholic solution 

 may be bleached by exposure to sunlight. I am in the habit 

 of keeping a bottle of this balsam on a window shelf for the 

 purpose of bleaching it. 



The advantages of this mounting material are, that it soon 

 becomes hard around the edges of the cover, and can be scraped 

 off to finish the slide; that it never crystallizes as other resinous, 

 mounting media frequently do, and, as has already been re- 

 marked, it improves the appearance of the object by age. 



I found large and thin sections very difficult to mount in the 

 ordinary way; viz., by spreading them on the slide with needles 

 or a brush, and therefore devised a plan which simplifies mount- 

 ing very much, and saves a great deal of time and vexation. 

 The sections, when transferred from the alcohol to the benzol, 

 spread themselves open and float on the surface until all the 

 alcohol evaporates and the benzol takes its place, when they 

 sink to the bottom. They can then be floated on to a cover 

 glass held near the bottom of the dish by means of a pair of 

 forceps, the ends of which are bent at right angles, or nearly so, 

 and lifted out, already arranged on the cover glass. A drop of 

 balsam is then placed on the section, and the cover, together 

 with the tissue and balsam, is laid on the slide and pressed 

 ■down. 



If glycerin is to be used as the mounting medium, this same 

 method may be employed with advantage. 



The great difficulty in mounting in glycerin consists in get- 

 ting rid of the surplus, and in cementing the cover glass to the 

 slide in such a way that the glycerin can not leak out. Both of 

 these obstacles may be overcome in the following manner: 

 After the specimen has been stained and made transparent, as 

 directed in Beale's latest work, it is placed on the slide with suf- 

 ficient glycerin to cover it, the cover laid on, and held in posi- 

 tion by a spring clip. All excess of glycerin is then washed 

 off with a gentle stream of water from a syringe or tap, and the 



