282 The Microscope. 



the last have been where I was making cover glass specimens of 

 bacteria, and was in a hurry for them to dry so that I could mount 

 at once. Neither is it, I believe, used in the University of Mich- 

 igan in tiie Histological Department. I find my mounts perfect, 

 even those stained with anilines after some four years, and in a 

 paper written in one of the journals of microscopy I casuall}' 

 mentioned it with some other clarifying agents. Turpentine 

 and creosote are used by many to get over the difficult^'^ of 

 strong o.lcohol ; these are very good, but personally I object to 

 the penetrating odors. I would like to say that I think a great 

 deal of ditliculty is made over mounting in l)alsam, which in 

 reality never or seldom exists. True, each method is not nearly 

 so difficult on practically demonstrating as by reading. I give 

 you the metliod I have alwa3fs employed for myself and also for 

 teaching, with success so far. Have a mounting card made so 

 that you can use it to centre the slip. In the i^entre of the slide 

 place a medium-sized drop (the second which falls off the rod is 

 about the size) ; carefully spread the balsam over the surfiice not 

 quite to the edge of the cover (when it may have been placed in 

 position). Lift the object from the clove oil, drain off most of 

 the oil, except in such sections as lung, brain, etc., and transfer 

 it to the slide in such a way that it is in the centre when 

 mounted, and do not draw the lifter beyond the ring, or the me- 

 dium runs a little outside the cover and makes an untidy mount. 

 See that the section has no folds, then take a clean cover glass 

 in the forceps and near the edge of it let fall a drop of balsam ; 

 invert the cover and place the point of a needle on the slip at 

 about the place where the edge of the cover is to be when mounted; 

 place the edge of the cover glass against the needle and gently 

 lower it till the drops meet and flow evenly ; when the balsam 

 gets to about the middle of the specimen slovi^ly draw away the 

 forceps almost parallel to the slip and the cover is then in place, 

 with few if any air bubbles under it. Do not press down the 

 cover with a needle or weight, for unless you have a quantity of 

 superfluous balsam it is not necessary ; put the slip away in a 

 warm place in a tray or cabinet, perfectly flat, and in drying the 

 balsam contracts and draws down the cover to the specimen. I 

 often ring slides at once with HoUis's glue, even sending them by 

 post 200 to 500 miles without the least harm. The two essen- 

 tials are to learn the amount and thinness of the balsam, and not 



