Journal of Applied Microscopy. 463 



reagents, but in years of teaching I have found it necessary to guard this point 

 with special care. Hgematoxylin and alcohol must be kept separate or you will 

 have more mud than color, and rinsing borax carmine with 95 per cent, alcohol 

 will ruin everything by precipitation. 



Mounting Aledia. — Which is the best, glycerine, glycerine jelly, or balsam ? 

 We will dispose of glycerine by counting it out entirely ; if gives the poorest 

 definition of all, and however well sealed, cells are liable to leak from expansion 

 of the fluid by heat. The comparative merits of balsam and glycerine jelly are 

 best determined by experiment. Balsam has three faults which render it objec- 

 tionable where the fine details of structure are to be preserved. It shrinks 

 protoplasm, and the process of dehydrating for mounting, distorts delicate tissue, 

 and the medium makes it worse. Its tendency is to make everything transpar- 

 ent, and sometimes so transparent as to be worthless. There is an acid in balsam 

 that is an enemy to color. The chemist that will furnish a neutral balsam will 

 be a benefactor. Balsam has its merits, and is indispensable where the object is 

 in itself opaque, or when outline definition mainly is wanted. It is easy to use, 

 and the objection of transparency may be in part overcome by cutting the section 

 thicker or staining deeper. 



For mounting in balsam, dehydrate by passing quite rapidly through 50, 

 70, and 95 per cent, alcohol to absolute, and clear in oil of cloves, or in xylol 

 which is better, if xylol balsam — which is to be preferred — is used. 



Personally I prefer glycerine jelly to all other media for general use ; it pre- 

 serves structure and color best, and gives a character of honesty to the slide. 

 Kaiser's formula is best as far as it goes, but to stand summer heat more gelatin 

 should be used than the formula calls for, and it should be carefully and faith- 

 fully filtered. It is not as easily used as balsam, but little difficulty will be 

 experienced if the following directions are followed : 



Work in a warm room. 



Heat, and keep hot while using, in a water bath. 



Mount from chemically pure glycerine and 95 per cent, alcohol, one volume 

 of each, kept till perfectly homogeneous, and filtered. 



Warm the slide, and place the jelly on it with a glass rod, kept clean. 



Place the object in the jelly, being sure that it is well covered. This may 

 require an additional drop. 



Hold the object in place and drain the slide to get rid of the glycerine and 

 alcohol. 



Cover the object again with jelly, and examine carefully under the dissecting 

 microscope for air bubbles, especially for stowatvays. Air bubbles should be 

 worked off with a dissecting needle and not picked out with the forceps. 



Cover the object again — take the cover glass between the thumb and finger 

 — breath on it — cover it well with jelly — take it by the edge with the forceps — 

 turn it over quickly — place it gently on the object at an angle, and apply a clip. 



If it is desirable to mount more than one object on a slide, place them in just 

 jelly enough to cover them safely from air, and give time to harden, after which 

 an additional layer may be added, and the cover placed as before, and held with 

 a clip. Next pass the slide over a spirit lamp, till the entire mass of jelly is 



