CH. VW] 



MOUNTING AND LABELING 



171 



anchor the cover-glass, then the preparation may be put on the turn-table and a 

 ring of cement put around the edge while whirling the turn-table. 



Fig. 141. A — Simple form of moist chamber made with a plate and bowl. B, 

 bowl serving as a bell jar ; P, plate containing the water and over which the bowl is 

 inverted ; S, slides on which are mounted preparations which are to be kept moist. 

 These slides are seen endwise and rest upon a bench made by cementing short pieces 

 of large glass tubing to a strip of glass of the desired length and width. 



B — Two cover -glasses (C) made eccentric, so that they may be more easily sepa- 

 rated by grasping the projecting edge. 



C — Slide (S) with projecting cover-glass (C). The projection of the cover en- 

 ables one to grasp and raise it without danger of moving it on the slide and thus 

 folding the substance under the cover. (From Proc. Amer. Micr. Soc. , 1891 ). 



(B) For objects in glycerin jelly, Earranls' solution or a resinous medium. 

 The mounting medium is first allowed to harden, then the superfluous medium is 

 scraped away as much as possible with a knife, and then removed with a cloth 

 moistened with water for the glycerin jelly and Farrants' solution or with alcohol, 

 chloroform or turpentine, etc., if a resinous medium is used. Then the slide is put 

 on a turn-table and a ring of the shellac cement added. (C) Balsam preparations 

 may be sealed with shellac as soon as they are prepared, but it is better to allow 

 them to dry for a few days. One should never use a cement for sealing prepara- 

 tions in balsam or other resinous media if the solvent of the cement is a solvent 

 also of the balsam, etc. Otherwise the cement will soften the balsam and finally 

 run in and mix with it, and partly or wholly ruin the preparation. Shellac is 

 an excellent cement for sealing balsam perparations, as it never runs in. Balsam 

 preparations are rarely sealed. 



§ 254. Example of Mounting in Glycerin Jelly. — For this select some stained 

 and isolated muscular fibres or other suitably prepared objects. (See under isola- 

 tion \ 259). Arrange them on the middle of a slide, using the centering card, and 

 mount in glycerin jelly as directed in § 252. Air bubbles are not easily removed 

 from glycerin jelly preparations, so care should be taken to avoid them. 



\ 255. Mounting Objects in Resinous Media. — While the media miscible 

 with water offer many advantages for mounting animal and vegetable tissues the 

 preparations so made are liable to deteriorate. In many cases, also, they do not 

 produce sufficient transparency to enable one to use high enough powers for the 

 demonstration of minute details. 



