CH- VII.-] 



MOUNTING AND LABELING. 



151 



away as carefully as possible with a moist cloth, then four minute drops 

 of cement are placed at the edge of the cover (Fig. 127), and allowed to 

 harden for half an hour or more. These will 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. 129. 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 , Farrant' s solution or a resinous me- 

 dium. The mounting medium is first allowed to harden, then the su- 

 perfluous 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 Farrant' s 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 the}' are prepared, but it is better to allow 

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

 ing preparations in balsam or other resinous media unless the solvent 

 of the cement is not a solvent 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 preparations, as it never runs in, and it serves to avoid any in- 

 jury to the preparation when cedar oil, etc., are used for homogeneous 

 immersion objectives. 



