480 PKEPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



less caution need be used, as the cover-glass, after a few days' setting, 

 will adhere with sufficient firmness to resist displacement. The 

 superfluous medium having been removed by the cautious use of a 

 knife, the slide and the margin of the cover may be completely 

 cleansed by a camel's-hair brush dipped in warm water ; and, when 

 quite dried, the slide, placed on the turn-table, may be sealed with 

 gold-size any other cement being afterwards added, either for 

 additional security or for ' appearance.' 



It is well in mounting in glycerin jelly to soak the object 

 previously in dilute glycerin, and we prefer to ' ring ' with benzole 

 and balsam, which should harden. Then coat the ring with shellac 

 varnish two or three times and permanently finish with thin, coats of 

 gold-size. 



When, on the other hand, the section or other preparation is to 

 be mounted in a resinous medium, it must have been previously pre- 

 pared for this in the modes described further on, which will present 

 it to the mounter either in some essential oil, or in xylol or benzol 

 or the like, or in alcohol. From either of these it may be transferred 

 to the cover or slide in the manner already described. 



The thin sections cut by the microtome, or membranes obtained 

 by dissection, do not require to be placed in cells when mounted in 

 any viscid medium ; since its tenacity will serve to keep off injurious 

 pressure by the cover-glass. 



Mounting Objects in * Natural ' Balsam. Although it is pre- 

 ferable for histological purposes to employ a solution of hardened 

 balsam, as directed under ' Mounting Media,' yet as there are main 

 objects for mounting for which the use of the ' natural ' balsam is 

 preferable, it will be well to give some directions for its use. When 

 sections of hard substances have been ground down on the slides to 

 which they have been cemented, it is much better that they should 

 be mounted without being detached, unless they have become clogged 

 with the abraded particles, and require to be cleansed out as is 

 sometimes the case with sections of the shells, spines, c., of echino- 

 derms, when the balsam by which they have been cemented is too 

 soft. If the detachment of a specimen be desirable, it may be 

 loosened by heat, and lifted off with a camel's-hair brush dipped in 

 oil of turpentine. But, where time is not an object, it is far better 

 to place the slide to steep in ether or chloroform in a capped jar 

 until the object falls off of itself by the solution of its cement. It 

 may then be thoroughly cleansed by boiling it in methylated spirit, 

 and afterwards laid upon a piece of blotting-paper to dry, after 

 which it may be mounted in fresh balsam 011 a slide, just as if it 

 had remained attached. The slide having been warmed 011 the 

 water-bath lid, a sufficient quantity of balsam should be dropped on 

 the object, and care should be taken that this, if previously loosened, 

 should be thoroughly penetrated by it. If any air-bubbles arise, 

 they should be broken with the needle-point. The cover having 

 been similarly warmed, a drop of balsam should be placed on it, and 

 made to spread over its surface ; and the cover should then be 

 turned over and let down on the object in the manner already de- 

 scribed. If this operation be performed over the water-bath, instead 



