THE MICROSCOPE AND ITS REVELATIONS. 



1 lifter 7 ( 201); its w^perforated end being employed, so as to carry with 

 the object a small pool of the fluid from which it nas been taken. This 

 will greatly 'facilitate the transfer of the object from the lifter to the slide; 

 as it may be readily floated off with the aid of a slight touch of a needle. 

 The fluid thus deposited with it having been drained away by blotting- 

 paper, the object may be treated (if desirable for thoroughly clearing it) 

 with a drop of Clove-oil, which should be deposited, not on the object, 

 but near it, and made to run to it by inclining the slide, so as, by running 

 under it, to rise through it and saturate it thoroughly. After about two 

 minutes, the clove-oil is to be drained away, and the Balsam or Dammar 

 solution applied by the glass rod; one drop being placed on the object, 

 and another on the cover, which is then to be turned and lowered-down 

 on the object in the manner already described. The presence of a few 

 air-bubbles may be here disregarded, as they will ultimately disappear; 

 but care must be taken that the resinous solution not only fills the space 

 between the cover and the slide, but extends beyond its entire margin, as 

 much shrinkage will be produced by the evaporation of the solvent. If 

 this precaution be attended-to, and ' appearance ' is not a serious consid- 

 eration, nothing more is requisite for the protection of the preparation; 

 since the margin of resin left by the evaporation of its solvent forms an 

 adequate cement, especially if the cover be secured by gummed-paper 

 from being loosened by a ' jar.' But if it be desired to replace this by a 

 black or colored cement, 1 the resin must first be scraped away with the 

 edge of an awl 4 carried along (not towards) the margin of the cover; and 

 the slide, being then cleaned with benzole, and finally wiped with methy- 

 lated spirit, may finally be ' ringed ' on the Turn-table. 



210. Mounting Objects in Canada Balsam. Although it is prefer- 

 able for Histological purposes to employ a solution of hardened Balsam, 

 yet as there are many 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 ( 194), 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, etc., of 

 Echinoderms, 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-hair brush dipped in Oil of Turpen- 

 tine. 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 then 

 falls off of itself by the solution of its cement. It may 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 on a slide, just as if it had remained attached. The slide having 

 been warmed on the water-bath lid, a sufficient quantity of balsam should 

 be pressed out from the syringe 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. 



1 The great Scientific investigators of Germany, who cut an entire "Worm into 

 thin transverse sections, carefully mounted in their order, would scorn to spend 

 time in such a mere ' finish,' which they would consider only worthy of Amateurs. 



2 The Author has found this implement, mounted in a small handle, far less 

 liable to disturb the cover, than the ' old penknife,' the slipping of whose point in 

 chipping-away hard resin has oftened occasioned him much mischief. 



