PRESERVATION. 



[ 



533 



] 



PRESERVATION. 



the object next added, and the cover ap- 

 phed. 



9. If the object be minute, its removal for 

 maceration in the turpentine is not requisite, 

 and might entail the loss of the object. It 

 must then be laid upon a slide, a drop or 

 two of turpentine added, and the whole 

 warmed until no air-bubbles are visible. 

 The cover is then removed, most of the tur- 

 pentine drained off, balsam added from the 

 warmed wire, and the cover applied as be- 

 fore. 



10. If air-bubbles remain in parts of a 

 minute object, a cover should be applied, 

 turpentine added, and the slide held over a 

 lamp until the turpentine boils, and the 

 bubbles disappear on cooling. The cover is 

 then removed, most of the turpentine al- 

 lowed to evaporate, the balsam added, and 

 the cover re-applied. 



11. Mounting in liquid. — The structure of 

 many objects is so altered by drying, that 

 they require to be mounted in some preser- 

 vative liquid. These, if of considerable size, 

 must be mounted in glass cells. 



12. The cells may consist of glass rings, i. e. 

 portions cut transversely from pieces of glass 

 tubes, of various sizes, according to the di- 

 mensions of the objects. In using these, 

 the ring is first warmed in the flame of a 

 spirit-lamp, being held by steel forceps ; one 

 of the ground surfaces of the ring is then 

 covered with marine glue or balsam pre- 

 viously melted in the same flame ; the sm*- 

 face of the slide to which the ring is to be 

 cemented is then heated in the flame, and 

 whilst it is hot, the surface of the ring coated 

 with the melted cement is apphed to it, and 

 the ring pressed firmly, so as to displace 

 the superfluous portions. When cold, these 

 are to be removed with the point of a knife ; 

 sometimes a little solution of potash, oil of 

 tiu-pentine, or naphtha is required for this 

 purpose. The cell is then complete, ex- 

 cepting the hd or cover, which consists of 

 a circular plate of thin glass, of slightly less 

 diameter than that of the outer margin 

 of the glass ring. The cell is now to be 

 filled with the preservative liquid, the object 

 placed in it, and the cover applied, being 

 made to slide over the upper surface of the 

 ring, so as to displace any excess of liquid, 

 and prevent the admission of air-bubbles. 

 If the quantity of liquid at first put into the 

 cell be not sufficient, more must be added, 

 until slight excess is present ; the superfluous 

 portions may be removed by a piece of blot- 

 ting-paper, and the margin of the cover and 



ling very carefully wdped clean with a silk 

 handkerchief, so that the surfaces may be 

 free from all traces of the preservative liquid. 

 The exposed parts of the upper surface of 

 the glass ring, and the adjacent margins of 

 the cover, are then to be coated lightly with 

 one of the liquid cements, by means of a 

 camel's-hair pencil ; and when the first coat 

 is dry, another must be laid on, so that the 

 edges of the cover and the adjacent parts of 

 the glass ring may be firmly cemented toge- 

 ther, and the cell completely closed, so that 

 no evaporation of the contained liquid can 

 take place. 



The important points in this process are, 

 that the heated cement used to fasten the 

 ring to the slide must accurately coat every 

 portion of the two sm'faces in apposition, 

 and that the surfaces to which the hquid 

 cement is applied must be perfectly clean 

 and dry, so that the cement may come into 

 contact with the surfaces of the glass. 



13. When the objects are very large, the 

 rings may be conveniently replaced by cells 

 constructed of slips of glass, arranged so as 

 to constitute four sides of a box, the bottom 

 of the box being formed by the slide, and 

 the top by a plate of thin glass : the pieces 

 should be cemented together by marine 

 glue. 



14. Smaller cells may be made with ma- 

 rine glue, melted, dropped upon a slide, and 

 flattened whilst w arm with a piece of wetted 

 glass, the superfluous portions and central 

 portion cut away with a knife ; should the 

 marine glue become loosened from the slide, 

 it may be re-fastened by heat, and if the 

 upper surface be not perfectly flat, it may 

 be made so by grinding with emery-powder 

 and water upon a plate of metal or upon a 

 stone. 



Minute objects may be mounted in liquid 

 in a variety of ways, the choice of which 

 will vary according to the option of the 

 microscopist. They are generally mounted 

 in shallow cells, the sides of which are formed 

 by varnish. 



15. The old method consisted in placing 

 the object upon a slide, adding a di-op or 

 two of the preservative liquid, applying the 

 glass cover, adding more of the liqiud, or 

 removing excess with blotting-paper, until 

 the space between the slide and cover is 

 accurately filled, then applying to the mar- 

 gin of the cover and the adjacent portions of 

 the shde a coat of some liquid cement, as 

 gold-size, black japan, &c. Objects thus 

 mounted keep well for a time, but the ce- 



