506 PKEPAEATION, MOUNTING, AND COLLECTION OF OBJECTS 



is soaked for a few hours in water in order to get rid of the greater 

 part of the alcohol (the alcohol should not be removed entirely, or 

 the mass may freeze too hard). It is then dipped for a few 

 moments into gum mucilage in order to make it adhere to the 

 freezing plate, and is frozen. The sections are brought into warm 

 water. If the mass have frozen too hard, cut with a knife warmed 

 with warm water.' 



Staining and mounting. The sections are brought into alcohol 

 of not more than 95 per cent, as fast as they are cut, and may now 

 either be stained or mounted at once. It is not in general 

 necessary nor even desirable to remove the mass from the sections 

 before staining or mounting. It is, no hindrance to staining, and on 

 being mounted in glycerin or balsam it becomes perfectly invisible. 



To mount in glycerin, nothing more is necessary than to add a 

 drop of glycerin and a cover. 



To mount in balsam, dehydrate in alcohol of not more than 95 

 per cent., and clear with an oil that does not dissolve collodion, such 

 as oil of origanum, bergamot oil, cedar oil, or with chloroform or 

 xylol. 



The foregoing relates to single sections. If it be desired to 

 mount a series of small sections under one cover, arrange them on 

 the slide and expose it for a few minutes to the vapours of a 

 mixture of ether and alcohol in a closed, tube. Then treat with 95 

 per cent, alcohol, clear and mount. 



If the sections are to be stained on the slide, care should be 

 taken when arranging them to let the celloidin of each section over- 

 lap that of its neighbour at the edges, so that the ether vapour may 

 fuse them all into a continuous sheet. Then on passing the slide 

 into any aqueous liquid the sheet will be detached, and may then 

 'be treated as a single section. 



If the sections should come off the knife creased, they may be 

 flattened by floating them on to oil of bergamot, after which they 

 may be got on to the slide and gently pressed on to it with a 

 cigarette paper or a piece of glossed tissue paper, after which they 

 may be exposed to the vapour of ether and alcohol as before. 



Series may also be affixed to the slide by means of Mayer's 

 albumen, as described above for paraffin sections. 



For the complicated manipulations involved in the methods of 

 Weigert, Obregia, and others, which are only necessary in very 

 special cases, the reader must be referred to Mr. A. Bolles Lee's 

 ' The Microtomist's Vade-mecum.' 



Grinding and Polishing Sections of Hard Substances. Sub- 

 stances which are too hard to be sliced in a microtome such as 

 bones, teeth, shells, corals, fossils of all kinds, and even some dense 

 vegetable tissues can only be reduced to the requisite thinness for 

 microscopical examination by grinding down thick sections until 

 they become so thin as to be transparent. General directions for 

 making such preparations will be here given j 1 but those special 



1 The following directions do not apply to siliceous substances, as sections of 

 these can only be prepared by those who possess a regular lapidary's apparatus, and 

 have been specially instructed in the use of it. 



