506 PREPARATION. MOUNTING, AND COLLECTION OF OBJECTS 



i^ soaked for a few hours in \vater in order to get rid of the greater 

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

 the mass mav free/e too hard). It is then flipped for a few 

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

 freezing plate, and is fro/en. The sections are brought into warm 

 water. If the mass have fro/en too hard, cut with a knife warmed 

 witli warm water.' 



Stain in i / nut! ninniitiity. 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 titan 95 

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

 as oil of origanum. her^amot oil, cedar oil. or with chloroform or 

 xylol. 



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

 mount a serie> 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, dear 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 mav 

 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 aflixed 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 he 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, (ieneral directions for 

 making such preparations will lie here given ;' but those special 



The fiillnu MIL; directions do not apply to .sv7/rr<///\ substances, as sections of 

 run only 1 )( . prepared by those who possess a regular lapidary's apparatus, and 

 ' specially instructed in the use of it. 



