PRESERVATION. 



[ 534 ] 



PRESERVATION. 



ment soou apparently runs into the space 

 between the cover and the shde, and the 

 object becomes spoiled. It is often requisite, 

 however^ to mount an object in this vva}^, 

 which may be lying upon a slide, perhaps in 

 some peculiar position which it is important 

 for it to retain ; when this is the case, the 

 electrical cement with balsam and tallow 

 should be used, and there is no fear what- 

 ever of change, provided spirit be not used 

 as the preservative liquid. 



16. Whenever it is possible, then, a cell- 

 wall should be previously formed, by laying 

 a ring or square of one of the liquid cements 

 upon the slide with a camel's-hair pencil, 

 and applying a continued heat until it be- 

 comes thoroughly hard when cold. The 

 cements generally used are — black japan; 

 gold-size with which a little finely powdered 

 litharge has been well mixed, immediately 

 applied, as it soon hardens; sealing-wax 

 varnish ; solution of marine glue in naphtha, 

 or of Canada balsam in sether, or the balsam 

 alone. If the upper surfaces of the rings or 

 squares formed of these compounds, when 

 thoroughly dry and hard, be not perfectly 

 flat, they may be made so by grinding alone, 

 or with emery and water, upon a piece of 

 metal, marble, or a stone. The object is 

 then placed in the cell, the preservative liquid 

 added, and the cell closed as above described. 



The following are the most important 

 preservative liquids and compounds : — 



Thwaites's liquid — Is thus prepared : to 

 16 parts of distilled water add 1 part of 

 rectified spirit, and a few drops of creosote 

 sufficient to saturate it ; stir in a small quan- 

 tity of prepared chalk, and then filter. With 

 this liquid mix an equal measure of camphor- 

 water, and before using, strain through fine 

 muslin. Recommended by Mr. Thwaites for 

 preserving freshwater Algae, as having but 

 little action upon the endochrome. 



Ralfs liquid. — Prepared with bay-salt and 

 alum, of each a grain, distilled water 1 oz. j 

 dissolve. Recommended as a readily pre- 

 pared substitute for the former, in the pre- 

 servation of the Algaj (Desmidiaceai). 



Acetate of alumina. — 1 part of the salt to 

 4 parts of distilled water. Mr. Topping finds 

 this the best preservative for delicate vege- 

 table colours. 



Distilled water. — Very often used for pre- 

 serving Algae ; but perhaps camphor-water 

 would be better. 



Camphor-water — Is prepared by digesting 

 distilled water with a lump or two of cam- 

 phor. 



Spirit and water. — Proof spirit may be 

 prepared by mixing 5 measures of rectified 

 spirit with 3 of water. It is frequently used 

 for preserving animal structures, organs, 

 injections, &c. Delicate preparations may 

 be kept in a mixture of 1 part of spirit with 

 5 parts of water. Dilute spirit should never 

 be used as a preservative, when it can possi- 

 bly be avoided. 



Creosote water — Is prepared by filtering a 

 satvu'ated solution of creosote in 1 part of 

 rectified spirit, after mixing it with 20 parts 

 of water. It is recommended for preserving 

 preparations of muscle, cellular tissue, ten- 

 don, cartilage, &c. 



Arsenious acid. — A preservative liquid is 

 made of this substance by boiling excess 

 of the acid with water, filtering the solution, 

 and adding 2 parts of water. It is a very 

 good preservative of animal tissues. 



Corrosive sublimate. — Harting recom- 

 mends a solution of this substance as the 

 best preservative for the corpuscles of the 

 bloocl, nerve,' muscular fibre, &c.; the strength 

 of the solution must vary from 1 part in 200 

 to 500 of water, according to the nature of 

 the object. Thus, the blood-corpuscles of 

 the frog require 1-400, those of birds 1-300, 

 of mammals 1-200. 



Salt {chloride of sodium) and water, 5 gr. 

 to the 1 oz. — Was long since recommended 

 for the preservation of tissues, but is not 

 much used, because fungi are apt to grow in 

 it, which might, however, be prevented by 

 saturating it with camphor by digestion. 

 M. Corti has found "a tolerably concentrated 

 solution" the best preservative for the deli- 

 cate structures and nerve-cells of the inter- 

 nal ear. 



Carbonate of potash. — 1 part dissolved in 

 from 200 to 500 of distilled water, is a good 

 preservative of the primitive nerve-tubes. 



Arsenite of potash. — 1 part dissolved in 

 160 of water has been found useful for pre- 

 serving the primitive nervC'tubes. 



Glycerine — May be used in the same 

 cases as chloride of calcium. If used in a 

 diluted state, fungi are apt to grow in it. 



Canada balsam (See Balsam, Canada). 

 — When rendered thinner by digestion with 

 a little aether at a gentle heat, it forms a 

 liquid cement. 



Gum-ivater (see Cements, p. 126. § 14). 

 — The solution should be very thick, so as 

 to flow with difficulty from the end of a 

 wire. It may be used like balsam, but mth- 

 out heat. The residue is very apt to crack 

 when dry ; this may be prevented by apply- 



