PRESERVATION. 



[ 636 ] 



PRESERVATION, 



preparations, as in the Mollusca, tlie fol- 

 lowing (C) should be used : — take of bay- 

 salt 8 oz., corrosive sublimate 2 grains, 

 water 1 quart. Marine animals require a 

 stronger liquid (D) of this kind, made by 

 adding about 2 oz. more salt to the last. 



Pacini's modification is made with corro- 

 sive sublimate 1 part, chloride of sodium 

 2 parts, glycerine 13 parts, and distilled 

 water 113 parts. The mixture should be 

 kept for two months ; and in use, 1 part 

 should be diluted with 3 parts of water, and 

 filtered. It is good for the preservation of 

 blood-corpuscles, nerves, ganglia, and 

 morbid cell-structures. 



iSalici/lic acid. Edwards found that a 

 saturated solution kept Volvox well. 



Deanes compound. — This is made with — 

 gelatine 1 oz., honey 5 oz., water 5 oz., 

 rectified spirit ^ ox., and 6 drops of creosote. 

 The gelatme is soaked in the water until 

 soft, the honey added, the mixture then 

 boiled, and when it has cooled somewhat, 

 the creosote mixed with the spirit added; 

 la>;tly, it is filtered through tine flannel. 

 This is used warm. 



That preservative liquid should always be 

 chosen which exerts least action upon the 

 structure of the object which it is requnded 

 to preserve. 



If drying the object does not destroy its 

 peculiar structure, and the object is not very 

 transparent, the balsam should be used. 



If the structure be destroyed by the pro- 

 cess of drying, and the obj ect be not impaired 

 by endosmosis, the chloride of calcium or 

 glycerine is best. Other circumstances may 

 render these preservatives desirable : thus 

 the minute parts of the moutli of the Aca- 

 rina are best seen and preserved in balsam, 

 Avhilst the general form of the body is best 

 retained when the animals are immersed in 

 chloride of calcium or glycerine. 



Objects to be mounted in a preservative 

 liquid should be placed in a watch-glass. 

 If they are alive they maybe placed in water, 

 and as much of this as possible should be 

 poured off or removed with a pipette or 

 blotting-paper, and the preservative liquid 

 added, and tliis operation repeated that the 

 water may be entirely displaced. 



The liquid cements used to close the cell 

 sliould be applied in several layers, each 

 being allowed to dry before the next is 

 applied. 



The preservative liquid must not bo capa- 

 ble of exerting any action upon the cements 

 used in making or closing the cell. 



If chloride of calcium or glycerine be used 

 as the preservative liquid, when the first 

 coat of liquid c^'ment used to close the cell 

 has become dry, the slide and cover should 

 be washed gently with a sponge and di- 

 stilled water, then dried with blotting-paper 

 or a silk handkerchief, and the next coat of 

 varnish applied. 



The great difficulty is to permanently 

 preserve moist objects; for whatever may 

 be the cement used, watery liquids almost 

 invariably escape in time, altliough the pre- 

 parations may remain good for some yeiu's. 

 No jjerfect cement is known, which on 

 thoroughly drying retains its hold on the 

 slide. Objects mounted in glycerine keep 

 best ; but in many instances the structure is 

 entirely destroyed by it. This difficulty may 

 be often overcome, by adding very diluted 

 glycerine to the object at first, replacing it 

 gradually by stronger as the water evapo- 

 rates, until at last the object becomes really 

 mounted in pure glycerine. 



Many moist objects may also be mounted 

 in balsam or dammara-solution, by lirst 

 macerating them in weak alcohol, then in 

 stronger, next in oil of cloves, and finally in 

 balsam. 



Even objects mounted in balsam are not 

 safe ; for when the balsam becomes really 

 dry, it separates from the slide, and air runs 

 in. Balsam thinned with turpentine, and 

 gradually added, perhaps with the aid of 

 gentle heat, will, however, restore the ori- 

 ginal condition. 'And the cement around 

 older objects should be varnished occa- 

 sionally with dilute balsam or dammara- 

 benzole solution. 



The deeper the cell, the less the chance 

 of the object being spoiled. 



As soon as objects are mounted, the slides 

 shoidd be labelled with a square or circular 

 piece of paper pasted upon them, the name 

 and other particulars being expressed in 

 writing. The name &c. may also be 

 Avritten upon slides with a diamond : but 

 the paper labels should always be used ; 

 otherwise much time will be lost in search- 

 ing for and distinguishing particular objects 

 in the cabinet. 



For preserving dried plants from mould 

 and. insects, the old method was to brush 

 them with a solution of a grain or two of 

 corrosive sublimate dissolved in an ounce 

 of spirit. The " Kew inixture " for the 

 same purpose, is made with corrosive sub- 

 limate and crystallized carboHc acid, of each 

 I oz., methylated spirit a pint. Perhaps 



