PRESERVATIVE FLUIDS. 283 



retained, but, unless much diluted, it alters the disposition of the 

 endochrome ; and confervoid growths are apt to make their ap- 

 pearance in it. The best proportion seems to be one part of 

 flycerine to two parts of camphor-water. The preparation 

 nown as Deanes G-elatine is one of the most convenient media 

 for preserving the larger forms of Confervse and other Micro- 

 scopic Algge, "as well as sections of such as are still more bulky. 

 This is prepared by soaking 1 oz. of gelatine in 4 oz. of water 

 until the gelatine is quite soft, and then adding 5 oz. of honey 

 previously raised to boiling heat in another vessel ; the whole is 

 then to be made boiling hot, and when it has somewhat cooled, 

 but is still perfectly fluid, 6 drops of creasote and j- oz. of spirit 

 of wine, previously mixed together, are to be added, and the 

 whole is to be filtered through fine flannel. This composition, 

 when cold, forms a very stiffjelly ; but it becomes perfectly fluid 

 on the application of a very slight warmth, and may then be used 

 like any other preservative liquid, care being taken, however, 

 that the slide and the glass cover are themselves gently warmed 

 before it comes into contact with them. A mixture of gelatine 

 and glycerine has been employed for the same purpose. Some 

 Vegetable Anatomists make great use of a solution of Chloride 

 of Calcium (muriate of lime) in three parts of water; its chief ad- 

 vantage being, that owing to its deliquescent property, it does 

 not dry up, even when the cell is not perfectly closed in. It has, 

 however, the disadvantages of not preserving colors, and of al- 

 tering the disposition of the cell-contents by its endosmotic 

 power. For the preservation of microscopic preparations of 

 Animal tissues, a mixture of one part of Alcohol and five of 

 water will generally answer very well, save in regard to the re- 

 moval of their colors. Where the preservation of these is aimed 

 at, the best medium will usually be G-oadby's Solution, which is 

 made by dissolving 4 oz. of bay salt, 2 oz. of alum, and 4 grains 

 of corrosive sublimate, in 4 pints of boiling water ; this should 

 be carefully filtered before it is used ; and for all delicate pre- 

 parations it may be diluted with an equal bulk, or even with 

 twice its bulk of water. This solution must not be used where 

 any calcareous texture, such as shell or bone, forms part of the 

 reparation ; and one of Mr. Goadby's other solutions (8 oz. of 

 >ay salt and 2 grs. of corrosive sublimate, to a quart of water, 

 or, in cases where the coagulating action of corrosive sublimate 

 on albuminous matters would be an objection, the substitution 

 of 20 grains of arsenious acid) may be used in its stead ; or 

 Thwaites's fluid, or Dr. Beale's modification of it, or Deane's 

 Gelatine may be tried. It is often quite impossible to predicate 

 beforehand what preservative fluid will answer best for a particu- 

 lar kind of preparation ; and it is consequently desirable, where 

 there is no lack of material, always to mount the same object in 

 two or three different ways, -marking on each slide the method 



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