A saturated solution of chromic acid is also used for the same purposes. The chief disadvantage which both this and Moeller's Solution possess in common is their colour — a rich golden one — which, of course, stains everything with which they come in contact. This, however, is easily removable by the Hydrate of Chloral formula (see Priestley Smith's formula, No. 14, Section 2, ante).
This last (Moeller's Solution) I have kept purposely until the end, as it is the formula which, in my opinion, fulfils all the four requirements stated in the opening paragraph, as desirable in the preservation of the lower vertebrates. On my appointment to the curatorship of the Leicester Museum I had occasion to overhaul the "pickles" and prepare some fresh specimens, and was very loth to use expensive spirits, or even methylated, for large fish, and therefore tried many things with varying results. At last I was driven back on Moeller's Solution, and by its aid saved some specimens which were slowly rotting in other fluids, and successfully "pickled" such flabby things as sharks' eggs, sea anemones, and large-sized "lump fish." It was then tried on common "dog-fish," one of which came out limp, yet perfectly tough, and was skinned as an experiment after a month's immersion.
One day two large "topers" (a small species of shark), about six feet long, were sent from Scarboro'. My taxidermist being very busy at the time, I decided to give Moeller a severe test and pickle them. Accordingly — their viscera only being removed — they were tumbled into a large tub containing 2 lb. of bichromate of potassa to 20 galls. of spring water. This was on 13th Sept., 1882; I looked at them on 17th July, 1883, and they were perfectly fresh, quite limp, unshrivelled, and yet so tough as to be capable of any treatment, even to being cast as models, or "set up" by the taxidermic art; and this after the lapse of ten calendar months — a time more than sufficient for even a sailing vessel to come from any part of the world.
I changed the solution once, the total cost from first to last being one shilling and fourpence. Had pure spirit been used, the expense would have been many pounds, to say nothing of the great shrivelling which would have taken place by now. I must therefore think that Moeller's solution is, for the purpose, one of the best things ever invented.
PRESERVATIVE FLUIDS FOR MOLLUSCA.
Generally speaking, pure alcohol is the best for this purpose. Chloride of zinc would doubtless be of considerable service, and I notice that Woodward, in his "Manual of the Molluscs," says that chloride of calcium, made by dissolving chalk, or the purer carbonate — white marble, — in hydro-chloric acid until effervescence ceases and a saturated solution is obtained, is most useful as a preservative, as it "keeps the specimen previously steeped in it permanently moist without injuring its colour or texture; while its antiseptic properties will aid in the preservation of matters liable to decay."
Possibly some of the beautiful preparations in the Fisheries Exhibition of 1883 were prepared in this manner, and such objects as the sea-anemones, with tentacles expanded as in life, may have been instantaneously killed by osmic acid.
LUTING FOR STOPPERS.
No doubt, every one notices how the ordinary wax, which is used as a protective coating for bottles or "preparation" jars, is attacked by the contained spirit in such a manner as to be useless as a preventive of evaporation. Ordinary sealing wax, "bottle wax," beeswax, or paraffin wax, being useless, we are driven back on a very old recipe of the French naturalist M. Peron, who claimed for it advantages which it certainly possesses.
No. 30. — "Lithocolle" for Sealing Bottles.