The following is the method of preparing this mixture: the alum is pulverised and put into a vessel capable of resisting heat; water being heated to ebullition is poured upon the alum; when cool, it is to be filtered through gray paper, and then mixed with alcohol. The same author recommends another liquor, thus composed, but of which the mixture is made cold.
| Common water, | 1 ℔. | |
| Alcohol, | 1 ℔. | |
| Alum, | 12 ℥. |
4. The Abbe Manesse, after various trials, more or less successful, has published the result of his experiments; he proposes as the best liquor, one composed as follows:
| Alum, | 1 ℔. | |
| Nitre, | 1 ℔. | |
| Sea salt, | 1 ℔. | |
| Common water, | 4 ℔. | |
| Alcohol, | 1 ℔. |
The water used should be distilled, so as to be freed of any foreign matter; the alum should be the most transparent that could be obtained, and the salt also should be purified before use. The liquor may be made cold, but it is always better to boil it, with the precaution not to add the spirits of wine until it has cooled.
All these liquors are inferior to spirits of wine, inasmuch as they are liable to freeze.
After having given this long list of the known means of preserving, and given in detail the representation of authors, it remains for us to judge of them, to determine their merit, and the degree of confidence that ought to be accorded to each, under the triple point of view of the preservation of objects of normal anatomy, of pathological anatomy, and of natural history.
1. Process of desiccation.—It can be of no utility for pathological anatomy, because it changes entirely the aspect and texture of parts, and in most cases it leaves no traces of the alterations which it is important to know. For normal anatomy, these preparations are, and always must be, from the simple fact of desiccation, a feeble resource, and really much inferior to the artificial subjects of M. Azoux; for this ingenious preparation, if it has many of the faults of dry anatomy, the objects are not so deformed as scarcely to be recognised.
Further, each of the preparations which tend to desiccation has its particular inconvenience: thus those of the deuto-chloride are numerous, as we have seen in the preceding chapter, and as have remarked in this the authors whom we have cited. We may add that the salts of mercury, of copper, and of lead, which, in combining with gelatine, form, it is true, an inalterable compound, have a great affinity for hydrosulphuric acid, and that there results from this affinity, a necessary deterioration of the objects, colouring them black. Sea salt does not possess durable preservative properties; and its affinity for water even facilitates the decomposition of the dried subjects which contain it. Alcohol is, doubtless, a good means, but it requires to be frequently renewed, until by its affinity for water it absorbs all which the organs contain; but alcohol costs forty cents a quart, and loses always by evaporation. Besides, parts thus prepared, are not less deformed than other dried parts, when subjected to desiccation.