Directions for making and preserving microscopical preparations / by Harting of Utrecht.

Date:
[1852]
Catalogue details

Licence: Public Domain Mark

Credit: Directions for making and preserving microscopical preparations / by Harting of Utrecht. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    2 of moistening such preparations with oil of turpentine, which, on evaporating, leaves upon the surface a very delicate varnish-like coating, which suffices for its protection. Most microscopical objects, however, require to be mounted in some fluid, the nature of which must be varied according to the properties of the substance which it is wished to preserve. The fluids which I employ are the follow- ing:— I.—Saturated Solution of Chloride of Calcium. 1st, This solution, which must be perfectly free from traces of iron, is of very general utility, and may be employed in all cases in which the substance to be preserved is of moderate firmness or hardness. In this solution all preparations of bones and teeth, sections of hairs, feathers, fish-scales, whalebone, &c., are best preserved. It may be also used with advantage for mounting specimens of many minute animalcules provided with a hard integument, such as cheese- mites, the itch-insect, small fresh-water Crustacea, and the like. It is likewise the best preservative for vegetable preparations, whose cell-walls or vessels have undergone a partial incrustation, and is also very useful for displaying the shells or loricce of the siliceous bacillarise and diatomacete. In using it, one only requires to lay the object on a slide, and to moisten it with a drop of the solution, taking care, at the same time, to remove the air- bells which may be formed here and there. Two pieces of paper, corresponding to the thickness of the object, are next pasted to the extremities of the slide, and the whole is then covered with a second glass plate of the same size. If it should now be foimd that too little fluid has been applied to the object, or that part of it has run off, a drop of the solution may be applied to the edge of the slide, and will find its way between the glasses by capillary attraction. A piece of thin paper may be inserted between the glasses, to promote the flow of the fluid to- wards the preparation, or to rectify the position of the object when it has become displaced. For attaching the strips of paper to the glass slides in this and other cases, the best material that can be used is starch paste, with which a little arsenious acid is mixed, in order to prevent the formation of a species of mould which is otherwise apt to gather round the preparations.—Vol. ii., p. 347-350. Of late I have discovered a fault in this mode of mounting preparations. In many which have been preserved in drops of the chloride of calcium solution, there have formed numerous branches of a species of Hygrocrocis, which spread from preparation to preparation, and from box to box, threatening totally to destroy all specimens which have been put up in this way. I have consequently discontinued the practice of mounting specimens in chloride of calcium solution, to which the air still has access; and when I now employ this or any other fluid, am careful to exclude the influence of the atmosphere by touching the edges of the covering-plate with a cement Avhich I have elsewhere described (see p. 376). This procedure has the additional advantage of not requiring the use of a satu- rated solution: it may be diluted, in proportion to the delicacy of the specimen, with from two to ten parts of water.—Vol. iii., p. 470.