Essays on the Microscope / Containing a Practical Description of the Most Improved Microscopes, a General History of Insects, etc., etc.

by George Adams

To examine BONES with the microscope. These should first be viewed as opake objects; afterwards, by procuring thin sections, they should be looked at as if transparent. The sections should be cut in all directions, and be well washed and cleaned; a degree of maceration will be useful in some cases. Or the bones may be put in a clear fire till they are red hot, and then taken out; by these means the bony cells will appear more conspicuous and visible, being freed from extraneous matter.

To examine the PORES OF THE SKIN. First, cut or pare off with a razor as thin a slice as possible of the upper skin; then cut a second from the same place; apply the last to the microscope.

The SCALES OF FISH should be soaked in water for a few days, and then be carefully rubbed, to clean them from the skin and dirt which may adhere to them.

To procure the scales of the eel, which are a great curiosity, and the more so, as the eel was not known to have any, till they were discovered by the microscope, take a piece of the skin of the eel that grows on the side, and while it is moist spread it on a piece of glass, that it may dry very smooth; when thus dried, the surface will appear all over dimpled or pitted by the scales, which lie under a sort of cuticle or thin skin; this skin may be raised with the sharp point of a penknife, together with the scales which will then easily slip out, and thus you may procure as many as you please.[43]

[43] Martin’s Micrographia Nova, p. 29.

On the lizard, the guana, &c. are two skins; one of these is very transparent, the other is thicker and more opake; by separating these we procure two beautiful objects.

The LEAVES of many trees, and some plants, when dissected, form a very pleasing object. To dissect them, take a few of the most perfect leaves you can find, and place them in a pan with clean water; let them remain three weeks or a month without changing the water, then take them up, and try if they feel very soft, and appear almost rotten; if so, they are sufficiently soaked. You are then to lay them on a flat board, and holding them by the stalk, draw the edge of the knife over the upper side of the leaf, which will take off most of the skin; turn the leaf, and do the same with the under side. When the skin is taken off on both sides, wash out the pulpy matter, and the fibres will be exhibited in a beautiful manner. By slitting the stalk you may separate the anatomized leaf into two parts. The skins that are peeled from the fibres will also make a very good object. The autumn is the best season for the foregoing operation, as the fibres of the leaves are much stronger at that season, and less liable to break.

Ores and MINERALS should all be carefully washed and cleansed with a small brush, to remove any extraneous matter that may adhere to them. Shells may be ground down on a hone, by which their internal structure will be displayed.

To view the circulation and examine the particles of the blood. The principal part the observer must aim at, in order to view the circulation of the blood, is to procure those small animals or insects that are most transparent, that by seeing through them he may be enabled to discover the internal motion. The particular kinds best adapted for the purpose will be enumerated in the descriptive catalogue at the end of this work.

If a small eel be used for this purpose, it must be cleansed from the slime which covers it; after which it maybe put either in the fish-pan, or a glass tube filled with water, and then placed under the microscope. If the eel be small enough, the circulation may be viewed in the most satisfactory manner. Leeuwenhoeck has given, in his 112th Epistle, an accurate description of the blood vessels in part of the tail of an eel. The same figure may also be seen in my father’s Micrographia Illustrata, fourth edition, [Plate XVII]. The tail of any other small fish may be applied in the same manner, or tied on a slip of flat glass, and be thus laid before the microscope. Flounders, eels, and gudgeons, are to be had at almost any time in London. N. B. By filling the tube with water, when an eel is used, it will in a great measure prevent the sliminess of the eel from soiling the glass.