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

by George Adams

The wings of BUTTERFLIES and MOTHS are covered with very minute scales or feathers, that afford a beautiful object for the microscope; near the shoulder, the thorax, the middle of the wing, and the fringes of the wings, they are generally intermixed with hair. The scales of one part, also, often differ in shape from those of another; they may be first scraped off or loosened from the wing with a knife, and then brushed into a piece of paper with a camel’s hair pencil; the scales may be separated from the hairs with the assistance of a common magnifying glass.

The proboscis of insects, as of the CULEX or GNAT, the TABANUS or BREEZE-FLY, &c. requires much attention and considerable care to be dissected properly for the microscope; and many must be prepared before the observer desides upon the situation and shape of the parts; he will often also be able to unfold in one specimen some parts that he can scarce discover in another. It is well known that the COLLECTOR OF THE BEE forms a most beautiful object; a figure of it is given in [plate XIII.] Fig. 3, shews it greatly magnified, and Fig. 4, of the natural size. In it is displayed a most wonderful mechanism, admirably adapted to collect and extract the various sweets from flowers, &c. To prepare this, it should first be carefully washed with spirit of turpentine, by which means it will be freed from the unctuous and melliferous particles which usually adhere to it; when dry, it must be again washed with a camel’s hair pencil, to disengage and bring forward the small hairs which form one part of its microscopic beauty.

The case which encloses THE STING OF THE BEE, the wasp, and the hornet, are so hard, that it is very difficult to extract them without breaking or otherwise injuring them. It will be found, perhaps, the best way to soak the case, and the rest of the apparatus for some time in spirit of wine or turpentine, then lay it on a piece of clean paper, and with a blunt knife draw out the sting, holding the sheath by the nail of the finger, or by any blunt instrument; great care is requisite to preserve the feelers, which when cleaned add much to the beauty of the object.

The EYES OF THE LIBELLULA or DRAGON-FLY, and different flies, of the LOBSTER, &c. are first to be cleaned from the blood and other extraneous matter; they should then be soaked in water for some days, after which you may separate one or two skins from the eye, which, if they remain, render it too opake and confused; some care is, however requisite in this separation, otherwise the skin may be made too thin, so as not to enable you to form an accurate idea of its organization.

The EXUVIÆ or CAST-OFF OF SKINS of insects are in general very pleasing objects, and require but little preparation. If they be curled or bent up, keep them in a moist atmosphere for a few hours, and they will soon become so relaxed that you may extend them with ease to their natural positions. The steam of warm water answers the purpose very well.

The BEARD OF THE LEPAS ANATIFERA or BARNACLE is to be soaked in clean soft water, and frequently brushed, while wet, with a camel’s hair pencil; it may then be left to dry; after which it must be again brushed with a dry pencil, to disengage and separate the hairs, which are apt to adhere together. A picture of this object is represented in [plate XIII.] Fig. 1, magnified; Fig. 2, natural size.

To view the MUSCULAR FIBRES, take a very thin piece of dried flesh, lay it upon a slip of glass, and moisten it with warm water; when this is evaporated, the vessels will appear plain and more visible, and by repeated macerations the parts may be further disengaged.

To examine FAT, BRAINS, and other similar substances, we are advised by Dr. Hooke to render the surface smooth, by pressing it between two thin plates of flat glass, by which the substance will be made much thinner and more transparent; otherwise, the parts lying thick one upon the other, it appears confused and indistinct.

Some substances are, however, so organized, that if their peculiar form be altered, the parts we wish to discover are destroyed; such as nerves, tendons, muscular fibres, pith of wood, &c. Many of these are best to be examined while floating in some convenient transparent fluid. For instance, very few of the fibres of any of the muscles can be discovered when they are viewed in the open air; but if placed in water or oil, great part of their wonderful fabric may be discovered. If the thread of a ligament be viewed in this manner, it will be seen to consist of an indefinite number of smooth round threads lying close together.

Objects of an elastic nature should be pulled or stretched out while they are under the microscope, that the texture and nature of those parts, whose figure is altered by being thus pulled out, may be more fully discovered.