stir out of our rooms. The very hairs on our head may be made objects of interesting investigation; and especially if we compare them with the hairs of other animals, and the appendages generally of the skin. The fine outer coating of the skin is composed of minute scales, which are flattened cells, and may be easily observed by scraping a portion of the skin on to a glass slide, with a drop of water on it. The nails, the hairs, and other appendages of the skin, are composed of the same kind of scales or cells. These cells are developed in little pits, or follicles, from which the hair is projected, as it were, by their growth from below. Under a low power the cells of the human hair cannot be observed. It presents, however, a well-marked distinction between the outside, or cortical layer, and the interior, or pulp. The latter, by a high power, especially if the hair has been first submitted to the action of sulphuric acid, will be found to contain cells more or less spherical, whilst the former contains cells more or less flattened. These project a little beyond the edge of the hair, so that its sides are not quite smooth. By lacing a hair between two pieces of cork, fine transverse sections of it may be made by means of a sharp razor. If these are put under the microscope, the pulpy portions will present a dark appearance in the centre. The hairs of animals offer a great variety in the disposition of the cells of which they are composed. The hairs of the mouse present a series of dark partitions running across the hair between the cells. In the younger hairs, these partitions are single, whilst in the older ones they appear double. The hairs from the ear of the mouse present these dark partitions very distinctly. Such hairs stand intermediate between true hair and wool. A piece of flannel, or blanket, will afford a good illustration of the latter. In this case it will be seen that the scales, or cells, of the cortical part, project beyond the surface, and render the wool rough. This roughness of the outside is supposed to render such hairs fitted to be used in the process of felting; the rough sides of the hairs adhering together. The chemical composition of the hair has also something to do with this process. Human, and other smooth hairs, will not felt.—Dr. Lankester's Half-hours with the Microscope.
The Scales of Insects.—The fine dust upon the wings of moths and butterflies, which is so readily removed when handled carelessly, is what is generally called scales. To these the wing owes the magnificent colours which so often are seen upon it; every particle being what may be termed a distinct flat feather. How these are placed (somewhat like tiles upon a roof) may be easily seen in the wing of any butterfly, a few being removed to aid the investigation. The form of them is usually that of the "battledore" with which the common game is played, but the handle or base of the scale is often short, and the broad part varies in proportionate length and breadth in different specimens. The markings upon these also vary, some being mostly composed of lines running from the base to the apex, others reminding us of network—bead-like spots only are seen in some—indeed, almost endless changes are found amongst them. These scales are not confined to butterflies and moths, nor indeed to the wings of insects. The different gnats supply some most beautiful specimens, not only from the wings, but also from the proboscis, &c.; whilst from still more minute insects, as the podura, scales are taken which were at one time esteemed as a most delicate test. The gorgeous colours which the diamond beetles also show when under the microscope are produced by light reflected from minute scales with which the insects are covered.
In mounting these objects for the microscope it is well to have the part of the insect from which the scales are usually taken as a separate slide, so that the natural arrangement of them may be seen. This is easily accomplished with the wings of butterflies, gnats, &c., as they require no extraordinary care. In mounting the scales they may be placed upon slides, by passing the wings over the surface or by gently scraping the wing upon the slide, when they must be covered with the thin glass. Of course, the necessity of any cell excepting that formed by the gold-size or other cement used to attach the cover. The scales of the podura should be placed upon the slide in a somewhat different manner. This insect is without wings, and is no longer than the common flea. It is often found amongst the sawdust in wine-cellars, continually leaping about by the aid of its tail, which is bent underneath its body. Dr. Carpenter says:—"Poduræ may be obtained by sprinkling a little oatmeal on a piece of black paper near their haunts; and after leaving it there for a few hours, removing it carefully to a large glazed basin, so that, when they leap from the paper (as they will when brought to the light), they may fall into the basin, and may thus separate themselves from the meal. The best way of obtaining their scales is to confine several of them together beneath a wine-glass inverted upon a piece of fine smooth paper; for the scales will become detached by their leaps against the glass, and will fall upon the paper." These scales are removed to the slide, and mounted as those from the gnats, &c. When the podura has been caught without the aid of the meal, it may be placed upon the slide, under a test-tube, or by any other mode of confinement, and thus save the trouble of transfer from the paper before mentioned. Another method is to seize the insect by the leg with the forceps and drag it across the slide, when a sufficient quantity of scales will probably be left upon