BY J. W. GRIFFITH, M.D., F.L.S., ETC. , MEMBER OF THE ROYAL COLLEGE OF PHYSICIANS; CONJOINT AUTHOR OF THE MICROGRAPHIC DICTIONARY, ETC. WITH TWELVE COLOURED PLATES, CONTAINING 451 FIGURES. colphon LONDON: JOHN VAN VOORST, PATERNOSTER ROW. MDCCCLXIV. [ The right of translation is reserved. ]...

T HE object of this little work is to furnish an elementary course of instruction in the use of the Microscope, and on its application to the examination of the structure of plants and animals. Assuming that the reader has had no previous acquaintance with the Microscope, or with the study of natural history, I have attempted to render the descriptions of the objects as simple as possible. At the same time, the technical terms have been added and explained, in order gradually to render them fami

T HE microscope (from μικρὁς, little, and σκοπέω, to see), so called because it enables us to see objects which are too small to be seen with the naked eye, consists of several parts, each of which has its special use. As the proper management of these is of great importance in the successful application of the instrument to minute investigations, we shall commence with the consideration of their names and uses, including those of the more important pieces of accessory apparatus. Microscope. —Th

T HE mounting or “putting up” of microscopic objects signifies their preparation in such way that they may be preserved for future reference and observation. As a general rule, objects should be mounted in that manner by which their structure is best and most clearly shown; but in certain instances the objects are mounted so as to make their structure difficult of detection, that they may form test-objects of the power and quality of the microscope. Some objects require to be mounted in the dry

W E may now enter upon the consideration of the microscopic structure of objects, beginning with those which are derived from the vegetable kingdom, as they are more easily procured and prepared for examination than those belonging to the animal kingdom; moreover they are not so transparent, and hence are more readily distinguished under the microscope, which is of importance in the case of an unpractised observer. Cells. —The elements of which all plants consist are cells. Cells, in their simpl

T HE vegetable elements and tissues which have been described form, either separately or by their combination in various ways, the organs of plants. To these we shall now pass, and consider the structure of the principal organs of the members of the vegetable kingdom. Leaves. —Leaves in their simplest form consist of a single sheet or layer of parenchymatous cells or cellular tissue, an example of which may be found in almost any moss ( Pl. III. fig. 30). The granules of chlorophyll will often b

T HE general appearance of plants belonging to the class of Ferns is so well known that it need scarcely be described, especially since the introduction of the glass plant-cases, by means of which the air can be kept so damp that ferns are now grown in the very heart of our cities. Their bright green and finely cleft leaves (PI. II. figs. 9 & 16) or fronds ( frons , a leaf) as the leaf-like organs of the lower plants are called, arising in tufts from the stems, give them the elegant appe

I NEED scarcely refer to the figures in Pl. III. to enable the reader to recognize the Mosses; every one knows them at once by their remarkably uniform general appearance, their miniature-plantlike form, their crowded little leaves, concealing the slender wiry stems, their growth in patches, and their curious urn-shaped fruits raised up on slender bristle-like stalks. The leaves of the mosses are simple, i. e. not cut into segments, and consist of one or two layers of cells. The thinness of the

T HE plants belonging to the Class Algæ grow in water, either in that of the sea or in fresh water; a few of them, however, being found on damp earth, damp walls, &c. The marine Algæ are commonly known as sea-weeds; but the fresh-water Algæ generally receive but little popular notice, forming, as they do, slimy masses or strata, of a green or brownish, sometimes red, colour. Algæ are of simple structure, consisting entirely of cells; in some these are single, in others, united end to end

T HE Lichens are found growing upon the bark of trees, old palings, &c. Those most easily seen with the naked eye form grey or coloured dryish patches or pendulous tufts; while the smaller ones are singly easily overlooked, from their minute size and close adhesion to the mátrix or body upon which they grow, forming, by their aggregation, the grey or otherwise-coloured dry and brittle coatings of almost every tree or decaying branch. The Lichens derive their nourishment from the air, and

T HE Fungi form the lowest class of plants: as examples of them, may be mentioned mushrooms, toadstools, puff-balls, the mould of paste, the blue mould of cheese, &c. The more minute Fungi are very common, forming beautiful microscopic objects, although they are rarely studied by the microscopic observer. Fungi live usually upon rotting or decaying vegetable substances, as rotten wood, the dead leaves and stems of plants, &c.; but sometimes they are found upon living plants, and

T HE tissues of which animals consist, like those of plants, are primarily derived from cells; in fact the essential part of the egg or óvum, from which all perfect animals originate consists at first only of a simple cell, with its nucleus and nucleolus. The animal cell-wall differs from that of the vegetable cell in its softness and delicacy—also in its chemical composition,—the former consisting of albúminous ( albúmen , white of egg) matter, while the latter is composed of cellular or vegeta

T HE animals belonging to this subkingdom are specially distinguished by the body and limbs being jointed: as familiar instances, may be mentioned the lobster, the wood-louse, spiders, insects, and worms. Taking the class Crustacea, to which the two first animals belong, we find interesting microscopic forms in the subclass Entomos´traca (ἔντομον, insect; ὄστρακον, shell). Entomostraca. —The animals contained in this Order are met with in every pool or pond, some of them inhabiting the sea. They

D ESCENDING in the scale of animal organization, we come next to the subkingdom Radiáta , or that in which the parts are arranged in a radiate manner around a centre. Of this there are three classes,—the Echinoder´mata (ἑχῖνος, hedgehog, δἑρμα, skin), containing the Sea-urchins ( Echínus ), Starfishes, &c., in which the skin is furnished with hard calcareous projecting spines or curiously formed imbedded calcareous corpuscles, forming a rudimentary skeleton; the Acaléphæ (ἁκαλἡφη, a nett

T HE members of this subkingdom are the lowest in the scale of animal organization, their bodies consisting of a soft gelatinous and structureless mass, which has a remarkable tendency to form little cavities or vacuoles in its substance, and is called sar´code (σἀρξ, flesh). They exhibit no organs, unless the cilia and certain variable processes formed of the common substance of the body, and which form their agents of locomotion, be considered as such,—this substance exercising the combined fu

W E shall now devote a few pages to the consideration of the nature of light, and the optical principles involved in the construction and use of the microscope. Two theories of light have been propounded. According to one, light consists of minute particles emanating from self-luminous bodies, as the sun, a candle, or a red-hot piece of iron; this is called the corpuscular theory. According to the other, light consists of waves or undulations like those of water or the ears of corn set in motion