view should never be lost sight of, nor disconnected, namely, the animal in respect to its own organism, and the animal in its relations to creation as a whole. By adopting too exclusively either of these points of view, we are in danger of falling either into gross materialism, or into vague and profitless pantheism. He who beholds in Nature nothing besides organs and their functions, may persuade himself that the animal is merely a combination of chemical and mechanical actions and reactions, and thus becomes a materialist. 28. On the contrary, he who considers only the manifestations of intelligence and of creative will, without taking into account the means by which they are executed, and the physical laws by virtue of which all beings preserve their characteristics, will be very likely to confound the Creator with the creature. 29. It is only as it contemplates, at the same time, matter and mind, that Natural History rises to its true character and dignity, and leads to its worthiest end, by indicating to us, in Creation, the execution of a plan fully matured in the beginning, and undeviatingly pursued; the work of a God infinitely wise, regulating Nature according to imm. table laws, which He has himself imposed on her. CHAPTER SECOND. GENERAL PROPERTIES OF ORGANIZED BODIES. SECTION I. ORGANIZED AND UNORGANIZED BODIES. 30. NATURAL HISTORY, in its broadest sense, embraces the study of all the bodies which compose the crust of the earth, or which are dispersed over its surface. 31. These bodies may be divided into two great groups; inorganic bodies, (minerals and rocks,) and living or organized bodies, (vegetables and animals.) These two groups have nothing in common, save the universal properties of matter, such as weight, extension, &c. They differ at the same time as to their form, their structure, their chemical composition, and their mode of existence. 32. The distinctive characteristic of inorganic bodies is ⚫est; the distinctive trait of organized bodies is independent motion, LIFE. The rock or the crystal, once formed, never changes from internal causes; its constituent parts or molecules invariably preserve the position which they have once taken in respect to each other. Organized bodies, on the contrary, are continually in action. The sap circulates in the tree, the blood flows through the animal, and in both there is, besides, the incessant movement of growth, decomposition, and renovation. 33. Their mode of formation is also entirely different. Unorganized bodies are either simple or made up of elements unlike themselves; and when a mineral is enlarged, it is simply by the outward addition of particles constituted like itself. Organized bodies are not formed in this manner. They always, and necessarily, are derived from beings similar to themselves; and once formed, they always increase interstitially, by the successive assimilation of new particles, derived from various sources. 34. Finally, organized bodies are limited in their duration. Animals and plants are constantly losing some of their parts by decomposition during life, which at length cease to be supplied, and they die, after having lived for a longer or shorter period. Inorganic bodies, on the contrary, contain within themselves no principle of destruction; and unless subjected to some foreign influence, a crystal or a rock would never change. The limestone and granite of our mountains remain just as they were formed in ancient geological epochs; while numberless generations of plants and animals have lived and perished upon their surface. SECTION II. ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 35. The exercise of the functions of life, which is the essential characteristic of organized bodies, (32,) requires a degree of flexibility of the organs. This is secured by means of a certain quantity of watery fluid, which pene trates all parts of the body, and forms one of its principal constituents. 36. All living bodies, without exception, are made up of tissues so constructed as to be permeable to liquids. There is no part of the body, no organ, however hard and compact it may appear, which has not this peculiar structure. It exists in the bones of animals, as well as in their flesh and fat; in the wood, however solid, as well as in the bark and flowers of plants. It is to this general structure that the term organism is now applied. Hence the collective name of organized beings,* which includes both the animal and the vegetable kingdoms. 37. The vegetable tissues and most of the organic structures, when examined by the microscope in their early states of growth, are found to be composed of hollow vesicles or cells. The natural form of the cells is that of a sphere or of an ellipsoid, as may be easily seen in many plants; for example, in the tissue of the house-leek, (Fig. 1.) The intervals which sometimes separate them from each other are called intercellular passages or spaces (m.) When the cellules are very numerous, and crowd each other, their outlines become angular, and the intercellular spaces disappear, as seen in figure 2, which represents Fig. 1. Formerly, animals and plants were said to be organized, because they are furnished with definite parts, called organs, which execute particular functions. Thus, animals have a stomach, a heart, lungs, &c.; plants have leaves, petals, stamens, pistils, roots, &c., which are indispensable to the maintenance of life and the perpetuation of the species. Since the discovery of the fundamental identity of structure of animal and Vegetable tissues, a common denomination for this uniformity of texture has been justly preferred; and the existence of tissues is now regarded as the basis of organization. the pith of the elder. They then have the form of a honey-comb; whence they have derived their name of cellules. Fig. 2. 38. All the organic tissues, whether animal or vegetable, originate from cells. The cell is to the organized body what the primary form of the crystal is to the secondary, in minerals. As a general fact, it may be stated α b that animal cells are smaller than vegetable cells; but they alike contain a central dot or vesicle, called nucleus. Hence such cells are called nucleated cells, (Fig. 3, a.) Sometimes the nucleus itself contains a still smaller dot, called nucleolus, (b.) Fig. 3. 39. The elementary structure of vegetables may be ob served in every part of a plant, and its cellular character has been long known. But with the animal tissues there is far greater difficulty. Their variations are so great, and their transformations so diverse, that after the embryonic period it is sometimes impossible, even by the closest examination, to detect their original cellular structure. 40. Several kinds of tissues have been designated in the animal structure; but their differences are not always well marked, and they pass into each other by insensible shades. Their modifications are still the subject of investigation, and we refer only to the most important distinctions. 41. The areolar tissue consists of a network of delicate fibres, intricately interwoven so as to leave numberless communicating interstices, filled with fluid. It is inter posed in layers of various thickness, between all parts of the body, and frequently accompanied by clusters of fat cells. The fibrous and the serous membranes are mere modifications of this tissue. 42 The cartilaginous tissue is composed of rucleated |