SCIENTIFIC LETTERS TO A LADY OF QUALITY.-LETTER II.

EVERY one, however inexperienced and unlettered, can distinguish an animal and a plant from a pebble. But place these three bodies together, and let the distinguishing characteristics of each be enumerated by one unacquainted with science, and they will be found insufficient to instruct the mind upon the nature of life and organization, and as to the properties of living bodies, their structure and composition. It is not enough for the natural philosopher merely to "know a hawk from a hand-saw," but he requires, by the aid of known sciences, to understand more of the globe which he inhabits, and of the beings with which he is associated and surrounded-a branch of human knowledge the most interesting, most beautiful, and most useful; and to the attainment of which we must apply the several tests of zoology, chemistry, mechanics, and other physical sciences, anatomy, and physiology. Zoology regards the external characters of animals, their habits, and their arrangement in the great system of nature. By chemistry we discover their composition; by the physical sciences many of their properties, and, in part, their functions: by anatomy we learn their structures; and by physiology, their vital functions and properties as living bodies.

Of the extreme depths of our globe we can only be informed by analogy, which teaches us that living beings inhabit the surface of the earth, or near it, exclusively; and that the rest of the earth consists of what is termed commonly inert matter. This term is, however, objectionable, inasmuch as that no matter whatever is really passive or inert. From the grand system of the universe to bodies many times smaller than a grain of sand, nothing in nature is inert, but is full of activity. Myriads of planets are perpetually rolling through the space around us in fixed paths, and turning upon their own axes; their surfaces constantly undergoing changes by which mountains are elevated or depressed, plains levelled out, valleys converted into watery wastes, islands appear and disappear. Below the surface, the bowels of the earth are in constant action; and the intestinal changes which go on from the expansion of internal heat find vent in earthquakes and volcanoes, as the safetyvalves of the great steam-engine of nature. Thus all is active in the colossal world; and while the tempest rages above, or the artillery of heaven resounds along the surface of the earth-while the lightning rends asunder the hardy and ancient tenants of the 'forest, and the earth trembles with inward commotion, the minutest particles of matter, only visible through a microscope, partake in the universal activity.

Mr. Browne, the celebrated botanist, and a general naturalist, discovered a vibratory motion going on in pulverized granite, flint, glass, &c. which is wholly unaccountable upon any principle of motion in the physical world hitherto ascertained, and which may therefore possibly be identified with that which governs the changes of organized bodies under different modifications.

What is commonly termed inert matter may with more propriety be called mineral. Mountains, rocks, stones, &c. are only relatively inert, inasmuch as they require some foreign power to move

them superior to the resistance which their gravity affords, not possessing, like organized bodies, different degrees of spontaneous powers of locomotion within themselves.

The materials of the earth are therefore divided into two distinct species of matter, the mineral and the organized. Our present business is with the latter species, the individuals of which are termed animals and plants. The terms organic, organized, and organization, are derived from these individuals being made up of distinctly different parts, called organs, each having separate functions. Organization is therefore meant to express the development of the textures forming these organs. And thus the organic world essentially differs from the inorganic, which consists of bodies made up of homogeneous parts. All the organs of the former, moreover, are so connected together in distinctly individual masses, as to admit of a perpetual flow of fluids in the entire body by means of tubes or vessels; and thus each organ is essential to the integrity of the whole system; whereas the component parts of a mineral body have no such relation to each other, are kept together merely by chemical attraction, and each part when separated exists independently of the original mass.

There are several particular circumstances in which the external characters of organized and unorganized bodies essentially differ. The organized textures are disposed in laminæ or layers, the interstices of which are occupied by a fluid; and these textures are characterized by an arrangement of fibres which are contractile. In man, and in animals, with some exceptions among the lowest, the body consists of solid, soft, and fluid matter. The solid textures give form and shape to the figure, and endue the body with solidity and strength, And all organized forms, universally, are fixed and determinate in their arrangement: they are also capable of generating similar forms, and of transmitting an uniformity of character and construction from parent to offspring without limit or deviation. From this determinate principle in the general system of organization we are enabled to group and classify plants and animals, so that the apparent variety and confusion are reducible to order and simplicity; but this principle is wholly inapplicable to the mineral creation, which is therefore very differently arranged.

Taking a general survey of the two species of matter, it is observable that the forms of mineral bodies are usually shaped out in right angles, while the surfaces of organized bodies are disposed to be curvilinear. This distinction becomes apparent upon the most casual observation.

Organization is to all appearance derived originally from a specific combination of mineral particles, modified by a power not existing in themselves, but superadded to the laws of matter; for when organized textures are broken up and converted into liquid and gaseous forms, they re-assume mineral combinations, and obey the physical laws entirely; so organized matter becomes dissipated, but not annihilated, and it is capable of re-organization. And, as life is an uncertain and variable tenure, living bodies are more changeable than the mineral; the latter being actuated by the more permanent influence of chemical agency, exclusively of vital influ

ence.

We have two methods of examining organized bodies; by anatomy and by chemistry, or by means of dissection and analysis. The former method developes the structures of the body, and shows them to consist of various kinds of textures wove by the hand of Nature. Thus we discover the body to be constructed of these materials— bone, flesh, skin, nerve, sinew, gristle, membrane, &c. which make up the corporeal organs; the form and peculiar structures of which are also examined anatomically and if we wish to examine the composition of these textures, we employ simple mechanical analysis. The products of this examination result in affording us what are called the proximate principles of organized bodies. For example: if we macerate bones in diluted muriatic acid, they separate into two portions, one hard and the other soft. The hard portion yields phosphate of lime and other earthy salts: the soft yields oil, gelatin, and albumen. These substances are therefore proximate principles of animal matter, and of bone especially. They are all compound substances; and, when distilled, are reduced to their several components in fluid and gaseous forms, which constitute the ultimate principles of organized matter, such as oxygen, hydrogen, nitrogen, or azote, and carbon, with a few other simple elements. If we submit some vegetable matter to analysis, we thus arrive at its proximate principles. Flour, for example, beat up with boiling water, forms paste, which being submitted to a light stream of water produces that elastic and tenacious substance called gluten. The water used to wash the paste is turbid from holding in suspension starch. Thus gluten and starch are proximate principles of vegetable matter. Again, the culinary process of boiling meat discovers three proximate principles-oil, gelatin, and fibrin. The oil floats at the top of the water, the gelatin is dissolved, and the colourless ragged shreds left are the fibrin. On cooling down, the dissolved gelatin becomes apparent as a solid mass, which we term jelly.

Chemistry has discovered that the predominant matter in the composition of the human body consists of fibrin, gelatin, and albumen, in different relative proportions. These are all therefore organic substances and as we descend in the scale of animals, these proportions vary, the gelatin prevails over the fibrin very much. The fibrin is the fleshy fibre, or thread of muscles; and the gelatin is that which is usually called jelly, such as is produced from calves' feet, &c. from the cooling down of good soups: and the albumen is the same substance as that which constitutes the white portion of the eggs we commonly feed upon.

These are the leading characteristics which anatomy and chemistry develop when applied to the examination of organized bodies. Beings of every kind are designed by nature to commence their existence as a part of such bodies, until their organization is sufficiently advanced to permit them to maintain an independent existence. The new being and the old also precisely agree in their form and structure. In the first instance, every animal and plant originates in a germ, or egg; or, as it is termed in vegetation, a seed. The form of beings so produced continues throughout life the same; each organ maintaining its original development, although con

stant changes are going on within. New matter is constantly admitting, assimulated to the old, and former materials discharged, simultaneously. While such processes continue, life is said to be going on; and when they cease, death has taken place, and the body becomes obedient to chemical laws without any of the modifying influence of life: and then decomposition occurs; the textures become dissolved, the structures of the organs broken up, and the entire body gradually becomes converted into liquid, pulverized, and gaseous matter. These changes are in accordance with the universal law of nature; they do not arise from any imperfection of structure, or deficiency in the system of nature, but they are the inevitable and necessary results of organization, or the temporary union of vitality with organic matter.

When we review the various forms of the animal creation superficially, all seems to be confusion and variety to such an extent as defies arrangement. But nature has regarded individual identity of form and structure with such a degree of attention, amidst all her sportings, that we are enabled to reduce the apparent chaos to order and systematic regularity. Every animal is so perfectly transmitted from the parent to the offspring, that the lapse of ages does not disturb the harmony of our grouping. In all essential points of structure the species is constantly preserved entire, as may be seen by examining the fossil remains of skeletons, and the drawings of ancient animals still extant in different countries. Every separate form so constitutes a distinct species. Thus the species homo, or the human species, is transmitted in our day precisely in the same undeviating form as we recognise it in the earliest accounts of its creation. The lion and the tiger have the same external form as delineated anciently, and their skeletons exactly resemble those imbedded in the crust of the earth. These identical resemblances constitute distinct species in zoology. Nevertheless, the harmony of resemblance transmitted is only to be understood as appertaining to the most prominent features. Minor variations exist, which are not taken into account in grouping different species. Thus there are observable differences as to size, figure, colour, and proportions, among individuals of the same species, while the general form retains an uniformity of outline. While nature pertinaciously maintains a settled plan of organization as to general uniformity, in the details of forms, she sports so variously as to render no two individuals ever created exactly alike. Even the two Dromios were distinguished by some peculiarities. The Siamese youths differ, and all twins have some points of difference. Personal resemblances are no doubt very frequently so strong as to be confounded easily. I knew an instance of a person paying his addresses to one sister, and offering to the other by mistake, was accepted and married; and he did not discover the blunder until he found his spouse cared not for the charms of music, an accomplishment which the original object of his affections possessed. I also knew of an instance in which a person ran away with a young lady, where he thought he had made a sudden conquest; but it turned out that she mistook him for his brother. Since, however, the ancients personified love as blind, such little mistakes are not to be wondered at,

although to the cool observant eye of the naturalist, perhaps, the trifling discrepancies overlooked occasionally will always be manifest.

All plants and trees have their leaves, blossoms, branches, and roots, which assume fixed characters transmitted in each species; yet no two of them agree precisely in every respect as to height, width, figure, &c. Every horse we see is distinguishable from some peculiar marks. A flock of sheep has a very general resemblance, but the shepherd knows each familiarly from the rest. Negroes have a very marked permanency of physical development. As Mathews says, in imitation of a conversation at a negro assembly-" Jeronimo and Cæsar are bery much alike; Oh bery! specially Cæsar,"-yet the resemblance is never perfect though ever so close there is ever some discrepancy in the features, or voice, manners, gestures, feelings, or thoughts, between every pair throughout the whole human race. Intellectual and mental differences will always exist as well as those of a physical description. Nor are these characteristic distinctions by any means capricious, but result from fixed laws as a part of Nature's great moral scheme, whence we derive an additional interest in her works, and her various forms gain external beauty. Nature also institutes some more prominent and important deviations, which constitute so many varieties of each species. The varieties are, however, far less common in the wilds of uncivilized countries, than among domesticated animals. Thus the varieties of the dog species, by crossing, are carried to an extraordinary extent. According to the definition of Cuvier, definite forms transmitted by generation are capable of being arranged in separate species, each including all the individual forms descending from one and the other, or from parents in common, and of such as resemble them, and bear a reciprocal affinity to each other.

The first step, therefore, of the naturalist in his system of arrangement is to constitute the species to which all individuals are referred. He then groups together such species as most resemble each other, and thus constitutes genera; and to arrive at these, the naturalist has recourse to more accurate and minute examination of individuals in each species, in order to form his comparisons correctly. In this manner the lion, the tiger, lynx, leopard, panther, and the cat species, are included in the genus felis, or cat. They have all the same characteristics in common; they are more or less savage, and prey upon other animals. In most respects their organization is the same; they possess great muscular strength, their necks and limbs are short and stout, they are furnished with large teeth for tearing flesh, and powerful jaws; and for seizing their prey they possess long, curved, sharp claws. The latter organs are not, however, fixed points of action, but are so attached as to be capable of extension or contraction as they may be wanted or not, so that in walking the claws are coiled up out of the way of the foot's pressure. Among the feline genus, the cat is the only species that is usually domesticated. It is not difficult to tame the others, but their size and strength render them rough play-fellows in a house; they are therefore employed only in hunting by the Indians. Kean, the celebrated actor, had a fine puma, one of the feline genus, whose gambols were often pro