페이지 이미지
PDF
ePub

vegetables and animals, structure is connected intimately with the vital power, and however convenient it may be in our systems to avail ourselves of external forms, those ought always to be preferred and selected, which have an intimate and vecessary relation to the most important functions of life-to the essential portions of their internal organization. Particular features, the claw of a bird, the teeth of a quadruped, the wings of an insect, will frequently indicate the character and the habits of the animal to which they belong-will give, perhaps, the history of the species. For these are all the results of structure. To structure, therefore, as the source of all affinity and discrepance in these departments of nature, our attention should be almost exclusively directed, and due importance must be allowed to those organs which most powerfully influence and regulate the character of the species and the functions of life.

Habit and instinct appear so necessarily to result from structure, that they might have been comprehended under the same head. . But they merit a separate notice, not only.on account of their intrinsic importance, but because they frequently serve to correct erroneous opinions and systems. They open of themselves, independent of scientific investigations, a wide field for study and observation. They indicate the use and application of organs, which no dissection, no abstract, perhaps, no analogical reasoning would ever have unfolded. They disclose the wise provision which Divine Providence has prepared for the preservation and propagation of each species, and they serve, as we have already remarked, to correct systematic arrangements, for, if in our classifications, we have associated beings whose habits are dissimilar, we may concludle with certainty, that we have overlooked some important, even if obscure, feature in their organization.

Qualities and Uses.- A knowledge of these are to man the most important result of his researches in natural history, and it will be a most valuable termination, if, in the ultimate views of science, the arrangements of system shall be made to accord with practical utility, that we shall be able by distinct, prominent and essential characters, to associate those substances and forms, and those only which are intimately allied, and avoid the incongruous combinations which have hitherto appeared even in the best systems; and, that the principles of classitication shall be made to conform to the apparent designs of nature, and shall at once develope the composition, properties, habits and instincts of all objects submitted to its examination. This, however, is still a doubtful result. We know not how far the views of nature herself correspond with our wishes, whether that be possible

which we consider as desirable. But no one can question the influence which extensive and accurate investigation may have on this inquiry, even if it were only to point out the exceptions and deviations from any plan, nor the immense benefit which would be derived from its accomplishment. To this object, the great efforts of man should be directed. Its attainment would complete his triumph over the material world, and give him that absolute dominion which has long been promised.

After this will remain an inquiry among the most curious, the most interesting, perhaps, ultimately, among the most momentous in the whole range of human investigation. I mean the relation of beings to each other, the power of organization, the influence of life, the gradation of the vital and intellectual functions, the whole forming, not as it has frequently been called, a chain of beings, for there is no continued series, but a web connecting every portion of the material, perhaps we may also add, the immaterial world. A web so wonderfully woven, as to form but one work, yet displaying in every part radiating centres of distinct circles; some closely allied to adjacent circles, some so slightly attached that we can with difficulty trace the film that unites them to their fellows. This must be the last term, the latest effort of science. We must know all the tribes, all the productions of nature, before we can comprehend and exhibit accurately their mutual connexion and dependence. Who shall summon together the inhabitants of the air, the ocean, and the land ? Who shall ever number up the living species, who shall trace out and recal those which are extinct and forgotten? These, perhaps, once occupied many of the broken and disordered portions of this web. We perceive every where marks of convulsions that have been permitted to disarrange the fabric of nature, who can tell the extent or the magnitude of these devastations ?

When we survey this great work of creation, its extent, its harmony, the magnificence of its outline, the perfection of its minute details, we cannot be surprised that its study should have engaged and occupied minds of the highest power, nor that such minds should have failed thoroughly to explain what infinite wisdom has devised, infinite power executed, and what mortal spirits may be permitted only partially to comprehend. Yet let us not despond. In the study of nature we tread in the footsteps of wisdom. We listen to a voice, which is the same yesterday, to-day and forever. And while the erring and fluctuating opinions of man, his crimes, his follies, his power pass away and are forgotten, the empire of nature is immutable, to us cternal--the knowledge of nature which is once accurate,

is forever true—the knowledge of nature which is once perfect, may be forever useful.

When we approach to examine the fabric of nature, so far as it is subjected to our inspection, we find ourselves immediately placed amidst differing, if not contending powers. We perceive ourselves inhabitants of a globe, which science informs us, is but one of an immense system, surrounded by other forms, some similar to our own, some wandering over the earth, roaming in different elements, or confined to one; some, though located in one spot, varying in size and aspect with the passing seasons; or by other substances apparently composing portions of the globe itself, immoveable and changing not. The first impression which the inind receives, and that which most attracts the attention, is the wide difference that exists between the earth itself and the diversified forms which occupy its surface, between the silent, still and joyless repose of matter, and the noisy, gay and animated voice of life. The suhstances which compose that portion of the earth, whether crust, or covering or projecting masses of its mighty frame, which is alone submitted to our researches, are passive, immovable, insensible; those which inhabit that surface, are for the most part, active, capable of moving from place to place at pleasure, and possess great sensibility. The former have neither growth nor voluntary action, they have no mode of increase, but by the casual addition of similar particles, united by the strong and universal law of attraction. They can remain unaltered for indefinite periods of time; they have no death, but they perish or rather are destroyed solely by the separation of their component particles. The latter all increase in size through their own agency, by the constant addition of particles which they have the power to collect and assimilate to their substances by the principle of life; they perish whenever this addition and assimilation cannot be continued ; and exist only for limited and indefinite periods. The former have no organization, are not produced by similar and pre-existent bodies, but are always and necessarily formed by the accidental contact of similar particles. They have no regular structure, but under certain circumstances, a modified attraction gives to each particle of matter a definite position, and generates the regular forms of crystallised bodies. The latter are all furnished with organs calculated and adapted to perform the functions of life, to collect, absorb and assimilate those particles which are necessary for their existence, and they always proceed from similar and pre-existing bodies.

VOL. II.NO.4.

We may pursue still further these distinctions and these contrasts. Unorganised bodies, whether in massive forms or in scattered fragments, have still the inseparable qualities of matter, extension, form, impenetrability, vis inertiæ; they are subjected to those unalterable laws, and, apparently, to those alone which govern the material world; to that attraction which extends its influence and its activity from the centre of the earth, from the smallest atom on its surface to the interminable confines of space; to those laws of cohesion or chemical affinity which are but modifications of attraction; to motion, involuntary however and external—to expansion, to contraction, but still from foreign causes or external impulses ; acted upon unceasingly, impassive in their own nature, obeying constantly definite and immutable laws. Unorganized matter is permanent and unchangeable, its particles may be separated or combined, but they are always the same. Though capable of modifications by combination, these combinations are only new aggregations of the same particles, and can be varied, reversed, destroyed. And the alterations which chemical combinations produce, are never counteracted by occult and inscrutable causes, like the influence of life in organized bodies.

Unorganized matter consists, therefore, as far as human observation can discover, of particles or molecules of a few distinct substances. These particles are independent and unalterable; combine them, mingle them, change the form, the proportions, the component particles of each combination, the elementary principles will be still unchanged, and may be again separated from all admixtures.

Organized bodies, besides the general properties of matter, possess a structure adapted to the functions of life. They are composed of fibres and tubes. They have parts sufficiently solid to develope and support their forms; fuids in constant motion or circulation to repair or preserve the solids. Their tissue is a species of net-work with the partitions more or less firm and compact, and the fluids pass along the cells or tubes, bearing foreign particles to every portion of the body, interposing new particles where nutriment or support is wanting, removing those that are superfluous or injurious—conveying to each different organ its peculiar secretions, to the surface those particles that pass off by exhalation. But while this motion appertains to the Auids, the impulse seems to be given by the contractile power of the solids, and this contractile power requires again in the solids both flexibility and the power of dilatation.

Such are the simple outlines of organization. Peculiar vessels or organs, receive in different modes, or by different laws, the

particles necessary to maintain the existence of each individual. These particles are either separated, in the first instance, as in vegetables, by the process of absorption, from those with which they are commingled, or being received, as in animals, in a peculiar sac or stoniach, placed, generally, near the centre of each individual, the process of separation then takes place. In the foriner case, nothing seems to be introduced into the circulation but what is necessary for the support and the particular secretions of each individual; in the latter, provision is necessarily made to expel the superfluous residuum of the materials promiscuously collected. The particles separated for the maintenance of the individual, are driven by the muscular power of the solids, and mingle with the system generally, as we have already stated. In this action of the solids and fluids, in this continued motion, life may be said to consist, inseparably connected with organization.

In organized bodies there is always one plan, however each may be diversely modified, and every member bears a necessary relation to the whole. All unite to form one being, and the organs that may be accidentally severed have no separate existence.

In the scale of life, some of these organs appear to be more important than others; and in each individual, one or more may be considered as essential.

Death seems to be the inevitable condition and consequence of life. In unorganized bodies, where there is no necessary change, no alteration that is not accidental, forms may continue unaltered for indefivite periods, through a succession of ages.But, in organized bodies, a gradual but unceasing change continues through the whole period of their existence, and limits by its effects, their duration. At first, they increase in their dimensions to a certain and determinate extent, afterwards, in most parts of their frame, the addition of nutriment only adds to its solidity, and as this last process never ceases, the increasing density of the solids finally prevents the circulation of the fluids, and life terminates because its functions can no longer be performed.

Every thing thus seems to differ between these two classes, form, origin, termination, physical and even chemical properties. They have nothing in com'non, but the general properties of matter. Unorganized bodies are, essentially, homogeneous, each of their parts taken separately, affords the properties of the whole; while organized bodies are essentially heterogeneous, and their parts or organs differ from each other by their functions, their position, and their composition. Hence, it

« 이전계속 »