The modcations undergone by organized and unorganized bodies are peculiar and cha racteristic in each class. In the first place modification or change is no necessary con dition to the existence of an unorganized body, as it is of one that is organized. A mineral in a state of complete isolation might remain eternally unchanged ; a plant or an animal, on the contrary, cannot be conceived as existing for a moment abstracted from the universe around it, and without undergoing change. A mineral, in the instant of its formation, acquires all the properties that distinguish it at any after-stage of its existence; in plants and animals, on the other hand, as we witness an origin, so we observe a series of modifications denominated ages,—they commence their ex istence, they increase in size, they attain ma turity, and they decline and ultimately die.
Any change which unorganized bodies ex hibit is accidental, and happens under the influence of agencies external to themselves ; the changes which organized beings undergo in the course they run from incipience to their end, are on the contrary necessary, and take place in consequence of powers inherent in themselves.
Any change which an unorganized body ex periences happens on its surface : its mass is increased or diminished by simple addition to or subtraction from its particles; it does not increase, neither does it shrink and decay in all its parts like plants and animals, in which increase and diminution take place at one and the same time from within and from without. Increase in the unorganized world happens through ,juxtaposition, in the organic through intus-susception. Organized conse quently, as they alone are generated, as they alone possess powers of self-preservation and of reproduction, so do they alone grow, advancing necessarily from infancy to maturity and old age, or exhibit what are called ages. (See AGE ) Organized bodies further meet our obser vation in two different states,—those, namely, of health and of disease, nothing correspond ing to which is encountered in the inorganic world.
Whatever has a beginning has also an end. But the mode in which organized and un organized bodies cease to be, and the influences that determine their periods of being, are ex tremely different. A mineral ends when the affinities that combined it, and the attraction of cohesion that held its particles together, are overcome. This language implies that its destruction is effected by agencies external to itself—by the action of other bodies, and of circumstances over which it has no controul. The destruction of a mineral is, therefore, in nowise necessary, neither is it spontaneous : abstract a mineral, as we have said, from all external agency, and its endurance is inde finite.
Very different is the case with regard to animals and vegetables ; as their continuance depends on the process of nutrition, their end hangs upon the cessation of this act; and as the tenure by which they enjoy existence is temporary, the machine of organization being calculated to endure but for a season, their death or destruction is both spontaneous and necessary. Organized bodies which alone owe their being to generation, which alone continue their existence, reproduce their kinds, grow, attain maturity, and become aged by virtue of powers inherent within themselves, so do they alone die.
The period of endurance of unorganized bodies may often be calculated approximatively according to their masses, their densities, the aptitudes of their elements to enter into new combinations, &c.; that of organized bodies cannot be inferred from these or any other merely mechanical principles. Indeed, data from which the duration of organized bodies may be estimated are altogether wanting. We only know that every species has within nar row limits a period which it cannot pass; but why this period should, in particular instances, be confined to a few weeks, months, or years, or be extended to centuries, we cannot tell.
Nor is it only whilst endowed with all their peculiar and inherent properties that organized differ from unorganized bodies. No longer manifesting their especial powers, organized bodies begin to be disintegrated ; their con stituent elements, held together in opposition to the laws of chemical affinity, become ame nable to these, and forthwith enter into new combinations, which imply the utter destruc tion of the organization as it had been formed, and hitherto preserved. Organized beings, as they alone die, so do they also alone undergo putrefaction— a process nothing precisely si milar to which occurs in the inorganic world.
From this review of the distinguishing pecu liarities of organized and unorganized bodies, it appears that organization implies vitality, and that organization and life are insepara ble conditions. It would be going too far to say that they were synonymous terms : organization is the mode of structure proper to living beings ; ye is the series of actions they exhibit. And this in fact appears to be about the least objectionable definition of life than can he given : life is the series qf actions manifested by organized beings; would we go farther, we must condescend upon an enumera tion of these actions,—namely, incipience by a genesis or creation ; temporary endurance as individual by nutrition, and indefinite continu ance as species by reproduction, modification during the term of existence known by the title of age, and end by death, to which spe cific acts or phenomena must be added the peculiar inherent power which living beings possess of overcoming the general physico chemical laws that dominate the rest of the universe.
Thus far we have discussed and contrasted the physical qualities and phenomena common to organized or living beings at large, with such as inhere or are manifested by unorganized bodies generally, more especially minerals; we have still left untouched those that severally pertain to the two grand divisions of the or ganized world, and that are peculiar to each living thing individually ; and here we shall find that the manifestations of vitality are al most as various as the species that people the earth. In the same manner as we have hitherto gone on contrasting first the material compo sition, and then the actions of organic and inorganic bodies, we shall still proceed by comparing the material composition and the capacities of action of the different .classes of organized beings first, and next of the several individuals composing these classes one with another.