particular figure, and follow up with so much nicety the same precise and geometrical arrangement through every stage of their growth, that we are able, in all common cases, to distinguish one kind of crystal from another by its geometrical figure alone; and with the same ease and in the same manner as we distinguish one kind of animal from another by its general make or generic structure. The form of these elementary particles we can no more trace to a certainty than the bond of their union; but there is great reason for believing them to be spheres or spheriods, as first conjectured by that most acute and indefatigable philosopher Dr. Hooke, and since attempted to be explained by Dr. Wollaston in a late Bakerian lecture.*

Such are the most striking powers that occur to us on a contemplation of the unorganized world. From unorganized let us ascend to organized nature. And here the first peculiar property that astonishes us is the principle of life itself; that wonderful principle equally common to plants and animals, which maintains the individuality, connects organ with organ, resists the laws of chemical change or putrefaction, which instantly commence their operation as soon as this agent or endowment ceases; and which, with the nicest skill and harmony, perpetuates the lineaments of the different kinds and species through innumerable generations. It is an agency which exists as completely in

* Phil. Trans. 1813. p. 51.

the seed or the egg as in the mature plant or animal: for as long as it is present, the seed or the egg is capable of specific developement and growth; but the moment it quits its connection, they can no more grow than a grain of gunpowder.

What now is this wonderful principle that so strikingly separates organized from inorganized matter? that, as I have observed on a former occasion, from the first moment it begins to act infuses energy into the lifeless clod; draws forth form, and order, and individual being from unshapen matter, and stamps with organization and beauty the common dust we tread upon?* I have called it an agent or endowment: is it nothing more than these? is it a distinct essence? and, if so, is this essence refined, etherialised matter, freed from the more obvious properties of grosser matter, or is it strictly immaterial? It has been said by different physiologists to be oxygene, caloric, the electric or the galvanic gass; but all this is mere conjecture; and even of several of these powers we know almost as little as we do of the vital principle itself, and are incapable of tracing them in the vegetable system.

The next curious energy we meet with in organized nature, and which also equally belongs to animals and vegetables, is instinct. This I have defined to be "the operation of the vital principle, or the principle of organized life by

* Vol. I. Ser. I. Lect. ix. p. 229.

!

the exercise of certain natural powers directed to the present or future good of the individual, or of its progeny." * But what are these powers, with which the vital principle is thus marvellously gifted, and which enables it, under different circumstances, to avail itself of different means to produce the same end? that directs plants to sprout forth from the soil, and expand themselves to the reviving atmosphere; fishes to deposit their eggs in the sands; birds in nests, of the nicest and most skilful contrivance; and the wilder quadrupeds to accomplish the same purpose in lairs or subterraneous caverns; that guides the young of every kind to its proper food, and, whenever necessary, teaches it how to suck? Are these powers also material, or are they immaterial? Are they simple properties issuing out of a peculiar modification of matter, or something superadded to the material frame?

In the confused language and confused ideas of various metaphysical hypotheses, and even of one or two that pretend to great exactness in these respects, instinct is made a part or faculty of the mind: and hence we hear of a moral instinct. But has the polype, then, or the hydatid a mind? Are we to look for a mind in the midst of sponges, corals, and funguses?—in the spawn of frogs, or the seeds of mushrooms? Instinct, however, the operation of the principle of life,

equally superintending the entire frame, and every separate part of it, guiding it to its perfect developement, exciting its peculiar energies, remedying its occasional evils, and providing for a future progeny, is equally to be traced in all of them? Are instinct, then, and mind the same thing? or is the vocabulary of the hypotheses I now advert to, and shall have occasion to examine more at large hereafter, so meagre and limited that it is necessary to employ the same term to express ideas that have no connection with each other, and which cannot, therefore, be thus expressed without the grossest confusion? It is high time to be more accurate, and to have both determinate words and determinate ideas; and it has been one object of this course of instruction to define what ought to be the real distinction between instinct, sensation, and intelligence.

But let us ascend a step higher in the great scale of life; let us quit the vegetable for the animal kingdom. If I take the egg or grain of a mustard-seed, and the egg of a silk-worm, where is the chemist or physiologist that will point out to me the diversity of their structure, or unfold the cause of those different faculties which they are to evince on future developement and growth? At present, so far as they appear to us, they are equally common matter, actuated by the same common living principle, directed to different ends. To give them developement and mature form, we equally expose them to

the operation of the sun and the atmosphere, and, in the case of the mustard-seed, of moisture: and we are not conscious of exposing them to any thing else; all which, again, so far as we are acquainted with them, are nothing but matter in different states of modification. Yet the animal egg produces a new and a much higher power, which we denominate sensation, while the vegetable egg produces nothing of the kind. What is sensation, and from what quarter has it been derived? Is it a mere property, or a distinct essence? Is it material, or is it immaterial?

This, also, has occasionally been called instinct, and been contemplated as of instinctive energy. With equal confusion it has also been called or contemplated as a property of mind. It is neither the one nor the other it is equally different from both. We trace, indeed, its immediate seat of residence; for we behold in the silk-worm a peculiar organ which does not exist in the mustard-plant, and to which, and which alone, sensation always attaches itself; and to this organ we give the name of a nervous system. But to become acquainted with the organ, in which sensation resides, is no more to become acquainted with the essence of sensation itself, than to know the principle of life because we know the general figure of the individual animal or vegetable in which it inheres; or than to know what gravitation is because we see the matter which it actuates.