[BH] This word is used by the author in an enlarged sense of propagation, for as generation applies to animated beings, so by this he includes the vegetable as well as animal system.
We shall now make a more minute inspection into this common property of animal and vegetable nature; this power of producing its resemblance; this chain of successive individuals, which constitutes the real existence of the species; and without attaching ourselves to the generation of man, or to that of any particular kind of animal, let us inspect the phenomenas of reproduction in general, let us collect facts, and enumerate the different methods nature makes use of to renew organized beings. The first, and as we think the most simple method, is, to collect in one body an infinite number of resembling organic bodies, and so to compose its substance, that there is not a part of it which does not contain a germ of the same species, and which consequently of itself might become a whole, resembling that of which it constitutes a part. This preparation seems to suppose a prodigious waste, and to carry with it profusion; yet it is a very common munificence of nature, and which manifests itself even in the most common and inferior kinds, such as worms, polypuses, elms, willows, gooseberry-trees, and many other plants and insects, each part of which contains a whole, and by the single effect of expansion alone may become a plant, or an insect. By considering organized beings in this point of view, an individual is a whole, uniformly organized in all its parts; a compound of an infinity of resembling figures and similar parts, an assemblage of germs, or small individuals of the same kind, which can expand in the same mode according to circumstances, and form new bodies, composed like those from whence they proceed.
By examining this idea thoroughly, we shall discover a connection between animals, vegetables, and minerals, which we could not expect. Salts, and some other minerals, are composed of parts resembling each other, and to all that composes them; a grain of salt is a cube, composed of an infinity of smaller cubes, which we may easily perceive by a microscope; these are also composed of other cubes still smaller, as may be perceived with a better microscope; and we cannot doubt, but that the primitive and constituting particles of this salt are likewise cubes so exceedingly minute as to escape our sight, and our imagination. Animals and plants which can multiply by all their parts, are organized bodies, of which the primitive and constituting parts are also organic and similar, of which we discern the aggregate quantity, but cannot perceive the primitive parts only by reason and analogy.
This leads us to believe that there is an infinity of organic particles actually existing and living in nature, the substance of which is the same with that of organized bodies. As we have just observed, in a structure of a similar kind, though of inanimate matter, that it was composed of an infinity of particles which have a perfect semblance to the whole body, and as there must perhaps be millions of small cubes of accumulated salts to form a sensible individual grain of sea-salt, so likewise millions of organic particles, like the whole, are required to form one out of that multiplicity of germs contained in an elm, or a polypus; and as we must separate, bruise, and dissolve a cube of sea-salt to perceive, by means of crystallization, the small cubes of which it is composed; we must likewise separate the parts of an elm or polypus to discover, by means of vegetation and expansion, the small elms or polypuses contained in those parts.
The difficulty of giving way to this idea arises from a prejudice strongly established, that there is no method of judging of the complex, except by the simple, and that, to conceive the organic constitution of a body we must reduce it to its simple and unorganized parts, and that it is more easy to conceive how a cube is composed of other cubes than how one polypus is composed of others; but if we attentively examine what is meant by simple and complex, we shall then find that in this, as in every thing else, the plan of nature is quite different from the very rough draught of it formed by our ideas.
Our senses, as is well known, do not furnish us with exact representations of external objects, insomuch that if we are desirous of estimating, judging, comparing, measuring, &c. we are obliged to have recourse to foreign assistance, to rules, principles, instruments, &c. All these helps are the works of human knowledge, and partake more or less of the abstraction of our ideas; this abstraction, therefore, is what is called the simple, and the difficulty of reducing them to this abstraction, the complex. Extent, for example, being a general and abstracted property from nature, is not very complex; nevertheless, to form a judgment of it, we have supposed extents without depth, without breadth, and even points without any extent at all. All these abstractions have been invented for the support of our judgment, and the few definitions made use of in geometry have occasioned a variety of prejudices and false conclusions. All that can be reduced by these definitions are termed simple, and all that cannot be readily reduced are called complex; from hence a triangle, a square, a circle, a cube, &c. are simple subjects, as well as all curves, whose geometrical laws we are acquainted with; but all that we cannot reduce by these abstracted figures and laws are complex. We do not consider that these geometrical figures exist only in our imagination; that they are not to be found in nature, or, at least, if they are discoverable there, it is because she exhibits every possible form, and that it is more difficult and rare to find simple figures of an equilateral pyramid, or an exact cube in nature, than compounded forms of a plant or an animal. In everything, therefore, we take the abstract for the simple, and the real for the complex. In Nature, on the contrary, the abstract has no existence, every thing is compounded; we shall never, of course, penetrate into the intimate structure of bodies: we cannot, therefore, pronounce on what is complex in a greater or lesser degree, excepting by the greater or lesser each subject has to ourselves and to the rest of the universe; from which reason it is we judge that the animal is more compounded than the vegetable, and the vegetable more than the mineral. This notion is just with relation to us, but we know not, in reality, whether the animal, vegetable, or mineral, is the most simple or complex; and we are ignorant whether a globule, or a cube, is more indebted for an exertion of nature, than a seed or an organic particle. If we would form conjectures on this subject, we might suppose that the most common and numerous things are the most simple but then animals would be the most simple, since the number of their kind far exceeds that of plants or minerals.
But without taking up more time on this discussion, it is sufficient to have shewn that the opinions we commonly have of the simple and complex are ideas of abstraction, that they cannot be applied to the compound productions of nature, and that when we attempt to reduce every being to elements of a regular figure, or to prismatic, cubical, or globular particles, we substitute our own imaginations in the place of realities; that the forms of the constituting particles of different bodies are absolutely unknown to us, and that, consequently, we can suppose, that an organized body is composed of organic particles, as well as that a cube is composed of other cubes.
We have no other rule to judge by than experience. We perceive that a cube of sea-salt is composed of other cubes, and that an elm consists of other smaller elms, because, by taking an end of a branch, or root, or a piece of the wood separated from the trunk, or a seed, they will alike produce a new tree. It is the same with respect to polypuses, and some other kinds of animals, which we can multiply by cutting off, and separating any of the different parts;[BI] and since our rule for judging in both is the same, why should we judge differently of them?
[BI] See Supplement to this Work, containing History of Birds, Fish, Insects, &c. vol. V. p. 377.