The second question, What can be the active power which causes this organic matter to penetrate and incorporate itself with this internal mould? By the preceding chapter it appears, that there exists in Nature powers relative to the internal part of matter, and which have no relation with its external qualities. These powers, as already observed, will never come under our cognizance, because their action is made on the internal part of the body, whereas our senses cannot reach beyond what is external; it is therefore evident, that we shall never have a clear idea of the penetrating powers, nor of the manner by which they act; but it is not less certain that they exist, than that by their means most effects of Nature are produced; we must attribute to them the effects of nutrition and expansion, which cannot be effected by any other means than the penetration of the most intimate recesses of the original mould: in the same mode as gravity penetrates all parts of matter, so the power which impels or attracts the organic particles of food, penetrates into the internal parts of organized bodies, and as those bodies have a certain form, which we call the internal mould, the organic particles, impelled by the action of the penetrating force, cannot enter therein but in a certain order relative to this form, which consequently it cannot change, but only augment its dimensions, and thus produce the growth of organized bodies; and if in the organized body, expanded by this means, there are some particles whose external and internal forms are like that of the whole body, from those reproduction will proceed. The third question, Is it not by a similar power the internal mould itself is reproduced? It appears, that it is not only a similar but the same power which causes expansion and reproduction, for in an organized body which expands, if there is some particle like the whole, it is sufficient for that particle to become one day an organized body itself, perfectly similar to that of which it made a part. This particle will not at first present a figure striking enough for us to compare with the whole body; but when separated from that body, and receiving proper nourishment, it will begin to expand, and in a short time present a similar being, both externally and internally, as the body from which it had been separated: thus a willow or polypus, which contain more organic particles similar to the whole than most other substances, if cut into ever such a number of pieces, from each piece will spring a body similar to that from whence it was divided.