This harmony of position in the double parts of animals is found also in vegetables; branches shoot out from buds on every side; the veins in the leaves are equally disposed as to the principal vein; and although symmetrical order appears to be less exact in vegetables than in animals, it is only because it is more varied, and its limits are more extended, and less precise; but we may nevertheless easily discover this order, and distinguish the simple and essential parts from those which are double, and the latter we must regard as having taken their origin from the former. We shall more fully discuss this point, as far as relates to vegetables, when we come to treat of them. It is not possible to determine under What form the double parts exist before expansion, nor in what manner they are folded, nor what figure results from their position by connection with the simple parts. The body of the animal, in the instant of formation, certainly contains every part which is to compose it; but the relative position of these parts must be very different then from what it becomes afterwards. It is the same with vegetables, for if we observe the expansion of a young leaf, we shall perceive that it is folded on both sides the principal vein, and that its figure does not resemble at that time what it afterwards assumes. When we amuse ourselves by folding paper to form crowns, boats, &c. the different folds of the paper seem to have no resemblance to the form which must result by the unfolding; we only see that these folds are always made in an uniform order, and exactly the same on one side as that we have made on t he other; but it would be a problem beyond known geometry, to determine the figures which may result from all the unfoldings of a certain given number of folds. All what immediately relates to the position, is beyond our mathematical sciences. This art, which Leibnitz calls _Analysis Situs_, is not yet found out; though the art, which would shew us the connections that result from the position of things, would perhaps be more useful than that which has only bulk for its object, for we have often more need to know the form than the matter.