3. The proof of Design, as shown in the works of Creation, is seen most clearly, not in mere physical arrangement, but in the structure of organized things;--in the constitution of plants and animals. In those parts of nature, the evidences of intelligent purpose, of wise adaptation, of skilful selection of means to ends, of provident contrivance, are, in many instances, of the most striking kind. Such, for example, are the structure of the human eye, so curiously adapted for its office of seeing; the muscles, cords, and pullies by which the limbs of animals are moved, exceeding far the mechanical ingenuity shown in human inventions; the provisions which exist, before the birth of offspring, for its sustenance and well-being when it shall have been born;--these are lucid and convincing proofs of an intelligent Creator, to which no ordinary mind can refuse its conviction. Nor is the evidence, which we here recognize, deprived of its force, when we see that many parts of the structure of animals, though adapted for particular purposes, are yet framed as a portion of a system which does not seem, in its general form, to have any bearing on such purposes.[1] The beautiful contrivances which exist in the skeleton of man, and the contrivances, possessing the same kind of beauty, in the skeleton of a sparrow, do not appear to any reasonable person less beautiful, because the skeleton of a man, and of a sparrow, have an agreement, bone for bone, for which we see no reason, and which appears to us to answer no purpose. The way in which the human hand and arm are made capable of their infinite variety of use, by the play of the radius and ulna, the bones of the wrist and the fingers, is not the less admirable, because we can trace the representatives and rudiments of each of these bones, in cases where they answer no such ends;--in the foreleg of the pig, the ox, the horse, or the seal. The provision for feeding the young creature, which is made, with such bounteous liberality, and such opportune punctuality, by the breasts of the mother, has not any doubt thrown upon its reality, by the teats of male animals and the paps of man, which answer no such purpose. That in these cases there is manifested a wider plan, which does not show any reference to the needs of particular cases; as well as peculiar contrivances for the particular cases, does not disturb our impression of design in each case. Why should so large a portion of the animal kingdom, intended, as it seems, for such different fields of life and modes of living;--beasts, birds, fishes;--still have a skeleton of the same plan, and even of the same parts, bone for bone; though many of the parts, in special cases, appear to be altogether useless (namely, the vertebrate plan)? We cannot tell. Our naturalists and comparative anatomists, it would seem, cannot point out any definite end, which is answered by making so many classes of animals on this one vertebrate plan.