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joining or articulation of the jaw; which gives the same advantage that we have, when we put a nut nearer the joint of the nut-cracker, that is, nearer the fulcrum. One disadvantage of this form and shortness of the bill would be, that the mandibles could not open wide enough to take in a large seed; but it is provided that the upper mandible shall move upon the skull, as well as the lower one. The form of the bill of the cross-bill looks like an imperfection, but it is attended with real advantages; it is not for crushing, but rather for splitting up a seed into halves, and tearing the cones of the fir-tree. One of the most curious provisions is in the bill of the sea crow; the mandibles are compressed into the form of simple laminæ, and the lower mandible projects beyond the upper one; so that, as he skims along the water, he dips his bill, and lifts his food, by the most appropriate instrument.]
The whiskers of feline quadrupeds, through branches of the fifth nerve, which enters their roots, possess a fine sensibility. Birds possess it also in a high degree, in their mouths. Ducks, and all that quaffer with their bills under water, have the sense very fine; and in the mandibles there are distributed branches of the fifth nerve, remarkably developed. Animals feel in the whole of their external surface; and of serpents we may say, that when they coil themselves round a body they exercise the organ of touch over their whole length. Still it is the fifth nerve of the brain, or nerves analogous to it, which, in the greater number of animals deficient in extremities, or in proper prehensile organs, ministers to the appropriation of food; the organs may vary in conformation, being sometimes only delicate palpi, sometimes horny processes; but in all, the senses of touch and of taste are bestowed through this-which is the nerve of sensation of the face, tongue, and lips, and the motor nerve of the muscles of the jaws, in man.
But we may repeat, that, necessary as these appendages, and this sensibility, are to the existence of the animals possessing them, the imperfections which they exhibit serve to show, by contrast, how happily the Hand is constructed. Our admiration is increased as we consider the sensibility to various impressions of touch, to varieties in the activity of the muscles, and to changes of posture, possessed by the human hand; and
all united to a facility of motion in the joints, for unfolding and turning the fingers in every possible degree and direction, without abruptness or angularity, and in a manner inimitable by any artifice of springs, pulleys, and levers.
THE ARGUMENT PURSUED.
So far as we have hitherto proceeded, examining our subject by comparative anatomy, we have been led to conclude that, independently of a system of parts marvellously combined to form the individual animal, another more comprehensive one exists, embracing all animals. However different animals may be in form and bulk, or to whatever condition of the globe they may have been adapted, a uniformity pervades the whole. We have seen no accidental deviation or deformity; but every change has been for a purpose, and every part has had its just relation. In all the varieties, we have witnessed the forms of the organs moulded with such a perfect accommodation to their uses, and the alterations produced in such minute degrees, that all notion of accidental external agency must be rejected.
We might carry our demonstration downward through the lower classes of animals. For example, in insects, we might trace the different modifications of the feet, from their most perfect or complex state, till they disappeared; or, following the changes in another direction, we might pursue them from their smallest beginning to the most perfect condition of the member, where thigh, leg, and tarsus are represented, as in the fly. We should, at first, discern the feet on the bodies of worms as fine cirri, like minute bristles, taking slight hold of the surfaces over which they creep. In the sea-mouse (aphrodita), we should perceive these bristles standing out from distinct wart-like processes, which are furnished with appropriate muscles. Then, in the myriapodes, the first order of insects, we should see each foot of the "many feet" possessing a distinct articulation. From that, we might pass to insects which have a thigh, leg, and foot, with the most perfect system of flexor, extensor, and adductor muscles; possessing, in fine, all that we most admire in human anatomy. Nay, it is more
curious to observe how the feet of true insects are again changed or modified to assume new offices-the anterior feet becoming feelers, organs of prehension, or hands. We thus perceive, that were it our object to examine the delicate and finely-adapted instruments of insects, it would be easy to trace, in almost every one of them, a succession of modifications. Among the vertebrata, we have seen the hand represented by a wing or a fin; so might we discover an opposite change in the wing of an insect. If we began with the fly which has two delicate and perfect wings protected beneath a case, we should find that the covers were capable of being raised, so as to admit of the ready expansion of the wings: in another, the case itself would be converted into a wing, and the fly be characterised by having four wings: proceeding to a third example, we should discover that this anterior wing was larger and more perfect than the posterior: in the fourth specimen, we should find that the erior ngs had disappeared, and that it was furnished with only two perfect ones: if we continued the examination, the next specimen would present an insect deprived of wings altogether. These are not freaks of nature, but new forms of the body; different appendages required for a different kind of poising of the fly in its flight. They are adaptations which succeed each other in the same regular series that has been observed to obtain in the larger animals; in which the intention cannot be mistaken.
A natural question forces itself upon us :-How are those varieties to be explained? The curious adaptation of a single member to different offices, and to different conditions of animals, has led to an extraordinary theory having been propounded in the present day,-that all animals consist of the same "elements." To say that, in every species of animal, however differing in form and structure, the chemical elements entering into the material of which they are formed, is the same, or that the material is attracted and assimilated by the performance of the same vital functions, would be just. But by elements, the authors adverted to mean certain constant pieces, which enter into the structure of the body; and which, they suppose, by being transposed and differently arranged, will explain all the diversities in the forms of animals. They illustrate their views by the analogy of building a mansion.
If there be, they say, a given quantity of materials, and these be disproportionately expended in ornamenting the portico and vestibule, the apartments for the family will be curtailed of their proper dimensions. So, according to the theory, if an elementary piece in an animal occupy a certain place, and be missed in the corresponding place of another animal, it must be sought for in some of the neighbouring organs.
But what foundation is there for saying that the aggrandisement of one member of an animal is attended with a proportional deficiency of another? The advocates of the theory rely much upon examples derived from the study of the bones; but the system fails even in them, as will presently be shown. Meantime, let us ask, is the addition of new parts to the stomach, by which its complexity is greatly increased, as in ruminating animals, attended with a diminution in the length of the intestinal canal, or more simplicity in its structure? On the contrary, is not a complex stomach necessarily connected with a long and irregular intestine? Does a complex intestinal canal render the solid viscera in juxtaposition less perfect? Does the compound heart imply a more simple condition of the lungs?
We have already stated that, in the higher orders of vertebrata, the bones of the shoulder perform a double office; that while they afford a perfect foundation for the motions of the upper extremity, they have an important share in the mechanism of respiration. Let us take an instance where the mode of breathing by the animal is inconsistent with what may be deemed the original design of the bones of the shoulder. In the batrachian order (p. 42), the ribs are absent. Where then, under the guidance of the theory, are we to look for them? If a bone be absent in the cavity of the ear of the bird, it directs us to seek for the bone in the jaw. But when a whole class of animals is deficient in thirty-two ribs, it fails to inform us where these. are to be found; or how the supposed "elements" are built up in adjacent structures. If, on the contrary, we adopt the principle, that parts are added or withdrawn, with a neverfailing relation to the function to be performed, we can comprehend that if the compages of the chest, to suit the peculiarities of the animal, be removed, and the shoulder be consequently deprived of support, the bones to which the extremity is fixed,