for the modulation of their notes. A tuneful bird is a ventriloquist. The seat of the song is in the breast. The use of the lungs in the system has been said to be obscure one use however is plain, though, in some sense, external to the system, and that is, the formation, in conjunction with the larynx, of voice and speech.* They are, to animal utterance, what the bellows are to the organ. For the sake of method, we have considered animal bodies under three divisions-their bones, their muscles, and their vessels; and we have stated our observations upon these parts separately. But this is to diminish the strength of the argument. The wisdom of the Creator is seen, not in their separate but their collective action; in their mutual subserviency and dependence; in their contributing together to one effect and one use. It has been said, that a man cannot lift his hand to his head without finding enough to convince him of the existence of a God. And it is well said: for he has only to reflect, familiar as this action is, and simple as it seems to be, how many things are requisite for the performing of it; how many things which we understand, to say nothing of many more, probably, which we do not; viz. first, a long, hard, strong bone, or tense membrane, which, in producing sounds, resembles the mechanism of a musical instrument. In the plate, this part of the larynx is a little turned up to show the tendinous band at this extremity stretched across it, which is furnished from the surrounding parts with muscles to modulate the tone. * Speech or pronunciation entirely depends on the air passing from the lungs, though at the same time it requires a particular disposition of the vocal tube for one sort of pronunciation the tongue is the principal agent of formation; for another it is the teeth; others are formed by the lips; whilst, for the production of others, the air must pass the nasal cavities. cylinder, in order to give to the arm its firmness and tension; but which being rigid, and in its substance inflexible, can only turn upon joints: secondly, therefore, joints for this purpose-one at the shoulder to raise the arm, another at the elbow to bend it; these joints. continually fed with a soft mucilage to make the parts slip easily upon one another, and holden together by strong braces, to keep them in their position: then, thirdly, strings and wires, i. e. muscles and tendons, artificially inserted for the purpose of drawing the bones in the directions in which the joints allow them to move. Hitherto we seem to understand the mechanism pretty well; and, understanding this, we possess enough for our conclusion: nevertheless, we have hitherto only a machine standing still; a dead organization-an apparatus. To put the system in a state of activity, to set it at work, a farther provision is necessary, viz. a communication with the brain by means of nerves. We know the existence of this communication, because we can see the communicating threads, and can trace them to the brain its necessity we also know, because if the thread be cut, if the communication be intercepted, the muscle becomes paralytic: but beyond this we know little; the organization being too minute and subtile for our inspection. *The functions of the brain and nervous system are at present involved in much mystery; we see only the surprising effects of their agency. That the mind may act on the body, and indeed superintend the whole fabric, it is necessary that this thinking immaterial agent should be provided with an immediate place of residence: that residence is the brain! And as we are destined to hold correspondence with the material beings that surround us, we must be supplied with organs fitted to receive the different kinds of impressions made upon them. For this purpose we are provided with the organs of sense: the eye is adapted to light; the ear to sound; the nose to smell; the mouth to taste; the skin to touch. But as the brain is the seat or source of sensation and volition, we must be furnished with a To what has been enumerated, as officiating in the single act of a man's raising his hand to his head, must be added likewise, all that is necessary, and all that contributes to the growth, nourishment, and sustentation of the limb, the repair of its waste, the preservation of its health: such as the circulation of the blood through every part of it; its lymphatics, exhalants, absorbents; its excretions and integuments. All these share in the result; join in the effect: and how all these, or any of them, come together without a designing, disposing intelligence, it is impossible to conceive. CHAPTER XI. OF THE ANIMAL STRUCTURE REGARDED AS A MASS. CONTEMPLATING an animal body in its collective ca medium of communication between the brain and external senses. Hence we are supplied with nerves. An impression received on the most remote part of the body, is propagated by the nerves to the brain, where, cognizance being taken of it, sensation is produced; again, a command emanating from the brain is transmitted along the nervous chords to the parts requisite to be put into motion, when the influence is immediately acknowledged, That these properties reside in the brain and nerves is almost self-evident. By directing my will to the muscles which move my fingers I easily bend them, because there is a direct communication with the brain by means of the nerves if these be divided I might will my fingers to move, but they would continue motionless. This proves that volition is connected with the brain. Again, if the nerves passing to the limb be divided, the most severe injury may be inflicted on it, yet no pain will be experienced, because the communication with the sensorium has been cut off. When, as in apoplexy, or an effusion of blood on the brain, it is compressed, loss of voluntary motion and sensation follows; notwithstanding the involuntary functions may for a time proceed in consequence of the nerves of organic life possessing some inherent and apparently independent power. By means of our nerves we are warned of those bodies which are noxious to us. By means of our nerves we receive all our corporeal enjoyment, and even the powers of the mind are extensively influenced by their actions. |