The nostrils are wide at the bottom, that a large quantity of effluvia may enter; narrow at the top, that, when entered, they may close their ranks, and act with greater vigour. Fine beyond all imagination, are the steams which exhale from fetid or fragrant bodies. The very best microscopes, which discover thousands and thousands of animalculæ in a drop of putrefied water, cannot bring one individual among these evanescent legions to our sight. Sight. How dreary would be our passage through this world without the sense of sight! Of what avail would be all the beauty of creation, and all the works of art, were we deprived of sight? But man, being endowed with this inestimable gift, is enabled to adore his Maker in the rising of the sun, in the variegated colours of the rainbow, in the heavens studded with stars, in the spots on the wing of the butterfly, and in the matter that shines in the glow-worm. The rays of light enter at the pupil of the eye, and proceed to the retina, or optic nerve, which is situated at the back part of the eyeball; and there they describe the figure, colour, and (excepting size) form a perfect representation of the object from which they proceed. The nerves are the only part of our frame capable of sensation; they appear, therefore, to be the instruments which the mind employs in its perceptions; for, a sensation always conveys an idea to the mind. Now, it is known, that our nerves can be affected only by contact; and, for this reason, the organs of sense cannot act at a distance; for instance, we are capable of smelling only particles which are actually in contact with the nerves of the nose. We have already observed, that the odour of a flower consists in effluvia, composed of very minute particles, which penetrate the nostrils, and strike upon the olfactory nerves, which instantly conveys the idea of smell to the mind. The nerves, which constitute the sense of sight, are not different in their nature from those of the other organs; they are merely instruments which convey ideas to the mind, and can be affected only on contact. Now, since real objects cannot be brought to touch the optic nerve, the image of them is conveyed thither by the rays of light proceeding from real objects, which actually strike upon the optic nerve, and form that image which the mind perceives. It would appear almost impossible that the extensive landscapes, which we frequently behold, should be represented on so small a space as the retina of the eye. It would be quite impossible for art to paint so small and distinct a miniature; but nature works with a surer hand, and a more delicate pencil. That power, which first caused my pulse to beat, while yet a fœtus in my mother's womb, can alone pourtray so admirable and perfect a miniature as that which is represented on the retina of the eye.* Hearing. Amazingly nice and exact must be the tension of the auditory nerves, since they correspond with the smallest tremors of the atmosphere, and easily distinguish their most subtile variations. They give existence to the charms of music, and reciprocate the rational entertainment of discourse. The eye perceives only the objects that are before it, but the ear warns us of transactions on every side. The eye is useless amid the gloom of night, but the ear admits its intelligence through the darkest medium. The eye is only on duty in our waking hours, but the ear is always ready to communicate any pleasure or danger. Touch. The papillæ of the fingers, or inside of the hand, may, by the operations of the mind, become erect or elevated; and being gently pressed or rubbed against a tangible body, they receive an impression, which is conveyed to the brain, and constitutes what we call touch. * This is illustrated by a very curious experiment, but which requires a little dexterity in order to perform it with success. We must shut up the doors and windows of a room, so as to render it totally dark; then bore in one of the shutters a round hole of a diameter equal to six-twelfths of that of the eye, and in that hole place the eye of an ox newly killed, and from which all the teguments have been taken, excepting the last, which immediately touches the vitreous humour. If this preparation be well made, and we have taken care not to change the natural form of the eye by pressing it, those who are in the room will see at the bottom of the eye, in an inverted position, the objects without, with all their motions and natural colours, and with a peculiarly bright appearance. Taste. The tongue is the organ of that sense called taste; and, from certain experiments, it appears that the power of taste is exercised by the tongue chiefly, although it is not confined to that member alone; for, on whatever part of the mouth, palate, or cheeks, we apply a sapid body, we do not perceive the sense of pain, but of taste; and from some bodies, as alum, pepper, &c. the sensation produced will be stronger and more distinct in these parts than any where else. The papilla of the tongue, which are larger and softer than those of the skin, and perpetually moist, perform the office of touch more exquisitely than the small and dry cutaneous papillæ. The papillæ of the tongue being raised a little protuberant to perform the office of taste, are affected in a particular manner by salts dissolved in water, or saliva, and applied against their tips or summits; which being distinguished by the mind, and referred to certain classes, are called tastes, either sour, sweet, acerb, bitter, saline, urinous, spirituous, aromatic, or pungent and acrid, insipid, putrid, and others, resulting partly from pure salts, and in part from an intermixture of the subtile animal, or vegetable oils, variously compounding and changing each other. Nature designed the difference of tastes to be felt by the tongue, that we might know and distinguish such foods as are most salutary; for, in general, there is not any one kind of wholesome aliment that is of a disagreeable taste; nor are there any ill-tasted substances that are fit for our nourishment. By excess, indeed, the most wholesome food becomes prejudicial. Nature has invited us to take necessary food, as well by the pain called hunger, as by the pleasure arising from the sense of taste. But brute animals, who have not, like us, the advantage of learning from each other by instruction, have the faculty of distinguishing flavours more accurately, by which they are admonished cautiously to avoid poisonous or unwholesome food; and therefore it is, that in herbivarous cattle, to which a greater diversity of noxious plants is offered among their food, the tongue is of a more exquisite texture, and furnished with larger and longer papillæ than in man, to whom they are less necessary. Feeling. While other senses have a particular place of residence, this is diffused through the whole frame, and is particularly fine at the extremities. Our feeling is finely tempered between the extremes ; neither so acute as in the eye, nor so obtuse as in the heel; for the one would produce continual pain, and the other would quite benumb the body, and almost annihilate the touch. Indeed, all our senses are most precisely fitted to our exigences: were any strained higher, they would be avenues of anguish; were they relaxed into greater insensibility, they would be useless incumbrances. Speech. This is the crowning gift, which improves the satisfaction, and augments the beneficial effects resulting from all the senses. This makes us gainers from the eyes and ears of others; from the ideas they conceive, and the observations they make. The tongue has neither bone nor joint; yet fashions itself with the utmost volubility into every shape and posture, which can express sentiment or constitute harmony. By this little collection of muscular fibres, we communicate the secrets of the breast, and make our thoughts audible. By this we instruct the ignorant, and comfort the distressed; we glorify God, which is its noblest employ, and we edify one another. The Voice. The human voice, melodious, sweet, and clear, THE NERVES. We are taught by modern anatomists that the nerves are the carriers of all pains and pleasures to the seat of sensation. K Know'st thou the nature of the human frame, The proofs of boundless wisdom there display'd? That every muscle may attend thy will; How every tendon acts upon its bone, And how the nerves receive their nicer tone; And give the wakeful mind intelligence. Abernethy observes—“The nervous system not only serves to inform us of the properties of surrounding objects by means of the organs of sense, but also to guard us against the application of any thing hurtful, as monitors teaching us to avoid it. Thus pain is very useful to us; but although from the nerves we occasionally suffer pain, yet in general, they are the source of pleasure by means of our senses. Let us suppose a man in a state of health. Is not his eye delighted by beautiful prospects, and his ear charmed with melody? Is he not regaled by the odours of herbs and plants? Does not his every want contribute to his gratification-the want of nourishment occasions hunger-fatigue requires rest! and where are there greater animal pleasures than in the gratification of such wants? Such is the state of an animal formed for enjoyment; but to this corporeal state man has added and affixed reason, which ought to furnish him with the greatest source of pleasure, if the intention of nature were not perverted. Finding gratification proceed from the satisfaction of his wants, he has absurdly increased their number in order to increase his enjoyment. For all natural wants nature has amply provided; but these fictitious wants cannot be gratified, and therefore he has made to himself a source of disquiet and discontent.” By nerves are meant the white ropey parts, which proceed from the brain and spinal marrow, and are spread over all the body by small ramifications. They are the seat and origin of all our faculties, of sensation and motion. From the medullary part of the cerebrum, cerebellum, and me |