« ПретходнаНастави »
minute; at 20 years, about 75; at 80, about 70; and in old age, 60 or 50.
465. For the purpose of renewing and nonrisbing the blood, food is taken in at the inouth, macerated by the teeth, and mixed with the saliva ; it is then carried into the stomach, (a bag like a highland bag-pipe,) where it is dissolved into a soft pap by a powerful liquid called the gastric juice.
466. This pap is then drawn from the stomach into the intestines ; where, by means of a liquid called bile, it is separated into a white milky liquid called chyle, and into the excrement.
The chyle is taken up, or absorbed, by myriads of tine tubes called the lacteals, which carry it to a main-pipe called the thoracic duct. This pipe ascends to the throat, where it empties the chyle into a large vein, and being mixed with the blood, is conveyed to the heart.
467. Of such subtle and wonderful contrivance is the organization of man! Similar, also, is the construction of the whole of animated nature, from the greatest to the smallest.
Within the package of the skin, and essential to life and comfort, are numerous bones for strength; hundreds of muscles and tendons for action ; nerves spread every where for sensation; hundreds of arteries, to carry out the blood; hundreds of veins to bring it back again; and hundreds of glands performing all kinds of secretions; besides an intinite numbes
of tubes caned lacteals and lymphatics,' to 'absorb and convey nutriment to the blood. 1. 468. Such being the complex construction of animal bodies, is it not rather wonderful that we last 70 or 80 years, than that we endure no Jonger! When it is considered also, that a muscle or a bone out of place, a vein or artery stopt in its circulation, or a nerve unduly acted upon, creates disease, pain, and misery; is it not wonderful, that we enjoy so large a portion of health and pleasure ?
Should not such considerations teach us the value of prudence and temperance ?
Thick, in yon stream of light, a thousand ways,
469. The nerves are soft white chords which arise from the brain, the focus of sensation, and disperse themselves in branches through all parts. of the body. Impressions are received by the brain from the adjacent organs of sense; and the brain exercises its commands over the muscles and limbs by means of the nerves.
Thus, the body is enabled to avoid what is hurtful, to flee from danger, and to pursue every thing useful and agreeable.
| 06.-Trees and vegetables have no nerves or seruna rium, because, ny they are unable to move und avoid danger, they could be of no use to them. The proper oh ject of vegetableforganization, appears to be to supply food to animated nature, and the wisdom of Providence is in nothing more evident than in the variety, whole someness, and abundance of vegetable provisions.
470. The car is placed in the most conveni. ent part of the body wear the brain, the common seat of all the senses, to give more speedy information.
In man it is of a form proper for the erect posture of his body; in birds, of a form proper for flight, and not protuberant ; in quadrupeds, its form is, in some, large, erect, and open; in others, covered ; in subterraneous quadruperis, the ears are short and lodged deep.
471. The structure of the ear is admirably contrived to collect the undulations of sound, and to convey them to the sensory in the brain. The first part is the auricle, or external ear, formed to stop and collect the sonorus undulations, and convey them to the concha, or large capacious round cell, at the entrance of the ear. Persons, whose cars are cut off, have a confused hearing, and are obliged to form a cavity round the ear with their hand.
In the interior is the auditory passage, coriously tunnelled and turned, to give sounds ao easy passage, and prevent their too furiously as saulting the more tender internal parts.
472. To prevent the entrance of noxious in tects, this passage is secured with a bitter nav. seous substance, called ear-wax. The next prio
cipal part is the membranum tympani, or drum of the ear, with its inner membrane, the four little appendant bones, and the three inner muscles to move them, and adjust the whole system to hear loud or soft sounds.
The passage behind the drum of the ear, is called the vestibulum, being the entrance to two other cavities, called the labyrinth, and the second cochlea, from its resemblance to a snailshell.
473. The principal organs of the sense of smelling are the nostrils and olfactory nerves ; the ramifications of which are distributed throughout the nostrils.
Smelling is performed by the odorous eMuvia in the air, being drawn into the nostrils by inspiration, and struck with such force against the olfactory nerves, as to shake them, and occasion ideas of sweet, fætid, sour, and aromatic,
474. The taste is that sensation which all things give to the tongue ; but some consider the palate, the upper part of the roof of the mouth, to be the instrument of taste.
The Creator seems to have established a very intimale union between the eye, the nose, and palate, by directing branches of the same nerves to each of these parts, by which means there exist all the necessary guards against pernicious fuod ; since, before it is admitted into the sto mach, it undergoes the trial of two of the senses and the scrutiny of the eye.
470. Feeling is the sense by which we acquire ideas of solid, hard, hot, cold, &c.
Some consider the four other senses merely as modifications of feeling.
The immediato organs of feeling are the pyramidal papillæ under the skin, which are little, soft, medullary, nervous prominences, lodged every where under the outermost skin.
Föcling is the most universal of our senses, spiders, flies, and ants, have this sense in greater perfection than wan. lu blind persons, ibe cofeet of sighit has been supplied by their exqui site touch, or sense of feeling.
470. From these five senses, flow all our schsitive perceptions, the result of experience; and all the various habits, qualities, passions, and powers of animals.
Certain practices called instincts, not the app.co parent result of experience, appear to us to be long to some animals, contrived by some waknown means of that all powerful Creator, whose wondrous and incomprehensible works inspire with rapture and devotion the being whom he has qualitied 10 exeuning and estimate them,
Ob8-To follow this wonderful scheme of creation into all its ramifications and varintion, and to trace all Its analogick, would all hundreds of volumen, and occupy Ayrs of observation, having, therefore, given the above general idea of animated movistence in its relation to r* Brunbolon, I woull proceed to a brief componeration of the Lomon CANCI referring my students to Bing ley's Animal Biography. 10 Button's Natural History, Mavor's Abridgenent, and to a multitude of other books on sucht Nobjects.
177. As a prop work, or substantial Provie to the body, the bones nie povedlo