صور الصفحة
PDF
النشر الإلكتروني

fibres of the roots being spread under ground, imbibe, from the moist earth, juice fit for their nourishment; this is conveyed by the stalk up into the branches and leaves, through little, and, in some plants, imperceptible tubes, and from thence, by the bark, returns again to the root; so that there is in vegetables, as well as animals, a circulation of the vital liquor. By what impulse it is moved, is somewhat hard to discover. It seems to be from the difference of day and night, and other changes in the heat of the air ; for the heat dilating, and the cold contracting those little tubes, supposing there be valves in them, it is easy to be conceived how the circulation is performed in plants, where it is not required to be so rapid and quick as in animals.

Nature has provided for the propagation of the species of plants several ways. The first and general is by seed. Besides this, some plants are raised from any part of the root set in the ground; others by new roots that are propagated from the old one, as in tulips; others by offsets, and in others, the branches set in the ground will take root and grow; and last of all, grafting and inoculation, in certain sorts, are known ways of propagation. All these ways of increasing plants make one good part of the skill of gardening; and from the books of gardeners may be best learnt.

1

CHAPTER X.

Of Animals.

There is another sort of creatures belonging to this our earth, rather as inhabitants than parts of it. They differ in this from plants, that they are not fixed to any one place, but have a freedom of motion up

and down, and, besides, have sense to guide them in their motions.

Man and brute divide all the animals of this our globe.

Brutes may be considered as either aerial, terrestrial, aquatic, or amphibious. I call those aerial which have wings, wherewith they can support themselves in the air. Terrestrial are those whose only place of rest is upon the earth. Aquatic are those whose constant abode is upon the water.

Those are called amphibious, which live freely in the air upon the earth, and yet are observed to live long upon the water, as if they were natural inhabitants of that element; though it be worth the examination to know whether any of those creatures that live at their ease, and by choice, a good while or at any time upon the earth, can live a long time together perfectly under water.

Aerial animals may be subdivided into birds, and flies.

Fishes, which are the chief part of aquatic animals, may be divided into shell-fishes, scaly fishes, and those that have neither apparent scales nor shells.

And the terrestrial animals may be divided into quadrupeds or beasts, reptiles, which have many feet, and serpents, which have no feet at all,

Insects, which in their several changes belong to several of the before-mentioned divisions, may be considered together as one great tribe of animals. They are called insects, from a separation in the middle of their bodies, whereby they are, as it were, cut into two parts, which are joined together by a small ligature; as we see in wasps, common flies, and the like.

Besides all these, there are some animals that are not perfectly of these kinds, but placed, as it were, in the middle betwixt two of them, by something of both; as bats, which have something of beasts and birds in them.

Some reptiles of the earth, and some of aquatics,

VOL. III.

Y

[ocr errors]

want one or more of the senses which are in perfecter animals; as worms, oysters, cockles, &c.

Animals are nourished by food, taken in at the mouth, digested in the stomach, and thence by fit vessels distributed over the whole body, as is described in books of anatomy.

The greatest part of animals have five senses, viz. seeing, hearing, smelling, tasting, and feeling. These, and the way of nourishment of animals, we shall more particularly consider; because they are common to man with beasts.

The way of nourishment of animals, particularly of man, is by food taken in at the mouth, which being chewed there, is broken and mixed with the saliva, and thereby prepared for an easier and better digestion in the stomach. When the stomach has performed its office upon

the food, it protrudes it into the guts, by whose peristaltic motion it is gently conveyed along through the guts, and, as it passes, the chyle, which is the nutritive part, is separated from the excrementitious, by the lacteal veins; and from thence conveyed into the blood, with which it circulates till itself be concocted into blood. The blood, being by the vena cava brought into the right ventricle of the heart, by the contraction of that muscle, is driven through the arteria pulmonaris into the lungs; where the constantly inspired air mixing with it, enlivens it; and from thence being conveyed by the vena pulmonaris into the left ventricle of the heart, the contraction of the heart forces it out, and, by the arteries, distributes it into all parts of the body; from whence it returns by the veins into the right ventricle of the heart, to take the same course again. This is called the circulation of the blood; by which life and heat are communicated to every part of the body.

In the circulation of the blood, a good part of it goes up into the head; and by the brains are separated from it, or made out of it, the animal spirits ; which,

[ocr errors]

by the nerves, impart sense and motion to all parts of the body

The instruments of motion are the muscles; the fibres whereof contracting themselves, move the several parts of the body.

This contraction of the muscles is, in some of them, by the direction of the mind, and in some of them without it; which is the difference between voluntary and involuntary motions, in the body.

CHAPTER XI.

Of the Five Senses.

OF SEEING.

THE

organ of seeing is the eye; consisting of variety of parts wonderfully contrived, for the admitting and refracting the rays of light; so that those that come from the same point of the object, and fall upon different parts of the pupil, are brought to meet again at the bottom of the eye, whereby the whole object is painted on the retina that is spread there.

That which immediately affects the sight, and produces in us that sensation which we call seeing, is light.

Light may be considered either, first, as it radiates from luminous bodies directly to our eyes; and thus we see luminous bodies themselves, as the sun, or a flame, &c. or secondly, as it is reflected from other bodies ; and thus we see a man, or a picture, by the rays of light reflected from them to our eyes.

Bodies, in respect of light, may be divided into three sorts; first, those that emit rays of light, as the sun and fixed stars ; secondly, those that transmit the rays of light, as the air; thirdly, those that reflect the rays of light, as iron, earth, &c. The first are called luminous; the second pellucid; and the third opake.

The rays of light themselves are not seen; but by them the bodies, from which they originally come; as the sun, or a fixed star; or the bodies, from which they are reflected; as a horse, or a tulip. When the moon shines, we do not see the rays which come from the sun to the moon, but by them we see the moon, from whence they are reflected.

If the eye be placed in the medium, through which the rays pass to it, the medium is not seen at all; for instance, we do not see the air through which the rays come to our eyes. But if a pellucid body, through which the light comes, be at a distance from our eye, we see that body, as well as the bodies from whence the rays come that pass through them to come to our eyes. For instance, we do not only see bodies through a pair of spectacles, but we see the glass itself. The reason whereof is, that pellucid bodies being bodies, the surfaces of which reflect some rays of light from their solid parts, these surfaces, placed at a convenient distance from the eye, may be seen by those reflected rays; as, at the same time, other bodies beyond those pellucid ones may be seen by the transmitted rays.

Opake bodies are of two sorts, specular, or not specular. Specular bodies, or mirrors, are such opake bodies, whose surfaces are polished; whereby they, reflecting the rays in the same order as they come from other bodies, show us their images.

The rays that are reflected from opake bodies always bring with them to the eye the idea of colour; and this colour is nothing else, in the bodies, but a disposition to reflect to the eye more copiously one sort of rays than another. For particular rays are originally endowed with particular colours; some are red, others blue, others yellow, and others green, &c.

Every ray of light, as it comes from the sun, seems a bundle of all these several sorts of rays; and as some of them are more refrangible than others; that is, are

[ocr errors]
« السابقةمتابعة »