Part 13 (1/2)
In like manner, the monoculus delights in putrid waters; the gnat eats the monoculus; the frog eats the gnat; the pike eats the frog; and the sea-calf eats the pike.
The bat and the goat-sucker make their excursions only at night, that they may catch the moths, which at that time fly about in great quant.i.ties.
The woodp.e.c.k.e.r pulls out the insects which lie hid in the trunks of trees.
The swallow pursues those which fly about in the open air. The mole feeds on worms and grubs in the earth. The large fishes devour the small ones.
And perhaps there is not an animal in existence, which has not an enemy to contend with.
Among quadrupeds, wild beasts are most remarkably pernicious and dangerous to others. But that they may not, by their cruelty, destroy a whole species, these are circ.u.mscribed within certain bounds: as to the fiercest of them, they are few in number, when compared with other animals; sometimes they fall upon and destroy each other; and it is remarked also, that they seldom live to a great age, for they are subject, from the nature of their diet, to various diseases, which bring them sooner to an end than those animals which live on vegetables. It has been asked, why has the Supreme Being const.i.tuted such an order in nature, that, it should seem, some animals are created only to be destroyed by others? To this it has been answered, that Providence not only aimed at sustaining, but also keeping a just proportion amongst all the species, and so preventing any one of them from increasing too much, to the detriment of men and other animals. For if it be true, as it a.s.suredly is, that the surface of the earth can support only a certain number of creatures, they must all perish, if the same number were doubled or trebled.
There are many kinds of flies, which bring forth so abundantly, that they would soon fill the air, and, like clouds, intercept the light of the sun, unless they were devoured by birds, spiders, and other animals.
Storks and cranes free Egypt from frogs, which, after the inundation of the Nile, cover the whole country. Falcons clear Palestine from mice.
Bellonius, on this subject, says, ”The storks come to Egypt in such abundance, that the fields and meadows are quite white with them. Yet the Egyptians are not displeased with them, as frogs are generated in such numbers, that, did not the storks devour them, they would over-run every thing. Besides, they also catch and eat serpents. Between Belba and Gaza, the fields of Palestine are often injured by mice and rats; and were these vermin not destroyed by the falcons, that come here by instinct, the inhabitants could have no harvest.”
The white fox is of equal advantage in the Lapland Alps; as he destroys the Norway rat, which, by its prodigious increase, would otherwise entirely destroy vegetation in that country.
It is sufficient for us to believe that Providence is wise in all its works, and that nothing is made in vain. When rapacious animals do us mischief, let us not think that the Creator planned the order of nature according to our private principles of economy; for the Laplander has one way of living, the European husbandman another, and the Hottentot differs from them both; whereas the stupendous Deity is one throughout the globe; and if Providence do not always calculate according to our method of reckoning, we ought to consider this affair in the same light as when different seamen wait for a fair wind, every one with respect to the port to which he is bound: these we plainly see cannot all be satisfied.
We shall conclude this branch, by turning once more to Man, and tracing him through his progressive stages of decay, until death puts a final period to his earthly existence.
The human form has no sooner arrived at its state of perfection, than it begins to decline. The alteration is at first insensible, and often several years are elapsed before we find ourselves grown old. The news of this unwelcome change too generally comes from without; and we learn from others that we grow old, before we are willing to believe the report.
When the body is come to its full height, and is extended into its just dimensions, it then also begins to receive an additional bulk, which rather loads than a.s.sists it. This is formed of fat, which, generally, at about the age of forty, covers all the muscles, and interrupts their activity. Every exertion is then performed with greater labour, and the increase of size only serves as the forerunner of decay.
The bones also become every day more solid. In the embryo they are almost as soft as the muscles and the flesh, but by degrees they harden, and acquire their proper vigour; but still, for the purpose of circulation, they are furnished through all their substance with their proper ca.n.a.ls.
Nevertheless, these ca.n.a.ls are of very different capacities during the different stages of life. In infancy they are capacious, and the blood flows almost as freely through the bones as through any other part of the body; in manhood their size is greatly diminished, the vessels are almost imperceptible, and the circulation is proportionably slow. But in the decline of life, the blood which flows through the bones, no longer contributing to their growth, must necessarily serve to increase their hardness. The channels which run through the human frame may be compared to those pipes that we see crusted on the inside, by the water, for a long continuance, running through them. Both every day grow less and less, by the small rigid particles which are deposited within them. Thus, as the vessels are by degrees diminished, the juices also, which circulate through them, are diminished in proportion; till at length, in old age, these props of the human frame are not only more solid, but more brittle.
The cartilages, likewise, grow more rigid; the juices circulating through them, every day contribute to make them harder, so that those parts which in youth are elastic and pliant, in age become hard and bony, consequently the motion of the joints must become more difficult. Thus, in old age, every action of the body is performed with labour, and the cartilages, formerly so supple, will now sooner break than bend.
As the cartilages acquire hardness, and unfit the joints for motion, so also that mucous liquor, which is always secreted between the joints, and which serves, like oil to a hinge, to give them an easy and ready play, is now grown more scanty. It becomes thicker and more clammy, more unfit for answering the purposes of motion, and from thence, in old age every joint is stiff and awkward. At every motion this clammy liquor is heard to crack; and it is not without a great effort of the muscles, that its resistance is overcome. Old persons have been known, that seldom moved a single joint without thus giving notice of the violence that was done to it.
The membranes that cover the bones, joints, and the rest of the body, become, as we grow old, more dense and more dry. Those which surround the bones soon cease to be ductile. The fibres, of which the muscles or flesh is composed, become every day more rigid; and while, to the touch, the body seems, as we advance in years, to grow softer, it is in reality increasing in hardness. It is the skin, and not the flesh, that we feel on such occasions. The fat, and the flabbiness of it, seem to give an appearance of softness, which the flesh itself is very far from having.
None can doubt this after trying the difference between the flesh of young and old animals. The first is soft and tender, the last is hard and dry.
The skin is the only part of the body that age does not harden; that stretches to every degree of tension; and we have often frightful instances of its pliancy, in many disorders which are incident to humanity. In youth, while the body is vigorous and increasing, it continues to give way to its growth. But although it thus adapts itself to our increase, its does not in the same manner conform to our decay. The skin, in youth and health, is plump, glossy, veined, and clear; but when the body begins to decline, it has not elasticity enough to shrink entirely with its diminution; it becomes dark or yellow, and hangs in wrinkles, which no cosmetic can remove. The wrinkles of the body in general proceed from this cause; but those of the face seem to proceed from another, namely, from that variety of positions into which it is put by the speech, the food, or the pa.s.sions. Every grimace, every pa.s.sion, and every gratification of appet.i.te, puts the visage into different forms.
These are visible enough in young persons; but what at first was accidental or transitory, becomes, by habit, unalterably fixed in the visage as it grows older.
Hence, as we advance in age, the bones, the cartilages, the membranes, the flesh, and every fibre of the body, becomes more solid, more dry, and more brittle. Every part shrinks, motion becomes more slow, the circulation of the fluids is performed with less freedom; perspiration diminishes; the secretions alter; the digestion becomes laborious; and the juices no longer serve to convey their accustomed nourishment. Thus the body dies by little and little, and all its functions are diminished by degrees; life is driven from one part of the frame to another; universal rigidity prevails; and death, at last, seizes upon the remnant that is left.
As the bones, the cartilages, the muscles, and all other parts of the body, are softer in women than in men, these parts must, of consequence, require a longer time to arrive at that state of hardness which occasions death. Women, therefore, ought to be longer in growing old than men, and this is, generally speaking, the case. If we consult the tables which have been drawn up respecting human life, we shall find that, after a certain age, they are more long-lived than men, all other circ.u.mstances the same.
Thus a woman of sixty has a greater probability, than a man of the same age, of living till eighty.
We shall close this chapter with an account of ANIMAL REPRODUCTIONS.
Here we discover a new field of wonders, that seems entirely to contradict the principles that we had adopted concerning the formation of organized bodies. It was long thought that animals could only be multiplied by eggs, or by young ones. But it is now found that there are some exceptions to this general rule, since certain animal bodies have been discovered, that may be divided into as many complete bodies as you please; for each part thus separated from the parent body, soon repairs what is deficient, and becomes a complete animal. It is now no longer doubtful that the polypus belongs to the cla.s.s of animals, though it much resembles plants, both in form, and in its mode of propagating. The bodies of these creatures may be either cut across or longitudinally, and the pieces will become so many complete polypi. Even from the skin, or least part, cut off from the body, one or more polypi will be produced; and if several pieces cut off be joined together by the extremities, they will perfectly unite, nourish each other, and become one body. This discovery has given rise to other experiments, and it has been found that polypi are not the only animals which live and grow after being cut in pieces. The earth-worm will multiply after being cut in two; to the tail there grows a head, and the two pieces then become two worms. After having been divided, they cannot be joined together again; they remain for some time in the same state, or grow rather smaller; we then see at the extremity which was cut, a little white b.u.t.ton begin to appear, which increases and gradually lengthens.