tender and the animals assimilating to the vegetable food, on which they ultimately subsist, are much larger in such places than in others. Thus, in the internal parts of South America and Africa, where the sun usually scorches all above, while inundations cover all below, the insects, reptiles, and other animals grow to a prodigious size: the earth-worm of America is often a yard in length, and as thick as a walking-cane; the boiguacu, which is the largest of the serpent kind, is sometimes forty feet in length; the bats in those countries are as big as a rabbit; the toads are bigger than a duck, and their spiders are as large as a sparrow. On the contrary, in the cold frozen regions of the north, where vegetable nature is stinted of its growth, the few animals in those climates partake of the diminution; all the wild animals, except the bear, are much smaller than in milder countries; and such of the domestic kinds as are carried thither quickly degenerate, and grow less. Their very insects are of the minute kinds, their bees and spiders being not half so large as those in the temperate zone.

The similitude between vegetables and animals is no where more obvious than in those that belong to the ocean, where the nature of one is admirably adapted to the necessities of the other. This element it is well known has its vegetables, and its insects that feed upon them in great abundance. Over many tracts of the sea a weed is seen floating, which covers the surface, and gives the resemblance of a green and extensive meadow. On the under side of these unstable plants millions of little animals are found, adapted to their situation. For as their ground, if I may so express it, lies over their heads, their feet are placed upon their backs; and as land animals have their legs below their bodies, these have them above. On land, also, most animals are furnished with eyes to see their food; but at sea, almost all the reptile kinds are without eyes, which might only give them prospects of danger at a time when unprovided with the means of escaping it.

Thus, in all places we perceive an obvious similitude between the animals and the vegetables of every region. In general, however, the most perfect races have the least similitude to the vegetable productions on which they are ultimately fed; while, on the contrary, the meaner the animal the more local it is found to be, and the more it is influenced by the varieties of the soil where it resides. Many of the more humble reptile kinds are not only confined to one country, but also to a plant-nay, even to a leaf. Upon that they subsist-increase with its vegetation, and seem to decay as it declines. They are merely the circumscribed inhabitants of a single vegetable; take them from that and they instantly die-being entirely assimilated to the plant they feed on, assuming its colour, and even its medicinal properties. For this reason there are infinite numbers of the meaner animals that we have never an opportunity of seeing in this part of the world; they are incapable of living separate from their kindred vegetables, which grow only in a certain climate.

Such animals as are formed more perfect lead a life of less dependence; and some kinds are found to subsist in many parts of the world at the same time. But of all the races of Animated Nature, man is the least affected by the soil where he resides, and least influenced by the variations of vegetable sustenance; equaily unaffected by the luxuriance of the warm climates, or the sterility of the poles, he has spread his habitations over the whole earth, and finds subsistence as well amidst the ice of the north as the burning deserts under the line. All creatures of an inferior nature, as has been said, have peculiar propensities to peculiar climates; they are circumscribed to zones, and confined to territories where their proper food is found in the greatest abundance; but man may be called the animal of every climate, and suffers but very gradual alterations from the nature of any situation.

As to animals of a meaner rank, whom man compels to attend him in the migrations, these being obliged to live in a kind of constraint and upon vegetable food, often different from that of their native soil, they very soon alter their natures with the nature of their nourishment, assimilate to the vegetables upon which they are fed, and thus assume very different habits as well as appearances. Thus, man, unaffected himself, alters and directs the nature of other animals at his pleasure, increases their strength for his delight, or their patience for his necessities.

This power of altering the appearance of things seems to have been given him for very wise purposes. The Deity, when He made the earth, was willing to give His favoured creature many opponents, that might at once exercise his virtues, and call forth his latent abilities. Hence we find, in those wide uncultivated wildernesses— where man, in his savage state, owns inferior strength, and the beasts claim divided dominion-that the whole forest swarms with noxious animals and vegetables; animals, as yet undescribed, and vegetables which want a name. In those recesses Nature seems rather lavish than magnificent in bestowing life. The trees are usually of the largest kinds, covered round with parasite plants, and interwoven at the tops with each other. The boughs, both above and below, are peopled with various generations, some of which have never been upon the ground, and others have never stirred from the branches on which they were produced. In this manner millions of minute and loathsome creatures pursue a round of uninterrupted existence, and enjoy a life scarce superior to vegetation. At the same time, the vegetables in those places are of the larger kinds, while the animal race is of the smaller: but man has altered this disposition of Nature--having, in a great measure, levelled the extensive forests, cultivated the softer and finer vegetables, destroyed the numberless tribes of minute and noxious animals, and taken every method to increase a numerous breed of the larger kinds. He thus has exercised a severe control; unpeopled Nature, to embellish it; and diminished the size of the vegetable in order to improve that of the animal kingdom.

To subdue the earth to his own use was, and ought to be, the aim of man; which was only to be done by increasing the number of plants and diminishing that of animals: to multiply existence was that alone of the Deity. For this reason, we find in a state of nature that animal life is increased to the greatest quantity possible; and we can scarce form a system that could add to its numbers. First, plants or trees are provided by Nature of the largest kinds; and consequently the nourishing surface is thus extended. In the second place, there are animals peculiar to every part of the vegetable, so that no part of it is lost. But the greatest possible increase of life would still be deficient were there not other animals that lived upon animals; and these are themselves in turn food for some other greater and stronger set of creatures. Were all animals to live upon vegetables alone, thousands would be extinct that now have existence, as the quantity of their provision would shortly fail. But, as things are wisely constituted, one animal now supports another; and thus all take up less room than they would by living on the same food; as, to make use of a similar instance, a greater number of people may be crowded into the same space if each is made to bear his fellow upon his shoulders.

To diminish the number of animals and increase that of vegetables has been the general scope of human industry; and if we compare the utility of the kinds, with respect to man, we shall find, that of the vast variety in the animal kingdom but very few are serviceable to him; and in the vegetable but very few are entirely noxious. How small a part of the insect tribes, for instance, are beneficial to mankind. and what numbers are injurious! In some countries they almost darken the air: a candle

cannot be lighted without their instantly flying upon it. and putting out the flame. The closest recesses are no safeguard from their annoyance; and the most beautiful landscapes of Nature only serve to invite their rapacity. As these are injurious from their multitudes, so most of the larger kinds are equally dreadful to him from their courage and ferocity. In the most uncultivated parts of the forest these maintain an undisputed empire; and man invades their retreats with fear and dread. These are terrible; and there are still more that are utterly useless to him which serve to take up the room that more beneficial creatures might possess, and incommode him rather with their numbers than their enmities. Thus, in a catalogue of land animals that amounts to more than twenty thousand, we can scarcely reckon up a hundred that are any way useful to him-the rest being either all his open or his secret enemies, immediately attacking him in person, or intruding upon that food he has appropriated to himself. Vegetables, on the contrary, though existing in great variety, are but few of them noxious. The most deadly poisons are often of great use in medicine; and even those plants that only seem to cumber the ground serve for food to that race of animals which he has taken into friendship or protection. The smaller tribes of vegetables, in particular, are culti vated as contributing either to his necessities or amusement; so that vegetable life is as much promoted by human industry as animal life is controlled and diminished.

Hence, it was not without a long struggle and various combinations of experience and art that man acquired his present dominion. Almost every good that he possesses was the result of the contest; for every day he was contending he was growing more wise; and pa tience and fortitude were the fruits of his industry.

From hence, also, we see the necessity of some animals living upon each other, to fill up the plan of Providence, and we may consequently infer the expediency of man's living upon all. Both animals and vegetables seem equally fitted to his appetites; and, were any religious or moral motives to restrain him from taking away life, upon any account, he would only thus give existence to a variety of beings made to prey upon each other, and, instead of preventing, multiply mutual destruction.

CHAP. II.

OF THE GENERATION OF ANIMALS.

Before we survey animals in their state of maturity, and performing the functions adapted to their respective natures, method requires that we should consider them in the more early periods of their existence. There has been a time when the proudest and the noblest animal was a partaker of the same imbecility with the meanest reptile; and, while yet a candidate for existence, equally helpless and contemptible. In their incipient state all are upon a footing-the insect and the philosopher being equally insensible, clogged with matter, and unconscious of existence. Where, then, are we to begin with the history of those beings that make such a distinguished figure in the creation? Or, where lie those peculiar characters in the parts that go to make up Animated Nature-that mark one animal as destined to creep in the dust, and another to glitter on the throne? This has been a subject that has employed the curiosity of all ages, and the philosophers of every age have attempted the solution. In tracing Nature to her most hidden recesses, she becomes too minute or obscure for our inspection; so that we find it impossible to mark her first differences, to discover the point where animal life begins, or the cause that conduces to set it in motion.

We know little more than that the greatest number of animals require the concurrence of a male and female to reproduce their kind; and that these, distinctly and invariably, are found to beget creatures of their own species. Curiosity has, therefore, been active in trying to discover the immediate result of this union; how far either sex contributes to the bestowing animal life, and whether it be to the male or female that we are most indebted for the privilege of our existence.

Hippocrates has supposed that fecundity proceeded from the mixture of the seminal liquor of both sexes, each of which equally contribute to the formation of the incipient animal. Aristotle, on the other hand, would have the seminal liquor in the male alone to contribute to this purpose, while the female supplied the proper nourishment for its support. Such were the opinions of these Fathers of Philosophers; and these continued to be adopted by the naturalists and schoolmen of succeeding ages with blind veneration. At length, Steno and Harvey, taking anatomy for their guide, gave mankind a nearer view of Nature just advancing into animation These perceived, in all such animals as produced their young alive, two glandular bodies near the womb, resembling that ovary or cluster of small eggs which is found in fowls; and, from the analogy between both, they gave these also the name of ovaria. These, as they resembled eggs, they naturally concluded had the same offices; and therefore they were induced to think that all animals, of what kind soever, were produced from eggs. At first, however, there was some altercations raised against this system; for, as these ovaria were separated from the womb, it was objected that they could not be any way instrumental in replenishishing that organ, with which they did not communicate. But upon more minute inspection, Fallopius, the anatomist, perceived two tubular vessels depending from the womb, which, like the horns of a snail, had a power of erecting themselves, of embracing the ovaria, and of receiving the eggs, in order to be fecundated by the seminal liquor. This discovery seemed for a long time after to fix the opinions of philosophers. The doctrine of Hippocrates was re-established, and the chief business of generation was ascribed to the female. This was for a long time the established opinion of the schools; but Leuwenhoeck once more shook the whole system, and produced a new schism among the lovers of speculation. Upon examining the seminal liquor of a great variety of male animals with microscopes, which helped his sight more than that of any of his successors, he perceived therein infinite numbers of little living creatures, like tadpoles, very brisk, and floating in the fluid with a seeming voluntary motion. Each of these, therefore, was thought to be the rudiments of an animal similar to that from which it was produced; and this only required a reception from the female, together with proper nourishment, to complete its growth. The business of generation was now, therefore, given back to the male a second time by mauy; while others suspended their assent, and chose rather to confess ignorance than to embrace error.

In this manner has the dispute continued for several ages, some accidental discovery serving at intervals to renew the debate and revive curiosity. It was a subject where speculation could find much room to display itself; and Mr. Buffon, who loved to speculate, would not omit such an opportunity of giving scope to his pro pensity. According to this most pleasing of all naturalists, the microscope discovers that the seminal liquor, not only of males but of females also, abounds in these moving little animals, which have been mentioned above, and that they appear equally brisk in either fluid. These he takes not to be real animals, but organical particles, which, being simple, cannot be said to be or ganized themselves, but go to the composition of all organized bodies whatsoever. In the same manner as u

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tooth in the wheel of a watch cannot be called either the wheel or the watch, and yet contributes to the sum of the machine. These organical particles are, according to him, diffused throughout all Nature, and to be found not only in the seminal liquor, but in most other fluids in the parts of vegetables, and all parts of Animated Nature. As they happen, therefore, to be differently applied, they serve to constitute a part of the animal or the vegetable whose growth they serve to increase, while the superfluity is thrown off in the seminal liquor of both sexes for the reproduction of other animals or vegetables of the same species. These particles assume different figures, according to the receptacle into which they enter; falling into the womb they unite into a fœtus; beneath the bark of a tree they pullulate into branches; and, in short, the same particles that first formed the animal into the womb contribute to increase its growth when brought forth.

To this system it has been objected, that it is impossible to conceive organical substances without being organized; and that, if divested of organization themselves, they could never make an organized body, as an infinity of circles could never make a triangle. It has also been objected, that it is more difficult to conceive the transformation of these organical particles than even that of the animal whose growth we are inquiring after; and this system, therefore, attempts to explain one obscure thing by another still more obscure.

But an objection still stronger than these has been advanced by an ingenious countryman of our own, who asserts that these little animals, which thus appear swimming and sporting in almost every fluid we examine with a microscope, are not real living particles, but some of the more opake parts of the fluid, that are thus increased in size, and seem to have a much greater motion than they have in reality-for, the motion being magnified with the object, the smallest degree of it will seem very considerable; and a being almost at rest may, by these means, be apparently put into violent action. Thus, for instance, if we look upon the sails of a windmill moving at a distance, they appear to go very slow; but if we approach them, and thus magnify their bulk to our eye, they go round with great rapidity. A microscope in the same manner serves to bring our eye close to the object, and thus to enlarge it: and not only increase the magnitude of its parts, but of its motion. Hence, therefore, it would follow, that these organical particles that are said to constitute the bulk of living nature are but mere optical illusions; and the system founded on them must, like them, be illusive.

These and many other objections have been made to this system, which, instead of enlightening the mind, serve only to show that too close a pursuit of Nature very often leads to uncertainty. Happily, however, for mankind, the most intricate inquiries are generally the most useless. Instead, therefore, of balancing accounts between the sexes, and attempting to ascertain to which the business of generation most properly belongs, it will be more instructive as well as amusing to begin with Animal Nature, from its earliest retirements and evanescent outlines, and pursue the incipient creature through all its changes in the womb till it arrives into open day.

The usual distinction of animals, with respect to their manner of generation, has been into the Oviparous and Viviparous kinds; or, in other words, into those that bring an egg which is afterwards hatched into life, and those that bring forth their young alive and perfect. In one of these two ways all animals were supposed to have been produced, and all other kinds of generation were supposed to be imaginary or erroneous. But later discoveries have taught us to be more cautious in making general conclusions, and even induced many to doubt whether animal life may not be produced merely from putrefaction.

Indeed, the infinite number of creatures that putrid substances seem to give birth to, and the variety of little insects seen floating in liquors by the microscope, ppear to favour this opinion. But, however this may be, the former method of classing animals can now by no means be admitted, as we find many animals that are produced neither from the womb nor from the sheil, but merely from cuttings; so that to multiply life in some creatures it is sufficient only to multiply the diss ction. This be ing the simplest method of generation, and that in which life seems to require the smallest preparation for its existence, I will begin with it, and so proceed to the two other kinds, from the meanest to the most elaborate The earth-worm, the millipedes, the sea-worm, and many marine insects, may be multiplied by being cut in pieces; but the polypus is noted for its amazing fertility; and from hence it will be proper to take the description. The structure of the polypus may be compared to the finger of a glove, open at one end and closed at the other. The closed end represents the tale of the polypus, with which it serves to fix itself to any substance it happens to be upon; the open end may be compared to the mouth; and, if we conceive six or eight small strings issuing from this end, we shall have a tolerable idea of its arms, which it can erect, lengthen, and contract at pleasure, like the horns of a snail. This creature is exceedingly voracious, and makes use of its arms as a fisherman does of his net, to catch and entangle such little animals as happen to come within its reach. It lengthens these arms several inches, keeps them separated from each other, and thus occupies a large space in the water in which it resides. These arms when extended are as fine as threads of silk, and have a most exquisite degree of feeling. If a small worm happens to get within the sphere of their activity, it is quickly entangled by one of these arms, and soon after the other arms come to its aid; these altogether shortening, the worm is drawn into the animal's mouth and quickly devoured, colouring the body as it is swallowed. Thus much is necessary to be observed of this animal's method of living to show that it is not of the vegetable tribe, but a real animal, performing the functions which other animals are found to perform, and endued with powers that many of them are destitute of. But what is most extraordinary remains yet to be told; for, if examined with a microscope, there are seen several little specks, like buds, which seem to pollulate from different parts of its body; and these soon after appear to be young polypi, and, like the large polypus, begin to cast their little arms about for prey in the same manner. Whatever they happen to ensnare is devoured, and gives a colour not only to their own bodies but to that of the parent-so that the same food is digested and serves for the nourishment of both. The food of the little one passes into the large polypus, and colours its body; and this in its turn digests, and swallows its food to pass into theirs. In this manner every polypus has a new colony sprouting from its body; and these new ones, even while attached to the parent animal, become parents themselves, having a smaller colony also budding from them-all at the same time busily employed seeking for their prey, and the food of any one of them serv. ing for the nourishment and circulating through the bodies of all the rest. This society, however, is every hour dissolving; those newly produced are seen at intervals to leave the body of the large polypus, and become shortly after the head of a beginning colony themselves.

In this manner the polypus multiplies naturally; but one may take a much readier and shorter way to increase them, and this only by cutting them in pieces. Though cut into thousands of parts, each part still retains its vivacious quality, and each shortly becomes a distinct and complete polypus; whether cut lengthwise or crosswise it is all the same-this extraordinary creature seems a gainer by our endeavours, and multiplics by

apparent destruction. The experiment had been tried times without number, and still attended with the same success. Here, therefore, naturalists who have been blamed for the cruelty of their experiments upon living animals may now boast of their increasing animal life instead of destroying it. The production of the polypus is a kind of philosophical generation. The famous Sir Thomas Brown hoped one day to be able to produce children by the same method as trees are produced; the polypus is multiplied in this manner; and every philosopher may thus, if he pleases, boast of a numerous, though I should suppose a very useless, progeny.

This method of generation from cuttings may be considered as the most simple kind, and is a strong instance of the little pains Nature takes in the formation of her lower and humbler productions. As the removal of these from inanimate to animal existence is but small, there are but few preparations made for their journey. No organs of generation seem provided-no womb to receive no shell to protect them in their state of transition. The little reptile is quickly fitted for all the offices of its humble sphere, and in a very short time arrives at the height of its contemptible perfection.

The next generation is of those animals that we see produced from the egg. In this manner all birds, most fishes, and many of the insect tribes, are brought forth. An egg may be considered as a womb detached from the body of the parent animal, in which the embryo is but just beginning to be formed. It may be regarded as a kind of incomplete delivery, in which the animal is disburthened of its young before its perfect formation. Fishes and insects, indeed, most usually commit the management of their eggs to hazard; but birds, which are more perfectly formed, are found to hatch them into maturity by the warmth of their bodies. However, any other heat of the same temperature would answer the end as well; for either the warmth of the sun or of a stove is equally efficacious in bringing the animal in the egg to perfection. In this respect, therefore, we may consider generation from the egg as inferior to that in which the animal is brought forth alive. Nature has taken care of the viviparous animal in every stage of its existence. That force which separates it from the parent separates it from life; and the embryo is shielded with unceasing protection till it arrives at exclusion. But it is different with the little animal in the egg; often totally neglected by the parent, and always separable from it, every accident may retard its growth, or even destroy its existence. Besides, art or accident may also bring this animal to a state of perfection; so that it can never be considered as a complete work of Nature in which so much is left for accident to finish or destroy.

But however inferior this kind of generation may be, the observation of it will afford great insight into that of nobler anim ls, as we an here watch the progress of the growing embryo in every period of its existence, and catch it in those very moments when it first seems steal ing into motion. Malpighi and Haller have been par ticularly industrious on this subject; and, with a patience almost equalling that of the sitting hen, have attended incubation in all its stages. From them, therefore, we have an amazing history of the chicken in the egg, and of its advances into complete formation.

It would be methodically tedious to describe those parts of the egg which are well known and obvious such as its shell, its white, and its yolk; but the disposition of these is not so apparent. Immediately under the shell lies that common membrane or skin which lines it on the inside, adhering closely to it everywhere, except at the broad end, where a little cavity is left filled with air, which increases as the animal within grows larger. Under this membrane are contained two whites, though seeming to us to be only one, each wrapped up in a membrane of its own-one white within the other the midst of all is the yolk, wrapped

round, likewise, in its own membrane. At each end of this are two ligaments, called "chalazo," which are, as it were, the poles of this microcosm, being white dense substances made from the membranes, and serving to keep the white and the yolk in their places. It was the opinion of Mr. Derham that they served also for another purpose; for a line being drawn from one ligament to the other would not pass directly through the middle of the yolk, but rather towards one side, and would divide the yolk into two unequal parts, by which means these ligaments served to keep the smallest side of the yolk always uppermost; and in this part he supposed the cicatricula or first speck of life to reside-which, by being uppermost, and consequently next the hen, would be thus in the warmest situation. But this is rather fanciful than true-the incipient animal being found in all situations, and not particularly influenced by any. This cicatricula, which is the part where the animal, first begins to show signs of life, is not unlike a vetch or a lentil, lying on one side of the yolk, and within its membrane. All these contribute to the little animal's convenience or support; the outer membranes and ligaments preserve the fluids in their proper places; the white serves as nourishment; and the yolk, with its membranes, after a time becomes a part of the animal's body. This is the description of a hen's egg, and answers to that of all others, how large or how small soever.

Previous to putting the eggs to the hen, our philo sophers first examined the cicatricula, or little spot already mentioned, and which may be considered as the most important part of the egg. This was found in those that were impregnated by the cock to be large'; but in those laid without the cock very small. It was found by the microscope to be a kind of bag, containing a transparent liquor, in the midst of which the embryo was seen to reside. The embryo resembled a composition of little threads, which the warmth of future incubation tended to enlarge, by varying and liquifying the other fluids contained within the shell, and thus pressing them either into the pores or tubes of their substance.

Upon placing the eggs in a proper warmth, either under the sun or in a stove, after six hours the vital speck begins to dilate like the pupil of the eye. The head of the chicken is distinctly seen, with the back-bone, somewhat resembling a tadpole, floating in its ambient fluid, but as yet seeming to assume none of the functions of animal life. In about six hours more the little animal is seen more distinctly; the head becomes more plainly visible, and the vertebræ of the back more easily perceivable. All these signs of preparation for life are increased in six hours more; and at the end of twentyfour hours the ribs begin to take their places, the neck begins to lengthen, and the head to turn to one side.

At this time, also, the fluids in the egg seem to have changed place; the yolk, which was before in the centre of the shell, approaches nearer to the broad end. The watery part of the white is in some measure evaporated through the shell, and the grosser part sinks to the small end. The little animal appears to turn towards the part of the broad end in which a cavity has been described, and with its yolk seems to adhere to the membrane there. At the end of forty hours the great work of life seems fairly begun, and the animal appears plainly to move; the back-bone, which is of a whitish colour, thickens; the head is turned still more on one side; the first rudiments of the eyes begin to appear; the heart beats, and the blood begins to circulate. The parts, however, as yet are fluid, but by degrees become more and more tenacious, and harden into a kind of jelly. At the end of two days, the liquor in which the chicken swims seems to increase; the head appears with two bladders in the place of eyes; the heart beats in the manner of every embryo where the blood does not circulate through the lungs. In about fourteen hours after this the chicken is grown more strong; its head, how

ever, is still bent downwards; the veins and arteries begin to branch, in order to form the brain; and the spinal marrow is seen stretching along the back-bone. In three days the whole body of the chicken appears bent; the head, with its two eye-balls with their different humours, now distinctly appear; and five other vesicles are seen, which soon unite to form the rudiments of the brain The outlines, also, of the thighs and wings begin to be seen, and the body begins to gather flesh. At the end of the fourth day the vesicles that form the brain approach ach other; the wings and thighs appear more solid; the whole body is covered with a jelly-like flesh; the heart, that was hitherto exposed, is now covered up within the body by a very thin, transparent membrane; and, at the same time, the umbilical vessels that unite the animal to the yolk now appear to come forth from the abdomen. After the fifth and sixth days the vessels of the brain begin to be covered over; the wings and thighs lengthen; the belly is closed up and tumid; the liver is seen within it very distinctly, not yet grown red, but of a dusky white; both the ventricles of the heart are discerned, as if they were two separate hearts, beating distinctly; the whole body of the animal is covered over; and the traces of the incipient feathers are to be seen. The seventh day the head appears very large; the brain is covered entirely over; the bill begins to appear between the eyes; and the wings, the thighs, and the legs have acquired their perfect figure. Hitherto, however, the animal appears as if it had two bodies; the yolk is joined to it by the umbilical vessels that come from the belly, and is furnished with its vessels, through which the blood circulates as through the rest of the body of the chicken, making a bulk greater than that of the animal itself. But towards the end of incubation the umbilical vessels shorten the yolk, and with it the intestines are thrust up into the body of the chicken by the action of the muscles of the belly; and the two bodies are thus formed into one. During this state all the organs are found to perform their secretions; the bile is found to be separated as in grown animals; but it is a fluid, transparent, and without bitterness; and the chicken then also appears to have lungs. On the tenth the muscles of the wings appear, and the feathers begin to push out. On the eleventh, the heart, which hitherto had appeared divided, begins to unite; the arteries which belong to it join into it, like the fingers into the palm of the hand. All these appearances only come more into view because the fluids the vessels had hitherto secreted were more transparent; but as the colour of the fluids deepen their operations and circulations are more distinctly seen. As the animal thus, by the eleventh day completely formed, begins to gather strength, it becomes more uneasy in its situation, and exerts its animal powers with increasing force. For some time before it is able to break the shell in which it is imprisoned it is heard to chirrup, receiving a sufficient quantity of air for this purpose from that cavity which lies between the membrane and the shell, and which must contain air to resist the external pressure At length, upon the twentieth day (in some birds sooner and later in others), the enclosed animal breaks the shell within which it has been confined with its beak; and, by repeated efforts, at last procures its enlargement.

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From this little history we perceive that those parts which are most conducive to life are the first that are begun the head and the back-bone, which no doubt enclose the brain, and the spinal marrow, though both are too limpid to be discerned, are the first that are seen to exist; the beating of the heart is perceived soon after: the less noble parts seem to spring from these-the wings, the thighs, the feet, and, lastly, the bill. Whatever, therefore, the animal has double, or whatever it can live without the use of, these are latest in productionNature first sedulously applying to the formation of the

nobler organs, without which life would be of short continuance, and begun in vain.

The resemblance between the beginning animal in the egg and the embryo in the womb is very striking; and this similitude has induced many to assert that all animals are produced from eggs in the same manner. They consider an egg excluded from the body by some. and separated into the womb by others, to be actions merely of one kind-with this only difference, that the nourishment of the one is kept within the body of the parent, and increases as the embryo happens to want the supply; the nourishment of the other is prepared all at once, and sent out with the beginning animal as entirely sufficient for its future support. But leaving this to the discussion of anatomists, let us proceed rather with facts than dissertations; and, as we have seen the progress of an oviparous animal, or one produced from the shell, let us likewise trace that of a viviparous animal, which is brought forth alive. In the investigation, Graaf has, with a degree of patience characteristic of his nation, attended the progress and increase of various animals in the womb, and minutely marked the changes they undergo. Having dissected a rabbit half an hour after impregnation, he perceived the horns of the womb that go to embrace and communicate with the ovary to be more red than before; but no other change in the rest of the parts. Having dissected another, six hours after, he perceived the follicules, or the membrane covering the eggs contained in the ovary to become reddish. In a rabbit dissected after twenty-four hours, he perceived in one of the ovaries three follicules, and in the other five, that were changed-being become from transparent dark and reddish. In one dissected after three days he perceived the horns of the womb very strictly to embrace the ovaries; and he observed three of the follicules in one of them much longer and harder than before; pursuing his inquisition, he also found two of the eggs actually separated into the horns of the womb, and each about the size of a grain of mustardseed; these little eggs were each of them enclosed in a double membrane, the inner parts being filled with a very limpid liquor. After four days, he found in one of the ovaries four, and in the other five, follicules emptied of their eggs; and in the horns correspondent to these he found an equal number of eggs thus separated; these eggs were now grown larger than before, and somewhat of the size of duck-shot, and could be blown from the part of the womb where they were by the breath. In seven days the eggs were found of the size of a pistolbullet, each covered with its double membrane, and these much more distinct than before. In nine days, having examined the liquor contained in one of these eggs, he found it from a limpid colour less fluid to have got a light cloud floating upon it. In ten days this cloud began to thicken, and to form an oblong body of the figure of a little worm; and in twelve days the figure of the embryo was distinctly to be perceived, and even its parts came into view. In the region of the breast he perceived two bloody specks, and two more that appeared of a whitish colour. Fourteen days after impregnation the head of the embryo was become large and transparent, the eyes prominent, the mouth open, and the rudiments of the ears beginning to appear; the back bone, of a whitish colour, was bent towards the breast; the two bloody specks, being now considerably increased, appeared to be nothing less than the outlines of the two ventricles of the heart; and the two whitish specks on each side now appeared to be the rudiments of the lungs. Towards the region of the belly the liver began to be seen, of a reddish colour, and a little intricate mass like ravelled thread discerned, which soon appeared to be the stomach and the intestines; the legs soon after began to be seen, and to assume their natural position; and from that time forth, all the parts being formed, every day only served to develop