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is turned ftill more on one fide: the first rudiments of the eyes begin to appear; the heart beats, and the blood begins already to circulate. In three days the whole body of the chick appears bent; the head, with its two eye-balls, with their different humours, diftinctly appear; and five other veficles are feen, which unite to form the rudiments of the brain. The outlines alfo of the thighs and wings begin to be feen, and the body begins to gather flesh. After the fifth and fixth days, the veffels of the brain begin to be covered over; the wings and thighs lengthen; the belly is closed up and tumid; the liver is feen within it, very diftinctly, not yet grown red, but of a very dufky white; both the ventricles of the heart are difcerned, as if they were two feparate hearts, beating dif tinctly; the whole body of the animal is covered over; and the traces of the incipient feathers are already to be feen. Hitherto, however, the animal appears as if it had two bodies; the yolk is joined to it by the umbilical veffels that come from the belly; and is furnished with its veffels, through which the blood circulates, as through the rest of the body of the chick, making a bulk greater than that of the animal itfelf. But towards the end of incubation, the umbilical veffels fhorten the yolk, and with it the inteftines are thruft up into the body of the chick, 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 fecretions: the bile is found to be feparated, as in grown animals; but is fluid, transparent, and without bitterness: and the chick then alfo appears to have lungs. On the eleventh, the heart,
which hitherto appeared divided, begins to unite; its arteries join into it, like the fingers into the palm of the hand. All thefe appearances only come more into view, because, the fe creted fluids deepening in colour, their operations and circulations are more diftinctly feen. For fome time before it is able to break the fhell, the animal is heard to chirrup, receiv ing air enough for this purpose, from that cavity which lies between the membrane and the shell. At length, upon the twentieth day, in fome birds fooner, and later in others, the inclofed animal breaks, with its beak, the hell within which it has been confined; and, by repeated efforts (ufually affifted by the parent hen), at last procures its enlargement.
From this little history we perceive, that those parts which are most conducive to life are first begun the head, and the back-bone, which no doubt inclofe the brain, and the fpinal marrow, though both are too limpid to be difcerned, are the first that are feen to exift; the beating of the heart is perceived foon after: the lefs noble parts feem to spring from thefe; the wings, the thighs, the feet, and, laftly, the bill,
Whatever, therefore, the animal has double, or whatever it can live without the ufe of, thefe are latest in production: nature first fedulously applying to the formation of the nobler organs, without which life would be of fhort continuance, or would be begun in vain.
Such is the account of thofe who have moft feduloufly traced the progrefs of vivification in this department: And (as it strikes me) on the fame principles is the yet higher degree of life communicated, and advanced; but as fuperior degrees require fuperior care, that care is entrusted only to the
parent, who does not produce her young till their life is further advanced.
That there fhould be fomewhat of a different mechanism employed to convey nourishment to a young life while forming part of its parent, from what is appointed to the egg, is very natural; and when this has been confidered, the hiftory of one may fuperfede the relation of the other.
I have hinted, that animals produce their young in various degrees of perfection, fome fo tender that they again retire to their parent's body, fome with little power of motion, fome without fight (as most, if not all beasts of prey), and, in short, all have a somewhat to acquire, whether it be feathers, or hair, or the use of faculties; all have fome deficiencies, though not of effentials to life.
If we trace this donation (life) from its beginning, we find many changes ere it arrives at maturity; birds fhed their feathers, and acquire fresh plumage; and this fo varied from their former, that they are totally new birds, fo far as plumage goes; their colours are very greatly heightened, commonly differently placed; and a confpicuous advance is vifible. Quadrupeds are perhaps lefs changed in their colours, yet receive hair of fuperior quality, and other advantages, Reptiles change their skins, and infects their natures,
What has been faid, naturally divides animal life into, Ift, the OVIPAROUS, or that evidently imparted by eggs; 2d, the VIVIPAROUS, or that of young produced alive. To the first we refer birds, infects, fish, &c. certainly the major part of lives. To the latter, fome reptiles, quadrupeds, and mankind, PART II, T
The wife and the foolish, talents and stupidity, have one. common origin; nor is it poffible to predict which shall eventually occur. All we know is, that certain caufes produce certain effects; that principles will have their force, and are infinitely variable. Only obferve the diverfity in the shapes and colours of the eggs of birds: one should think an oval form incapable of fuch mutation, here being fomewhat rounded, there fomewhat lengthened; here raised, there flatted; no doubt these very forms have relation to the future offspring; but what, who can tell! No doubt they contain that precife fhape which is beft adapted to the make of the inclofed fœtus; but what determines them to that particular fhape, we know not; what affinity their spots have to the parent, or to its young, we are ignorant. It cannot be merely as marks, fince fome birds do not know their own eggs (though perhaps most do) and eggs neglected by their parent yet have spots.
There reigns much obfcurity and uncertainty over whatever principles emerge into life; nor are the fuftenance and continuance of life much less embarraffed. We fee effects, but their caufes escape us; we defire to examine the Why, and the Wherefore, but our difquifitions, like our faculties, are limited; and we find ourselves circumfcribed to an acquaintance with the result, without power to analyse the combination. This will further appear, the more clofely we inspect animated compofition, the more intensely we bend our inquiring attention; as will be proved in our enfuing Discourse.
E have, I suppose, all of us heard of thofe fceptical principles, which refufed to believe what they could not account for; which denied a confequence, unless acquainted with the previous fteps which led to it; which thought every combination, its relations, its degrees, its importance, its fubfequences, muft be explained and demonftrated before any dependance might be placed upon it. That thofe infected with these principles fhould doubt their own existence, is no unna, tural event; on fuch principles all is doubt; for, fay they, our fenfes are our only means of information, but these are con stantly liable to deception; how should we trust them? Such will ever be the refult of grafping at too much; we are incapable of knowledge beyond limited degrees, within which we find ample scope for ingenuity and diligence, and have little occafion to figh for other worlds to conquer; fo much yet remains not only unconquered, but undiscovered.
There is no one in this auditory, I prefume, who doubts of his existence, or his prefence, who requires additional evidence to prove himself alive; yet if afked, what is life? a very impotent answer is all human skill can offer. Do we know the first principle whereby we lift up our hands whereby fight or hearing are performed? whereby, in fact, any one property