and which order is necessary to be preserved, for the carrying on of the important functions which it has to execute in the animal economy. Let us see, therefore, how a danger so serious, and yet so natural to the length, narrowness, and tubular form, of the part, is provided against. The expedient is admirable: and it is this. The intestinal canal, throughout its whole process, is knit to the edge of a broad fat membrane called the mesentery. It forms the margin of this mesentery, being stitched and fastened to it like the edging of a ruffle being four times as long as the mesentery itself, it is what a sempstress would call, "puckered or gathered on" to it. This is the nature of the connexion of the gut with the me 5. The kidneys are lodged in a bed of fat. 6. The pancreas, or sweetbread, is strongly tied to the peritoneum, which is the great wrap-sentery; and being thus joined to, or rather made ping-sheet, that encloses all the bowels contained a part of, the mesentery, it is folded and wrapped in the lower belly.t up together with it. Now the mesentery having a considerable dimension in breadth, being in its substance, withal, both thick and suety, is capa 7. The spleen also is confined to its place by an adhesion to the peritoneum and diaphragm, and by a connexion with the omentum. It is possible of a close and safe folding, in comparison of ble, in my opinion, that the spleen may be merely what the intestinal tube would admit of, if it had a stuffing, a soft cushion to fill up a vacancy or remained loose. The mesentery likewise not hollow, which, unless occupied, would leave the only keeps the intestinal canal in its proper place package loose and unsteady for supposing that and position under all the turns and windings of it answers no other purpose than this, it must be its course, but sustains the numberless small vesvascular, and admit of a circulation through it, sels, the arteries, the veins, the lympheducts, and in order to be kept alive, or be a part of a living above all, the lacteals, which lead from or to albody. most every point of its coats and cavity. This membrane, which appears to be the great support and security of the alimentary apparatus, is itself strongly tied to the first three vertebrae of the loins.* may not compress or obstruct the ascending vena 8. The omentum, epiplöon, or cawl, is an apron tucked up, or doubling upon itself, at its lowest part. The upper edge is tied to the bottom of the stomach, to the spleen, as hath already been observed, and to part of the duodenum. The reflected edge also, after forming the doubling, comes up behind the front flap, and is tied to the colon and adjoining viscera.§ III. A third general property of animal forms is beauty. I do not mean relative beauty, or that of one individual above another of the same species, or of one species compared with another species; but I mean, generally, the provision which is made in the body of almost every animal, to adapt its appearance to the perception of the animals with which it converses. In our own species, for example, only consider what the parts and materials are, of which the fairest body is composed; and no farther observation will be necessary to 9. The septa of the brain probably prevent one part of that organ from pressing with too great a weight upon another part. The processes of the dura mater divide the cavity of the skull, like so many inner partition walls, and thereby confine each hemisphere and lobe of the brain to the chamber which is assigned to it, without its being liable to rest upon, or intermix with, the neigh-show how well these things are wrapped up, so bouring parts. The great art and caution of as to form a mass which shall be capable of sympacking, is to prevent one thing hurting another. metry in its proportion, and of beauty in its This, in the head, the chest, and the abdomen, of aspect; how the bones are covered, the bowels an animal body, is, amongst other methods, pro- concealed, the roughnesses of the muscle smoothed vided for by membranous partitions and wrap- and softened; and how over the whole drawn pings, which keep the parts separate. an integument, which converts the disgusting materials of a dissecting-room into an object of attraction to the sight, or one upon which it rests, at least, with ease and satisfaction. Much of this effect is to be attributed to the intervention of the cellular or adipose membrane, which lies immediately under the skin; is a kind of lining to it; is moist, soft, slippery, and compressible; every where filling up the interstices of the muscles, and forming thereby their roundness and flowing line, as well as the evenness and polish of the whole The above may serve as a short account of the manner in which the principal viscera are sustained in their places. But of the provisions for this purpose, by far, in my opinion, the most curious, and where also such a provision was most wanted, is in the guts. It is pretty evident, that a long narrow tube (in man, about five times the length of the body) laid from side to side in folds upon one another, winding in oblique and circuitous directions, composed also of a soft and yielding substance, must, without some extraor-surface. dinary precaution for its safety, be continually displaced by the various, sudden, and abrupt motions of the body which contains it. I should expect that, if not bruised or wounded by every fall, or leap, or twist, it would be entangled, or be involved with itself; or, at the least, slipped and shaken out of the order in which it is disposed, All which seems to be a strong indication of design, and of a design studiously directed to this purpose. And it being once allowed, that such a purpose existed with respect to any of the productions of nature, we may refer, with a considerable degree of probability, other particulars to the same intention; such as the teints of flowers, the plumage of birds, the furs of beasts, the bright * Keill's Anat. p. 45. scales of fishes, the painted wings of butterflies and beetles, the rich colours and spotted lustre of many tribes of insects. agreeable and disagreeable, no foundation in the sense itself? What is true of the other senses, is most probably true of the eye, (the analogy is ir resistible,) viz. that there belongs to it an original There are parts also of animals ornamental, and the properties by which they are so, not sub-constitution, fitted to receive pleasure from some servient, that we know of, to any other purpose. impressions, and pain from others. The irides of most animals are very beautiful, without conducing at all, by their beauty, to the perfection of vision; and nature could in no part have employed her pencil to so much advantage, because no part presents itself so conspicuously to the observer, or communicates so great an effect to the whole aspect. I do not however know, that the argument which alleges beauty as a final cause, rests upon this concession. We possess a sense of beauty, however we come by it. It in fact exists. Things are not indifferent to this sense; all objects do not suit it; many which we see, are agreeable to it; many others disagreeable. It is certainly not the effect of habit upon the particular object, because the most agreeable objects are often the most rare; many, which are very common, continue to be of fensive. If they be made supportable by habit, it is all which habit can do; they never become agreeable. If this sense, therefore, be acquired, it is a result; the produce of numerous and complicated actions of external objects upon the senses, and of the mind upon its sensations. With this result, there must be a certain congruity to enable any particular object to please: and that congruity, we contend, is consulted in the aspect which is given to animal and vegetable bodies. In plants, especially in the flowers of plants, the principle of beauty holds a still more considerable place in their composition; is still more confessed than in animals. Why, for one instance out of a thousand, does the corolla of the tulip, when advanced to its size and maturity, change its colour? The purposes, so far as we can see, of vegetable nutrition, might have been carried on as well by its continuing green. Or, if this could not be consistently with the progress of vegetable life, why break into such a variety colours? This is no proper effect of age, or of declension in the ascent of the sap; for that, like the autumnal teints, would have produced one colour on one leaf, with marks of fading and withering. It seems a lame account to call it, as it has been called, a disease of the plant. Is it not more probable, that this property, which is independent, as it should seem, of the wants and utilities of the plant, was calculated for beauty, intended for display. IV. The skin and covering of animals is that upon which their appearance chiefly depends; and it is that part which, perhaps, in all animals is most decorated, and most free from impurities. But were beauty, or agreeableness of aspect, entirely out of the question, there is another purpose answered by this integument, and by the collocation of the parts of the body beneath it, which is of still greater importance; and that purpose is concealment. Were it possible to view through the skin the mechanism of our bodies, the sight would frighten us out of our wits. "Durst we make a single movement," asks a lively French writer, "or stir a step from the place we were in, if we saw our blood circulating, the tendons pulling, the lungs blowing, the humours filtrating, and all the incomprehensible assemblage of fibres, tubes, pumps, valves, currents, pivots, which sustain an existence at once so frail, and so presumptuous?" V. Of animal bodies, considered as masses, there is another property, more curious than it is generally thought to be; which is the faculty of standing: and it is more remarkable in two-leg A ground, I know, of objection, has been taken against the whole topic of argument, namely, that there is no such thing as beauty at all; in other words, that whatever is useful and familiar, comes of course to be thought beautiful; and that things appear to be so, only by their alliance with these qualities. Our idea of beauty is capable of being in so great a degree modified by habit, by fashion, by the experience of advantage or pleasure, and by associations arising out of that experience, that a question has been made, whether it be not altogether generated by these causes, or would have any proper existence without them. It seems, however, a carrying of the conclusion too far, to deny the existence of the principle, viz. a native capacity of perceiving beauty, on account of an influence, or of varieties proceeding from that influence, to which it is subject, seeing that princi-ged animals than in quadrupeds, and, most of all, ples the most acknowledged are liable to be affect- as being the tallest, and resting upon the smallest ed in the same manner. I should rather argue base, in man. There is more, I think, in the matthus: The question respects objects of sight. ter than we are aware of. The statue of a man, Now every other sense hath its distinction of placed loosely upon its pedestal, would not be seagreeable and disagreeable. Some tastes offend cure of standing half an hour. You are obliged the palate, others gratify it. In brutes and insects, to fix its feet to the block by bolts and solder; or this distinction is stronger and more regular than the first shake, the first gust of wind, is sure to in man. Every horse, ox, sheep, swine, when at throw it down. Yet this statue shall express all liberty to choose, and when in a natural state, the mechanical proportions of a living model. It that is, when not vitiated by habits forced upon it, is not, therefore, the mere figure, or merely placing eats and rejects the same plants. Many insects the centre of gravity within the base, that is suffiwhich feed upon particular plants, will rather die cient. Either the law of gravitation is suspended than change their appropriated leaf. All this looks in favour of living substances, or something more like a determination in the sense itself to particu- is done for them, in order to enable them to uplar tastes. In like manner, smells affect the nose hold their posture. There is no reason whatever with sensations pleasurable or disgusting. Some to doubt, but that their parts descend by gravitasounds, or compositions of sound, delight the ear; tion in the same manner as those of dead matter. others torture it. Habit can do much in all these The gift, therefore, appears to me to consist in a cases, (and it is well for us that it can; for it is faculty of perpetually shifting the centre of grathis power which reconciles us to many necessi-vity, by a set of obscure, indeed, but of quick ties:) but has the distinction, in the mean time, of balancing actions, so as to keep the line of di VI. Regarding the human body as a mass; regarding the general conformations which obtain in it; regarding also particular parts in respect to those conformations; we shall be led to observe what I call "interrupted analogies." The following are examples of what I mean by these terms; and I do not know how such critical deviations can, by any possible hypothesis, be ac rection, which is a line drawn from that centre to the ground, within its prescribed limits. Of these actions it may be observed, first, that they in part constitute what we call strength. The dead body drops down. The mere adjustment, therefore, of weight and pressure, which may be the same the moment after death as the moment before, does not support the column. In cases also of extreme weakness, the patient cannot stand upright. Secondly, that these actions are only in a small degree voluntary. A man is seldom conscious of his voluntary powers in keeping himself upon his legs. A child learning to walk is the greatest posture-maker in the world: but art, if it may be so called, sinks into habit; and he is soon able to poise himself in a great variety of attitudes, with out being sensible either of caution or effort. But still there must be an aptitude of parts, upon which habit can thus attach; a previous capacity of motions which the animal is thus taught to ex-counted for without design. ercise and the facility with which this exercise 1. All the bones of the body are covered with a is acquired, forms one object of our admiration. periosteum, except the teeth; where it ceases, and What parts are principally employed, or in what enamel of ivory which saws and files will hardmanner each contributes its office, is, as hath al-ly touch, comes into its place. No one can doubt ready been confessed, difficult to explain. Per- of the use and propriety of this difference; of the haps the obscure motion of the bones of the feet" analogy" being thus "interrupted;" of the rule, may have their share in this effect. They are put which belongs to the conformation of the bones, in action by every slip or vacillation of the body, stopping where it does stop: for had so exquisitely and seem to assist in restoring its balance. Cersensible a membrane as the periosteum invested tain it is, that this circumstance in the structure the teeth, as it invests every other bone of the body, of the foot, viz. its being composed of many small their action, necessary exposure, and irritation, bones, applied to and articulating with one ano-would have subjected the animal to continual pain. ther, by diversely shaped surfaces, instead of being General as it is, it was not the sort of integument made of one piece, like the last of a shoe, is very which suited the teeth; what they stood in need remarkable. I suppose also that it would be diffi- of, was a strong, hard, insensible, defensive coat : cult to stand firmly upon stilts or wooden legs, and exactly such a covering is given to them, in though their base exactly imitated the figure and the ivory enamel which adheres to their surface. dimensions of the sole of the foot. The alteration 2. The scarf-skin, which clothes all the rest of of the joints, the knee-joint bending backward, the body, gives way, at the extremities of the toes the hip joint forward; the flexibility, in every di- and fingers, to nails. A man has only to look at rection, of the spine, especially in the loins and his hand to observe with what nicety and precineck, appear to be of great moment in preserving sion that covering, which extends over every other the equilibrium of the body. With respect to this part, is here superseded by a different substance, last circumstance, it is observable, that the verte- and a different texture. Now, if either the rule bræ are so confined by ligaments as to allow no had been necessary, or the deviation from it accimore slipping upon their bases, than what is just dental, this effect would not be seen. When I sufficient to break the shock which any violent speak of the rule being necessary, I mean the motion may occasion to the body. A certain de-formation of the skin upon the surface being progree also of tension of the sinews appears to be duced by a set of causes constituted without deessential to an erect posture; is by the loss. sign and acting, as all ignorant causes must act, of this, that the dead or paralytic body drops down. by a general operation. Were this the case, no The whole is a wonderful result of combined account could be given of the operation being suspowers, and of very complicated operations. In-pended at the fingers' ends, or on the back part of deed, that standing is not so simple a business as the fingers, and not on the fore part. On the we imagine it to be, is evident from the strange other hand: if the deviation were accidental, an gesticulations of a drunken man, who has lost the error, an anomalism; were it any thing else than government of the centre of gravity. settled by intention; we should meet with nails upon other parts of the body. They would be scattered over the surface, like warts or pimples. 3. All the great cavities of the body are enclosed We have said that this property is the most worthy of observation in the human body: but a bird, resting upon its perch, or hopping upon a spray, affords no mean specimen of the same faculty. Aby membranes, except the skull. Why should chicken runs off as soon as it is hatched from the not the brain be content with the same covering egg; yet a chicken, considered geometrically, and as that which serves for the other principal organs with relation to its centre of gravity, its line of di- of the body? The heart, the lungs, the liver, the rection, and its equilibrium, is a very irregular so stomach, the bowels, have all soft integuments, lid. Is this gift, therefore, or instruction? May and nothing else. The muscular coats are all soft it not be said to be with great attention, that na- and membranous. I can see a reason for this disture hath balanced the body upon its pivots ? tinction in the final cause, but in no other. The I observe also in the same bird a piece of use-importance of the brain to life, (which experience ful mechanism of this kind. In the trussing of a proves to be immediate,) and the extreme tenderfowl, upon bending the legs and thighs up towards ness of its substance, make a solid case more nethe body, the cook finds that the claws close of cessary for it, than for any other part: and such a 3 H 36* their own accord. Now let it be remembered, that this is the position of the limbs, in which the bird rests upon its perch. And in this position it sleeps in safety; for the claws do their office in keeping hold of the support, not by any exertion of voluntary power, which sleep might suspend, but by the traction of the tendons in consequence of the attitude which the legs and thighs take by the bird sitting down, and to which the mere weight of the body gives the force that is necessary. case the hardness of the skull supplies. When the smallest portion of this natural casket is lost, how carefully, yet how imperfectly, is it replaced by a plate of metal! If an anatomist should say, that this bony protection is not confined to the brain, but is extended along the course of the spine, I answer that he adds strength to the argument. If he remark, that the chest also is fortified by bones; I reply, that I should have alleged this instance myself, if the ribs had not appeared subservient to the purpose of motion, as well as of defence. What distinguishes the skull from every other cavity is, that the bony covering completely surrounds its contents, and is calculated, not for motion, but solely for defence. Those hollows, likewise, and inequalities, which we observe in the inside of the skull, and which exactly fit the folds of the brain, answer the important design of keeping the substance of the brain steady, and of guarding it against concussions. When we pass on to smaller animals, or to the inhabitants of a different element, the resemblance becomes more distant and more obscure; but still the plan accompanies us. And, what we can never enough commend, and which it is our business at present to exemplify, the plan is attended, through all its varieties and deflections, by subserviences to special occasions and utilities." 1. The covering of different animals (though whether I am correct in classing this under their anatomy, I do not know.) is the first thing which presents itself to our observation; and is, in truth, both for its variety and its suitableness to their several natures, as much to be admired as any part of their structure. We have bristles, hair, wool, furs, feathers, quills, prickles, scales; yet in this diversity both of material and form, we cannot change one animal's coat for another, without evidently changing it for the worse; taking care however to remark, that these coverings are, in many cases, armour as well as clothing; intended for protection as well as warmth. The human animal is the only one which is naked, and the only one which can clothe itself. This is one of the properties which renders him an animal of all climates, and of all seasons. He can adapt the warmth or lightness of his covering to the temperature of his habitation. Had he been born with a fleece upon his back, although he might have been comforted by its warmth in high latitudes, it would have oppressed him by its weight and heat, as the species spread towards the equator. CHAPTER XII. Comparative Anatomy. What art, however, does for men, nature has, in many instances, done for those animals which are incapable of art. Their clothing, of its own accord, changes with their necessities. This is particularly the case with that large tribe of qua WHENEVER we find a general plan pursued, yet with such variations in it as are, in each case, required by the particular exigency of the subject to which it is applied, we possess, in such plan and such adaptation, the strongest evidence that can be afforded of intelligence and design; an evidence which most completely excludes every other hypothesis. If the general plan proceeded from any fixed necessity in the nature of things, how could it accommodate itself to the various wants and uses which it had to serve under different circumstances, and on different occasions? Arkwright's mill was invented for the spinning drupeds which are covered with furs. Every of cotton. We see it employed for the spinning | dealer in hare skins, and rabbit-skins, knows how of wool, flax, and hemp, with such modifications much the fur is thickened by the approach of of the original principle, such variety in the same winter. It seems to be a part of the same constiplan, as the texture of those different materials tution and the same design, that wool, in hot rendered necessary. Of the machine's being put countries, degenerates, as it is called, but in truth together with design, if it were possible to doubt, (most happily for the animal's ease) passes into whilst we saw it only under one mode, and in one hair; whilst, on the contrary, that hair, in the form; when we came to observe it in its different dogs of the polar regions, is turned into wool, or applications, with such changes of structure, such something very like it. To which may be referadditions and supplements, as the special and par- red, what naturalists have remarked, that bears, ticular use in each case demanded, we could not wolves, foxes, hares, which do not take the water, refuse any longer our assent to the proposition, have the fur much thicker on the back than the "that intelligence, properly and strictly so called, belly: whereas in the beaver it is the thickest (including under that name, foresight, considera- upon the belly; as are the feathers in water fowl. tion, reference to utility,) had been employed, as We know the final cause of all this; and we well in the primitive plan, as in the several changes know no other. and accommodations which it is made to undergo." The corering of birds cannot escape the most Very much of this reasoning is applicable to vulgar observation. Its lightness, its smoothwhat has been called Comparative Anatomy. In ness, its warmth;-the disposition of the feathers their general economy, in the outlines of the plan, all inclined backward, the down about their stem, in the construction as well as offices of their prin- the overlapping of their tips, their different concipal parts, there exists between all large terres-figuration in different parts, not to mention the trial animals a close resemblance. In all, life is variety of their colours, constitute a vestment for sustained, and the body nourished, by nearly the the body, so beautiful, and so appropriate to the same apparatus. The heart, the lungs, the sto-life which the animal is to lead, as that, I think, mach, the liver, the kidneys, are much alike in all. we should have had no conception of any thing The same fluid (for no distinction of blood has equally perfect, if we had never seen it, or can been observed) circulates through their vessels, now imagine any thing more so. Let us suppose and nearly in the same order. The same cause (what is possible only in supposition) a person therefore, whatever that cause was, has been con- who had never seen a bird, to be presented with cerned in the origin, has governed the production, a plucked pheasant, and bid to set his wits to of these different animal forms. work, how to contrive for it a covering which The commendation, which the general aspect of the feathered world seldom fails of exciting, will be increased by farther examination. It is one of those cases in which the philosopher has more to admire, than the common observer. Every feather is a mechanical wonder. If we look at the quill we find properties not easily brought together-strength and lightness. I know few things more remarkable than the strength and lightness of the very pen with which I am writing. If we cast our eye to the upper part of the stem, we see a material made for the purpose, used in no other class of animals, and in no other part of birds; tough, light, pliant, elastic. The pith, also, which feeds the feathers, is, amongst animal sub-place, is as follows: when two laminæ are pressstances, sui generis; neither bone, flesh, mem-ed together, so that these long fibres are forced brane, nor tendon.* far enough over the short ones, their crooked parts fall into the cavity made by the crooked parts of the others; just as the latch that is fasten as if nothing had happened to it. Draw your finger down the feather, which is against the grain, and you break, probably, the junction of some of the contiguous threads; draw your finger up the feather, and you restore all things to their former state. This is no common contrivance and now for the mechanism by which it is effected. The threads or lamine above-mentioned are interlaced with one another: and the interlacing is performed by means of a vast number of fibres, or teeth, which the lamina shoot forth on each side, and which hook and grapple together. A friend of mine counted fifty of these fibres in one twentieth of an inch. These fibres are crooked; but curved after a different manner: for those which proceed from the thread on the side towards the extremity of the feather, are longer, more flexible, and bent downward; whereas those which proceed from the side towards the beginning, or quill-end of the feather, are shorter, firmer, and turn upwards. The process then which takes But the artificial part of the feather is the beard, or, as it is sometimes, I believe, called, the vane. By the beards are meant, what are fastened oned to a door, enters into the cavity of the catch each side of the stem, and what constitute the fixed to the door-post, and there hooking itself, breadth of the feather; what we usually strip off fastens the door; for it is properly in this manner, from one side or both, when we make a pen. The that one thread of a feather is fastened to the separate pieces or lamina, of which the beard is other. composed, are called threads, sometimes filaments, or rays. Now the first thing which an attentive observer will remark is, how much stronger the beard of the feather shows itself to be, when pressed in a direction perpendicular to its plane, than when rubbed, either up or down, in the line of the stem; and he will soon discover the structure which occasions this difference, viz. that the lamina whereof these beards are composed, are flat, and placed with their flat side towards each other; by which means, whilst they easily bend for the approaching of each other, as any one may perceive by drawing his finger ever so lightly upwards, they are much harder to bend out of their plane, which is the direction in which they have to encounter the impulse and pressure of the air, and in which their strength is wanted, and put to the trial. shall unite the qualities of warmth, levity, and least resistance to the air, and the highest degree of each; giving it also as much of beauty and ornament as he could afford. He is the person to behold the work of the Deity, in this part of his creation, with the sentiments which are due to it. This is one particularity in the structure of a feather; a second is still more extraordinary. Whoever examines a feather, cannot help taking notice, that the threads or lamina of which we have been speaking, in their natural state, unite; that their union is something more than the mere apposition of loose surfaces; that they are not parted asunder without some degree of force; that nevertheless there is no glutinous cohesion between them; that therefore, by some mechanical means or other, they catch or clasp among themselves, thereby giving to the beard or vane its closeness and compactness of texture. Nor is this all: when two lamine, which have been separated by accident or force, are brought together again, they immediately reclasp: the connexion, whatever it was, is perfectly recovered, and the beard of the feather becomes as smooth and firm The quill part of a feather is composed of circular and longitudinal fibres. In making a pen you must scrape off the coat of circular fibres, or the quill will split in a ragged, jagged manner, making what boys call cat's teeth. This admirable structure of the feather, which it is easy to see with the microscope, succeeds perfectly for the use to which nature has designed it; which use was not only that the laminæ might be united, but that when one thread or lamina has been separated from another by some external violence, it might be reclasped with sufficient facility and expedition.* In the ostrich, this apparatus of crochets and fibres, of hooks and teeth, is wanting: and we see the consequence of the want. The filaments hang loose and separate from one another, forming only a kind of down; which constitution of the feathers, however it may fit them for the flowing honours of a lady's head-dress, may be reckoned an imperfection in the bird, inasmuch as wings, composed of these feathers, although they may greatly assist it in running, do not serve for light. But under the present division of our subject, our business with feathers is, as they are the covering of the bird. And herein a singular circumstance occurs. In the small order of birds which winter with us, from a snipe downwards, let the external colour of the feathers be what it will, their Creator has universally given them a bed of black down next their bodies. Black, we know, is the warmest colour: and the purpose here is, to keep in the heat, arising from the heart and circulation of the blood. It is farther likewise remarkable, that this is not found in larger birds; for which there is also a reason:-small birds are much more exposed to the cold than large ones; forasmuch as they present, in proportion to their bulk, a much larger surface to the air. If a turkey were divided into a number of wrens (supposing the shape of the turkey and the wren to be simi The above account is taken from Memoirs for a Natural History of Animals, by the Royal Academy of Paris, published in 1701, p. 219. |