opinion, to bear down all doubt that can be raised upon the subject. And what I wish, under the title of the present chapter, to observe, is, that if other parts of nature were inaccessible to our inquiries, or even if other parts of nature presented nothing to our examination but disorder and confusion, the validity of this example would remain the same. If there were but one watch in the world, it would not be less certain that it had a maker. If we had never in our lives seen any but one single kind of hydraulic machine, yet, if of that one kind we understood the mechanism and use, we should be as perfectly assured that it proceeded from the hand, and thought, and skill of a workman, as if we visited a museum of the arts, and saw collected there twenty different kinds of machines for drawing water, or a thousand different kinds for other purposes. Of this point, each machine is a proof independently of all the rest. So it is with the evidences of a Divine agency. The proof is not a conclusion which lies at the end of a chain of reasoning, of which chain each instance of contrivance is only a link, and of which, if one link fail, the whole falls; but it is an argument separately supplied by every separate example. An error in stating an example, affects only that example. The argument is cumulative, in the fullest sense of that term. The eye proves it without the ear; the ear without the eye. The proof in each example is complete; for when the design of the part, and the conduciveness of its structure to that design, is shewn, the mind may set itself at rest; no future consideration can detract any thing from the force of the example.

CHAPTER VII.

OF THE MECHANICAL AND IMMECHANICAL PARTS AND FUNCTIONS OF ANIMALS AND

VEGETABLES.

It is not that every part of an animal or vegetable has not proceeded from a contriving mind; or that every part is not constructed with a view to its proper end and purpose, according to the laws belonging to, and governing the substance or the action made use of in that part; or that each part is not so constructed as to effectuate its purpose whilst it operates according to these laws; but it is because these laws themselves are not in all cases equally understood; or, what amounts to nearly the same thing, are not equally exemplified in more simple processes, and more simple machines; that we lay down the distinction, here proposed, between the mechanical parts and other parts of animals and vegetables

* The immechanical properties of plants are just as full of instances of contrivance as those of animals. Thus, in their juices, which are always so regular and so uniform-so sweet in some, so acid or bitter in others, tasteless in many, yet saline in several; the order and the regularity are alike incomprehensible. Neither by any contrivance of ours can this order of things be altered. Thus, the wild sorrel still secretes its acid, if nourished with sugar and water only. The sea-kale (crambe maritima) which grows wild on the sea-shore, will yet secrete in its juices common salt when growing in our most inland gardens.

Neither can a plant be made to absorb one salt in preference to another. If common salt, and Glauber salt, and muriate of lime, in equal proportions, are dissolved in water; and a plant of mint placed in the solution; the vegetable will readily absorb a considerable proportion of common salt, and less of the Glauber; but the muriate of lime is entirely rejected. The plant will not imbibe a particle.

The very power which the plant thus exercises is totally incomprehensible by any of our chemical investigations; for to effect the same separation of the salts, the chemical analyst has to perform a series of decomposi

tions, and many other chemical operations must be gone through before the desired result can be obtained; a process which the sprig of mint performs at once.

The unchemical reader is not to imagine that this separation, by the plant, of the salts is the effect of mere filtration, or some other simple process; since by no manipulation of this kind can the effect be produced. The most delicate filters in the world are utterly useless in an attempt to separate a salt from its solution.

Then again, certain plants shew a decided preference for particular salts. The sun-flower and the nettle grow most luxuriantly in those soils which contain saltpetre (nitrate of potash), and as this salt is produced in old walls, and under buildings, there the nettle is sure to be

found.

Lucern, sainfoin, or red clover, have less fondness for saltpetre, but they absorb sulphate of lime (gypsum) readily, and only flourish where it is found in the land. Other plants care for neither. Thus the wheat, or the oat plant, do not grow more luxuriantly by their addition to the soils on which they are cultivated.

The absorbent powers of the plant are not confined to soluble matters, for the most insoluble substances, such as clay, flint, chalk, manganese, and phosphate of lime,

For instance: the principle of muscular motion, viz. upon what cause the swelling of the belly of the muscle, and consequent contraction of its tendons, either by an act of the will, or by involuntary irritation, depends, is wholly unknown to us. The substance employed, whether it be fluid, gaseous, elastic, electrical, or none of these, or nothing resembling these, is also unknown to us: of course, the laws belonging to that substance, and which regulate its action, are unknown to us. We see nothing similar to this contraction in any machine which we can make, or any process which we can execute. So far (it is confessed) we are in ignorance, but no farther. This power and principle, from whatever cause it proceeds, being assumed, the collocation of the fibres to receive the principle, the disposition of the muscles for the use and application of the power, is mechanical: and is as intelligible as the adjustment of the wires and strings by which a puppet is moved. We see, therefore, as far as respects the subject before us, what is not mechanical in the animal frame, and what is. The nervous influence (for we are often obliged to give names to things which we know little about)—I say, the nervous influence, by which the belly, or middle of the muscle, is swelled, is not mechanical. The utility of the effect we perceive; the means, or the preparation of means, by which it is produced, we do not. But obscurity as to the origin of muscular motion brings no doubtfulness into our observations, upon the sequel of the process. Which observations relate, 1st, to the constitution of the muscle; in consequence of which constitution, the swelling of the belly or middle part is necessarily and mechanically followed by a contraction of the tendons: 2dly, to the number and variety of the muscles, and the corresponding number and variety of useful powers which they supply to the animal; which is astonishingly great: 3dly, to the judicious (if we may be permitted to use that term in speaking of the Author, or of the works, of nature), to the wise and well-contrived disposition of each muscle for its specific purpose; for moving the joint this way, and that way, and the other way; for pulling and drawing the part, to which it is attached, in a determinate and particular direction; which is a mechanical operation, exemplified in a multitude of instances. To mention only one: The tendon of the trochlear muscle of the eye, to the end that it may draw in the line required, is passed through a cartilaginous ring, at which it is reverted, exactly in the same manner as a rope in a ship is carried over a block or round a stay, in order to make it pull in the direction which is wanted. All this, as we have said, is mechanical; and is as accessible to inspection, as capable of being ascertained, as the 'mechanism of the automaton in the Strand. Supposing the automaton to be put in motion by a magnet (which is probable), it will supply us with a comparison very apt for our present purpose. Of the magnetic effluvium, we know perhaps as little as we do of the nervous fluid. But, magnetic attraction being assumed (it signifies nothing from what cause it proceeds), we can trace, or there can be pointed out to us, with perfect clearness and certainty, the mechanism, viz. the steel bars, the wheels, the joints, the wires, by which the motion so much admired is communicated to the fingers of the image; and to make any obscurity, or difficulty, or controversy in the doctrine of magnetism, an objection to our knowledge or our certainty, concerning the contrivance, or the marks of contrivance, displayed in the automaton, would be exactly the same thing, as it is to make our ignorance (which we acknowledge) of the cause of nervous agency, or even of the substance and structure of the

are found in plants, and not in minute proportions only. Flint, for instance, abounds to such an extent in the Dutch rush, that it is employed by the turners, to polish wood, horn, and even brass.

Flint (siler) is found also in the wheat plant, abounding in the straw, where its presence imparts the requisite firmness to enable it to support the loaded ear, but is hardly traceable in the seed where it is not required.

Is not this contrivance ? or is all this arrangement also chance? The progress of chemistry since Paley wrote, and Dr. Black, his chemical instructor, experimentalized, has unfolded many a beautiful vegetable phenomenon, just as mystic, just as astonishing as any thing met with in animal chemistry; one vegetable principle after another has been discovered. Quinine, iodine, morphia, and many others, have been made subservient to our use, and the

field is yet not nearly exhausted, but still the conclusion is the same; the deeper the chemist penetrates, the more numerous are the contrivances he observes. The ablest, the most unwearied of chemists have devoted themselves to the investigation with an energy worthy of such a research; but none of these philosophers have arisen from their toils, with the conclusion that chance had any thing to do with the formation of a plant.

It is true that the celebrated and vain-glorious naturalist Buffon had a different opinion, that he saw none of these mysteries, and that he ignorantly inscribed under a statue of himself, "A genius equal to the majesty of nature." Yet, as was well observed by Sir J. E. Smith, the late president of the Linnæan Society, "a blade of grass is amply sufficient to confound all his pretensions."

nerves themselves, a ground of question or suspicion as to the reasoning which we institute concerning the mechanical part of our frame. That an animal is a machine, is a proposition neither correctly true nor wholly false. The distinction which we have been discussing will serve to show how far the comparison, which this expression implies, holds; and wherein it fails. And whether the distinction be thought of importance or not, it is certainly of importance to remember, that there is neither truth nor justice in endeavouring to bring a cloud over our understandings, or a distrust into our reasonings upon this subject, by suggesting that we know nothing of voluntary motion, of irritability, of the principle of life, of sensation, of animal heat, upon all which the animal functions depend; for our ignorance of these parts of the animal frame concerns not at all our knowledge of the mechanical parts of the same frame. I contend, therefore, that there is mechanism in animals; that this mechanism is as properly such, as it is in machines made by art; that this mechanism is intelligible and certain; that it is not the less so, because it often begins or terminates with something which is not mechanical; that whenever it is intelligible and certain, it demonstrates intention and contrivance, as well in the works of nature, as in those of art; and that it is the best demonstration which either can afford.

But whilst I contend for these propositions, I do not exclude myself from asserting, that there may be, and that there are, other cases, in which, although we cannot exhibit mechanism, or prove indeed that mechanism is employed, we want not sufficient evidence to conduct us to the same conclusion.

There is what may be called the chemical part of our frame; of which, by reason of the imperfection of our chemistry, we can attain to no distinct knowledge; I mean, not to a knowledge, either in degree or kind, similar to that which we possess of the mechanical part of our frame. It does not, therefore, afford the same species of argument as that which mechanism affords; and yet it may afford an argument in a high degree satisfactory. The gastric juice, or the liquor which digests the food in the stomach of animals, is of this class. Of all menstrua, it is the most active, the most universal. In the human stomach, for instance, consider what a variety of strange substances, and how widely different from one another, it, in a few hours, reduces to a uniform pulp, milk, or mucilage.

The remark of Paley as to the superiority of mechanism to chemistry for the purposes of popular illustra tion needs no confirmation, although there are certain chemical investigations into the composition of the "elements," as they were formerly called, which in an admirable manner demonstrate the contrivance and skill of their divine Author. Thus, in the air we breathe, many and vague were the notions originally entertained with regard to its composition. It was soon, however, determined that in the act of breathing, only a portion of the air inspired was retained by the lungs; and to this, in consequence, the name of vital air, or oxygen gas, was given. To the respired or rejected portion the name of azote, or nitrogen gas, was applied; and by careful analysis it has been determined that these two gases constitute the atmosphere in which we live and breathe, in the proportion of twenty-one parts oxygen, and seventy-nine parts nitrogen. The oxygen is alone necessary to maintain the breathing of animals and to support combustion. The nitrogen is merely added, as far as our knowledge extends, as a dilutant to modify the otherwise too active action of the oxygen upon the lungs, and upon our fires. If we attempt to breathe pure oxygen gas, the lungs are so strongly excited that death speedily ensues; and if any ignited body is placed in the same gas, the combustion is so rapid that hardly any substance can be burnt with sufficient slowness or the required regularity. Had our atmosphere been formed entirely of oxygen, our present easily manageable fires would have burnt with an uncontroulable violence.

The addition of a large proportion of nitrogen, by diluting the oxygen, modifies its active powers without

destroying their effect. The careful proportion too in

which this mixture is made commands our serious attention; chance had no hand in its composition, for if the proportion only of the two gases are altered, and they are then combined, strangely different substances are produced. Thus, twenty-six parts nitrogen, and seventy-four parts oxygen, form nitric-acid or aqua-fortis; and sixty-three and a half parts nitrogen, and thirty-six and a half parts oxygen, form nitrous oxyde, the laughing gas chemists (Davy's Researches, p. 291. Henry's Chem., vol. xviii. p. 359. Thomson, vol. ii. p. 90); and by merely varying the proportions, the chemist produces many other substances, such as nitrous gas, and nitrous acid.

of

The regular proportion of the two gases existing in the atmosphere of all parts of the world equally commands our astonishment. Repeated and careful examinations by the most eminent chemists have demonstrated that these never vary. The composition of air taken in the open country and in the centre of the most populous cities, whether collected upon the summits of the most elevated mountains or in the lowest valleys, is exactly the same. Probably the means by which this unvarying proportion is preserved, is only partially known to us; but this we do know, the oxygen consumed by animals, and by our fires, is constantly and copiously restored to the atmosphere by the leaves of all vegetables growing in the light. Winds, if they served no other beneficial purpose, would be advantageous in preserving the uniform composition of our atmosphere. They hurry away the vitiated air of towns, and bring in its place that which has been purified by vegetation in the agricultural districts.

It seizes upon every thing, it dissolves the texture of almost every thing, that comes in its way. The flesh of perhaps all animals; the seeds and fruits of the greatest number of plants; the roots, and stalks, and leaves of many, hard and tough as they are, yield to its powerful pervasion. The change wrought by it is different from any chemical solution which we can produce, or with which we are acquainted, in this respect as well as many others, that, in our chemistry, particular menstrua act only upon particular substances. Consider moreover that this fluid, stronger in its operation than a caustic alkali or mineral acid, than red precipitate, or aqua-fortis itself, is nevertheless as mild, and bland, and inoffensive to the touch or taste, as saliva or gum-water, which it much resembles. Consider, I say, these several properties of the digestive organ, and of the juice with which it is supplied, or rather with which it is made to supply itself, and you will confess it to be entitled to a name, which it has sometimes received, that of "the chemical wonder of animal nature *."

Still we are ignorant of the composition of this fluid, and of the mode of its action; by which is meant that we are not capable, as we are in the mechanical part of our frame, of collating it with the operations of art. And this I call the imperfection of our chemistry; for, should the time ever arrive, which is not perhaps to be despaired of, when we can compound ingredients, so as to form a solvent which will act in the manner in which the gastric juice acts, we may be able to ascertain the chemical principles upon which its efficacy depends, as well as from what part, and by what concoction, in the human body, these principles are generated and derived.

In the meantime, ought that, which is in truth the defect of our chemistry, to hinder us from acquiescing in the inference, which a production of nature, by its place, its properties, its action, its surprising efficacy, its invaluable use, authorises us to draw in respect of a creative design?

Another most subtile and curious function of animal bodies is secretion. This function is semi-chemical and semi-mechanical; exceedingly important and diversified in its effects, but obscure in its process and in its apparatus. The importance of the secretory organs is but too well attested by the diseases, which an excessive, a deficient, or a vitiated secretion is almost sure of producing. A single secretion being wrong, is enough to make life miserable, or sometimes to destroy it. Nor is the variety less than the importance. From one and the same blood (I speak of the human body) about twenty different fluids are separated; in their sensible properties, in taste, smell, colour, and consistency, the most unlike one another that is possible; thick, thin, salt, bitter, sweet: and, if from our own we pass to other species of animals, we find amongst their secretions not only the most various, but the most opposite properties; the most nutritious aliment, the deadliest poison; the sweetest perfumes, the most fœtid odours. Of these the greater part, as the gastric juice, the saliva, the bile, the slippery mucilage which lubricates the joints, the tears which moisten the eye, the wax which defends the ear, are, after they are secreted, made use of in the animal economy; are evidently subservient, and are actually contributing, to the utilities of the animal itselft.

The gastric liquid and the phemonena of digestion are more fully described in the tenth chapter.

The simplicity of design, which characterises the works of the great Architect of the world, is well displayed in the variety of forms and effects which the same ingredients are made to produce, as their proportions are varied. For this purpose, the chemical comparison of blood, with four of the secretions formed from it, is not devoid of interest.

Serum of blood has been carefully analysed by M. Berzelius; he found in it the following ingredients:Water, albumen, muriate of potash and soda, lactate of soda, soda, phosphate of soda.

The same distinguished chemist found saliva to be composed of water, animal matter, mucus, muriate of potash, salts of soda, pure soda; and human bile, of water,

picromel (a peculiar animal matter), albumen, soda, phosphate of lime, common salt, phosphate of soda, with some lime.

Tears are composed of water, mucus, common salt, soda, phosphate of lime, phosphate of soda.

The liquid which lubricates the joints, of water, fibrous matter, albumen, muriate of soda, soda, phosphate of lime.-Thomson's Chemistry, vol. iv. p. 506, 7, 12, 23. In the analysis of vegetable substances, a still more extraordinary simplicity of design is developed : thus many substances, such as gum, sugar, starch, wax, camphor, wood, oxalic acid, and many others, are made entirely out of the same substances.

It was a wild dream of some of the Greek philosophers, that of one substance only the world was originally formed; and to this opinion, Dr. Hook, Sir Isaac Newton,

Anr. of Phil. vol. ii. p. 202, 379.

Other fluids seem to be separated only to be rejected. That this also is necessary (though why it was originally necessary, we cannot tell), is shewn by the consequence of the separation being long suspended; which consequence is disease and death. Akin to secretion, if not the same thing, is assimilation, by which one and the same blood is converted into bone, muscular flesh, nerves, membranes, tendons; things as different as the wood and iron, canvass and cordage, of which a ship with its furniture is composed. We have no operation of art wherewith exactly to compare all this, for no other reason perhaps than that all operations of art are exceeded by it. No chemical election, no chemical analysis or resolution of a substance into its constituent parts, no mechanical sifting or division, that we are acquainted with, in perfection or variety come up to animal secretion. Nevertheless, the apparatus and process are obscure; not to say absolutely concealed from our inquiries. In a few, and only a few instances, we can discern a little of the constitution of a gland. In the kidneys of large animals, we can trace the emulgent artery dividing itself into an infinite number of branches; their extremities every where communicating with little round bodies, in the substance of which bodies, the secret of the machinery seems to reside, for there the change is made. We can discern pipes laid from these round bodies towards the pelvis, which is a basin within the solid of the kidney. We can discern these pipes joining and collecting together into larger pipes: and when so collected, ending in innumerable papillæ, through which the secreted fluid is continually oozing into its receptacle. This is all we know of the mechanism of a gland, even in the case in which it seems most capable of being investigated. Yet to pronounce that we know nothing of animal secretion, or nothing satisfactorily, and with that concise remark to dismiss the article from our argument, would be to dispose of the subject very hastily and very irrationally. For the purpose which we want, that of evincing intention, we know a great deal. And what we know is this. We see the blood carried by a pipe, conduit, or duct, to the gland. We see an organised apparatus, be its construction or action what it will, which we call that gland. We see the blood, or part of the blood, after it has passed through and undergone the action of the gland, coming from it by an emulgent vein or artery, i. e. by another pipe or conduit. And we see also at the same time a new and specific fluid issuing from the same gland by its excretory duct, i. e. by a third pipe or conduit; which new fluid is in some cases discharged out of the body, in more cases retained within it, and there executing some important and intelligent office. Now supposing, or admitting, that we know nothing of the proper internal constitution of a gland, or of the mode of its acting upon the blood; then our situation is precisely like that of an unmechanical looker-on, who stands by a stocking-loom, a corn-mill, a carding-machine, or a threshing-machine, at work, the fabric and mechanism of which, as well as all that passes within, is hidden from his sight by the outside case; or, if seen, would be too complicated for his uninformed, uninstructed understanding to comprehend. And what is that situation? This spectator, ignorant as he is, sees at one end a material enter the machine, as unground grain the mill, raw cotton the carding-machine, sheaves of unthreshed corn the threshing-machine; and when he casts his eye to the other end of the apparatus, he sees the material issuing from it in a new state; and, what is more, in a state manifestly adapted to future uses; the grain in meal fit for the making of bread, the wool in rovings ready for spinning into threads, the sheaf in corn dressed for the mill. Is it necessary that this man, in order to be convinced that design, that intention, that contrivance has been employed about the machine, should be allowed to pull it to pieces; should be enabled to examine the parts separately; explore their action upon one another, or their operation, whether simultaneous or successive, upon the material which is presented to them; he may long to do this to gratify his curiosity; he may desire to do it to improve his

66

and Boscovich, evidently inclined. Davy, who certainly thought it probable, well denominates such an hypothesis a sublime chemical speculation *;" and in another place he adds," the more the phenomena of the universe are studied, the more distinct their connection appears, the more simple their causes, the more magnificent their

design, and the more wonderful the wisdom and power of their Author†." Davy, in early youth, was a sceptic: he describes his conversion, and the reasons for it, in his beautiful little work, "The last Days of a Philosopher," p. 153.

* Chemical Philosophy, p. 489.

+ Ibid. 60.