Abridgment of the Contemplation of Nature By Mr. Bonnet, of GENEVA

 

  1. In our researches into the gradual progression of beings and organical economy, we had frequent occasion to compare vegetables and animals with each other. Let us here collect in one view’, those various marks of analogy which are scattered hither and thither: let us represent’ them as in a picture, wherein by a nearer description of them, they will agreeably attract our attention. We will afterward inquire if there’ be any character which essentially distinguishes the vegetable from the animal.

2. A seed is an organized body, which under various coverings, thicker or thinner, and more or less numerous, contains within it a plant in miniature. A whitish substance, of a spongy nature, fills the capacity of the seed. Small vessels which proceed from the germ, are in every part of this substance, dividing and sub-dividing it. After being laid in the earth, moistened and warmed to a certain degree, the seed begins to shoot up. The moisture which has penetrated its outward folds, dissolves the spongy substance and mixes with it. Of this mixture is formed a kind of milk, which being carried to the embryo by the little vessels, furnishes it with a nourishment adapted to its extreme delicacy. The radical or little root’ begins by this means to’ unfold itself. It increases in bulk and extent every day. In a short time it becomes sensible of too close a confinement: it makes an effort to come forth. A small orifice, made in the exterior surface of the seed, facilitates its egress. The root insensibly sinks into the earth, and derives from thence more substantial and copious nourishment. The small stalk, which till this time lay hid under the coverings of the seed, now begins to show itself. The tegunrents unfold themselves in order to admit a free passage for it Strengthened by an accession of fresh juices. it pierces through the earth, and advances into the air.

3. An egg is an organized body, which under divers teguments, of various strength anti number, encloses an animal in miniature. A fluid matter of a glutinous nature, fills the inside of the egg. A number of infinitely small vessels spread themselves out in this matter, and are connected with the germ by different branches. Being warmed in a sufficient degree, either by nature, or art, the inside of the egg begins to receive life. By means of a gentle heat, the matter surrounding the germ insinuates itself into the small ramifications, from whence it passes into the heart, whose motion it augments. Thus the animal becomes a living creature. It increases in size and strength every day, by receiving fresh supplies of more nourishing and perfect juices. After these juices are exhausted, the animal has acquired all the growth it was capable of in the egg. It finds the apartment assigned it to be too narrow. It endeavours to set itself at liberty. Nature has provided it with an easy method of effecting this, either by arming it with instruments proper for piercing or tearing the coverings which enclose it, or by giving to the egg such a structure as favours its efforts. The animal is produced, and enjoys a new life.

4. The seed then is to the plant what the egg is to the animal. But the plant is not only oviparous but also viviparous; and the foetus is the same with respect to the animal, as the bud is to the vegetable.

Being concealed under the rind, the bud there receives its first growth. It is minutely inclosed in membranous teguments, analagous to those of the seed. It adheres to the bark by small fibres, which transmit a nourishment to it, adapted to its state. When it has arrived to a certain bulk, it penetrates the rind in order to come forth. At its first appearance, it bears the infolding coverings along with it, from which it is soon released. However, being as yet too feeble to subsist without the aliment provided by the mother, it continues to cleave to her; and cannot for a long time be separated without endangering it.

Being lodged in the matrix, the foetus there receives its first growth. It is there contained at first in miniature, in the membranous enclosures resembling those of the egg. It shoots forth small vessels in the matrix, which conveys thither the nourishment necessary to promote its growth. When it has arrived to a certain size, it bursts the enclosures, and comes into the world. Some times the enclosures accompany it at its issuing forth. After it is produced, the little animal is not always able to provide for itself without the assistance of the dam. She must still furnish it with sustenance which it cannot dispense with, for a certain time without danger.

5. The plant is nourished by the incorporation of substances, received from without: these matters are very heterogeneous. Being pumped by the pores of the roots, or by those of the leaves, they are conveyed into the utriculi, where they ferment and digest. They pass into the ligneous fibres, which transmit them to the proper vases, where they appear under the form of a juice, which is or less coloured. The ramifications of the proper vases afterward distribute them into all the parts, to which they are united by new filtrations.

Tubes made of a silvered blade, which are elastic, and turned spirally like a spring, accompany the vessels which contain the sap in their course. Being appointed for the purpose of respiration, these tubes introduce a fresh elastic air into the plant, which prepares and subtilizes the sap, and probably colours it, besides contributing to its motion: the superfluous matter, or that part which is not so proper to be mixed with the plant, is conveyed to the surface of the leaves, whence it evaporates by in insensible, but very copious transpiration, Globules. vesicles, or other excretory organs, which are distributed among the young shoots or leaves, procure an evacuation of the grosser matter, anti such as is of a stronger consistence.

The animal is nourished by the incorporation of matter which proceeds from without. This matter is very heterogeneous. Being received by the mouth, it is conveyed into the stomach and intestines, where it undergoes different preparations : it passes into the lacteal veins and their dependencies, or in other like vessels, whereby it is transmitted into the blood vessels, where it appears under the form of a fluid more or less coloured, or flowing. The ramifications of the blood vessels afterward disperse it into all parts, with which it incorporates itself by new preparations.

Pipes composed of cartilaginous rings, or of a silvered and elastic blade, turned spiral wise, communicate with the blood vessels, or follow them in their course. As they are appropriated to respiration, they introduce into the animal a fresh and elastic air, which prepares, attenuates, and probably colours the blood, contributing likewise to its motion. The superfluous matter, or such part of it as is improper to be united with the animal, is carried to the surface of’ the skin, from whence it evaporates by an insensible, but very copious transpiration. Glands, or other emunctory organs, placed in different parts of the body, procure the evacuation of the grosser matter.

6. The plant grows by unfolding, or the gradual extension of its parts in length and width. This extension is followed by a certain degree of hardness contracted by the fibres. It diminishes as the hardness increases. It entirely ceases when the fibres are so far hardened as not to yield to the force which tends to enlarge their surface.

The plants which become hardened the latest, are those which are the longest time in growing. Herbs grow and harden faster than trees. Some of them cease to grow at the end of a few weeks, or even a few days. Among the last, some continue to grow for a great number of years, and even for ages.

We observe analogous differences between individuals of the same species. Some harden sooner, grow in a less degree, or continue smaller; others harden later, anti become larger.

The bud has nothing ligneous or woody in it. Being herbaceous in every part of its substance, it becomes ligneous by degrees. Its stalk is formed of a prodigious number of concentric blades one in another, which are disposed according to its length, and compose different bundles of fibres, which are themselves formed of a prodigious number of lesser fibres.

At the centre of the stalk is placed the pith ; and the spaces which are left between the blades, are likewise filled with a pithy substance.

From the thickness of the blades results its growth in width ; from the lengthening of the blades its growth in length proceeds. All the blades grow and harden one after another. Every blade grows and hardens alike successively throughout its whole length. That part of every blade which grows and hardens first of all, is that which composes the base of the stalk. The blade which grows arid hardens first, is !he innermost, or that which immediately encompasses the pith. This blade is again covered with another, which being more ductile extends itself the more. A third blade encloses this last, which as it hardens still later, is a longer time in its growth. The case is the same with regard to a fourth, fifth, or sixth. All these thus diminishing in thickness, and inclining towards the axis of the stalk, as they approach its upper extremity, form so many little cones engrafted into each other from whence proceeds the conic figure of the stalk and branches.

From the assemblage of little cones which become hardened during the first year, is formed a cone of a woody nature, which determines the growth of that year. This cone is enclosed in another herbaceous cone, which is only the rind, and which the following year will produce a second ligneous cone, &c. When the wood is once formed, it does not extend itself any farther. So that in cicatrices, grafts, and different kinds of tumors, the rind is the only part that is employed. By stretching, thickening, or swelling itself, the rind insensibly forms a roll, an(l produces excrescences which are more or less considerable, in proportion to the ease with which it is distended, or according to the quantity of juices it receives.

7. The animal grows by expansion, or by the gradual extension of its parts in every sense. To this extension there succeeds a hardness in the fibres. The extension diminishes as the hardness increases. It ceases when the hardness has arrived to such a pitch, as not to admit of the fibres giving way to the force which contributes to enlarge their coats.

Those animals, in which this hardness is formed latest, are longest in their growth. insects grow and harden in a much less time than great animals. Some of them cease growing at the end of some weeks and sometimes in a few days. Of the latter, some continue growing for a great number of years, and even some ages.

One may observe analogous differences in the growth of individual of the same species: some of which that harden later than others acquire a greater bulk.

The foetus, in its original state, contains nothing of a bony nature As it is membranous throughout, it only becomes bony by degrees ‘The bones are composed of a prodigious number of blades, folded in each other lying according to the length of the bone, and forming various collections of fibres, which are themselves composed of the reunion of a great number of little fibres.

In the centre of the bone is placed the marrow. The spaces between the blades are filled with a medullary substance.

From the thickening of the blades the growth of the bone proceeded From the lengthening of them, their extending in length. All these blades grow and harden after one another. Each blade grows and becomes hard in a like successive manner throughout its whole length That part of the blade which grows and hardens first, composes the body of the bone: which immediately encloses the marrow. This blade is again covered with a second, which being more ductile, stretches itself in a greater degree. A third blade again enfolds this, which as it hardens later than the others, is a longer time in its growth. It is the same with respect to a fourth, fifth, or sixth. As they all thus diminish in thickness, and detach themselves from the axis of the bone, the nearer they approach to its extremities, they form so many little columns, infolded within each other, which increase in diameter at their extremities. From hence we deduce the figure peculiar to long bones.

The growth of the hone during the first year, is attributed to the number of blades which become hardened in that year. This bone ‘is covered over again with a great number of membranous blades., that hear the name of periosteum, which as they gradually extend and harden, conduce to the increase of the bone in every part of it. The bone when it is once formed, extends itself no farther.

Thus in fractures, anchyloses, and the different species of excrestences, whether natural or accidental, the periosteum is the only part of the bone that labours. By stretching, thicking or swelling itself, the periosteum restores to the bone insensibly, produces a callosity, and forms greater or less tumors, in proportion to the facility wherewith it extends itself, or as it is more or less supplied with juices, or with such as are more or less viscous.

3. The dust or fine powder of the stamina, is the principle which fertilizes the seed. The pistil is the place where this fecundation is performed.

Being contained in certain vesicles, the fecundating dust is discovered in them by a microscope, under the appearance of a group of minute, regular bodies, for the most part of a spherical or elliptic form, which being moistened, open themselves, and emit a thin vapour, in which there floats a great number of exceeding small sees, which seem to move on all sides. The dust itself, when dropt j11tO water, moves several ways with great rapidity.

The pistil is composed of three principal parts the base, the cups. and the top. The base contains one or more cavities, where the grain is lodged. The cups are long funnels, whose base or aperture it turned towards the top. This is generally furnished with several nipples each of which is perforated, having their diameter corresponding with that of a small grain of the dust.

Being in the tower part of the cup, the minute grains are pressed in them more and more by the straitness of these pipes. They are ‘therein moistened with a juice that lines their sides. They open themselves and eject the seminal vapour, which penetrates to the peed, and promotes fecundation.

Several- species of plants have two sorts of individuals, viz. 1. Such individuals as only bear stamina, and these are males; and two individuals that have only the pistil, which are females.

In a great number of species, every individual is an hermaphrodite, which unites both sexes, the stamina and the pistil. Sometimes this union happens in the same flower ; then the stamina surround the pistil. At other times it is only effected on the same branch; so that the stamina are placed on one part, and the pistil on another.

9.  The seminal liquor is the principle of fecundation in the egg. The matrix or ovaries are the places where it is performed.

Being enclosed, in’ the seminal vessels, the fecundating liquor appears in them, through a microscope, like a mass of small regular bodies of different lengths, which seem to separate themselves into a great number of extremely minute grains, moving different ways Sometimes these corpuscles resemble cases with springs, which when moistened, open themselves, and dart forth a limpid matter abounding with a great number of very small grains.

The matrix consists of three principle parts, or dependencies; the fundus or bottom, the fallopian tubes, and the ovaries. The fundus contains one or more cavities, in which the embryos receive nourishment and expand themselves: it has an orifice in the fore part. The fallopian tubes are a kind of long funnels, whose aperture is directed towards the ovaries, where it ends. The ovaries are a mass of vesicles that are real eggs.

When the most subtle part of the seminal liquor has arrived through the fallopian tubes to the ovaries, it there fecundates one or more eggs. These afterward descend by these tubes into the matrix, where they are fixed and unfold themselves. In oviparous females the eggs are contained in a kind of bowel, wherein they receive their growth: the seminal liquor makes them fruitful.

Most animals consist of two sorts of individuals; male and female

But there are other species, of which every individual is an hermaphrodite, which unites the two, although it cannot fecundate itself. In some species, where a distinction of sexes is observed, there is no coupling, properly so called; the male only communicates his liquor to the eggs which the female has deposited. Finally, some species are propagated without any apparent or external fecundation.

10. A plant does not only multiply by seeds and buds; it is like wise propagated by suckers and sprigs. It may also be multiplied by slips, and by ingrafting.

A tree sends forth small buds from various parts of its surface. These buds increase in bulk; they open and disclose the shoot; which extends itself every day. While it is expanding itself, other still smaller sprigs shoot from it. These in their turn are succeeded by lesser ones; all of which are so many trees in miniature; and the nourishment received by one of these sprigs is communicated to the whole plant.

When it has attained to a certain size, and is separated from the trunk, either by nature or otherwise, these shoots sustain themselves, and become so many distinct trees. Being cut into pieces according to their width, or even their length, these shoots will grow again of themselves, and will become as many trees as they were made slips of.               The leaves themselves when separated from their shoots, may afford so many complete plants. Being fastened closely to each other, or inserted in one another, several of these shoots, whether taken from the same or from different individuals, will unite together in so intimate a manner, that they will receive reciprocal nourish. meat, and form one individual whole.

The animal is not only propagated by eggs and living young, but likewise by shoots. It may also be multiplied by slips and ingrafting. A polypus sends forth little buds from different parts of his body. These buds grow big and lengthen insensibly. Every one of them is a young shoot. While it is unfolding itself, there springs from it other smaller shoots. These in their turn produce smaller still. All these shoots are so many little polypuses, and the nourishment one of these polypuses receives, is communicated to their whole number. When they have arrived to a certain size, they separate themselves from the trunk, and become so many individuals.

Being cut into little bits, either transversely or lengthwise, the polypuses grow up again from the ruins, and become as many complete ones as they were pieces. The very skin, or even the least fragment of them, is capable of affording one or several polypuses.

11.  The generation of vegetables is not constantly regular. The laws by which they operate are sometimes infringed. Prom them arise various species of monsters. Sometimes they are compounded leaves, whose smaller ones are more or less numerous, or more irregularly shaped, or distributed with less symmetry than usual. Sometimes there are flowers which have neither stamina nor pistils, and whose petals being greatly multiplied, seem to have absorbed these essential parts. Sometimes two fruits cleave together by a natural graft or are enclosed in each other. Sometimes there are flowers or fruits whose form differs widely from that which is peculiar to the species. Lastly, there are productions which do not properly belong to any particular species, because they derive their original from seeds that have been fecundated by dust of a different species.

The generation of animals is not constantly regular: the laws by which it is governed, are sometimes disturbed; whence are produced the different species of monsters. Sometimes there are hands and feet, whose fingers or toes are fewer or more in number, or formed in an irregular manner, or otherwise disposed than usual. Sometimes there are foetuses, in which the parts of generation are obliterated. Sometimes there are two eggs or two foetuses that cleave to each other by a natural cohesion, or that are contained in one another. Sometimes there are eggs or foetuses whose form is greatly different from that which is pepuliar to the species. Lastly, there are productions that partake of two species, because they are produced from such females as are fecundated by males of different species.

12. The laws respecting the nutrition and growth of vegetables are liable to greater disorders than those of generation. From hence are derived the different kinds of maladies the plant is subject to. Some of these maladies only attack the leaves, and produce on them spots of different colours, wrinkles, pustules, scabs. Others attack the principal viscera, and occasion choakings, obstructions, stagnations, tumors, cancers, effusion. Others take their seat in the flower or fruit. Others affect the ligneous bodies, which they cause to moulder away, whilst the bark remains whole. Others come from little plants or divers insects, which being on the outside or inside of vegetables, convert their nourishment to their own advantage, or change the organization of it. Others derive their origin from a change of climate, aliment, or culture.

The laws of the nutrition and the growth of the animals are more frequently disturbed than those of generation. From hence proceed the various species of disorders to which an animal is exposed. Among these maladies, there are some which attack only the skin, and produce spots of various colours, wrinkles, pustules, pimples. Others attack the principal bowels, and occasion oppressions, obstructions, stagnations, tumors, abscesses, overflowings. Others are seated in the organs of generation. Others seize the bones, and beget rottenness in them, whilst the periosteum continues sound. Others have their source from different insects, which, being lodged either without within the animals, divert the nourishment of them to their own fit, or alter the constitution of them. Others are caused by the change of climate, nourishment, or breeding.

13. Finally, the plant after having escaped a variety of maladies which threatened its life, cannot elude the effects of old age, that creeps into it, nor the stroke of death, the inevitable consequences of it. Being hardened by time, the vessels lose their exercise, and are stuffed up. The liquors contained in them no longer move with the same facility, nor continue to be filtrated and pumped out with the same precision. They stagnate and corrupt; and this corruption being soon communicated to the vessels that enclose them, the vital functions cease, the plant dies and crumbles into dust.

Lastly, the animal, after having been preserved from those diseases which conspired against him, cannot escape old age, nor death that follows in his train.

When, the vessels are grown hard through time they lose their action and are stopped up. The liquors do not circulate in them with the same degree of quickness, and they are filtered and pumped up but in a very imperfect manner. They stand still and are altered, and this alteration soon communicating itself to the vessels that Contain them, circulation ceases, the animal dies, and is reduced to dust.

14. We have carried the parallel between plants and animals from their birth to their death. The parts of which they consist, very evidently establish the great analogy there is betwixt these two classes of organized bodies.

But there are other sources of comparisons, we have either avoid ed to dwell upon, that we might not render our description confused, or have only slightly touched upon, under certain points of view. Such are those presented to us by place, number, fecundity, form, structure, circulation of liquors, locomotive faculty, feeling, and nutrition.

We will take a transient survey of these sources, and without endeavouring to exhaust them, content ourselves with barely pointing out their most remarkable and characteristical contents.

Vegetables and animals reside in the same dwelling-place. Being appointed to people and adorn our globe, they are dispersed over its whole surface, and are placed near each other, in order to enable them to afford a reciprocal assistance. Like two great trees growing in the same soil, the animal and vegetable kingdoms entwine their branches together and extend their boughs and roots to the extremity of the world

The outside and inside of the earth, mountains and vallies, barren and fertile places, countries undiscovered and bid in dark obscurity, the region is of the north and south, rivulets, rivers, ponds, lakes, and seas, have their vegetables and animals.

Many species of plants and animals seem to thrive alike in different climates. Other species are amphibious, and live as well out of the water as in it. The bulrush and frog flourish in meadows, and at the bottom of ponds. Others are parasites, and are nourished by the juices they extract from different species. Such are the misletoe and the louse.

Lastly, some parasite species supply their necessities, in their turn, from other parasites. The misletoe has his liverworts, and certain lice have their lice.

15. There are upwards of twenty thousand species of plants known to us, and new discoveries of them are made every day. A microscopical botany has extended the dominions of the ancient. Mosses, mushrooms, liverworts, whose families are innumerable, now take place amongst vegetables, and present the curious with flowers and seeds which before they were unacquainted with. The microscope discovers plants to our view, where we never suspected them. Freestone is often covered with spots of different colours, commonly brown or blackish. Glass, notwithstanding its fine polish, is not exempt from such spots. We observe hoariness on almost all bodies. These spots and this hoariness are found to be gardens, meadows, and forests in miniature, whose plants that are infinitely small, afford us nevertheless some prospects of their flowers and seeds.

But although vegetables are very numerous in their species, yet they are much less so than animals. Emery species of plant has not only its particular species of animals, but there are many species of plants which nourish several species of animals. The oak alone finds nourishment for above 200 species of them. Some attack the roots of this tree, which they dig into, and produce therein various tuberosities. Others fix themselves in the trunk, where they make crooked furrows. Some insinuate themselves into the bark and wood: whilst others penetrate the interior parts, whence they extract the juice Some feed only on the leaves. Others fold or roll them up with a great deal of art. Some form them into nuts. Others find both lodging and nourishment in the fruit. Nay, gather but a flower by chance, either a daisy, poppy, or rose, and you will observe on it a multitude of insects.

In short, where can we turn our eyes without beholding animals Nature has strewed them every where with a bountiful hand. They were her most excellent productions; she has been liberal of them. She has inclosed animals within animals; she has ordained one animal to be a world for others. which should find therein nourishment in proportion to their wants. The air, vegetable and animal liquor corrupt matter, dirt, dung, dry wood, shells, and even stones, and all animated, all swarm with inhabitants. What do I say The itself sometimes appears to be one entire collection of animals. The light, which glitteringly reflects on it in the night-time, during hot weather, is produced by an infinite number of very minute glow. worms, of a yellowish brown colour, and soft substance, not caterpillars, every part of which, after being divided, and even putrefied, shines with the same brightness as when the worm was whole and living. A species of sea-flies are also luminous, and communicate their lustre to the waters. There issues from within them a globular matter, which is likewise phosphorous.

Herbs are more numerous in their species and individuals than shrubs and trees. Insects are more numerous, in respect to their: species and individuals, than birds and quadrupeds. There are more ranuneuluses than rose-bushes, and more blades of grass than Oaks. There are more butterflies than fowls, and more vine-fretters than dogs.

16. The magnificence of the creation shines in no part of it with greater lustre, than in the prodigious fecundity of a great number of plants and animals. One single individual may give birth to thousands, or even millions of individuals like itself. Being formed agreeable to those proportions which are only known to that adorable Wisdom that’ has established them, this great people was at first enclosed within the narrow compass of a rind or ovary. In this dark abode they receive their first life, begin to grow, and are disposed to appear on the mast theatre of the visible world.

If we consider things in a general view, vegetables will be found to be more fruitful than animals. We shall be farther convinced of this, by comparing trees with quadrupeds.

Trees produce annually, sometimes for many ages, and their productions are always very numerous. Large quadrupeds, as the elephant, the mare, the hind, the cow, &c. have seldom more than one at a time, rarely two, and the number they breed is always very moderate. Lesser quadrupeds, such as the dog, the hare, the cat, the rat, increase in a much greater degree; but their fecundity is but inconsiderable, when compared to that of ligneous plants. The elm produces yearly upwards of three hundred thousand seeds; and this astonishing multiplication may continue above a century.

Fishes and insects nearly resemble vegetables in fecundity. A tench lays about ten thousand eggs; a carp about twenty thousand; and a cod, a million. An insect which produces the itch, lays four or five thousand eggs; a female bee, forty-five or fifty thousand.

To this amazing fecundity is opposed that of the wild poppy, mustard. fern. And we must not forget, that most vegetables are propagated different ways; whereas, animals are for the most part propagated only by one.

A tree may be made to form as many trees as it has branches, boughs, and even leaves. Plants, which are principally designed to supply the necessities of animals, cannot be endued with too great a degree of fecundity.

17. There is hardly any sight more interesting than that which  infinitely varied forms of plants and animals afford. If one compares the less perfect species with the more perfect, or the species of the same class with each other, he is equally struck with the diversity of models, by which nature has performed her works in the vegetable and animal kingdoms. He passes with astonishment from the swinebread to the sensitive plant, from the mushroom to the carnation, from the nightshade to the oak, from the ivy to the fir tree. He considers with surprise, the prodigious multitude of mushrooms and liverworts, and can never enough admire the fecundity of nature in the production of these plants.

As he goes on to plants that are more elevated in the scale, he stops with pleasure to examine those plants that have stalks, from the grass which grows between the stones to that precious plant whose ear furnishes us with the most wholesome food. He considers the various plants that creep, from the tender bind-weed, to the vine branch which crowns our hills. He likewise takes a survey of those trees which bear fruit with stones, from the wild plum tree to the peach, whose fruit does not excite our admiration more by the softness of its velvet covering and beautiful colour, than by the abundance and exquisite taste of the liquor it yields.

If from the vegetable, he transports himself into the animal kingdom, the prospect becomes still more interesting, lie sees opposed to each other in the same portrait, the polypus and sea-dog, the day. fly and flying-fish, the dancing-bird and eagle, the grasshopper and flying-squirrel, the ant and stag, the cricket and rhinoceros, the wood louse and crocodile, the scorpion and the ape.

Another picture presents him with a view of the prodigious number of butterflies and flies; in considering which he is astonished at nature’s complaisance in thus diversifying these little animals, so different from the great ones by their forms, and which have been treated as defective or imperfect beings.

Transferring next his survey to those species of animals immediately higher, he contemplates shell fish, from that whose precious liquor dyes the garments of kings, to the sailor that rows with so much grace and skill on the inconstant waves. He observes the different species of fish, from the dangerous cramp fish to the powerful nerval, and from the pretty golden fish of China, to the dolphin, that cleaver the billows with the swiftness of a dart.

He likewise takes a view of those birds that live on herbs and seeds, from the linnet, that delights us with his melody, to peacock that pompously displays in our court-yards the gold azure with which he is enriched. lie also observes the birds of prey from the fierce merlin to the eagle, whose strength courage have raised him to the sovereignty over the birds. He next reviews the quadrupeds, from the light and timorous hare to the plant, whose enormous corpulency attracts every eye, and from the wily fox to that noble and generous quadruped which seems formed to have dominion over the animal creation.

Plants, though prodigiously various in their forms, are yet less so than animals. There are fewer gradations from the truffle to the sensitive plant, or from the nightshade to the oak, than there are from the oyster to the ostrich, or from the sea-nettle to the ouran-outang. Plants being essentially more simple than animals, have not given birds to so many combinations.

The forms of animals afford us a singularity which is extremely remarkable, and sufficient to distinguish them from vegetables; I mean those admirable metamorphosis which the same insects exhibit to us, which are sometimes so opposite, that it does not appear to be the same animal.

But may we not compare the bud in which a plant or flower is infolded, to the covering of a chrysalis which conceals the butterfly from our sight And as the plant cannot produce seeds till the flower has issued from the bud, so neither can the butterfly propagate till it has cast off the sheath of the chrysalis.

18. It is not so easy to compare plants and animals in their interior forms or structure, as it is in their exterior. We may judge of the one by a single glance of the eye: we must bestow a particular attention to judge of the other. We penetrate with greater difficulty into the inside of the plant, than into that of an animal. The micro-scope, scalpel, and injections, which are so serviceable to us in the anatomy of animals, assist us very imperfectly in that of plants. It is likewise true, that this part of organical economy has been less studied.

But how imperfect soever the anatomy of plants may be, we are able to discover some of their principal vessels. These may be ranged under two general classes: the longitudinal, that extend the whole length of the plant; and the transverse vessels, or such as are placed across it. The sappy vessels and trachaean belong to the first class; the utriculi or insertions to the second. The vessels containing the sap seem designed to convey the juice. The utriculi, or little bags appear intended for digesting it.

Some plants seem to be entirely composed of utriculi: such are certain species of roofs and sea plants. whose texture is almost together vesicular, it is the same with those animals which seem to of stomach only, as the polypus and tape-worm.

 One of the principal characters by which we may distinguish insects from large animals, is, that the former have no bone within them. What they have of a bony or scaly nature is placed on their outside for a support or defence to the more delicate parts underneath, or to sustain the body with greater advantage. Thus we see that in almost all insects, properly so called, the head, corset, legs, rings, &c. are either wholly, or for the most part, doubly covered with scales.

Herbs differ from trees as insects from large animals. They have  ligneous body in their centre. What they have of a ligneous nature, appears on the outside, and serves to protect the weaker parts 0f the plant. Thus we find plants with tubes are strengthened by knots placed at regular distances; so that the lowermost knots which are designed for the base, are stronger and nearer each other than the upper ones. It is on the same account that the roots of many herbaceous plants, as well as the calixes of flowers, and the capsules or coverings of the seeds, are made almost ligneous.

Herbs grow and become hard sooner than trees. Insects than great animals. Herbs and insects, being of a softer consistence than trees and large animals, extend themselves with greater ease, and sooner arrive at the period of their extension. Besides, the concentric beds of the bark of trees, and those of the periosteum of animals, being far more numerous than the relative beds of herbs and insects, must needs require a longer time for their growth.

We may distinguish two kinds of parts in organized bodies ; to wit, similar and dissimilar. The former are composed of fibres of the same kind; the latter of fibres of various sorts. The nerves, arteries, veins, lymphatic vessels are the similar parts of our bodies; the brain, heart, lungs, stomach, the dissimilar. Plants are almost entirely composed of similar parts. The vessels containing the sap, the trachaea, and utriculi, are of this kind These different vessels are pretty uniformly dispersed throughout the whole body of the plant: they enter into the composition of all its parts. They are to be met with in the root, stalk, branches, leaves, flowers and fruits The least fragment, the smallest leaf, is a representation of the whole, an abridgment of the plant.

There are likewise animals which are nearly composed of similar parts. Of this number are many species of long worms, and some aquatic millipedes, nettles, and sea-stars, polypuses, moths, earth worms. All these animals are formed in such a manner, that each part of them, even the smallest, corresponds in miniature to the whole in all parts.

In the long worms I just mentioned, we observe very distinctly a stomach, a heart, and some very small vessels which seem dependent on the latter. There is likewise no room to doubt that there is beneath the stomach, a medullary string, like that observed in other species of worms and caterpillars. Their viscera are not distributed in certain regions of the body: they are universally dispersed throughout its whole length; so that we may truly affirm that these insects are brain, all stomach, all heart. But this brain, stomach, and heart appear extremely simple: the first is scarce any thing more than a nervous piece of net-work, the second a membranous bag, and the third a grand artery.

Polypuses, which are more simple in their structure, are only a kind of bowel, sown with an infinite number of small seeds, which are tinged with the colour of the aliment.

Tape-worms partake of the structure of polypuses, but seem to be more compounded. They are formed of a chain of flat, membranous, and whitish rings, joined together like the divisions of a reed. Each ring has on its upper part, or on one of its sides, a more or less sensible eminence, in the centre of which is a small round aperture, The middle of the ring is full of vessels of a purple or whitish colour, which perform a labour that attracts the attention of the observer. The rest of the ring is filled with an infinite number of small white seeds. Such is essentially the structure of the tape-worm in its whole extent; there is no perfect variety or resemblance between all the rings, the assemblage of which composes a kind of ribband or lace, which extends sometimes several hundred feet in length.

Earth-worms are, of all the insects I have mentioned, those whose inside seems to be the most compounded, chiefly because in them the two sexes are united: but the most essential organs of life are distributed in them likewise through the whole length of the animal.

Organized bodies, whose structure is so simple and uniform, that each part of them has in a small compass an organization resembling that of the whole in a greater extent, enjoy divers prerogatives that have been denied to organized bodies of a more complicated structure. The first of these are not destroyed when divided asunder. Their different portions continue to live, and the wounds which. have been given to them easily consolidate. These parts vegetate, receive nourishment, produce new organs, and multiply. Such wonders as these the vegetables and insects we have lately treated of exhibit every day; wonders which we have not sufficiently admired in the former, and which perhaps we too much admire in the latter.

Large animals do not furnish us with the same phenomena. The consolidation of their wounds, and the re-union of their fractures, although oftentimes attended with circumstances which render them very remarkable, strike us but slightly when compared with what we observe analogous in polypuses, and other insects that multiply by slips. The motions we perceive in certain parts of great animals, when separated from the body, or after the death of the animal, affect us only with a slender degree of surprise, when we consider the of different parts of worms, or those of some mellipedes.

But may there not be some misconception in these different judgments We judge of the effect produced, as considered in itself, and separate from the circumstances accompanying it; whereas we should Judge of it with relation to the greater or less degree of composition whereof the body, in which this effect is produced, consists. There as much, and indeed more to be admired in the consolidation of certain wounds or in the re-union of certain fractures of our body, than there is in the consolidation of the wounds of polypuses, or in the re-union of parts which have been separated from them. A very simple machine is easily repaired; a machine that is extremely compounded, cannot be repaired with the same facility. When we reflect on the prodigious number of similar and dissimilar parts contained in the composition of the bodies of great animals, and particularly in that of the human body; when we attend to the strict connexion of all these parts, and to the degrees of composition in each of them, we cannot sufficiently wonder that the various accidents which happen to these bodies are not attended with greater consequences; we shall at the same time perceive the reason why they are not enabled to propagate like bodies whose organization is more simple.

But independently of the greater or less degree of the composition of parts necessary to life, as soon as these parts are found placed in different regions of a body, and are not dispersed throughout its whole length, such a body cannot be multiplied by slips. The Author of Nature, by denying, in his wisdom, this property to large animals, by confining the sources of life in them within a narrow circle, has secured them from harm by many advantages. Compare the result of the motions or actions of a sea-worm with that of the motions or actions of an ape, and you will soon perceive which of these animals has been most favoured.

Finally, organized bodies, to which a power has been granted of multiplying by a method which seems to tend to their destruction, are such as are exposed to the greatest dangers, and whose life is necessarily threatened every moment with a thousand various accidents.

19. Amongst the motions we observe in the animal machines, that of the circulation holds the first rank, either by its importance, or its nature, duration, and the number of organs by means whereof it is performed. There is in this motion an air of grandeur that seizes forcibly on the mind, and which, by making it sensible of the narrow limits of human understanding, penetrates it with the most profound respect, and fills it with the highest admiration of the infinite mind which illustriously shines in the Divine Author of it.

In the centre of the breast, between two spongy masses, known by the name of lungs, is deposited a fleshy pyramid, whose base bears two small funnels like ear-rings, which communicate with two cavities contained in the inside of the pyramid, and which divide it according to its length into two chambers or ventricles: the right Ventricle and the left. This pyramid is the heart, the main spring of the machine. It has two principal orders of muscular fibres; some of which pass obliquely from the base to the point, others cut the latter trans versely. From the exercise of these fibres two opposite motions result; one of dilatation, the other of contraction. The heart seems to execute these motions by turning on itself like a screw. Its point moves towards or from the base, by rising or falling obliquely.

Two great vessels, viz, an artery and a vein, communicate with each ventricle. The artery,* which communicates with the right ventricle, conveys the blood to the lungs. The vein, which communicates with the same ventricle, forms the principal trunk of the veins, and carries back the blood from all parts to the heart. The artery: which goes into the left ventricle, is the chief trunk of the arteries, and that which conveys the blood to all parts. The veins which ends at the same ventricle, transmits to it the blood that has been conveyed from the lungs.

The principal trunks of veins and arteries, are divided into several branches at a small distance from the heart. Some tend towards the upper extremities, others towards the inferior.

The arteries and veins decrease in diameter, and are ramified more or less according to their distance from their origin. There is no part to which these do not distribute one or more ramifications.

When they have arrived at the most remote parts, the arteries have an intercourse with the veins.

The arteries are composed of several membranes, placed on each other. The veins have similar membranes, but more slender and weaker. The veins were not designed to exercise the same power as the arteries. These latter must necessarily, like the heart, and for the same end, dilate and contract themselves: they have therefore been provided with a very elastic membrane. The exercise of the veins should not be violent.

At the root of the arteries, and in the inner part of the veins, are placed little sluices or valves, which by sinking and rising again, open and shut the canal. These valves are deposited in the veins, in a contrary sense from that for which they are in the arteries. We shall presently account for the cause of this difference.

20.  After having been masticated and dissolved in the mouth and stomach, the aliment descends into the intestines, where it receives a new preparation by the mixture of two liquors, one of which is furnished by the liver, and is called the bile ; and the other by a species of glands situated under the stomach.

*The pulmonary artery.  The venea cava. The grand artery, or the aorta.  The pulminary vein

The aliment is thus converted into a kind of grayish pulp, which has received the name of chyle. Being shifted from place to place by the vermicular or peristaltic motion of the intestines, and strongly pressed against their sides at the instant of their contraction, the chyle penetrates into extreme small vessels, which open themselves in the internal membrane of the intestinal canal. These vessels transmit the chyle to very small glands which are covered with a kind of membrane situated in the midst of the intestines, and round which they are in a manner rolled. After being filtrated in these glands, the chyle is received by other vessels, which convey it into a concavity placed along the spine, and which pours it into a vein situated under the left clavicle. There it enters into the blood, and loses the name of chyle From this vein the new blood passes into the upper branch of the principal trunk of veins, which carries it towards the heart. It passes into the right lobe, which opens at its approach, and by closing immediately, forces it into the right ventricle, which is dilated in order to receive it. The heart instantly contracts itself; the valves with which the ventricle is furnished, raising themselves to oppose the reflux of the blood into the lobe, it is compelled to pass the artery, which is appointed to carry it to the lungs. The valves, which are placed at the entrance of this artery, sink down; the artery dilates, and the blood advances into the cavity. The valves rise again, and prevent its return towards the heart. The artery contracting itself, the blood is impelled farther, and, by these alternate dilatations and contractions of the vessel, it is conveyed to the lungs, where it runs through every part of them. The ramifications of the trachea, which are dispersed in the viscera, carry thither a fresh and elastic air, which, by acting on the lungs, dilates, winds them about, extends and opens them, and by that means facilitates the course of the blood into the smallest ramifications of the artery. Besides, being impregnated with this air, the blood becomes thereby attenuated, is warmed, and receives a more lively colour.  After its arrival at the extremities of the artery, it passes into that of the pulmonary, vein, which conducts it to the left ventricle of the heart. This latter by contracting itself, pushes it into the aorta, which by continually dividing and subdividing itself, distributes this balsamic liquor to all the parts, in order to promote their growth, or support, and occasions different secretions.

*The pancrease and pancreatic juice.  The primary lacteal reins. The mesentery and mesenteric glands. The secondary lacteal veins. The thoracic duct. ** The bronchia. See note page 69 of the first volume. The principal trunk of arteries

21. Such is the admirable mechanism of the circulation of the blood in men, and in those animals which we are best acquainted with. But. now greatly does this imperfect sketch fall short of the reality incapable are these outlines of expressing the beauties of this noble subject! And who can account for the manner by which the strength: of life is repaired and recruited Who can conceive the cause of that perpetual motion of the heart, which continues without intermission for the space of seventy, eighty, or a hundred years, which has lasted for ages in the first race of men, and which remains almost as long in some species of animals Rave we discovered the exact part where the artery is changed into a vein Have we disclosed the mystery of the secretion of those spirits, whose prodigious subtility and activity give them a near resemblance to light Can we even determine in what manner the grossest secretions are performed Do we under. stand the true mechanism of muscular motion Have we been able to find out the source of that great strength which often so far exceeds that of the heart All these dependencies on circulation are yet un revealed to us. The gloom of night still wraps these regions in dark obscurity, and you are earnestly desirous of chasing it away from before that sun which alone can dispel these shades. Will the dawn of that day ere long gild the horizon of the learned world Or is the time of its breaking forth upon us yet afar off

But if we are not able to discover the whole, we may at least see enough of it to excite our admiration; and the sketch which I have just drawn of the circulation, is sufficient to enable us to conceive the highest ideas of the Sovereign mind, which has appointed the manner, duration, and end of it.

Far less magnificent in its plans, less skilful in the execution of them, hydraulics offer to us but faint images of this miracle; in those machines, by means of which water is raised above the mountains, in order to its being distributed into every quarter of a great city, and made to circulate and issue forth, under a hundred various forms, into those gardens which art and nature vie with each other in adorning and embellishing.

The works of the Creator must be compared with the works of the Creator. Ever like Himself, He has impressed on all his productions a character of nobleness and excellence, which demonstrates the grandeur of their origin. From that immense mass of water that encompasses the great continents, there incessantly arises an ocean of vapours, which being rarefied by the combined action of the sun and air, spread themselves in the upper region of the atmosphere, where they remain suspended in equilibrio, being intermixed with the fluid in which they float, and gravitate with it. Collected afterward into clouds more or less dense, and borne on the wings of the winds, they fly across the celestial plans. which they adorn with their rich colours, and continually ‘variegated forms. Fixed at length on the mountain tops, they pour upon them abundant rains, which being collected in the vast reservoirs, embosomed within them, furnish, by a happy circulation, a supply to fountains. rivers, lakes, and seas. Like veins and arteries, the rivers flow meandering, and branching  ‘the surface of the earth, they run through immense countries; water, fertilize, and unite them by a reciprocal commerce, and majestically rolling their waves toward the sea, plunge themselves into it, in order to be again exhaled in vapours, and re-enter afresh into the channels of this magnificent circulation.

22. Does the sap circulate in plants as the blood circulates in animals is this new mark of analogy between these two classes of organized bodies as real as it has appeared to be Small bladders full of air, which have been thought to be discovered within the leaves, have convinced us that they were the lungs of the plant.

But there have not been discovered in plants, vessels analogous to veins and arteries. No organ has been seen in them capable of performing the functions of the heart. A tree which is planted a contrary way, with the roots at top and the branches in the ground, lives, grows, bears fruit; from its roots, branches shoot forth; from its branches, roots. The same is observed with respect to slips and layers. A young branch, or young fruit, after being grafted on a subject foreign to itself, incorporates with it, and derives from thence the same degree of growth it would have received from the plant whence it was detached. Experiments demonstrate that the motion of the sap depends entirely on the alternatives of heat arid cold, and the ‘vicissitudes of day and night. It is evident that the sap rises in the day from the roots to the leaves, and falls in the night from the leaves to the roots. In a word, the course of the sap nearly resembles that of the liquor contained in the tube of a thermometer. All is reduced to a simple counterpoise.

23. The nourishment of the more perfect animals requires to be more wrought than that of plants. Hence the necessity of the circulation of the blood. The preparations of the sap do not require such a punctual, regular, and constant motion; bare poisings suffice. Large animals eat but at particular times : a pressing sensation which induces them to take nourishment, does not continually act upon them. The different preparations their aliment should undergo, would be disturbed or interrupted, were a fresh supply to be received within them before the former was sufficiently digested.

Plants, on the contrary, are in a state of perpetual suction; they draw in nourishment continually, and in a very great quantity, in the day time by their roots, in the night by their leaves. There is a plant which receives and transpires, in the’ space of twenty-four hours, twenty times more than a man.

But if plants differ so much from large animals by circulation, on the other hand some species of animals seem nearly to resemble plants by their want of this circulation. Not the least appearance of this motion is to be perceived in the polypus, the tape-worm, the pond-muscle, and divers other shell-fish.

24.  One of the ancients defined a plant to be a rooted animal. He would undoubtedly have defined an animal to have been a wandering plant. The locomotive faculty is one of those characters which present themselves first, when we compare the vegetable kingdom with the animal. We see plants that are constantly fixed on the earth

Being incapable of seeking their nourishment, it is ordained that this nourishment shall seek them. The greatest part of animals, on the contrary, are subjected to the care of providing their own substinence Nature has not always deposited near them such nourishment as necessary for their support. She has thought proper to oblige them to procure it for themselves, often with much labour. And the different methods by which she has instructed each species to obtain this end, much diversify the scene of our world.

Whilst the ploughman opens the earth, to entrust with it the seeds necessary to support him, the mole and the mole-cricket are clearly for themselves different route, in the same, to search for the food allot ted to them. The huntsman pursues his prey with an obstinate resolution: triumphing in his swiftness and strength. At other times preferring craft he becomes master of it by laying snares for it. The tyger rushes on the fawn sporting in the meadow. The cat watches motionless and silent, till the young mouse issues forth from its retreat, that she may dart upon it in a moment. Some species of animals,. resembling mankind by their prudence, lay up provisions against a time of scarcity; build themselves magazines, in which are observed’ such just proportions, as to give us cause to doubt whether it was the workmanship of a brute, were we not convinced that this brute itself is the work of Sovereign Reason.

25.  How great is the distance in this respect from the beaver and bee, to the gall or cochineal insect, the oyster, the sea-nettle, and several other kinds of insects and shell-fish The gall-insect, being confounded, by his immobility and form, with the tree on which he lives, contents himself with extracting its juice. Carried by the wave to the sea-shore, the oyster remains fixed there, and all its motions consist in opening and closing its shell. The sea-nettle,* and all the different polypuses with pipes, being continually fixed to the same place, open amid shut like a flower; extend and contract themselves like a sensitive plant; stretch out arms, by means of which they seize insects. This is their principal character, and the least equivocal character of their animality.

*This is what is called the vegetable sea-nettle. There is a fish so called which swims by a particular contraction of its parts.

Thus it appears that the locomotive faculty is not more proper ‘for distinguishing the vegetable from the animal, and those other character which we have before treated of. in the mean time, what can  more distinct in appearance than a plant is from an animal Or ‘what more easy to characterize in the sight of the major part of mankind But when once we are convinced that ‘every thing in nature is shadowed over, we are not surprised at the difficulties we meet with in our attempts to distinguish beings. We expect to see the species enter again into each other: and confine ourselves to the smallest latitude, or to that which is attended with the least uncertainty. In this principle we will conclude the parallel: let us see whether feeling, and the manner by which animals and vegetables are nourished, will furnish us with any thing more characteristical.

26. If there be any faculty which seems peculiar to the animal, it is certainly that of feeling. Being united to an organized substance, by ties which perhaps are known to God only, this soul composes with this substance a mixed being, a being which partakes of the nature of bodies, and of that of spirits. As a portion of matter, it is a machine which is admirable in its structure, and on which corporeal objects act mechanically. As a spiritual substance, it is affected at the presence of spiritual objects in a manner which does not seem to have any relation with that by which material substances act on each other. From the expression of external objects on the machine there results a certain motion in the machine. From this motion there follows a certain sensation in the soul, which is succeeded by the reaction of the spiritual substance on the corporeal; a reaction which manifests feeling from without, and which is the expression or sign of it.

The various sensations in the animal may be reduced to these two general classes, pleasure and pain, separated from each other by degrees which are frequently insensible, and issuing from the same origin. The expression of pleasure and pain is not alike in all animals; because the organs, by means whereof the soul manifests her sentiments, are not the same in all.

There are species in which feeling is manifested by a greater number of signs: more varied, more expressive. What expression, for instance, is there in the air, the motions, and the various attitudes of an ape, a horse, a dog, a cat There is not much less expression in birds than in quadrupeds. Fishes do not express themselves with the same clearness and energy; they form a dumb people, amongst whom the language by signs is little practised: but the extreme vivacity of their motions seems in part to compensate for their sterility of expression. Reptiles, shell-fish, and insects, which are still at a greater distance from us than fishes, express to us their feelings in a more obscure manner: but which, notwithstanding, we can conceive to certain degree, and often acknowledge to be very expressive.

On the contrary, we do not discover in the plant any Sign of feeling All in that seems to be purely mechanical. Its life appears to be less a life than a simple duration. We cultivate a plant or we destroy it, without experiencing any thing similar to what we meet with when we cherish an animal, or put it to death. We see the p1

shoot forth, grow, flourish and bud, as we perceive the hand of a clock to have passed over the points of the dial.

These considerations lead us to consider feeling as a character proper for distinguishing the vegetable from the animal.

27. Since then the faculty of feeling furnishes us but with a doubtful character for distinguishing the vegetable from the mal, which is that we should have recourse to with this view I think we have exhausted them all : we have at least treated of them all in a cursory manner. But we have not examined them all under their various aspects. There is one of them, which being considered in a certain point of view, may perhaps procure us what we have in vain searched for in the others.

We may now consider the position of those organs by which plants and animals receive their nourishment. These organs in plants are the roots and leaves. Both of them are furnished with pores, by means of which they pump in the nutricious juice. These pores terminate at small vessels, which transmit the juice into the inner part: or, rather, these pores are only the extremity of these vessels.

Animals have organs which are entirely analogous to roots and leaves ; I mean lacteal veins, or vessels which answer the same purpose. These veins open themselves in the intestines, and pump the chyle into them, which they convey into the channels of circulation. An animal is then an organized body, which is nourished by roots placed within him. A plant is an organized body, which receives its nourishment by means of roots placed on its outside.

Yet an animal which is nourished by pores distributed on its outside, renders this character ambiguous. The tape-worm seems such an animal. It forms in the intestines a great number of plaits: and sometimes entirely fills the capacity of this canal. Each of the rings that compose it, and whose length is rarely more than one or two lines is pierced with a small, round aperture, by which one may see the chyle issue, which the worm is full of, and which constitutes its principal nourishment. If this aperture is a kind of sucker, by the help of which the insect pumps the chyle that surrounds it, this method of nourishing itself varies but little from that of plants.

But without seeking very far for examples of animals that are nourished like plants, this is the case of all animals, whether oviparous or viviparous, whilst they are enclosed in the egg, or in the belly of their mother. The umbilical vessels may be considered in the egg or in the matrix, as roots which imbibe the nourishment. It is the same with respect to insects that multiply by shoots. Whilst the young one still adheres to its mother, it is nourished in a manner little different from that which is peculiar to branches. Animal grafts nearly resemble vegetable in this particular.

Lastly, the skin of the human body imbibes, like the leaves of plants the vapours with which the air abounds: and although men draw in much less nourishment by this means than vegetables, it is nevertheless true that their skin and leaves have, in regard to this circumstance, a great affinity to each other. Perhaps we may be able some time or other, to discover animals which are nourished by their skin only, as certain plants are by their leaves.

28. Do we then in vain seek for a peculiar character, whereby we ‘may distinguish the vegetable from the animal I perceive a new property which will perhaps furnish us with what we seek for.

A muscular fibre contracts of itself on the touch of all bodies, whether solid or liquid. This property is known by the name of irritability. It has nothing in it common to sensibility. The parts which are most sensible are not irritable, and the parts which are most irritable, are not sensible. Neither ought we to confound irritability with elasticity. A dry fibre is very elastic, and not at all irritable. Animals purely gelatinous are not elastic, and are notwithing very irritable, in short, the fibres of old men, though much more elastic than those of infants, are much less irritable.

We have seen that the heart is a real muscle. If we extract it from the breast it will continue to move till it has lost its natural heat. The heart of a viper or tortoise beats strongly for the space of twenty or thirty hours after the death of the animal. Water or air, when introduced into the ventricle, are sufficient to restore to the heart the motion it has lost.

The peristaltic motion of the intestines is likewise owing to their irritability. But the fbllowing is what we should not have guessed at. If they are plucked hastily from the lower belly, and cut into pieces, all these pieces will crawl like worms, and contract themselves on the slightest touch.

So that not only every muscle, but also every fragment of a muscle, and even every muscular fibre, contract themselves more or less on being touched by any body whatsoever, especially if that body be of a stimulating nature. And as the fibre contracts so it likewise recovers of itself, and this alternate exercise lasts for a time proportionable to the degree of irritability.

It is evident from all the experiments that the vital parts are the most irritable. The heart is the most irritable of all, and next to that, the intestines and diaphragm.

The nature of irritability is unknown: we only judge of it its effects. It probably resides in the elastic fluid which is interspersed between the lamellae of the fibre. The nerves are not irritable; but if a nerve be pricked, the muscle at which it terminates will contract itself. The nerves may then give motion to muscles; but they do not communicate an irritability to them which they are not possessed of themselves; they only put it into action. and thus they are ministers of the affections of the soul.

Irritability then seems to be what constitutes the vital Power is the animal ; and this prosperity has not been perceived in the vegetable. Is it not then the distinguishing character we seek for

Chapter 11 - Of the Industry of Animals