Thus much as to the progress of French knowledge respecting those parts of nature which are in themselves invisible, and of which we cannot tell whether they have a material existence, or whether they are mere conditions and properties of other bodies.[1065] The immense value of these discoveries, as increasing the number of known truths, is incontestable: but, at the same time, another class of discoveries was made, which, dealing more palpably with the visible world, and being also more easily understood, produced more immediate results, and, as I shall presently show, exercised a remarkable influence in strengthening that democratic tendency which accompanied the French Revolution. It is impossible, within the limits I have assigned to myself, to give anything like an adequate notion of the marvellous activity with which the French now pushed their researches into every department of the organic and inorganic world; still it is, I think, practicable to compress into a few pages such a summary of the more salient points as will afford the reader some idea of what was done by that generation of great thinkers which flourished in France during the latter half of the eighteenth century.

If we confine our view to the globe we inhabit, it must be allowed that chemistry and geology are the two sciences which not only offer the fairest promise, but already contain the largest generalizations. The reason of this will become clear, if we attend to the ideas on which these two great subjects are based. The idea of chemistry, is the study of composition;[1066] the idea of geology, is the study of position. The object of the first is, to learn the laws which govern the properties of matter; the object of the second is, to learn the laws which govern its locality. In chemistry, we experiment; in geology, we observe. In chemistry, we deal with the molecular arrangement of the smallest atoms;[1067] in geology, with the cosmological arrangement of the largest masses. Hence it is that the chemist by his minuteness, and the geologist by his grandeur, touch the two extremes of the material universe; and, starting from these opposite points, have, as I could easily prove, a constantly increasing tendency to bring under their own authority sciences which have at present an independent existence, and which, for the sake of a division of labour, it is still convenient to study separately; though it must be the business of philosophy, properly so called, to integrate them into a complete and effective whole. Indeed it is obvious, that if we knew all the laws of the composition of matter, and likewise all the laws of its position, we should likewise know all the changes of which matter is capable spontaneously, that is, when uninterrupted by the mind of man. Every phenomenon which any given substance presents must be caused either by something taking place in the substance, or else by something taking place out of it, but acting upon it; while what occurs within must be explicable by its own composition, and what occurs without must be due to its position in relation to the objects by which it is affected. This is an exhaustive statement of every possible contingency, and to one of these two classes of laws every thing must be referrible; even those mysterious forces which, whether they be emanations from matter, or whether they be merely properties of matter, must in an ultimate analysis depend either on the internal arrangement, or else on the external locality of their physical antecedents. However convenient, therefore, it may be, in the present state of our knowledge, to speak of vital principles, imponderable fluids, and elastic æthers, such terms can only be provisional, and are to be considered as mere names for that residue of unexplained facts, which it will be the business of future ages to bring under generalizations wide enough to cover and include the whole.

These ideas of composition and of position being thus the basis of all natural science, it is not surprising that chemistry and geology, which are their best, but still their insufficient representatives, should in modern times have made more progress than any other of the great branches of human knowledge. Although the chemists and geologists have not yet risen to the full height of their respective subjects,[1068] there are few things more curious than to note the way in which, during the last two generations, they have been rapidly expanding their views—encroaching on topics with which, at first sight, they appeared to have no concern—making other branches of inquiry tributary to their own—and collecting from every quarter that intellectual wealth which, long hidden in obscure corners, had been wasted in the cultivation of special and inferior pursuits. This, as being one of the great intellectual characteristics of the present age, I shall hereafter examine at considerable length; but what I have now to show is, that in these two vast sciences, which, though still very imperfect, must eventually be superior to all others, the first important steps were made by Frenchmen during the latter half of the eighteenth century.

That we owe to France the existence of chemistry as a science, will be admitted by everyone who uses the word science in the sense in which alone it ought to be understood, namely, as a body of generalizations so irrefragably true, that, though they may be subsequently covered by higher generalizations, they cannot be overthrown by them; in other words, generalizations which may be absorbed, but not refuted. In this point of view, there are in the history of chemistry only three great stages. The first stage was the destruction of the phlogistic theory, and the establishment, upon its ruins, of the doctrines of oxidation, combustion, and respiration. The second stage was the establishment of the principle of definite proportions, and the application to it of the atomic hypothesis. The third stage, above which we have not yet risen, consists in the union of chemical and electrical laws, and in the progress we are making towards fusing into one generalization their separate phenomena. Which of these three stages was in its own age the most valuable, is not now the question; but it is certain that the first of them was the work of Lavoisier, by far the greatest of the French chemists. Before him several important points had been cleared up by the English chemists, whose experiments ascertained the existence of bodies formerly unknown. The links, however, to connect the facts, were still wanting; and until Lavoisier entered the field, there were no generalizations wide enough to entitle chemistry to be called a science; or, to speak more properly, the only large generalization commonly received was that by Stahl, which the great Frenchman proved to be not only imperfect, but altogether inaccurate. A notice of the vast discoveries of Lavoisier will be found in many well-known books:[1069] it is enough to say, that he not only worked out the laws of the oxidation of bodies and of their combustion, but that he is the author of the true theory of respiration, the purely chemical character of which he first demonstrated; thus laying the foundation of those views respecting the functions of food, which the German chemists subsequently developed, and which, as I have proved in the second chapter of this Introduction, may be applied to solve some great problems in the history of Man. The merit of this was so obviously due to France, that though the system now established was quickly adopted in other countries,[1070] it received the name of the French chemistry.[1071] At the same time, the old nomenclature being full of old errors, a new one was required, and here again France took the initiative; since this great reformation was begun by four of her most eminent chemists, who flourished only a few years before the Revolution.[1072]

While one division of the French thinkers was reducing to order the apparent irregularities of chemical phenomena, another division of them was performing precisely the same service for geology. The first step towards popularizing this noble study was taken by Buffon, who, in the middle of the eighteenth century, broached a geological theory, which, though not quite original, excited attention by its eloquence, and by the lofty speculations with which he connected it.[1073] This was followed by the more special but still important labours of Rouelle, Desmarest, Dolomieu, and Montlosier, who, in less than forty years, effected a complete revolution in the ideas of Frenchmen, by familiarizing them with the strange conception, that the surface of our planet, even where it appears perfectly stable, is constantly undergoing most extensive changes. It began to be understood, that this perpetual flux takes place not only in those parts of nature which are obviously feeble and evanescent, but also in those which seem to possess every element of strength and permanence, such as the mountains of granite which wall the globe, and are the shell and encasement in which it is held. As soon as the mind became habituated to this notion of universal change, the time was ripe for the appearance of some great thinker, who should generalize the scattered observations, and form them into a science, by connecting them with some other department of knowledge, of which the laws, or, at all events, the empirical uniformities, had been already ascertained.

It was at this point, and while the inquiries of geologists, notwithstanding their value, were still crude and unsettled, that the subject was taken up by Cuvier, one of the greatest naturalists Europe has ever produced. A few others there are who have surpassed him in depth; but in comprehensiveness it would be hard to find his superior; and the immense range of his studies gave him a peculiar advantage in surveying the operations and dependencies of the external world.[1074] This remarkable man is unquestionably the founder of geology as a science, since he is not only the first who saw the necessity of bringing to bear upon it the generalizations of comparative anatomy, but he is also the first who actually, executing this great idea, succeeded in coördinating the study of the strata of the earth with the study of the fossil animals found in them.[1075] Shortly before his researches were published, many valuable facts had indeed been collected respecting the separate strata; the primary formations being investigated by the Germans, the secondary ones by the English.[1076] But these observations, notwithstanding their merit, were isolated; and they lacked that vast conception which gave unity and grandeur to the whole, by connecting inquiries concerning the inorganic changes of the surface of the globe with other inquiries concerning the organic changes of the animals the surface contained.

How completely this immense step is due to France, is evident not only from the part played by Cuvier, but also from the admitted fact, that to the French we owe our knowledge respecting tertiary strata,[1077] in which the organic remains are most numerous, and the general analogy to our present state is most intimate.[1078] Another circumstance may likewise be added, as pointing to the same conclusion. This is, that the first application of the principles of comparative anatomy to the study of fossil bones was also the work of a Frenchman, the celebrated Daubenton. Hitherto these bones had been the object of stupid wonder; some saying that they were rained from heaven, others saying that they were the gigantic limbs of the ancient patriarchs, men who were believed to be tall because they were known to be old.[1079] Such idle conceits were for ever destroyed by Daubenton, in a Memoir he published in 1762;[1080] with which, however, we are not now concerned, except that it is evidence of the state of the French mind, and is worth noting as a precursor of the discoveries of Cuvier.

By this union of geology and anatomy, there was first introduced into the study of nature a clear conception of the magnificent doctrine of universal change; while at the same time there grew up by its side a conception equally steady of the regularity with which the changes are accomplished, and of the undeviating laws by which they are governed. Similar ideas had no doubt been occasionally held in preceding ages; but the great Frenchmen of the eighteenth century were the first who applied them to the entire structure of the globe, and who thus prepared the way for that still higher view for which their minds were not yet ripe,[1081] but to which in our own time the most advanced thinkers are rapidly rising. For it is now beginning to be understood, that since every addition to knowledge affords fresh proof of the regularity with which all the changes of nature are conducted, we are bound to believe that the same regularity existed long before our little planet assumed its present form, and long before man trod the surface of the earth. We have the most abundant evidence that the movements incessantly occurring in the material world have a character of uniformity; and this uniformity is so clearly marked, that in astronomy, the most perfect of all the sciences, we are able to predict events many years before they actually happen; nor can any one doubt, that if on other subjects our science were equally advanced, our predictions would be equally accurate. It is, therefore, clear, that the burden of proof lies not on those who assert the eternal regularity of nature, but rather on those who deny it; and who set up an imaginary period, to which they assign an imaginary catastrophe, during which they say new laws were introduced and a new order established. Such gratuitous assumptions, even if they eventually turn out to be true, are in the present state of knowledge unwarrantable, and ought to be rejected, as the last remains of those theological prejudices by which the march of every science has in its turn been hindered. These and all analagous notions work a double mischief. They are mischievous, because they cripple the human mind by imposing limits to its inquiries; and above all they are mischievous, because they weaken that vast conception of continuous and uninterrupted law, which few indeed are able firmly to seize, but on which the highest generalizations of future science must ultimately depend.

It is this deep conviction, that changing phenomena have unchanging laws, and that there are principles of order to which all apparent disorder may be referred,—it is this, which, in the seventeenth century, guided in a limited field Bacon, Descartes, and Newton; which in the eighteenth century was applied to every part of the material universe; and which it is the business of the nineteenth century to extend to the history of the human intellect. This last department of inquiry we owe chiefly to Germany; for, with the single exception of Vico, no one even suspected the possibility of arriving at complete generalizations respecting the progress of man, until shortly before the French Revolution, when the great German thinkers began to cultivate this, the highest and most difficult of all studies. But the French themselves were too much occupied with physical science to pay attention to such matters;[1082] and speaking generally, we may say that, in the eighteenth century, each of the three leading nations of Europe had a separate part to play. England diffused a love of freedom; France, a knowledge of physical science; while Germany, aided in some degree by Scotland, revived the study of metaphysics, and created the study of philosophic history. To this classification some exceptions may of course be made; but that these were the marked characteristics of the three countries, is certain. After the death of Locke in 1704, and that of Newton in 1727, there was in England a singular dearth of great speculative thinkers; and this not because the ability was wanting, but because it was turned partly into practical pursuits, partly into political contests. I shall hereafter examine the causes of this peculiarity, and endeavour to ascertain the extent to which it has influenced the fortunes of the country. That the results were, on the whole, beneficial, I entertain no doubt; but they were unquestionably injurious to the progress of science, because they tended to divert it from all new truths, except those likely to produce obvious and practical benefit. The consequence was, that though the English made several great discoveries, they did not possess, during seventy years, a single man who took a really comprehensive view of the phenomena of nature; not one who could be compared with those illustrious thinkers who in France reformed every branch of physical knowledge. Nor was it until more than two generations after the death of Newton, that the first symptoms appeared of a remarkable reaction, which quickly displayed itself in nearly every department of the national intellect. In physics, it is enough to mention Dalton, Davy, and Young, each of whom was in his own field the founder of a new epoch; while on other subjects I can only just refer, first, to the influence of the Scotch school; and, secondly, to that sudden and well-deserved admiration for the German literature of which Coleridge was the principal exponent, and which infused into the English mind a taste for generalizations higher and more fearless than any hitherto known. The history of this vast movement, which began early in the nineteenth century, will be traced in the future volumes of this work: at present I merely notice it, as illustrating the fact, that until the movement began, the English, though superior to the French in several matters of extreme importance, were for many years inferior to them in those large and philosophic views, without which not only is the most patient industry of no avail, but even real discoveries lose their proper value, for want of such habits of generalization as would trace their connexion with each other, and consolidate their severed fragments into one vast system of complete and harmonious truth.

The interest attached to these inquiries has induced me to treat them at greater length than I had intended; perhaps at greater length than is suitable to the suggestive and preparatory character of this Introduction. But the extraordinary success with which the French now cultivated physical knowledge is so curious, on account of its connexion with the Revolution, that I must mention a few more of its most prominent instances: though, for the sake of brevity, I will confine myself to those three great divisions which, when put together, form what is called Natural History, and in all of which we shall see that the most important steps were taken in France during the latter half of the eighteenth century.

In the first of these divisions, namely, the department of zoology, we owe to the Frenchmen of the eighteenth century those generalizations which are still the highest this branch of knowledge has reached. Taking zoology in the proper sense of the term, it consists only of two parts, the anatomical part, which is its statics, and the physiological part, which is its dynamics: the first referring to the structure of animals; the other, to their functions.[1083] Both of these were worked out, nearly at the same time, by Cuvier and Bichat; and the leading conclusions at which they arrived, remain, after the lapse of sixty years, undisturbed in their essential points. In 1795, Cuvier laid down the great principle, that the study and classification of animals was to be, not as heretofore, with a view to external peculiarities, but with a view to internal organization; and that, therefore, no real advance could be made in our knowledge except by extending the boundaries of comparative anatomy.[1084] This step, simple as it now appears, was of immense importance, since by it zoology was at once rescued from the hands of the observer, and thrown into those of the experimenter: the consequence of which has been the attainment of that precision and accuracy of detail, which experiment alone can give, and which is every way superior to such popular facts as observation supplies. By thus indicating to naturalists the true path of inquiry, by accustoming them to a close and severe method, and by teaching them to despise those vague descriptions in which they had formerly delighted, Cuvier laid the foundation of a progress which, during the last sixty years, has surpassed the most sanguine expectations. This, then, is the real service rendered by Cuvier, that he overthrew the artificial system which the genius of Linnæus had raised up,[1085] and substituted in its place that far superior scheme which gave the freest scope to future inquiry; since, according to it, all systems are to be deemed imperfect and provisional so long as any thing remains to be learned respecting the comparative anatomy of the animal kingdom. The influence exercised by this great view was increased by the extraordinary skill and industry with which its proposer followed it out, and proved the practicability of his own precepts. His additions to our knowledge of comparative anatomy are probably more numerous than those made by any other man; but what has gained him most celebrity is, the comprehensive spirit with which he used what he acquired. Independently of other generalizations, he is the author of that vast classification of the whole animal kingdom into vertebrata, mollusca, articulata, and radiata;[1086] a classification which keeps its ground, and is one of the most remarkable instances of that large and philosophic spirit which France brought to bear upon the phenomena of the material world.[1087]

Great, however, as is the name of Cuvier, a greater still remains behind. I allude, of course, to Bichat, whose reputation is steadily increasing as our knowledge advances, and who, if we compare the shortness of his life with the reach and depth of his views, must be pronounced the most profound thinker and the most consummate observer by whom the organization of the animal frame has yet been studied.[1088] He wanted, indeed, that comprehensive knowledge for which Cuvier was remarkable; but though, on this account, his generalizations were drawn from a smaller surface, they were, on the other hand, less provisional: they were, I think, more complete, and certainly they dealt with more momentous topics. For the attention of Bichat was preëminently directed to the human frame[1089] in the largest sense of the word; his object being so to investigate the organization of man, as to rise, if possible, to some knowledge concerning the causes and nature of life. In this magnificent enterprise, considered as a whole, he failed; but what he effected in certain parts of it is so extraordinary, and has given such an impetus to some of the highest branches of inquiry, that I will briefly indicate his method, in order to compare it with that other method which, at the same moment, Cuvier adopted with immense success.

The important step taken by Cuvier was, that he insisted on the necessity of a comprehensive study of the organs of animals, instead of following the old plan of merely describing their habits and external peculiarities. This was a vast improvement, since, in the place of loose and popular observations, he substituted direct experiment, and hence introduced into zoology a precision formerly unknown.[1090] But Bichat, with a still keener insight, saw that even this was not enough. He saw that, each organ being composed of different tissues, it was requisite to study the tissues themselves, before we could learn the way in which, by their combinations, the organs are produced. This, like all really great ideas, was not entirely struck out by a single man; for the physiological value of the tissues had been recognized by three or four of the immediate predecessors of Bichat, such as Carmichael, Smyth, Bonn, Bordeu, and Fallopius. These inquirers, however, notwithstanding their industry, had effected nothing of much moment, since, though they collected several special facts, there was in their observations that want of harmony and that general incompleteness always characteristic of the labours of men who do not rise to a commanding view of the subject with which they deal.[1091]

It was under these circumstances that Bichat began those researches, which, looking at their actual and still more at their prospective results, are probably the most valuable contribution ever made to physiology by a single mind. In 1801, only a year before his death,[1092] he published his great work on anatomy, in which the study of the organs is made altogether subservient to the study of the tissues composing them. He lays it down, that the body of man consists of twenty-one distinct tissues, all of which, though essentially different, have in common the two great properties of extensibility and contractility.[1093] These tissues he, with indefatigable industry,[1094] subjected to every sort of examination; he examined them in different ages and diseases, with a view to ascertain the laws of their normal and pathological development.[1095] He studied the way each tissue is affected by moisture, air, and temperature; also the way in which their properties are altered by various chemical substances,[1096] and even their effect on the taste.[1097] By these means, and by many other experiments tending in the same direction, he took so great and sudden a step, that he is to be regarded not merely as an innovator on an old science, but rather as the creator of a new one.[1098] And although subsequent observers have corrected some of his conclusions, this has only been done by following his method; the value of which is now so generally recognized, that it is adopted by nearly all the best anatomists, who, differing in other points, are agreed as to the necessity of basing the future progress of anatomy on a knowledge of the tissues, the supreme importance of which Bichat was the first to perceive.[1099]

The methods of Bichat and of Cuvier, when put together, exhaust the actual resources of zoological science; so that all subsequent naturalists have been compelled to follow one of these two schemes; that is, either to follow Cuvier in comparing the organs of animals, or else to follow Bichat in comparing the tissues which compose the organs.[1100] And inasmuch as one comparison is chiefly suggestive of function, and the other comparison of structure, it is evident, that to raise the study of the animal world to the highest point of which it is capable, both these great plans are necessary; but if we ask which of the two plans, unaided by the other, is more likely to produce important results, the palm must, I think, be yielded to that proposed by Bichat. Certainly, if we look at the question as one to be decided by authority, a majority of the most eminent anatomists and physiologists now incline to the side of Bichat, rather than to that of Cuvier; while, as a matter of history, it may be proved that the reputation of Bichat has, with the advance of knowledge, increased more rapidly than that of his great rival. What, however, appears to me still more decisive, is, that the two most important discoveries made in our time respecting the classification of animals, are entirely the result of the method which Bichat suggested. The first discovery is that made by Agassiz, who, in the course of his ichthyological researches, was led to perceive that the arrangement by Cuvier according to organs, did not fulfil its purpose in regard to fossil fishes, because in the lapse of ages the characteristics of their structure were destroyed.[1101] He, therefore, adopted the only other remaining plan, and studied the tissues, which, being less complex than the organs, are oftener found intact. The result was the very remarkable discovery, that the tegumentary membrane of fishes is so intimately connected with their organization, that if the whole of a fish has perished except this membrane, it is practicable, by noting its characteristics, to reconstruct the animal in its most essential parts. Of the value of this principle of harmony, some idea may be formed from the circumstance, that on it Agassiz has based the whole of that celebrated classification, of which he is the sole author, and by which fossil ichthyology has for the first time assumed a precise and definite shape.[1102]

The other discovery, of which the application is much more extensive, was made in exactly the same way. It consists of the striking fact, that the teeth of each animal have a necessary connexion with the entire organization of its frame; so that, within certain limits, we can predict the organization by examining the tooth. This beautiful instance of the regularity of the operations of nature was not known until more than thirty years after the death of Bichat, and it is evidently due to the prosecution of that method which he sedulously inculcated. For the teeth never having been properly examined in regard to their separate tissues, it was believed that they were essentially devoid of structure, or, as some thought, were simply a fibrous texture.[1103] But by minute microscopic investigations, it has been recently ascertained that the tissues of the teeth are strictly analogous to those of other parts of the body;[1104] and that the ivory, or dentine, as it is now called,[1105] is highly organized; that it, as well as the enamel, is cellular, and is, in fact, a development of the living pulp. This discovery, which, to the philosophic anatomist, is pregnant with meaning, was made about 1838; and though the preliminary steps were taken by Purkinjé, Retzius, and Schwann, the principal merit is due to Nasmyth and Owen,[1106] between whom it is disputed, but whose rival claims we are not here called upon to adjust.[1107] What I wish to observe is, that the discovery is similar to that which we owe to Agassiz; similar in the method by which it was worked out, and also in the results which have followed from it. Both are due to a recognition of the fundamental maxim of Bichat, that the study of organs must be subordinate to the study of tissues, and both have supplied the most valuable aid to zoological classification. On this point, the service rendered by Owen is incontestable, whatever may be thought of his original claims. This eminent naturalist has, with immense industry, applied the discovery to all vertebrate animals; and in an elaborate work, specially devoted to the subject, he has placed beyond dispute the astonishing fact, that the structure of a single tooth is a criterion of the nature and organization of the species to which it belongs.[1108]

Whoever has reflected much on the different stages through which our knowledge has successively passed, must, I think, be led to the conclusion, that while fully recognizing the great merit of these investigators of the animal frame, our highest admiration ought to be reserved not for those who make the discoveries, but rather for those who point out how the discoveries are to be made.[1109] When the true path of inquiry has once been indicated, the rest is comparatively easy. The beaten highway is always open; and the difficulty is, not to find those who will travel the old road, but those who will make a fresh one. Every age produces in abundance men of sagacity and of considerable industry, who, while perfectly competent to increase the details of a science, are unable to extend its distant boundaries. This is because such extension must be accompanied by a new method,[1110] which, to be valuable as well as new, supposes on the part of its suggester, not only a complete mastery over the resources of his subject, but also the possession of originality and comprehensiveness,—the two rarest forms of human genius. In this consists the real difficulty of every great pursuit. As soon as any department of knowledge has been generalized into laws, it contains, either in itself or in its applications, three distinct branches; namely, inventions, discoveries, and method. Of these, the first corresponds to art; the second to science; and the third to philosophy. In this scale, inventions have by far the lowest place, and minds of the highest order are rarely occupied by them. Next in the series come discoveries; and here the province of intellect really begins, since here the first attempt is made to search after truth on its own account, and to discard those practical considerations to which inventions are of necessity referred. This is science properly so called; and how difficult it is to reach this stage, is evident from the fact, that all half-civilized nations have made many great inventions, but no great discoveries. The highest, however, of all the three stages, is the philosophy of method, which bears the same relation to science that science bears to art. Of its immense, and indeed supreme importance, the annals of knowledge supply abundant evidence; and for want of it, some very great men have effected absolutely nothing, consuming their lives in fruitless industry, not because their labour was slack, but because their method was sterile. The progress of every science is affected more by the scheme according to which it is cultivated, than by the actual ability of the cultivators themselves. If they who travel in an unknown country, spend their force in running on the wrong road, they will miss the point at which they aim, and perchance may faint and fall by the way. In that long and difficult journey after truth, which the human mind has yet to perform, and of which we in our generation can only see the distant prospect, it is certain that success will depend not on the speed with which men hasten in the path of inquiry, but rather on the skill with which that path is selected for them by those great and comprehensive thinkers, who are as the lawgivers and founders of knowledge; because they supply its deficiencies, not by investigating particular difficulties, but by establishing some large and sweeping innovation, which opens up a new vein of thought, and creates fresh resources, which it is left for their posterity to work out and apply.

It is from this point of view that we are to rate the value of Bichat, whose works, like those of all men of the highest eminence,—like those of Aristotle, Bacon, and Descartes,—mark an epoch in the history of the human mind; and as such, can only be fairly estimated by connecting them with the social and intellectual condition of the age in which they appeared. This gives an importance and a meaning to the writings of Bichat, of which few indeed are fully aware. The two greatest recent discoveries respecting the classification of animals are, as we have just seen, the result of his teaching; but his influence has produced other effects still more momentous. He, aided by Cabanis, rendered to physiology the incalculable service, of preventing it from participating in that melancholy reaction to which France was exposed early in the nineteenth century. This is too large a subject to discuss at present; but I may mention, that when Napoleon, not from feelings of conviction, but for selfish purposes of his own, attempted to restore the power of ecclesiastical principles, the men of letters, with disgraceful subserviency, fell into his view; and there began a marked decline in that independent and innovating spirit, with which during fifty years the French had cultivated the highest departments of knowledge. Hence that metaphysical school arose, which, though professing to hold aloof from theology, was intimately allied with it; and whose showy conceits form, in their ephemeral splendour, a striking contrast to the severer methods followed in the preceding generation.[1111] Against this movement, the French physiologists have, as a body, always protested; and it may be clearly proved that their opposition, which even the great abilities of Cuvier were unable to win over, is partly due to the impetus given by Bichat, in enforcing in his own pursuit the necessity of rejecting those assumptions by which metaphysicians and theologians seek to control every science. As an illustration of this I may mention two facts worthy of note. The first is, that in England, where during a considerable period the influence of Bichat was scarcely felt, many, even of our eminent physiologists, have shown a marked disposition to ally themselves with the reactionary party; and have not only opposed such novelties as they could not immediately explain, but have degraded their own noble science by making it a handmaid to serve the purposes of natural theology. The other fact is, that in France the disciples of Bichat have, with scarcely an exception, rejected the study of final causes, to which the school of Cuvier still adheres: while as a natural consequence, the followers of Bichat are associated in geology with the doctrine of uniformity; in zoology, with that of the transmutation of species; and in astronomy, with the nebular hypothesis: vast and magnificent schemes, under whose shelter the human mind seeks an escape from that dogma of interference, which the march of knowledge every where reduces, and the existence of which is incompatible with those conceptions of eternal order, towards which, during the last two centuries, we have been constantly tending.

These great phenomena, which the French intellect presents, and of which I have only sketched a rapid outline, will be related with suitable detail in the latter part of this work, when I shall examine the present condition of the European mind, and endeavour to estimate its future prospects. To complete, however, our appreciation of Bichat, it will be necessary to take notice of what some consider the most valuable of all his productions, in which he aimed at nothing less than an exhaustive generalization of the functions of life. It appears, indeed, to me, that in many important points Bichat here fell short; but the work itself still stands alone, and is so striking an instance of the genius of the author, that I will give a short account of its fundamental views.

Life considered as a whole has two distinct branches;[1112] one branch being characteristic of animals, the other of vegetables. That which is confined to animals is called animal life; that which is common both to animals and vegetables is called organic life. While, therefore, plants have only one life, man has two distinct lives, which are governed by entirely different laws, and which, though intimately connected, constantly oppose each other. In the organic life, man exists solely for himself; in the animal life he comes in contact with others. The functions of the first are purely internal, those of the second are external. His organic life is limited to the double process of creation and destruction: the creative process being that of assimilation, as digestion, circulation, and nutrition; the destructive process being that of excretion, such as exhalation and the like. This is what man has in common with plants; and of this life he, when in a natural state, is unconscious. But the characteristic of his animal life is consciousness, since by it he is made capable of moving, of feeling, of judging. By virtue of the first life he is merely a vegetable; by the addition of the second he becomes an animal.

If now we look at the organs by which in man the functions of these two lives are carried on, we shall be struck by the remarkable fact, that the organs of his vegetable life are very irregular, those of his animal life very symmetrical. His vegetative, or organic, life is conducted by the stomach, the intestines, and the glandular system in general, such as the liver and the pancreas; all of which are irregular, and admit of the greatest variety of form and development, without their functions being seriously disturbed. But in his animal life the organs are so essentially symmetrical, that a very slight departure from the ordinary type impairs their action.[1113] Not only the brain, but also the organs of sense, as the eyes, the nose, the ears, are perfectly symmetrical; and they as well as the other organs of animal life, as the feet and hands, are double, presenting on each side of the body two separate parts which correspond with each other, and produce a symmetry unknown to our vegetative life, the organs of which are, for the most part, merely single, as in the stomach, liver, pancreas, and spleen.[1114]

From this fundamental difference between the organs of the two lives, there have arisen several other differences of great interest. Our animal life being double, while our organic life is single, it becomes possible for the former life to take rest, that is, stop part of its functions for a time, and afterwards renew them. But in organic life, to stop is to die. The life, which we have in common with vegetables, never sleeps; and if its movements entirely cease only for a single instant, they cease for ever. That process by which our bodies receive some substances and give out others, admits of no interruption; it is, by its nature, incessant, because, being single, it can never receive supplementary aid. The other life we may refresh, not only in sleep, but even when we are awake. Thus we can exercise the organs of movement while we rest the organs of thought; and it is even possible to relieve a function while we continue to employ it, because, our animal life being double, we are able for a short time, in case of one of its parts being fatigued, to avail ourselves of the corresponding part; using, for instance, a single eye or a single arm, in order to rest the one which circumstances may have exhausted; an expedient which the single nature of organic life entirely prevents.[1115]

Our animal life being thus essentially intermittent, and our organic life being essentially continuous,[1116] it has necessarily followed that the first is capable of an improvement of which the second is incapable. There can be no improvement without comparison, since it is only by comparing one state with another that we can rectify previous errors, and avoid future ones. Now, our organic life does not admit of such comparison, because, being uninterrupted, it is not broken into stages, but when unchequered by disease, runs on in dull monotony. On the other hand, the functions of our animal life, such as thought, speech, sight, and motion, cannot be long exercised without rest; and as they are constantly suspended, it becomes practicable to compare them, and, therefore, to improve them. It is by possessing this resource that the first cry of the infant gradually rises into the perfect speech of the man, and the unformed habits of early thought are ripened into that maturity which nothing can give but a long series of successive efforts.[1117] But our organic life, which we have in common with vegetables, admits of no interruption, and consequently of no improvement. It obeys its own laws; but it derives no benefit from that repetition to which animal life is exclusively indebted. Its functions, such as nutrition and the like, exist in man several months before he is born, and while, his animal life not having yet begun, the faculty of comparison, which is the basis of improvement, is impossible.[1118] And although, as the human frame increases in size, its vegetative organs become larger, it cannot be supposed that their functions really improve, since, in ordinary cases, their duties are performed as regularly and as completely in childhood as in middle age.[1119]

Thus it is, that although other causes conspire, it may be said that the progressiveness of animal life is due to its intermittence; the unprogressiveness of organic life to its continuity. It may, moreover, be said, that the intermittence of the first life results from the symmetry of its organs, while the continuity of the second life results from their irregularity. To this wide and striking generalization, many objections may be made, some of them apparently insuperable; but that it contains the germs of great truths I entertain little doubt, and, at all events, it is certain that the method cannot be too highly praised, for it unites the study of function and structure with that of embryology, of vegetable physiology, of the theory of comparison, and of the influence of habit; a vast and magnificent field, which the genius of Bichat was able to cover, but of which, since him, neither physiologists nor metaphysicians have even attempted a general survey.

This stationary condition, during the present century, of a subject of such intense interest, is a decisive proof of the extraordinary genius of Bichat; since, notwithstanding the additions made to physiology, and to every branch of physics connected with it, nothing has been done at all comparable to that theory of life which he, with far inferior resources, was able to construct. This stupendous work he left, indeed, very imperfect; but even in its deficiencies we see the hand of the great master, whom, on his own subject, no one has yet approached. His essay on life may well be likened to those broken fragments of ancient art, which, imperfect as they are, still bear the impress of the inspiration which gave them birth, and present in each separate part that unity of conception which to us makes them a complete and living whole.

From the preceding summary of the progress of physical knowledge, the reader may form some idea of the ability of those eminent men who arose in France during the latter half of the eighteenth century. To complete the picture, it is only necessary to examine what was done in the two remaining branches of natural history, namely, botany and mineralogy, in both of which the first great steps towards raising each study to a science were taken by Frenchmen a few years before the Revolution.

In botany, although our knowledge of particular facts has, during the last hundred years, rapidly increased,[1120] we are only possessed of two generalizations wide enough to be called laws of nature. The first generalization concerns the structure of plants; the other concerns their physiology. That concerning their physiology is the beautiful morphological law, according to which the different appearance of the various organs arises from arrested development: the stamens, pistils, corolla, calyx, and bracts being simple modifications or successive stages of the leaf. This is one of many valuable discoveries we owe to Germany; it being made by Göthe late in the eighteenth century.[1121] With its importance every botanist is familiar; while to the historian of the human mind it is peculiarly interesting, as strengthening that great doctrine of development, towards which the highest branches of knowledge are now hastening, and which, in the present century, has been also carried into one of the most difficult departments of animal physiology.[1122]

But the most comprehensive truth with which we are acquainted respecting plants, is that which includes the whole of their general structure; and this we learnt from those great Frenchmen who, in the latter half of the eighteenth century, began to study the external world. The first steps were taken directly after the middle of the century, by Adanson, Duhamel de Monceau, and, above all, Desfontaines; three eminent thinkers, who proved the practicability of a natural method hitherto unknown, and of which even Ray himself had only a faint perception.[1123] This, by weakening the influence of the artificial system of Linnæus,[1124] prepared the way for an innovation more complete than has been effected in any other branch of knowledge. In the very year in which the Revolution occurred, Jussieu put forward a series of botanical generalizations, of which the most important are all intimately connected, and still remain the highest this department of inquiry has reached.[1125] Among these, I need only mention the three vast propositions which are now admitted to form the basis of vegetable anatomy. The first is, that the vegetable kingdom, in its whole extent, is composed of plants either with one cotyledon, or with two cotyledons, or else with no cotyledon at all. The second proposition is, that this classification, so far from being artificial, is strictly natural; since it is a law of nature, that plants having one cotyledon are endogenous, and grow by additions made to the centre of their stems, while, on the other hand, plants having two cotyledons are exogenous, and are compelled to grow by additions made, not to the centre of their stems, but to the circumference.[1126] The third proposition is, that when plants grow at their centre, the arrangement of the fruit and leaves is threefold; when, however, they grow at the circumference, it is nearly always fivefold.[1127]

This is what was effected by the Frenchmen of the eighteenth century for the vegetable kingdom:[1128] and if we now turn to the mineral kingdom, we shall find that our obligations to them are equally great. The study of minerals is the most imperfect of the three branches of natural history, because, notwithstanding its apparent simplicity, and the immense number of experiments which have been made, the true method of investigation has not yet been ascertained; it being doubtful whether mineralogy ought to be subordinated to the laws of chemistry, or to those of crystallography, or whether both sets of laws will have to be considered.[1129] At all events it is certain that, down to the present time, chemistry has shown itself unable to reduce mineralogical phenomena; nor has any chemist, possessing sufficient powers of generalization, attempted the task except Berzelius; and most of his conclusions were overthrown by the splendid discovery of isomorphism, for which, as is well known, we are indebted to Mitscherlich, one of the many great thinkers Germany has produced.[1130]

Although the chemical department of mineralogy is in an unformed and indeed anarchical condition, its other department, namely, crystallography, has made great progress; and here again the earliest steps were taken by two Frenchmen, who lived in the latter half of the eighteenth century. About 1760, Romé De Lisle[1131] set the first example of studying crystals, according to a scheme so large as to include all the varieties of their primary forms, and to account for their irregularities, and the apparent caprice with which they were arranged. In this investigation he was guided by the fundamental assumption, that what is called an irregularity, is in truth perfectly regular, and that the operations of nature are invariable.[1132] Scarcely had this great idea been applied to the almost innumerable forms into which minerals crystallize, when it was followed up with still larger resources by Haüy, another eminent Frenchman.[1133] This remarkable man achieved a complete union between mineralogy and geometry; and, bringing the laws of space to bear on the molecular arrangements of matter, he was able to penetrate into the intimate structure of crystals.[1134] By this means, he succeeded in proving that the secondary forms of all crystals are derived from their primary forms by a regular process of decrement;[1135] and that, when a substance is passing from a liquid to a solid state, its particles are compelled to cohere, according to a scheme which provides for every possible change, since it includes even those subsequent layers which alter the ordinary type of the crystal, by disturbing its natural symmetry.[1136] To ascertain that such violations of symmetry are susceptible of mathematical calculation, was to make a vast addition to our knowledge; but what seems to me still more important is, that it indicates an approach to the magnificent idea, that every thing which occurs is regulated by law, and that confusion and disorder are impossible.[1137] For, by proving that even the most uncouth and singular forms of minerals are the natural results of their antecedents, Haüy laid the foundation of what may be called the pathology of the inorganic world. However paradoxical such a notion may seem, it is certain that symmetry is to crystals what health is to animals; so that an irregularity of shape in the first, corresponds with an appearance of disease in the second.[1138] When, therefore, the minds of men became familiarized with the great truth, that in the mineral kingdom there is, properly speaking, no irregularity, it became more easy for them to grasp the still higher truth, that the same principle holds good of the animal kingdom, although, from the superior complexity of the phenomena, it will be long before we can arrive at an equal demonstration. But, that such a demonstration is possible, is the principle upon which the future progress of all organic, and indeed of all mental science, depends. And it is very observable, that the same generation which established the fact, that the apparent aberrations presented by minerals are strictly regular, also took the first steps towards establishing the far higher fact, that the aberrations of the human mind are governed by laws as unfailing as those which determine the condition of inert matter. The examination of this would lead to a digression foreign to my present design; but I may mention that, at the end of the century, there was written in France the celebrated treatise on insanity, by Pinel; a work remarkable in many respects, but chiefly in this, that in it the old notions respecting the mysterious and inscrutable character of mental disease are altogether discarded:[1139] the disease itself is considered as a phenomenon inevitably occurring under certain given conditions, and the foundation laid for supplying another link in that vast chain of evidence which connects the material with the immaterial, and thus uniting mind and matter into a single study, is now preparing the way for some generalization, which, being common to both, shall serve as a centre round which the disjointed fragments of our knowledge may safely rally.

These were the views which, during the latter half of the eighteenth century, began to dawn upon French thinkers. The extraordinary ability and success with which these eminent men cultivated their respective sciences, I have traced at a length greater that I had intended, but still very inadequate to the importance of the subject. Enough, however, has been brought forward, to convince the reader of the truth of the proposition I wished to prove; namely, that the intellect of France was, during the latter half of the eighteenth century, concentrated upon the external world with unprecedented zeal, and thus aided that vast movement, of which the Revolution itself was merely a single consequence. The intimate connexion between scientific progress and social rebellion, is evident from the fact, that both are suggested by the same yearning after improvement, the same dissatisfaction with what has been previously done, the same restless, prying, insubordinate, and audacious spirit. But in France this general analogy was strengthened by the curious circumstances I have already noticed, by virtue of which, the activity of the country was, during the first half of the century, directed against the church rather than against the state; so that in order to complete the antecedents of the Revolution, it was necessary that, in the latter half of the century, the ground of attack should be shifted. This is precisely what was done by the wonderful impetus given to every branch of natural science. For, the attention of men being thus steadily fixed upon the external world, the internal fell into neglect; while, as the external corresponds to the state, and the internal to the church, it was part of the same intellectual development, that the assailers of the existing fabric should turn against political abuses the energy which the preceding generation had reserved for religious ones.

Thus it was that the French Revolution, like every great revolution the world has yet seen, was preceded by a complete change in the habits and associations of the national intellect. But besides this, there was also taking place, precisely at the same time, a vast social movement, which was intimately connected with the intellectual movement, and indeed formed part of it, in so far as it was followed by similar results and produced by similar causes. The nature of this social revolution I shall examine only very briefly, because in a future volume it will be necessary to trace its history minutely, in order to illustrate the slighter but still remarkable changes which in the same period were going on in English society.

In France, before the Revolution, the people, though always very social, were also very exclusive. The upper classes, protected by an imaginary superiority, looked with scorn upon those whose birth or titles were unequal to their own. The class immediately below them copied and communicated their example, and every order in society endeavoured to find some fanciful distinction which should guard them from the contamination of their inferiors. The only three real sources of superiority,—the superiority of morals, of intellect, and of knowledge,—were entirely overlooked in this absurd scheme; and men became accustomed to pride themselves not on any essential difference, but on those inferior matters, which, with extremely few exceptions, are the result of accident, and therefore no test of merit.[1140]

The first great blow to this state of things, was the unprecedented impulse given to the cultivation of physical science. Those vast discoveries which were being made, not only stimulated the intellect of thinking men, but even roused the curiosity of the more thoughtless parts of society. The lectures of chemists, of geologists, of mineralogists, and of physiologists, were attended by those who came to wonder, as well as by those who came to learn. In Paris, the scientific assemblages were crowded to overflowing.[1141] The halls and amphitheatres in which the great truths of nature were expounded, were no longer able to hold their audience, and in several instances it was found necessary to enlarge them.[1142] The sittings of the Academy, instead of being confined to a few solitary scholars, were frequented by every one whose rank or influence enabled them to secure a place.[1143] Even women of fashion, forgetting their usual frivolity, hastened to hear discussions on the composition of a mineral, on the discovery of a new salt, on the structure of plants, on the organization of animals, on the properties of the electric fluid.[1144] A sudden craving after knowledge seemed to have smitten every rank. The largest and the most difficult inquiries found favour in the eyes of those whose fathers had hardly heard the names of the sciences to which they belonged. The brilliant imagination of Buffon made geology suddenly popular; the same thing was effected for chemistry by the eloquence of Fourcroy, and for electricity by Nollet; while the admirable expositions of Lalande caused astronomy itself to be generally cultivated. In a word, it is enough to say, that during the thirty years preceding the Revolution, the spread of physical science was so rapid, that in its favour the old classical studies were despised;[1145] it was considered the essential basis of a good education, and some slight acquaintance with it was deemed necessary for every class, except those who were obliged to support themselves by their daily labour.[1146]

The results produced by this remarkable change are very curious, and from their energy and rapidity were very decisive. As long as the different classes confined themselves to pursuits peculiar to their own sphere, they were encouraged to preserve their separate habits; and the subordination, or, as it were, the hierarchy, of society was easily maintained. But when the members of the various orders met in the same place with the same object, they became knit together by a new sympathy. The highest and most durable of all pleasures, the pleasure caused by the perception of fresh truths, was now a great link, which banded together those social elements that were formerly wrapped up in the pride of their own isolation. Besides this, there was also given to them not only a new pursuit, but also a new standard of merit. In the amphitheatre and the lecture-room, the first object of attention is the professor and the lecturer. The division is between those who teach and those who learn. The subordination of ranks makes way for the subordination of knowledge.[1147] The petty and conventional distinctions of fashionable life are succeeded by those large and genuine distinctions, by which alone man is really separated from man. The progress of the intellect supplies a new object of veneration; the old worship of rank is rudely disturbed, and its superstitious devotees are taught to bow the knee before what to them is the shrine of a strange god. The hall of science is the temple of democracy. Those who come to learn, confess their own ignorance, abrogate in some degree their own superiority, and begin to perceive that the greatness of men has no connexion with the splendour of their titles, or the dignity of their birth; that it is not concerned with their quarterings, their escutcheons, their descents, their dexter-chiefs, their sinister-chiefs, their chevrons, their bends, their azures, their gules, and the other trumperies of their heraldry; but that it depends upon the largeness of their minds, the powers of their intellect, and the fullness of their knowledge.

These were the views which, in the latter half of the eighteenth century, began to influence those classes which had long been the undisputed masters of society.[1148] And what shows the strength of this great movement is, that it was accompanied by other social changes, which, though in themselves apparently trifling, become full of meaning when taken in connexion with the general history of the time.