Chapter II: Preface: By the Author (1)

The work which I now offer to the public, will appear to them new, I trust, in three points of view; 1st, in the _plan_ that has been adopted; 2d, in most of the _facts_ which it contains; and 3d, in the _principles_ which constitute its doctrine.

1st. The _plan_ consists in considering separately and presenting with all their attributes, each of the simple systems, which, by their different combinations, form our organs. The basis of this plan is anatomical, but the details that it embraces belong also to medicine and physiology. It has nothing in common, but the name, with what has been lately advanced upon the anatomy of systems; my Treatise on the Membranes alone gives an outline of it.

2d. The _facts_ and observations in this work, in addition to what is already known, form a very numerous series. I shall not give an analysis of them; the reader will supply it, how little soever he may know of works on Anatomy and Physiology. Experiments on living animals, trials with different reagents on organized textures,[1] dissection, examinations after death, observations upon man in health and disease, these are sources whence I have drawn them, and they are the sources of nature. I have not, however, neglected authors, those especially who make the science of the animal economy a science of facts and experiments.

[1] I have in this and every other instance translated the French word _tissu_ by the English word _texture_. I know many writers have adopted the French term, but I think it unnecessary, to say the least, to employ a foreign word, when one of our own language can be used with quite as much precision. _Tr._

I will make but one remark upon the experiments contained in this work; amongst them will be found a series upon the simple textures, which I subjected successively to desiccation, putrefaction, maceration, ebullition, stewing, and to the action of the acids and the alkalies. It will be easily seen, that it was not the object of these experiments to determine the composition, or ascertain the different elements, and consequently give a chemical analysis of simple textures; for this purpose they would have been insufficient; but their object was to establish the distinctive characters of these simple textures, to show that each has a peculiar organization, as each has a peculiar life, and to prove by the different results which they gave, that the division which I have adopted is not speculative, but that it rests upon the diversity of their intimate structure. The different re-agents, which I used, were only to assist me where the scalpel was insufficient, and on this account, therefore, I presume these experiments will have some influence upon Anatomy.

3d. The general _doctrine_ of this work has not precisely the character of any of those which have prevailed in medicine. Opposed to that of Boerhaave, it differs from that of Stahl and those authors who, like him, refer every thing in the living economy, to a single principle, purely speculative, ideal, and imaginary, whether designated by the name of _soul_, _vital principle_, or _archeus_. The general doctrine of this work consists in analyzing with precision the properties of living bodies, in showing that every physiological phenomenon is ultimately referable to these properties considered in their natural state; that every pathological phenomenon derives from them augmentation, diminution, or alteration; that every therapeutic phenomenon has for its principle the restoration of the part to the natural type, from which it has been changed; in determining with precision the cases in which each property is brought into action; in distinguishing accurately in physiology as well as in medicine, that which is derived from one, and that which flows from others; in ascertaining by rigorous induction the natural and morbific phenomena which the animal properties produce, and those which are derived from the organic; and in pointing out when the animal sensibility and contractility are brought into action, and when the organic sensibility and the sensible or insensible contractility. We shall be easily convinced upon reflection, that we cannot precisely estimate the immense influence of the vital properties in the physiological sciences, before we have considered these properties in the point of view in which I have presented them. It will be said, perhaps, that this manner of viewing them is still a theory; I will answer, that it is a theory like that which shows in the physical sciences, gravity, elasticity, affinity, &c. as the primitive principles of the facts observed in these sciences. The relation of these properties as causes to the phenomena as effects, is an axiom so well known in physics, chemistry, astronomy, &c. at the present day, that it is unnecessary to repeat it. If this work establishes an analogous axiom in the physiological sciences, its object will be attained.

GENERAL OBSERVATIONS.

There are in nature two classes of beings, two classes of properties, and two classes of sciences. The beings are either organic or inorganic, the properties vital or non-vital, and the sciences physiological or physical. Animals and vegetables are organic—minerals are inorganic. Sensibility and contractility are vital properties; gravity, elasticity, affinity, &c. are non-vital properties. Animal and vegetable physiology, and medicine form the physiological sciences; astronomy, physics, chemistry, &c. are the physical sciences. These two classes of sciences have relation only to different phenomena; there are two other classes that correspond to these, which relate to the internal and external forms of bodies and their description. Botany, anatomy, and zoology, are the sciences of organic bodies; mineralogy, &c. of the inorganic. The first will occupy us, and we shall fix our attention especially upon the relations of living bodies with one another, and their relations with those that do not live.

I. _General remarks upon physiological and physical sciences._

The differences between these sciences are derived essentially from those existing between the properties that preside over the phenomena, which are the object of each class of sciences. So immense is the influence of these properties, that they are the principle of all phenomena; whether we examine those of astronomy, of hydraulics, of dynamics, of optics, of acoustics, &c. we shall finally arrive by a connexion of causes to gravity, to elasticity, &c. as the end of our researches. So the vital property is the primum mobile to which we must ascend, whether we consider the phenomena of respiration, of digestion, of secretion, circulation, inflammation, fevers, &c.—In giving existence to every body, nature has imprinted upon it a certain number of properties, that particularly characterize it, and by means of which it contributes in its own manner, to all the phenomena that are developed, succeed, and continually connect themselves in the universe. Cast your eyes upon that which surrounds you; turn them upon objects the most distant; whether, aided by the telescope, they examine those that swim in space, or, armed with the microscope, they enter the world of those, whose minuteness almost evades our view, every where you will find on one side physical properties, on the other vital properties, brought into action; every where you will see inert bodies gravitating upon each other, and reciprocally attracting; living bodies gravitate also, but above all they feel, and possess a motion which they owe only to themselves.

These properties are so inherent in bodies, that we cannot conceive of their existence without them. They constitute their essence and their attribute. To exist and to enjoy them are two things inseparable. Suppose that of a sudden they are deprived of them; instantly all the phenomena of nature cease, and matter alone exists. Chaos was only matter without properties; to create the universe, God endowed it with gravity, elasticity, affinity, &c. and to a part he gave sensibility and contractility.

This mode of considering the vital and physical properties, sufficiently shews, that we cannot ascend above them in our explanations, that they afford the principles, and that these explanations are to be deduced from them as consequences. The physical sciences, as well as the physiological, then, are composed of two things; 1st. the study of phenomena, which are effects; 2d. the research into the connexions that exist between them and the physical or vital properties, which are the causes.

For a long time these sciences have not been so considered; every fact that was observed, was made the subject of a particular hypothesis. Newton was the first to remark, that however variable the physical phenomena were, they could all be referred to a certain number of principles. He analyzed these principles and found that attraction enjoyed the most important place among them. Attracted by each other and by their sun, the planets describe their eternal courses; attracted to the centre of our system, the waters, air, stones, &c. move or tend to move towards it: it is truly a sublime idea, and one that serves as the basis to all the physical sciences. Let us render homage to Newton; he was the first who discovered the secret of the Creator, viz. A simplicity of causes reconciled with a multiplicity of effects.

The epoch of this great man was the most remarkable of human wisdom. Since that period, we have had principles from which we draw facts as consequences. This epoch, so advantageous to the physical sciences, was nothing to the physiological; what do I say? it retarded their progress. Mankind soon saw nothing but attraction and impulse in the vital phenomena.

Boerhaave, though brilliant in genius, suffered himself to be dazzled by a system which misled all the men of learning of his age, and which made a revolution in the physiological sciences, that may be compared to that effected in the physical, by the vortices of Descartes. The plausibility of the theory and the celebrated name of its author, gave to this revolution an empire, which, though rotten in its foundation, was not easily overthrown.

Stahl, less brilliant than profound, rich in the means that convince, though deficient in those that please, formed for the physiological sciences an epoch more worthy of notice than that of Boerhaave. He perceived the discordance between the physical laws and the functions of animals; this was the first step towards the discovery of the vital laws, but he did not discover them. The soul was to him every thing in the phenomena of life; it was much to neglect attraction and impulse. Stahl perceived that these were not true, but the truth escaped him. Many authors, following his steps, have referred to a single principle, differently denominated by each, all the vital phenomena. This, called the vital principle by Barthez, archeus by Van Helmont, &c. is a speculation that has no more reality than that which would refer to a single principle all the physical phenomena. Among these we know that some are derived from gravity, some from elasticity, others from affinity, &c. The same in the living economy, some are derived from sensibility, others from contractility.

Unknown to the ancients, the laws of life have begun to be understood during the last age only. Stahl had already remarked the tonic motions, but he did not generalize their influence. Haller was engaged particularly with sensibility and irritability; but in limiting one to the nervous system, and the other to the muscular, this great man did not consider them in the correct point of view; he made them almost insulated properties. Vicq d'Azyr changed them into functions in his physiological division and ranked them with ossification, digestion, &c. that is, he confounded the principle with the consequence. Thus you see, notwithstanding the labours of a crowd of learned men, how much the physiological sciences still differ from the physical. In these, the chemist refers all the phenomena that he observes to affinity: the natural philosopher, in his science, every where sees gravity, elasticity, &c. In the others, we have not as yet ascended, at least in a general manner, from the phenomena to the properties from which they are derived. Digestion, circulation, or the sensations, do not bring the idea of sensibility or contractility to the mind of the physiologist, as the movement of a watch proves to the mechanician that elasticity is the primum mobile of its motion; or as the wheel of a mill or of any machine, which running water sets in motion, proves to the natural philosopher that gravity is the cause. To place upon the same level in this respect these two classes of sciences, it is evidently necessary to form a just idea of vital properties. If their limits are not accurately assigned, we cannot with precision analyze their influence. I shall present here only general considerations on this point, which has been treated sufficiently in my Researches upon Life; what I shall add now will be but as a supplement to what has been explained in that work.

II. _Of vital properties, and their influence upon all the phenomena of the physiological sciences._

To assign the limits of these properties, we must follow them from bodies that are hardly developed, to those which are the most perfect. In the plants that seem to form the transition from vegetables to animals, you discover only an internal motion that is scarcely real; their growth is as much by the affinity of particles and consequently by juxta-position, as by a true nutrition. But in ascending to vegetables better organized, you see them continually pervaded by fluids, that circulate in numerous capillary canals, which mount, descend, and run in a thousand different directions, according to the state of the forces that regulate them. This continual motion of fluids is foreign to the physical properties, the vital ones only direct it. Nature has endowed every portion of a vegetable with a faculty of feeling the impression of fluids, with which their fibres are in contact, and of reacting upon them in an insensible manner, to favour their course. The first of these faculties I call organic sensibility, the other, insensible organic contractility. This is very obscure in most vegetables; it is the same in the bones of animals. These two properties govern not only the vegetable circulations, which correspond in some measure to the capillary system of animals, but also the secretion, absorption, and exhalation of vegetables. Remark, in fine, that these bodies have only functions relative to their properties; that all the phenomena that animals derive from properties which they have more than vegetables, as the great circulation and digestion, for which there must be sensible organic contractility; as the sensations, for which there must be animal sensibility; and locomotion, the voice, &c. for which animal contractility is necessary; remark, I say, that these functions are essentially foreign to vegetables, since they have not vital properties to place them in action.

For the same reason the catalogue of their diseases is less extensive. They have not the class of nervous diseases, in which the animal sensibility takes so great a part; they have not those of convulsions or paralysis, which are formed by an augmented or diminished animal contractility; they have not those of fevers, or gastric diseases, which evidently arise from a disorder in the sensible organic contractility. The diseases of vegetables are tumours of various kinds, increased exhalations, marasmus, &c.; they all indicate a derangement in the organic sensibility and in the corresponding insensible contractility.

If we pass from vegetables to animals, we see the lowest of these, the zoophites, receive into a sac, which is alternately filled and emptied, the aliments that are to nourish them; we see them begin to unite sensible organic contractility or irritability to the properties which they have in common with vegetables, and consequently commence the performance of different functions, digestion in particular.

Thus far the organized bodies live wholly within themselves; they have no relation with that which surrounds them; animal life is wanting in them, or at least if it has commenced in these animo-vegetables, its rudiments are so obscure that we can hardly discover them. But this life begins to display itself in the superior classes, in worms, insects, mollusca, &c. On the one hand, the sensations, and on the other, locomotion, which is inseparable from them, are more or less fully developed. Then the vital properties necessary to the exercise of these new functions, are added to the preceding. Animal sensibility and contractility, obscure in the lower species, become more perfect, as we approach quadrupeds, and locomotion and the sensations become also more extensive. Sensible organic contractility then increases, and in proportion to that, digestion, circulation of the great vessels, &c. which are governed by it, receive a development which is constantly growing more perfect.

If we strictly examine the immense series of living bodies, we shall see the vital properties gradually augmenting in number and energy, from the lowest of plants to the first of animals, man; we shall see the lowest plants obedient to vital and physical properties; all plants are governed only by these, which, in them, consist of insensible contractility and organic sensibility; the lowest animals begin to add sensible organic contractility to these properties, afterwards animal sensibility and contractility. We know the expression of Linnæus, which he has used to characterize minerals, vegetables, and animals. The following would be more correct: 1st. physical properties for minerals; 2d. physical properties and organic vital properties, except[2] sensible contractility, for vegetables; 3d. physical properties, all the organic vital properties, and the animal vital properties, for animals.

[2] Several plants certainly possess a considerable degree of sensible organic contractility; the mimosa pudica (sensitive plant) is a well known example, though there are several others that enjoy this property to almost as great an extent; particularly the hedysarum gyrans, the oxalis sensitiva, and the berberis vulgaris. "A very remarkable degree of irritability, not exceeded by the sensitive plant, exists in the flowers of the barberry, (berberis vulgaris.) When these are fully expanded, the stamens are found spread out on the inside of the corolla. In this situation, if the inside of the filament be touched with a pin or straw, it instantly contracts and throws the anther violently against the stigma. This fact, which has been particularly described by Dr. Smith, in the English barberry, is not less remarkable and distinct in the American varieties of the shrub." Bigelow's Florula Bostoniensis. _Tr._

Man and the neighbouring species, which are the particular object of our researches, enjoy then evidently, all the vital properties, some of which belong to organic life, the others to animal life. 1st. Organic sensibility and insensible contractility have all the phenomena of the capillary circulation, of secretion, of absorption, exhalation, nutrition, &c. evidently dependant upon them in a state of health. In treating, therefore, of these functions, we must always ascend to these properties. In the state of disease, all the phenomena that suppose a disorder in these functions, are clearly derived from an injury of these properties. Inflammation, formation of pus, induration, resolution, hemorrhage, unnatural augmentation or suppression of secretions; increased exhalation, as in dropsies; diminished, or wholly wanting, as in adhesions; absorption, disordered in some way or other; nutrition, altered more or less, or presenting unnatural phenomena, as in the formation of tumours, cysts, cicatrices, &c.: these are morbid symptoms, that evidently suppose some injury or disorder in these two preceding properties. 2d. Sensible organic contractility, which, like the preceding, is not separated from the sensibility of the same nature, governs especially in a state of health, the movements necessary to digestion and the circulation of the great vessels, at least for the red and black blood of the general system, for the excretion of urine, &c. In the state of disease, all the phenomena of vomiting, of diarrhœas, and a great part of those numberless ones of the pulse, may ultimately be referred to a disorder of the sensible organic contractility. 3d. All the external sensations, those of seeing, hearing, smelling, tasting, and feeling, and the internal, as those of hunger, thirst, &c. are derived in a state of health from the animal sensibility. In disease, what part does not this property perform? Pain and its innumerable modifications, itching, smarting, tickling, the sensation of heaviness, weight, lassitude, throbbing, pricking, pulling, &c. &c. are not these only different alterations of animal sensibility? A hundred different words would not express the diversity of painful sensations that morbid affections bring with them. 4th. Animal contractility is the principle of locomotion and the voice; convulsions, spasms, palsies, &c. are derived from an augmentation or diminution of this property. Examine all the physiological and all the pathological phenomena, and you will see that there is no one which cannot be ultimately referred to some one of the properties of which I have just spoken. The undeniable truth of this assertion, brings us to a conclusion not less certain in the treatment of diseases, viz. that every curative method should have for its object the restoration of the altered vital properties to their natural type. Every remedy, which, in local inflammation, does not diminish the augmented organic sensibility; which, in œdema and dropsy, does not increase this weakened property; and which does not reduce animal contractility in convulsions, and elevate it in paralysis, fails in its object, and is contraindicated.

To what errors have not mankind been led in the employment and denomination of medicines? They created deobstruents, when the theory of obstruction was in fashion, and incisives, when that of the thickening of the humours prevailed. The expressions of diluents and attenuants, and the ideas that are attached to them, were common before this period. When it was necessary to blunt the acrid particles, they created inviscants, incrassants, &c. Those who saw in diseases only a relaxation or tension of the fibres, the _laxum_ and _strictum_ as they called it, employed astringents and relaxants. Refrigerant and heating remedies were brought into use by those who had a special regard in diseases to an excess or a deficiency of caloric. The same identical remedies have been employed under different names according to the manner in which they were supposed to act. Deobstruent in one case, relaxant in another, refrigerant in another, the same medicine has been employed with all these different and opposite views; so true is it that the mind of man gropes in the dark, when it is guided only by the wildness of opinion.

There has not been in the materia medica, a general system; this science has been governed by the different theories that have successively predominated in medicine; each has, if I may so express myself, flowed back upon it. Hence the vagueness and uncertainty that it presents at this day. An incoherent assemblage of incoherent opinions, it is perhaps of all the physiological sciences, that which best shows the caprice of the human mind. What do I say? It is not a science for a methodical mind, it is a shapeless assemblage of inaccurate ideas, of observations often puerile, of deceptive remedies, and of formulæ as fantastically conceived as they are tediously arranged. It has been said that the practice of medicine was disgusting; I add further, that it is not in some respects the study of a reasonable man, when its principles are derived from the greatest part of the works on the materia medica. Take away those medicines, the effect of which is known only by accurate observation, as evacuants, diuretics, sialagogues, anti-spasmodics, &c. those consequently that act upon a particular function; what knowledge have we of the remainder?

It is, without doubt, extremely difficult at present to class remedies according to their modus operandi; but it is undeniable that all have for their object, the restoration of the vital forces to the natural type, from which they have been driven by disease. Since the morbid phenomena may be considered as different alterations of these forces, the action of remedies should also be viewed as the means by which these alterations are to be brought back to the natural type. Upon this principle, each of the properties has its class of appropriate remedies.

1st. We have seen that there is in inflammations an increase of organic sensibility and insensible contractility; diminish then this increase by cataplasms, fomentations, and local baths. In some dropsies, in white-swellings, &c. there is a diminution of these properties; raise them by the application of wine and all those substances that are called tonics. In every species of inflammation, suppuration, tumours of different kinds, ulcers, obstructions; in every alteration of secretion, exhalation, or nutrition, the remedies act peculiarly upon the insensible contractility, to increase, diminish, or alter it in some way. All those that are called resolvents, tonics, stimulants, emollients, &c. act upon this property. Observe, that these remedies are of two kinds: 1st. general; as wine, ferruginous substances, oftentimes the acids, &c.; these re-animate insensible contractility, and give tone to the whole system: 2d. particular; thus this property is separately excited by nitre in the kidnies, mercury in the salivary glands, &c.

2d. Many remedies act particularly upon the sensible organic contractility; such are emetics, which produce a contraction of the stomach; cathartics, and drastics especially, which create a strong contraction of the intestines. Art does not excite the heart in the same manner as these viscera; we do not artificially increase its movements as we do those of the stomach in gastric diseases. It will, perhaps, hereafter be attempted, especially if it is true that fever may often be a method of cure, and then it will not, I think, be difficult to find the means of effecting it. At other times, we have to diminish sensible organic contractility, and then remedies are employed that act in a manner opposite to the preceding, as in stopping vomitings, in diminishing intestinal irritation, &c.

3d. Animal sensibility has also remedies that are peculiar to it. But they act in two ways—1st. in diminishing pain in the part where it is seated, as different applications upon tumours, obstructions, &c.: 2d. in acting upon the brain that perceives the pain; thus all narcotic preparations, taken internally, remove the sensation of pain, while the cause still subsists. In cancer of an ulcerated uterus, the disease continues its progress with activity, but the prudent physician stupifies the brain so much, that it is incapable of perceiving it. It is essential to distinguish accurately these two actions of remedies upon the animal sensibility. They are totally different from each other.

4th. Medicinal substances have also their influence on animal contractility. Every thing that produces an active excitement on the external surface of the body, as vesicatories, frictions, smarting, &c. tends to re-animate in paralysis this benumbed faculty. All those substances that paralyze the cerebral action, prevent the brain from governing the muscles of animal life; when these muscles, therefore, are convulsively agitated, these substances are true anti-spasmodics.

In presenting these observations, I do not mean to offer a new plan for the materia medica. Medicines are too complicated in their action to be arranged anew, without more reflection than I profess as yet to have bestowed on the subject. Moreover, an inconvenience common to every classification, would here present itself: the same medicine acts often upon many vital properties. An emetic, while it brings into action the sensible organic contractility of the stomach, excites the insensible contractility of the mucous glands, and oftentimes the animal sensibility of the nervous villi. The same observation may be made with regard to the stimulants of the bladder, of the intestines, &c. My only object is to show, that in the action of substances applied to the body to heal it, as in the phenomena of diseases, every thing must be referred to the vital properties, and that their augmentation, diminution, or alteration, are ultimately the invariable object of our curative method.

Some authors have considered diseases only as increased strength or weakness, and have consequently divided medicines into tonics and debilitants. This idea is true in part, but it is false when we generalize it too much. For every vital force there are means proper to raise it when too much diminished, and to lessen it when too much elevated. But tonics and debilitants are certainly not applicable to every case. You would not weaken animal contractility, augmented in convulsions, as you would insensible organic contractility increased in inflammation; neither would you increase them by the same means. The morbid phenomena that organic contractility and animal sensibility experience, are not cured by the same method. There are medicines proper for each vital force. Moreover, it is not only in increase or diminution that the vital forces err, but they are besides disordered; the different modifications that insensible contractility and organic sensibility can undergo, produce in wounds and ulcers a diversity of suppuration, in glands a diversity of secretion, in exhaling surfaces a diversity of exhalations, &c. It is necessary, therefore, that medicines should not only diminish or increase each of the vital forces, but that they should moreover restore them to the natural modification from which they have been altered.

What I have just said is particularly applicable to the strictum and laxum of many authors, who every where see but these two things. The strictum may be properly applied to inflammation, the laxum to dropsies, &c.; but what have these two states of the organs in common with convulsions, with disorder of the intellect, with epilepsy, with bilious affections, &c.? It is the peculiarity of those who have a general theory in medicine, to endeavour to bend every phenomenon to it. The fault of generalizing too much, has been perhaps more injurious to science, than that of viewing each phenomenon separately.

These observations are, I think, sufficient to show, that every where in the physiological sciences, in the physiology of vegetables and of animals, in pathology, in therapeutics, &c. there are vital laws, that govern the phenomena which are the object of these sciences; and that there is not one of these phenomena that does not flow from these essential and fundamental laws, as from its source.

If I should take a survey of all the divisions of physical sciences, you would see that the physical laws were ultimately the sole principle of all their phenomena; but this is so well known that it is not necessary to do it. I will consider an important subject, and one to which we are naturally led by the preceding observations. I mean, a parallel between physical and vital phenomena, and consequently between physical and physiological sciences.

III. _Characteristics of the vital properties, compared with those of the physical._

When we consider, on one side, the phenomena which are the object of the physical sciences, and those that are the object of the physiological, we see how immense is the space that separates their nature and their essence. But this difference arises from that which exists between the laws of the one and the other.

Physical laws are constant and invariable; they are subject neither to augmentation or diminution. A stone does not gravitate towards the earth with more force at one time than another; in every case marble has the same elasticity, &c. On the other hand, at every instant, sensibility and contractility are increased, diminished, or altered; they are scarcely ever the same.

It follows, therefore, that the physical phenomena are never variable, that at all periods and under every influence they are the same; they can, consequently, be foreseen, predicted, and calculated. We calculate the fall of a heavy body, the motion of the planets, the course of a river, the ascension of a projectile, &c.: the rule being once found, it is only necessary to make the application to each particular case. Thus heavy bodies fall always in a series of odd numbers; attraction is in the inverse ratio of the square of the distances, &c. On the other hand all the vital functions are susceptible of numerous variations. They are frequently out of their natural state; they defy every kind of calculation, for it would be necessary to have as many rules as there are different cases. It is impossible to foresee, predict, or calculate, any thing with regard to their phenomena; we have only approximations towards them, and even these are often very uncertain.

There are two things in the phenomena of life, 1st. the state of health; 2d. that of disease; hence there are two distinct sciences; physiology considers the phenomena of the first state, pathology those of the second. The history of the phenomena in which the vital forces have their natural type, leads us to consider as a consequence, those phenomena that take place when these forces are altered. But in the physical sciences there is only the first history; the second is never found. Physiology is to the movements of living bodies, what astronomy, dynamics, hydraulics, hydrostatics, &c. are to those of inert ones; but these last have no such correspondent sciences as pathology. There is nothing in the physical sciences that corresponds to therapeutics in the physiological. For the same reason, every idea of medicament is absurd in the physical sciences. The object of a medicament is the restoration of properties to their natural type; but, the physical properties, never losing this type, have of course no need of restoration.

We see then that the peculiar instability of the character of the vital laws is the source of an immense series of phenomena, which form a peculiar order of sciences. What would become of the universe, if the physical laws were subject to the same commotions and the same variations as the vital? Much has been said of the revolutions of the globe, of the changes that the earth has undergone, of the overthrows that ages have gradually brought about, and upon which ages have accumulated without producing others: but you would see these overthrows and these general commotions in nature at every instant, if the physical properties had the same character as the vital.

For the same reason, that the phenomena and laws of the physical and physiological sciences are unlike, the sciences themselves are essentially different. The manner of presenting the facts and of prying into their causes, the experimental art, &c. every thing bears a different stamp; and it is absurd to confound them. As the physical sciences were perfected before the physiological, mankind thought that they could illustrate the latter by connecting them with the former; but they have confused them; and this was inevitable, for the application of the physical sciences to physiology, was the explication of the phenomena of living bodies by the laws of the inert. Here then is a false principle, and all the consequences drawn from it must be erroneous. Let us leave to chemistry its affinity, and to physics its elasticity and gravity, and let us employ in physiology only sensibility and contractility; I except, however, those cases where the same organ becomes the seat of vital and physical phenomena, as the eye and the ear, for example. It is on this account, that the general character of this work is wholly different from those on physiology, and even that of the celebrated Haller. The works of Stahl illustrate well the advantage of neglecting all those pretended accessory aids, which overthrow the science in attempting to support it. But as this great physician had not analyzed the vital properties, he could not present their phenomena in their true point of view. Nothing is more vague and indefinite than the words, _vitality_, _vital action_, _vital influx_, &c. when we do not precisely limit their meaning. Suppose that mankind had created some general and vague words, which were to correspond to all the non-vital properties, and which gave no precise or definite ideas; if you were every where to use these terms, if you did not determine that which belonged to gravity, that which depended on affinity, and that which was the result of elasticity, you would never be understood. Let us say as much in regard to the physiological sciences. The art is much indebted to many physicians of Montpellier for having deserted the theory of Boerhaave, and having followed in preference that given by Stahl. But in leaving a bad path, they have taken another so tortuous, that they will never, I think, find its termination.

Ordinary minds, in reading, stop at insulated facts that are presented; they do not embrace, at one view, the principles of the work. Oftentimes the author himself incautiously follows the impression given to a science in the age in which he writes. But the man of genius every where pauses at this impression, which should be henceforth entirely different in physical and physiological works. It is necessary to use a different language; for most of the words that are carried from the physical into the physiological sciences, continually refer to ideas that have no connexion with them. You see the living solids constantly undergoing composition and decomposition, every moment taking and rejecting new substances; on the other hand, inert bodies remain the same, and keep the same constituent principles, until friction and other causes destroy them. So in the elements of inert bodies, there is a constant uniformity, and an invariable identity in their principles, which is known when they have been once analyzed; whilst the principles of the living fluids are so continually changing, that it is necessary that many analyses should be made, under every possible circumstance. We shall see the glands and exhaling surfaces pour out, according to the degree of their vital forces, a great variety of modifications of the same fluid; what do I say? they pour out a variety of fluids really different; for are not the sweat and the urine poured out under one circumstance, and the sweat and the urine under another, two distinct fluids? There are a thousand examples that would incontestably establish this assertion.

It is the nature of vital properties to exhaust themselves; time wastes them. Elevated in the commencement of life, they remain stationary at the adult age, and afterwards are debilitated and become nothing. Prometheus, it is said, having formed some statues of men, snatched fire from heaven to animate them. This fire is the emblem of the vital properties; while it burns, life is supported; when it is extinguished, it ceases. It is, then, a part of the essence of these properties, to animate matter for a determinate time only; hence there are necessary limits to life. On the other hand, the physical properties, constantly inherent in matter, never abandon it; so that inert bodies have no limits to their existence, but what accident gives to them.

By nutrition the particles of the matter of inanimate bodies pass into living bodies, and vice versa; and we can evidently conceive that this matter has been endowed through an immense series of ages with physical properties. These properties are given to it at the creation, and will leave it only when the world shall end. This matter, in passing into living bodies, in the space that separates these two epochs, a space that immensity only can bound, this matter, I say, becomes possessed, at intervals, of vital properties, which are then united to physical properties. Here, then, is a great difference in matter, with regard to these two kinds of properties; one it enjoys by intermissions only, the other it possesses constantly.

I could add many other considerations, that would still further establish the difference between the physical and vital laws, and consequently between the physical and vital phenomena, and as a consequence from these, the difference of the general character and methods of the physical and physiological sciences. I could show, that inert bodies are formed at hazard, by juxta-position or a combination of their particles, while living bodies, on the contrary, exist in consequence of a certain function, viz. generation; that the first increase in the same manner as they are formed, by juxta-position or the combination of new particles; the others by an internal movement of assimilation, which requires different preliminary functions; these constantly experiencing composition and decomposition; those remaining always internally in the same condition, undergo no other modifications than such as are derived from chance and the physical laws. The existence of inert bodies ceases as it commenced, by mechanical laws, by friction, or by new combinations; living bodies afford in their natural destruction, a phenomenon as uniform as in their production; they pass suddenly to a new state when life abandons them, and undergo putrefaction, desiccation, &c. which they did not before, because the physical properties being restrained by the vital, could not produce these phenomena; inert bodies, on the other hand, always preserve the same modifications. Though a stone or a metal, when broken or dissolved, ceases to exist, their particles will always be the same. But some authors have already presented a great part of this parallel; let us content ourselves with drawing from it a consequence often deduced from other facts, I mean the difference of the laws that preside over the two classes of functions.

But there is an essential difference between vital and physical properties; I refer to sympathies.

All inert bodies show no communication in their different parts. Though the extremity of a stone, or of a metal, may be altered in any way by chemical dissolution, or by mechanical agents, the other parts are not affected; it is necessary to touch them by a direct action. On the contrary, every thing is so connected and tied together in the living body, that no one part can be disordered in its functions, without being immediately perceived by the rest. All physicians have known the singular consent that exists between our different organs, both in a state of health and disease, but principally in the latter. How easy would be the study of diseases, if they were stripped of every thing derived from sympathy! Who does not know that these complaints often predominate over those that arise from the injury of the diseased organ? Who does not know that the cause of sleep, of exhalation, of absorption, of secretion, of vomiting, of diarrhœa, of retention of urine, of convulsions, &c. is oftentimes very far from the brain, from the exhalants, from the absorbents, from the glands, from the stomach, from the intestines, from the bladder, from the voluntary muscles, &c.?

How little soever we reflect on the sympathetic phenomena, it will be evident that they are only unnatural developments of vital forces which are called into action in an organ by the influence that it receives from those that have been directly excited. In this view all the systems are dependant upon each other. This important point of doctrine will be treated at so much length, in this work, particularly under the article on the nervous system that it is useless to insist much upon it here.

We shall see sympathies call into action always those vital properties especially that prevail in a system; animal sensibility in the nerves, contractility of the same kind in the voluntary muscles, insensible organic contractility in the involuntary, sensible contractility in the glands, in the serous, mucous, synovial, cutaneous surfaces, &c. We shall see them assume the character of the vital properties of the organs in which they are developed, their progress will be chronic in the bones, cartilages, &c. acute in the muscles, skin, &c. We shall see them observe in the frequency of their development, the laws of nutrition and growth, to appear oftener in the nervous and vascular system of the child, in the pulmonary organs in youth, and in the abdominal contents in adult age. But let us pass to other subjects.

IV. _Of the vital properties and their phenomena, considered in relation to the solids and fluids._

Every organized body is composed of fluids and of solids. The first are, in one point of view, the materials, and in another the residue of the second. 1st. They are the materials, for from the aliments which convey through the intestines, the elements of nutrition, even to the interior of the organs where these elements are deposited, they form evidently a part of the chyle and the blood. 2d. They are the residue, for after having remained some time in the organs, these nutritive particles are taken up, enter again into the blood, and afterwards make a part of the secreted fluids, and of those that form cutaneous and mucous exhalations, which are thrown out externally.

There are then fluids for composition and others subservient to decomposition. The solids are the termination of the first, which come from without, and the place from which the second are sent back. The fluids of composition and decomposition are not all insulated; the chyle, the materials that enter by cutaneous absorption, the principles that the lungs draw from the air, &c. are especially of the first kind. The fluids secreted and exhaled upon the mucous and cutaneous surfaces, appear to be exclusively of the second. But the blood is a common centre, in which the elements that enter, and those that go out, circulate together.

This being admitted, let us see what part the fluids and the solids enjoy in the vital phenomena. This must evidently depend on the properties they possess; and in reflecting on the vital properties which we know, it is evident, that every idea of fluidity is foreign to them, that fluidity cannot be the seat of any contraction nor of organic and animal sensibility, &c. I will not speak here of the pretended spontaneous movements of the blood, of the subtle fluids that it contains, according to some authors, and which can on occasion expand or contract it; all this is but an assemblage of vague ideas, that are confirmed by no experiment. Moreover, all the phenomena of the living economy show us manifestly the fluids in a state almost passive, and the solids, on the other hand, always essentially active. It is the solids that every where receive the excitement, and act in consequence; the fluids are only the excitants. This constant impression of the second upon the first, constitutes every where continual sensations that are not referred to the brain, and which are consequently not perceived; this is organic sensibility, and differs from the animal in this, that the mind has no consciousness of these sensations, which do not go beyond the organs in which they take place.

Since, on one side, the vital properties are essentially seated in the solids, and on the other, the morbid phenomena are but alterations of these properties, it is evident that these phenomena reside especially in the solids, and that to a certain limit the fluids are foreign to them. Every kind of pain, all spasms and irregular movements of the heart, that constitute the innumerable variations of the pulse, have their seat in the solids.

Let us not believe, however, that the fluids are nothing in diseases; they oftentimes carry the fatal principle of them. They possess, then, in disease, the same place as in the state of health, in which the solids are the active agents of all the phenomena that we observe, but their action is inseparable from that of the fluids. That the heart may contract, that the capillary system may close itself, it is necessary that fluids should first go there. In proportion as the fluids are in their natural state, the excitement is natural; but when this is changed from any cause, as by the introduction of foreign substances, at that instant they become unnatural excitants; the functions are disordered, and diseases supervene. You see, then, that the fluids can oftentimes be the principle of diseases, and the vehicle of morbific matter. But this subject merits further consideration.

Here we can apply the distinction of fluids into those of composition and those of decomposition. The first, which enter the system in various ways, go into the blood, which, on one account, belongs to them, but on another, to the fluids of decomposition. It is incontestable, 1st. that the chyle can be loaded with a variety of foreign substances, and carry into the blood the fatal principles of disease, as when putrid and badly digested matter, principles of contagion mixed with our aliment, &c. are found in the primæ viæ. 2d. Is it not established by many proofs, that cutaneous absorption oftentimes introduces into the blood the causes of disease, and, 3dly. that substances foreign to the constituent principles of the air, and adapted to excite disease, may accidentally get into that fluid through the medium of the lungs? these things we cannot doubt. Here, then, there are already three ways open to the principles of morbific matter, as we shall moreover have reason to be convinced in the course of this work. 4th. There is another accidental one, that arises from wounds, cuts, bites, lacerations, &c. by means of which destructive principles are oftentimes conveyed into the animal economy. Under these four we might produce a variety of cases, in which the fluids are the first causes of diseases, by conveying their essential principles and becoming unnatural excitants to the solids, in which they produce phenomena contrary to the natural order. But it is evident, that it is those fluids especially destined to the composition of the organs that thus carry morbific principles; these are especially their vehicle, and convey the disease. On the other hand, the fluids destined to the decomposition tend to carry the disease out of the system. We have seen that these fluids are every where poured upon the mucous and cutaneous surfaces, either by exhalation or secretion, as the sweat, the urine, &c.: and it is by these fluids that a crisis is produced. Physicians have exaggerated to an infinite degree the influence of these morbific humours, thus driven out; but we cannot doubt that this doctrine has oftentimes a real foundation. If these fluids are sometimes the vehicles of disease, it is when they enter unnaturally into the system, as when the bile passes into the mass of blood, when the absorbed urine enters this fluid, &c.

After all that has just been said, it is evident, that it is necessary to distinguish accurately diseases themselves, or rather the whole of the symptoms that characterize them, according to the principles that produce or support them. Almost all the symptoms are in the solids, but the cause can be in them as well as in the fluids. An example will render this more clear; the heart can contract unnaturally; 1st. because its organic sensibility is increased whilst the blood itself remains the same; 2d. because the blood is either augmented, as in plethora, or altered in its nature, as in putrid fevers, &c. while the organic sensibility of the heart does not vary. The excitement may be double, or the organ may be twice as susceptible as common, the effect is the same; an acceleration of the pulse takes place. The solid always takes the principal part in the disease; it is always that which contracts, but in the first case the cause was in the solid, in the second it was not.

This example gives an idea of what occurs in diseases, in all of which the solids are especially in action; but the cause of this action, sometimes exists in them, and sometimes not. It is no doubt essentially necessary to seek the distinction of these cases. The following reflections are made with this view. 1st. I distinguish, in the present question, diseases into two classes; 1st. into those which especially affect animal life; 2d. into those that particularly disorder organic life. I say particularly, for such is the connexion of these two lives, that the one can hardly be altered without the other; thus fevers that affect organic life, produce cerebral effects that agitate the animal: thus also primitive cerebral affections influence sympathetically the circulation, respiration, &c. But certainly we cannot deny, that there are some affections, whose principal and primitive character is a disorder of the animal life; such are convulsions, spasms, paralysis, mania, epilepsy, catalepsy, &c. But it appears that the cause of these diseases is almost always in the solids, and that the fluids most commonly are not affected. Therefore you see that crises, in every case are foreign to these diseases. Hypochondria, hysteria, melancholia, &c. though they appear to reside more particularly in the solids, can yet be in a degree dependant on the fluids, as different examples will prove.

Diseases, on the other hand, that particularly affect organic life, as fevers, inflammations, &c. may have their principle as well in the fluids as in the solids. Hence the reason, that these diseases are subject to crisis, and are cured by evacuants, alteratives, &c.