of experiment that we can penetrate into the fanctuary of nature, without risk of bewildering ourelves. I owe much to the works of Fontana; and it is by following the footsteps of that great philofopher often, by leaving them fometimes, and by thaining the miftakes into which he has fallen, that I perfuade myself I have found the truth. I fhall not here (peak of the new views of the phyfiology of the human body, and of difeafes which immediately follow from the refa'ts of my experiments, nor shall I enter into the detail of thefe experiments, because they will be related in a work I mean to publish in Germany next year. I hall only now give fome detached propofitions unaccompanied with the proofs, which may ferve as a profpectus of my work, and which may attract the attention of fome philofophers.

All organ fed nature is compofed of folids and of fluids. The folid parts of animals and of plants are compofed of three forts of primitive fibres; viz. the earthy, the fenfible, and

the irritable fibre.

The earthy fibre forms the bones of animals, and the wood of plants. It is inorganic, infenfible, in-irritable; is fubject to no other laws than thofe of unorganised matter, and has no life but in combination with the irritable fibre.

The fenfible or nervous fibre, is that which conftitutes the nerves in animals. Plants are deftitute of this fpe cies of fibre: at least it has not as

yet been discovered in the vegetable kingdom. It is totally incapable of irritability or contraction. It is acted upon only by the irritable fibre. Each mufcular contraction produces a change in the adjoining nervous fibre; this change, in the living animal, reaches to the origin of the nerve in the brain or fpinal marrow, and is called fenfation. Thus every ftimulus which acts on the living irritable fibre produces in it immediately con

traction, and mediately fenfation that is, no ftimulus can act on the nerve, but by the intervention of the mufcular fibre. When this latter has loft its irritability, and is become either paralytic or gangrenous, there can be no fenfation, although the contiguous nerve fhould be perfectly found. When, on the other hand, by any accident the nerve is become fenible, or has been destroyed, the mufcular fibre will continue to contract upon the application of a ftimulus, but no tenfation will follow, becaufe the connection between the mufcular fibre and the origin of the nerve is deftroyed. Senfation and motion are, therefore, two properties of organized matter effentially differ ent. Senfation is only a fecondary property which depends on the irritable fibre, and cannot exift without it. Irritability, on the contrary, is a primary property, effential to the living irritable fibre, and abfolutely dependent on the nerves. I know that this propofition is contrary to the cpinion generally received, which makes irritability depend on the influence of the nerves. I too, adopted this opinion, but manifold experi ments have convinced me that it is erroneous,

Not only does the irritable fibre act on the fenfible and produce fenfation, but the fenfible fibre reacts on the irritable and produces contraction This is the caufe of voluntary motions, of convulfions, and of what are called nervous difeafes. The action of the nerves on the muscular fibre is in nothing different from that of any other fimulus, and I fhall therefore call it the nervous stimulus.

The irritable fibre, improperly called the mufcular fibre, pervades all organised matter. On it depends organic motion, fenfation, and even life; and on it the bodies that furround it continually act by ftimulating it and forcing it to contract. It is of this fibre that I am about to

Speaka

fpeak, and of the laws that are the confequence of the irritability it is endowed with. But before eatring upon this difcuffion, it will be neceffary to prove, that the irritable fibre is univerfally diffufed through all organied bodies. Its exiflence is known and generally admitted in animals. with warm blood, and in fome that have cok! blood, fuch as frogs, lizards, tortoifes, ferpents, eels, and files. Infects, worias, and plants are not Jefs endowed with iritably. The fpiral tongue of butterflies is exceedingly irritable, and contracts upon being ftimulated, even after having been cur in pieces and feparated from the an mal. The irritability of oyf ters, of medule, and of polyp, is well known. The nautilus rifes from the bottom of the fea to the furface, by alternately contracting and di lating its irritable fibres. The pendant chryfalis of the papilio urtice is very irritable, efpecially for a few days after its formation. The fkin with which the caterpillar was covered, and which it has juft quitted, acts as a ftimulus on the newly form ed chryfalis, which is feen to contract and dilate alternately, till the dried fkin falls off. Swammerdam faw and figured the muscular fibres, and cbferved their alternate contractions and dilatations in the loufe, and even in the fetus of a loufe inclofed in a microfcope; others have obferved the fame in other infects, and in microfcopic animals.

The existence of the irritable fibre in the vegetable kingdom, is proved by facts not lefs fingular. The leaves of the Drofera rotundifolia and longifolia contract, when touched with the point of a pin, and dilate when the ftimulus is removed. The leaves of the Averrhea carambola contract when touched, compreffed, or pierced. The leaves of many fpecies of Mimofa, efpecially thofe of the Minefa pudica, contract upon being touched, or when

4

expofed to the action of electricity, the burning glafs, ammoniac, mufk, opium, or any other ftimulus. The fame phenomena are obfervable in the Onoclea fenfiilis, Oxalis fenfitiva, Dix nea mufcipula, Hedyfarum gyrans, &c. The parts of fructification especially are very irritable. The ftamina of the Berberis vul-aris, of the Heliotropium, of the Calendula, of the Ciftus "appenninus, of the Lilium fuperbum, or the Cactus, of the Forskrihea tenaciffima, and of feveral others, contra& on the application of a ftimulus. The ftigmata and pitils exhibit the fame phenomenon.

The existence of the irritable fibre in all org nifed bodies being thus proved, there ariles another question, wel! worthy the attention of the philofopher. Is this irritable fibre the fame, and fubject to the fame laws in every part of nature; or is it diffetently modified in different animals, and in different plants? Are effects fimilar in appearance, produced by different caufes? This problem is impartant, but of difficult folution. In the deduction of general rules from forme particular phenomena, we are in danger of bewildering ourselves in the labyrinth of analogy, where fo many talking phi ofophers have loft themfelves, because they have pretumed to enter it without the clue of experience. This has been my guide, and after repeated experiments and ob fervations, I confider it as demonftrated, that the irritable fibre is the fame, and fubject to the fame laws, throughout all organifed nature. This truth being difcovered, has prefented to me an ample harveft, which the fickle of the philofopher has never touched.

There are three kinds of irritable fibre: the straight, which is found in the mufcles of animals, in the leaves, ftamina, and feveral other parts of plants; the spiral fibre, found in the arteries, veins, lymphatic veffels, inteftines, and in general in all the vef

fels,

fels, and cylindric or conic mufcles of animals and plants; the circular fibre, or what we call the fphincters. The ftraight fibre contracts in length or is fhortened in contraction, the two ends approaching one another at the inftant it is touched, or any of its parts, by a ftimulus.

The fpiral fibre, in contraction, diminishes the diameter of the vefels which it forms. The contraction does not take place at the fame inftant through the whole length of the fibre as in the preceding, but is communicated fucceffively to its different parts. The contraction begins at the place to which the ftimulus is applied, and is continued in the direction of the ordinary motion of the fibre, to its termination. By this contraction, which is alfo called peristaltic motion, the fluids contained in the veffels are impelled forwards, and circulation goes on. This circulation takes place in vegetables, as well as in animals, and is carried on in both by the peritaltic motion, which is the effect of the irritability with which the fibres are endowed.

The circular fibre when it contracs, clofes the opening of thofe veffels, at the end of which it is generally placed.

The irritable fibre, when feparated from the animal or plant, preferves its irritability for fome time, and continues to contract upon the application of a stimulus. It even preferves this property, when cut into pieces, as we may obferve, by cutting the fpiral tongue of a butterfly, or the ftamina of plants. All the pieces ftill contract, which proves, that the fmalleft portion of the irritable fibre poffeffes its particular irritability, independent of the reft.

The fluids of animals, and of plants, are endowed with irritability, as well

The degree of irritability in the folids and fluids changes continually, and differs according to the age and fyftem of the fame animal or plant, and according to the fex, organifation, and fize, of the different individuals. It is alfo accumulated by the abftraction of habitual stimuli, and is exhausted by the application of ftimulants, too frequently repeated or too strong. We may remark three different ftates of the irritable fibre, or three different degrees of irritability, of which it is fufceptible.

1. The ftate of health. peculiar to each individual, which I fhall calf the tone of the fibre.

2. The state of accumulation, produced by the abftraction of habitual ftimuli.

3. The ftate of exhauftion produ ced by the action of too ftrong a ftimulus.

The Late of health, or tone of the fibre, conlifts in a certain quantity of the irritable principle, neceffary to its prefervation, or in an equilibrium between the acting ftimulus, and the irritability furnished by the lungs and the circulation †.

When the fum of the ftimuli acting on the fibre is not ftrong enough to deprive it of all its excefs of irritability, the irritable principle is accumulated in the fibre, which is then in the ftate of accumulation: and ftimuli produce contractions which are much stronger than when the

fibre was in tone.

When the fum of the ftimuli, acting on the fibre, is too great, the fibre

fibre is deprived, not only of its excefs of irritability, but alfo of a part of the irritable principle neceffary to its tone, or rather, the fibre lofes more irritability than it receives, and is confequently in a state of exhauftion, either temporary or irreparable.,

In the ftate of temporary exhauftion the fibre lofes its tone, and fuffers a defect of irritability. A ftimulus applied at this time, will not make it contract, except it be very ftrong. After fome time the irritable principlé will be again accumulated in the fibre, and it will then contract. It is only by degrees, however, that it recovers its irritability. This, I venture to affirm, is a fact, as new as important, and it explains a great number of phenomena hitherto inexplicable. The motion of the heart, the menftrual flux, the periodical motions of animals and plants, as well as their periodical difeafes, are explained by it; that is, they are explicable only on this principle, that a ftimulus, tho' always prefent, and continuing to act on the fibre, produces no fenfible effect till the irritability of the cxhauffed fibre is again accumulated.

The total or irreparable exhauftion of the fibre, confifts in the lofs of all its irritability, in what is called gangrene. The fibre changes colour, becomes livid or black, becomes fubject to the laws of unorganifed matter, begins to decompofe and to become putrid. A very strong ftimulus will, by its action, reduce a fibre to this state in a fhort time. Such, for inftance, is the ftate of the fibre in animals killed by ftrong poifons, by the bite of the rattlefnake, &c. The irritability of many infects, and of moft plants, is irreparably spent by the ftimulus of the venereal act, fo that they die immediately after the work of generation is performed.

The irritable fibre, from the fift moment of its exiftence, to its diffolution, being conftantly furrounded by bodies which act on it, and on

which it reacts by its contraction, follows, that during the whole period of life, the irritable fibre is in conti nual action, that life confifts in ac tion, and is not a palive ftate as fome authors have maintained. Befides, external objects having no immediate action on the nerves, but acting on them and producing different fenfations, only by the intervention of the irritable fibre, it is clear, that the ideas which we have of external objects are not agreeable to those ob jects, but are changed and modified by the irritable fibre which tranfmits them to us. Hence objects appear different to us, according to the dif ferent ftates of that fibre.

Thus

The irritable fibres in any individual, whether animals or plants, compofe a fyftem of fibres, the integ rant parts of which act continually on the whole, while the whole reacts on the particular parts, fo that any ftimulus which acts on one fibre of the fyitem will deprive it of a part of its irritability; but that lofs will foon be repaired by the fyftem, and each fibre will furnih in proportion a part of its rritability to fupply the lofs fuitained by any fingle bre. a weak ftimulus, continually acting on a part of the fyftem, fuch as flow poifons, the abufe of fpirituous liquors, a hidden ulcer, &c. in time exhaust the whole fyftem and caufe death. For the fame reafon a very ftrong ftimulus partially applied, fuch as the diftilled water of the lauro-cerafus, opium, the poifon of the raule-fnake, &c. will inftantaneoufly exhauft the irritability of the whole fyftem and kill the animal. By many experiments, I am certain, that the mufcles of animals, killed by fuch ftimul, are perfectly deftitute of irritability.

The irritable fibres of a fyftem are not all poffeffed of the fame degree of irritability. They have different capacities for the irritable principle according to their dillance from the

heart

heart. Fibres equally diftant from the heart, have the fame capacity, and a ftimulus which affects one af. fects all at the fame time, and in the fame manner. Hence the fympathy of different parts equally remote.

When the irritable fibre has loft its tone, either from an excefs or defect of the irritable principle, it is difeafed, and the fyftem it belongs to fuffers and becomes difeafed by fym pathy. All the diseases, whether of animals or plants, may be referred to two claffes. f, Diseases of accumutation, proceeding from the accumu lation of the irritable principle by the diminished action of habitual ftimuli. 2d, Diseases of exhauftion, proceeding from the defect of the irritable principle, by the increased action of ha bitual, or the addition of new ftimuli.

Medicines cure difeafes, by acting on the irritable fibre, and by exhausting its irritability in cafes of accumulation, or by diminishing the action of habitual stimuli, and of course a total exhauftion in cafes of exhauftion. The effect of poifons is expli cable in the fame way.

Poifons, medicines, and in general all the furrounding bodies act only on the irritable fibre, and therefore affect the system exactly in the fame manner. Fontana concludes, after having made fix thousand experiments, that the poison of the viper kills animals by acting on the blood. But frogs, that live a long time after their heart has been cut out, and which are confequently entirely deprived of blood, are killed as quickly by the poifon of the viper, as if their blood had not been let out.

Thofe ftimuli which I call habitual, because they are more or lefs in perpetual action on the irritable fibre, are heat, light, food, air, the circulation of the blood, the generative, and the nervous ftimulus. So long as the action of thefe ftimuli is in proportion to the degree of irritability in VOL. XII. No. 68.

P

the fyftem, and as the fum of their action is nearly equal to the fun of the irritable principle, abforbed by the lungs, and diftributed by the circulation, the whole fyftem will be in health, and the fibres which conftitute it, will be in tone. When one of thefe ftimuli, or feveral of them, act with greater force than ordinary, or when the fibre becomes more irritable, while the degree of their ac tion is the fame, the exhauftion of the fyftem, and one of the difcafes, which are the confequence of it, will follow. The abftraction of one, of of feveral of these ftimuli, will produce an accumulation of irritability in the fyftem, and one of the difcafes, which are the confequence of this, will follow.

[We shall conclude this extract, with the following obfervations of the author.]

If my principles are true, fays he, medicine, which has hitherto been an art of mere conjecture, will be brought in time to the certainty of calculation, and after tables fhall be conftructed to exprefs the force or intenfity of the ftimulus, the degree of irritability in the fibre, and the certain figns by which thefe may be known, the calculation will be fo fimple and eafy, that it will make a part of education. Befides, the irritable fibre being the fame throughout all organifed nature, diseases, and their remedies will confequently be the fame for all organifed beings; there will then be no diftinction between medicine, the velerinary art and agriculture, but thefe fciences will be confounded, and form only one, under the name of univerfal Phyfiology. The art of pharmacy and of writing prescriptions, will become ufelefs; a bottle filled with alcoliol, or liquid laudanum, will be fubftituted to the enormous quantity of drugs which are contained in the fhops of apothecaries. The traffic in medicines-but hold. By continuing my predictions,