M. Thillaye showed me portions of skin taken from a cemetery, in which every thing that filled the dermoid spaces had disappeared, and in which these spaces and their dried fibres formed a real membranous sponge through which the light could everywhere be seen. In this case the reverse of what is seen in long continued macerations had taken place, in which the fatty cellular texture, changed into a solid, white substance, preserves, as I have said, the form of the spaces which it filled, whilst the dermoid fibres reduced to the pulpy state, are easily removed. In the first case it is the mould only which is left; in the second it is the substance which is contained in it.
In chronic leucophlegmasia, the sub-cutaneous serum gradually extends along the cellular elongations of the spaces of the dermis, separates their fibres, consequently enlarges these spaces, and sometimes penetrates even tothe epidermis, which it breaks in different places, and through the crevices of which it escapes. In this case, there is not resolution of the skin into cellular texture, as it is called, but a separation of the dermoid fibres, which always remain.
I do not presume that the cellular texture of the chorion extends to its external surface, under the epidermis; for when this has been removed, fleshy granulations are not formed, now, in all the parts where the cellular texture is found, these granulations are produced, when the parts are laid bare.
The arteries winding in the sub-cutaneous cellular texture, furnish an infinite number of small branches which are introduced with the cellular parcels into the most internal dermoid spaces, afterwards pass into those that are nearer, approximate by winding and anastomosing a thousand times through the spaces of the external surface of the chorion, finally go through the pores of this surface, and give rise to that external capillary net-work of which we have spoken in the article upon the reticular body, and to which in the ordinary state but very little red blood comes. In this course through the dermoid spaces, but few small arteries remain in the fibres of the chorion itself, as fine injections prove. These fibres resemble in this respect those of the aponeuroses through which many vessels pass, but which have but few belonging to their own texture.
The veins follow nearly the motion of the arteries, but in an inverse direction. After having passed through the dermoid spaces and the cellular texture which fills them, they go to the great sub-cutaneous trunks, which run a long course, form, as we have seen, a system wholly distinct by its position from that of the arteries and which can be often traced through the integuments. Not seenin the natural state, the venous ramifications of the spaces of the chorion are considerably dilated in the subjacent cancerous tumours, and make the skin which covers these tumours appear to be marked with blue lines, which always grow larger as the tumour increases. Whenever there is a considerable distention of the cutaneous organ by an aneurism, pregnancy, dropsy, &c. this dilatation also takes place, provided the cause of the distention pursues a chronic course; for nothing similar is seen in acute affections, whatever swellings may have taken place, as in those consequent upon fractures, upon compound luxations, &c.
All the black blood formed in the skin goes into the general venous system; no portion belongs to the abdominal.
Their distribution is nearly the same as that of the blood vessels. Many very considerable branches, as different divisions of the musculo-cutaneous, the internal cutaneous, the lumbar, the saphena, the anterior tibial, the intercostals, the cervicals, &c. form a kind of sub-cutaneous nervous system, from which go all the branches that enter the dermis. These branches, in passing through the dermoid spaces with the arteries and the veins, appear to anastomose often together, go through the pores which terminate the spaces on the interior, and no doubt form the papillæ. Observe even that on the hand where the papillæ are very evident, there are, in proportion to the surface, many more sub-cutaneous nerves than any where else.
Many absorbents creep under the skin; it is here that they can be the most easily studied. All the veins are surrounded with them; various fasciculi are observed in theirinterstices; so that a layer of absorbents, arranged in the form of a continuous layer, seems to separate, in the extremities, the aponeurosis and the skin. There is no doubt that the origin of the most of these vessels exists in the chorion, that they carry to the blood the fat and the cellular lymph of its spaces, and the nutritive matter of its fibres. But is there a particular order of branches opening upon the surface of the epidermis to absorb in certain cases foreign substances? This question cannot be answered by anatomical inspection. But the following considerations appear to me to throw great light upon it.
1st. The sub-cutaneous absorbents, visible by injections, are too numerous in proportion for the mere purpose of carrying back the fat and serum of the neighbouring parts.
2d. There are many medicines which appear to be evidently absorbed; such are mercury in the venereal disease, various purgative and emetic substances, febrifuges even, as cinchona, which, when applied by friction, have produced their effects as well as if taken by the stomach; cantharides often act upon the kidneys, when the tincture is used as a liniment, narcotic substances sometimes occasion a weight in the head and drowsiness when they have been externally applied, &c. These different effects are well known and many authors have given examples of them.
3d. There is we know absorption of different kinds of virus, of that of hydrophobia, of the small-pox, of the venom of the viper, &c. an absorption, it is true, which rarely takes place when the epidermis is whole, but which uniformly does, when this being removed, the matter is found in contact with the external capillary net-work of which we have spoken. I would remark even that the different kinds of inoculation of the small-pox, of the vaccine disease, &c. evidently prove both the existenceand importance of this net-work, to which heretofore sufficient attention has not been paid. There are many contagious principles which are absorbed through the epidermis; such are those of the plague which the clothes communicate and those of different pestilential fevers which penetrate by the skin more than by respiration. I believe cutaneous absorptions from which diseases arise may be divided in the following way:
1st. Absorptions which take place through the epidermis, and which produce an effect{1st, local, as the itch, herpes, tinea capitis, &c. &c.2d, general, as pestilential diseases, putrid fevers taken in an unhealthy place, &c. &c.2d. Absorptions which take place only when the epidermis is removed, and from which arises an effect{1st, local, as the vaccine disease, the small-pox, &c. &c.2d, general, as hydrophobia, the venom of the viper, a wound with an instrument impregnated with putrid matter, &c. &c.
We see by this table that the absorbents when charged with injurious substances, sometimes do not transmit them beyond the part and sometimes carry them to the blood, which conveys them to the different organs of the economy. Some authors have thought that in those cases in which the effects of the absorption become general, there is rather nervous action and sympathetic phenomena, than the transmission of an injurious matter into the circulation, and that consequently the solids take almost an exclusive part in these diseases. But to remove all doubt upon this point it is sufficient to observe, 1st, that, in the absorption of many contagious substances, for example, when from the puncture of the finger with a scalpel impregnated with putrid substances, a pain is produced, there is even a redness along the whole course of the absorbents of the arm, and the axillary glands afterwards swell; 2d, that by transfusing into the veins most of the substances that are applied in frictions, effects analogous to those which take place in these frictions are produced. Thus purgatives and emetics, transfused or absorbed, actupon the intestines and stomach the same as if introduced in any other way. It seems to me that sufficient use has not been made of the experiments of the last age upon transfusions. By comparing their effect with that which takes place upon the cutaneous organ, I think that it is impossible not to admit a morbific principle in the blood, at the time of contagious diseases.
3d. After the use of mercury taken in frictions, the emanations of this metal from the animal fluids, act evidently upon silver when placed in the mouth, the rectum, &c. I am persuaded even that the blood which in the natural state exerts but very little action upon this metal, would alter it then. Accoucheurs know that the waters of the amnios of those women who have made use of mercurial frictions exhibit the same phenomenon.
4th. Many substances that are not medicinal can be transmitted to the blood by cutaneous absorption. Water appears to enter it in this way, in the rapid production of certain dropsies, in those cases related of travellers, who wanting fresh water on the ocean, have in part quenched their thirst by surrounding themselves with damp clothes, &c. When our garments are impregnated with the oil of turpentine, the urine soon acquires an odour that is owing to the principles transmitted to the blood by absorption. Many judicious philosophers have asserted that the weight of the body has been increased by a walk in the morning.
I have observed that after remaining in the dissecting room some time, the intestinal flatus frequently acquires an odour exactly similar to that which the bodies in putrefaction exhale. In the following way I convinced myself that it was the skin as much as the lungs that absorbed these odorous particles. I closed my nostrils, and fitted a long tunnel to my mouth, which passing out of the window allowed me to breathe the external air. The flatus from my bowels, after I had remained an hour in asmall dissecting room, at the side of two very fetid bodies, acquired an odour nearly similar to theirs. I have observed also that by touching for a long time fetid substances, the flatus acquires more of this odour, than by remaining only in an air loaded with cadaverous exhalations. Then the absorbents carry at first these exhalations to the blood, which afterwards throws them out by the mucous surface of the intestines. Thus when the urine is absorbed, the saliva, the mucous juices, &c. have an urinous odour.
I could accumulate many other proofs of cutaneous absorption; but I have selected only the principal. Many others have been cited; Haller in particular, to whom I refer, has multiplied examples of it.
I would remark however that cutaneous absorptions have a character of remarkable irregularity; that under the same apparent influence, they sometimes take place and sometimes do not. It is thus that most often we absorb nothing in a bath, that we escape or take contagions, that the vaccine disease is or is not communicated, that the variolous inoculation is also often uncertain, &c. This is not astonishing. It requires a certain degree of sensibility in the skin for the absorption of this or that substance; above or below this degree, the absorbents repel this substance. Thus in the intestinal canal, if you raise by a purgative, the ordinary degree of sensibility of the lacteals, they cease immediately for a time to take up drinks, chyle, &c. and every thing passes off by the anus. Now a thousand causes act incessantly upon the skin; a thousand irritants by turns applied to it make the degree of its organic sensibility vary every instant, increase, diminish and remove it from that which is necessary for absorption. Is it astonishing then that this function should exhibit so many varieties? Many modern philosophers have produced numerous negative facts against cutaneous absorption. What do these facts prove? onlythe varieties of sensibility which I have noticed; but they do not destroy the mass of positive facts, generally acknowledged and which together form a body of proof which nothing can oppose. Thus we have seen the mucous surfaces variable in their vital forces on account of the variety of their excitants, vary also in their absorption. If in the serous membranes, in the cellular texture, in the work of nutrition for the organs, this function is uniform, it is because being constantly in contact with the same bodies, the surfaces where it is going on have an uniform degree of organic sensibility.
Many facts, in relation especially to contagions seem to prove that a state of weakness is favourable to cutaneous absorption. 1st. Children and women absorb more easily than strong and vigorous men. 2d. Many physicians have observed that in the night in which the cutaneous organ is in a state of remission in this respect, as it is not stimulated by external objects, contagious diseases are more easily taken. 3d. I have remarked that most of the pupils who have fallen sick during my dissections, had carried to their chambers portions of subjects, the emanations from which had been able to affect them during sleep. 4th. We know that practitioners recommend, that persons should not expose themselves to contagious miasmata during hunger, as the forces are then languid on account of the emptiness of the stomach.
The external capillary system which surrounds the chorion and embraces the papillæ, appears to be the origin of these vessels, as it is the termination of the arteries of the dermoid spaces. The exhalants take up their fluid there, which they throw out upon the epidermis. We have no anatomical knowledge as to their form, their length, their course and their direction; but their existence is incontestibly proved, 1st, by injections, which are sometimes poured out upon the whole cutaneous surface; 2d, by the sanguineous exhalation which takes place in some diseases in which there is a real bloody sweat; 3d, by the natural sweat and by transpiration, which can evidently have no other agents, though some authors have admitted that there were certain pretended glands for the secretion of these fluids.
An infinite number of calculations has been made to ascertain the quantity of fluid which the cutaneous exhalants usually pour out. We are dismayed when we read the result of the labours of many philosophers upon this point, when we go over the calculations, enormously multiplied, of Dodard, Sanctorius, Keil, Robinson, Roye, &c. To what do all these calculations, for which the life of a single man would perhaps be insufficient, tend? To prove to us that when we start from a false principle, the whole chain of consequences drawn from it is false, though these consequences may be rigorously deduced from each other. In fact, most philosophers have considered the skin as a kind of fountain with numerous capillary tubes, always throwing out in the same time the same quantity of fluids, and being able consequently to be subjected, like inert capillaries which pour out fluids, to proportions and calculations of quantity. But the results of these calculations have soon proved how mistaken their authors were. Read these results, and you will see that none of them agree, that frequently very great differences characterize them. Is this astonishing? A thousand causes make the transpiration vary at every instant. Temperament, exercise, rest, digestion, sleep, watchfulness, the passions, &c. increase or diminish the action of the cutaneous exhalants. I do not speak of the difference from climate, seasons, &c. which is still more decided.
An attempt has even been made recently to ascertain, what belongs to the urine, to the transpiration, to the pulmonary perspiration and to the excrements, to calculate the relation which exists between the quantities thrown out in these four ways; useless researches! We might obtain from them results for one man, which would not be applicable to others. Thus see if we have ever been able to make a single useful application to physiology or pathology of all these immense labours on transpiration. What would you say of a man who, during the days of the equinox, in which the state of the atmosphere was every minute changing, should try to establish proportions between the quantities of rain which fell in every quarter of an hour, or of one who endeavoured to fix relations between the quantities of fluids which are evaporated in given times, from the surface of a vessel under which the intensity of the heat which warmed the water varied every instant. The comparison is just. We might be able to say in general, at the end of a given time, nearly how many pounds of substances went from the body; and yet this varies in every individual. But to attempt to say in a general manner what, in this common quantity, the urine and transpiration separately furnish, is to prove that we do not understand the nature of the vital forces.
We have already observed, that all our knowledge upon the varieties of transpiration, is reduced to some general data; that, for example, in cold seasons and climates, it is by the internal emunctories that the residue of nutrition and digestion principally passes off, whilst in warm climates and seasons, it is the cutaneous organ that principally throws it out.
The skin on the one hand, and the kidneys and pulmonary surface on the other, are then in this respect, in a constantly inverse activity. Physicians very well know this difference in regard to the urine and sweat; they know that when one is increased, the other is diminished: that in winter the urine contains principles of various kinds, and that in summer the transpiration has a salt tasteand other peculiar characters which it owes to the substances which are foreign to it in the first season. But they have not so well examined the relation of the transpiration with the sweat; this determined me to make the following experiments:
I wished to know what is the state of the respiratory fluid in summer, in which there is much transpiration, and in which all the heterogeneous principles consequently go out by the skin. To obtain this fluid which is exhaled in insensible vapour, I placed a clean, empty bottle in a pail filled with ice and the muriate of soda, and I respired a long time in it, taking care not to allow any saliva to fall in. The parietes, chilled by the external ice, condensed into small icicles the vapour of my breath, on the internal surface of the vessel. When I had made a certain quantity of these, I withdrew the bottle; then by putting it into tepid water, the icicles immediately melted, and I had in a liquid state my respiration, which was before in vapour. Now I have been struck with two things in this experiment, 1st, with the small quantity of fluid that I was able to obtain, though I had respired for an hour, and afterwards made two men respire each an hour; 2d, with this, that most of the reagents have no action upon this fluid. Nitric, sulphuric and muriatic acids, lapis infernalis, and alkohol produce no effect when mixed with it. In evaporating a small quantity in the concavity of a watch chrystal, no residuum is left; placed in a spoon over the flame of a candle, it experiences no alteration from the heat. In a word, I have been almost tempted to believe that it was nothing but water. I confess however that this experiment ought to be carefully repeated.
The little fluid obtained made me believe that the form of the vessel was not well adapted to the purpose, because it did not present sufficient surface and the vapour of the lungs was too little divided. I took then the spiral cylinder of a small alembic which I surrounded with ice in a pail; I made a man breathe through it, and I obtained in fact more fluid, but infinitely less however than I expected, considering the great cloud that is formed in winter by respiration. In an hour, two ounces of fluid only were condensed, which I weighed comparatively with water, and found a little heavier, a proof that some principles are mixed with its aqueous portion, and with which I am unacquainted.
I am convinced that in winter I should have condensed much more vapour; the inspection of an animal that breathes proves it even, as I have just said. I am persuaded also, that like the urine, the respiratory fluid is then charged with principles which, during summer, pass off by the skin, though I have not however any experimental data upon this essential point, which I propose to clear up the approaching winter. I think even that many colds depend upon this. In fact, many of these principles thrown out by the mucous surface of the bronchia, not soluble in the air, like their aqueous vehicle, stagnate upon this surface, irritate and excite a cough which throws them off. On this account, we cough much in winter, as we have often occasion to bathe in summer, when the saline substances, which are accumulated upon the skin by the exhalation that takes place there, cannot be evaporated by the air. Hence why also in many affections of the lungs, in which the mucous glands and the bronchial exhalants do not increase the quantity of fluid they usually pour out, but only separate with it, on account of their change of organic sensibility, substances which the air cannot dissolve, hence, I say, why in these affections there is a constant cough; for, as I have said, when a substance remains for any time upon the mucous system, it irritates, and it makes an effort to get rid of it. I believe that this elucidates the cause of many coughs, which have been considered as nervous, on account of the small quantity of expectoration, and which are only a means that nature employs to supply the want of the evaporation of the air.
I think that physiologists have not paid sufficient attention, either as it respects the bronchia or the skin, to the part which can be evaporated, and to that which cannot. Some animals seem to throw out more of these principles that cannot be evaporated, than man; hence why it is necessary to curry horses every day, and even to bathe them often, in order to cleanse their skins which the air would leave dirty. Fourcroy and Vauquelin have remarked that there is never phosphate of lime in the urine of these animals; this substance appears to pass out with the sweat, and to be chrystalized on the surface of the skin, from which it is removed by friction and water. I can hardly conceive how the hairs can be the emunctories of it; it appears to me to be more natural to think from analogy, that it is by the sweat that it escapes. I presume that the rain, in the natural state is as necessary to these animals as to plants. The first do not avoid it; many even expose themselves to it; it serves as a bath for them, removes the saline particles the air does not dissolve, and washes the skin.
The cutaneous exhalants do not appear to be everywhere equally abundant. The face and chest contain many of them; we sweat easily in these places. On the back and the extremities they are less numerous. It is rare that we sweat on the palms of the hands and the soles of the feet. Besides this varies remarkably in different individuals. I know two sisters, belonging to a family in which phthisis has been frequent, whose chests are however well formed, and who have never had any sign of an affection of the lungs, and yet when they are warm they always sweat from the chest. We know that in some the sweat appears most usually in the face, and in others on the cranium.
Have the nerves any influence upon the cutaneous exhalation? In many cases of paralysis, the patients sweat from the sound side. I have attended, for two months past, a man at the Hôtel Dieu, who after an apoplexy, had hemiplegia so that the left side of the body was immoveable, and who only sweats from this side, so that an evident line of demarcation is visible the whole length of the median line. On one side the skin is dry, and on the other it is very moist. I know cases are related in which opposite phenomena have taken place; but they do not destroy the observation that is uniformly made, that the sweat takes place equally upon the sound and the diseased side. Besides, who does not know that when the nervous action is annihilated in a limb, a blister acts upon it as usual? Do convulsions, in which the nervous action is so much raised, increase cutaneous exhalation? Have the states of extreme sensibility, in which all the cutaneous nerves are so susceptible of receiving all impressions, the least known influence upon sweating? Let us acknowledge then that in cutaneous exhalation, as in secretion, we know nothing of the nature of the nervous influence, if it does exist.
Besides the insensible transpiration and the sweat, which are thrown out by the skin, this organ is constantly lubricated by an oily fluid, which occasions, when coming out of a bath, the water with which it does not unite, to collect in small drops upon the body, which greases the linen when it remains too long in contact with the skin, catches the dust that is floating in the air, makes, it remain upon the skin, and retains many foreign substances coming with the sweat from without or within.
This fluid is in general much more abundant in negroes, whose skin is on this account disagreeable, than in European nations in whom it abounds especially in placesprovided with hair, particularly on the cranium. If left without dressing, the hair becomes greasy, unctuous and shiny; it seems even that this abundance of oily fluid is destined to support their suppleness. Thus art imitates nature in the preparation of it, and greasy substances almost always enter into the dressings of the toilet. It appears that there is less of this fluid in other parts where there are hairs. It oozes in very small quantity from the soles of the feet and the palms of the hands, no doubt on account of the thickness of the epidermis. When we wash these last, the water collects in small drops on the back of them, and not in the palms, which are easily and uniformly wet; there is never any of it deposited on the surface of the nails. This cutaneous oil, retained in certain places, as in the axilla, the perineum, the folds of the scrotum, &c. becomes mixed there with certain principles of the transpiration, and often exhales a fetor that is almost insupportable.
This oily fluid, of the nature of which we know but little, is not like the transpiration or the fat exposed to evident increase and diminution; it is always found in nearly the same proportion. It appears to preserve the suppleness of the skin, by preventing it from cracking. The ancients sought no doubt to imitate its action over the whole skin, as we imitate by pomatum its functions in regard to the hair, by the oily unctions which they made upon the body. This we know was much practised among the Romans.
Whence comes this cutaneous oil? It can be furnished from three sources, 1st, from transudation; 2d, secretion; 3d, exhalation.
Some have thought that the sub-cutaneous fat oozed through the pores to form it; but the scrotum which is destitute of this fat is one of the most oily parts. The skin of the cranium, which is so to the highest degree, is hardly at all fatty. That of the cheeks which coversmuch fat, is scarcely lubricated with it, &c. In emaciation the skin is often as unctuous as in corpulency, though it is not always the case. Finally, in all the other functions, physical transudation is proved to be nothing; would it exist then here alone?
Those who admit the secretion of the cutaneous oil, (and they are the greatest number,) place the source of it in the small glands that are called sebaceous, and which they say are every where spread under the skin. We see some small tubercles upon the convexity of the ear, upon the nose, &c.; but in most of the other parts it is impossible to distinguish any thing; we see only the small eminences of which I have spoken and which make the skin rough; now they have nothing in common with these glands, the existence of which I do not deny, but which I confess I have many times in vain sought for.
This has made me think that there is perhaps an order of exhalants destined to separate the cutaneous oil, and which is distinct from that of the exhalants which throw out the transpiratory matter. There is in the cellular texture exhalants for fat and others for serum. Certainly no gland presides there over the secretion of the fat. It is the same with the marrow which the exhalants of the medullary membrane furnish. There is I think as much probability in the supposition of the exhalation, as of that of the secretion of the cutaneous oil.
Besides, we must not confound this oil, either with that ceruminous matter which certain glands pour out on the edges of the eyelids and behind the ears, and which is forced out by pressure in the form of little worms, or with that whitish substance that is collected between the glans and the prepuce, and which is so evidently furnished by small glands.
These properties are much developed in the skin. The alternations of emaciation and corpulency through which our organs, the limbs especially, pass sometimes from a determinate size to one double or even treble, and afterwards return to their primitive state, prove these properties; and so do all the different tumours, deposits of pus, external aneurisms, sudden engorgements which accompany great contusions, aqueous collections in the abdomen, pregnancy, scirrhi, numerous affections which increase the size of the testicle, hydrocele, &c. We see in all these cases the skin at first extended and dilated, then contracting when the cause of the distension has ceased, and occupying the place in which it was originally circumscribed.
The remarkable separation which the two edges of a wound experience, that is made by a cutting instrument, is owing to the contractility of texture. This separation which takes place upon the dead body, proves what we have already often remarked, viz. that the properties of texture, absolutely inherent in the organic texture, are foreign to the vital forces from which they only borrow an increase of energy; thus the cutaneous retraction is much stronger during life in a longitudinal or transverse wound. But it is particularly in amputation that we observe this increase of contractility from the vital action. No part, not even the muscles retract so much as the skin; hence the precept so much recommended in this operation of saving the integuments as much as possible; hence theessential modifications that have been made in the ancient methods. The muscular retraction is more sudden; but this, which is more durable, ultimately prevails; so that in the ancient mode of amputation, where every part was cut at the same level, they had a conical stump, the summit of which was formed by the bone, in which was next seen the muscles, arteries, &c. and in which the skin representing the base, terminated on the side of the limb.
There are however many cases in which the dermoid extensibility is less than it at first seems to be. For example, in large sarcoceles, the skin of the neighbouring parts of the scrotum being drawn, is applied upon the tumour, and makes up for the extensibility that is wanting in the skin of this part; that of the penis especially is almost wholly employed to cover the tumour; so that this organ disappears. It is to the limits placed to the cutaneous extensibility that must also be referred the following phenomenon; in a wound with loss of substance, the fleshy granulations, in contracting by the evacuation of the white substance that filled them, draw the neighbouring skin in order to cover the wound; now this drawing produces not only an extension but a real locomotion. Hence why when the skin, naturally tense and adherent, cannot yield to this locomotion, the cicatrices are formed with so much difficulty, as we see upon the cranium, the sternum, &c.; why on the contrary on the scrotum, the fold of the axilla, &c. they take place with so little; why in dissecting out tumours, it is so much recommended to save the sound integuments, &c.
When the skin is stretched, the fibres which compose the spaces that have been spoken of, separate from each other, and these spaces become broader. Their breadth becomes especially evident on the internal surface of the dermis; for as all the pores of the external surface pierce obliquely its texture, the distension of this texture only diminishes the length of the small canal they form, butdoes not enlarge the orifice of it; thus whilst the internal surface contains interstices of considerable size, this remains uniform, but allows us to see these interstices, which render it more transparent where they exist; hence that appearance like marble on the skin of the abdomen of women who have had many children.
When the skin is contracted, the internal spaces are drawn together and even effaced. The external surface which has none of these, cannot diminish so much in breadth, so that there is a disproportion in the breadth of the internal and external surface; hence, as I have said, the convexity of the latter in the horny hardening produced by boiling water; hence also the inequalities and external roughness which takes place when cold acts powerfully upon us, and which contracts the dermoid texture. Besides, this phenomenon only takes place when the contractility is evident in the ordinary state; for if there has been previous distention, the cells already enlarged, return only in contracting to their natural state, and there is no disproportion in the extent of the internal and external surfaces of the skin.
In most of the extensions, there is a diminution of the thickness of the dermoid texture. It is only when it is dilated by the infiltration of water in its spaces, as in leucophlegmasia, that it increases in thickness by diminishing in density. In chronic inflammation, in engorgement, and in various alterations of which the dermoid texture is the seat, it loses in part the faculty of stretching; it breaks with ease when it is distended. This is what happens in some aneurisms, in those of the aorta especially that have produced an absorption of the sternum. A slow inflammation seizes upon the skin that covers the tumour, and it breaks with a degree of distention infinitely below what it bears in a sound state, if the death of the patient does not prevent this fatal rupture, two examples of which I have seen in the ward of lyingin women at the Hôtel Dieu. In this state of inflammation, the distention is very painful, whilst it is not so in the ordinary state.
The skin loses also its contractile power in most of the chronic affections of which it is the seat, and which alter its texture.
Are there some days in which the skin is more contracted, and others in which it is looser and more expanded? I believe so, from observing the marks left after small-pox, which are much more apparent and deeper some days than others.
These are strongly marked in this system. We might say, that nature by giving an excess of life to this dermoid covering, has wished to establish a striking line of demarcation, and to make us perceive the difference between the inorganic bodies with which its external surface is in contact, and the organized textures that its internal surface covers. I shall consider these vital properties as in all the other systems; some belong to animal life and others to organic.
The animal sensibility exists in the highest degree in the skin. It presides over the feeling, which is more acute and delicate there than in most of the other textures. It is also the cause of touch, a double function which is very different.
The feeling is the faculty of perceiving the impression of the surrounding bodies. It gives us the sensations of heat and cold, moisture and dryness, hardness and softness, &c. It has relation then, 1st, to the existence; 2d, to the general modifications of external bodies. Its exercise precedes that of all the other senses which cannotbe exercised until after its action. It is necessary to the sight, to hearing, smelling and the taste, as it is to the touch. It depends only upon a particular modification of the animal sensibility; it is nothing but this property considered in exercise. Thus when the particular modifications of this sensibility which preside over the other senses have been destroyed, when the eye is insensible to light, the ear to sounds, the tongue to tastes and the pituitary membrane to odours, these different organs still preserve the faculty of feeling, both the presence of bodies and their general attributes.
The touch has only relation to the particular modifications of bodies; it is the source of our notions upon their external forms, their dimensions, size, direction, &c. It differs essentially from the four other senses.
1st. In this, that it does not require, like the feeling, any particular modification of sensibility. The hand is a little more sensible than the rest of the skin; but there is not a great difference, and we should touch bodies almost as well, if that of the abdomen covered the phalanges. On the contrary, each sense has a peculiar sensibility which places it exclusively in relation with a determinate body in nature. The pituitary membrane would be struck by light in vain, if placed at the bottom of the eye like the retina; the palatine membrane if it lined the nasal fossæ, would not perceive odours, &c.
2d. The touch is exercised only upon masses, more or less considerable parcels. The other senses are brought into action by the insensible and infinitely multiplied particles of bodies, as the luminous, savoury particles, &c.
3d. Most of the other senses do not require the previous exercise of the will. Odours, light and sounds strike upon their respective organs, and often produce, without our attending to them, their respective sensations. It is the same with feeling; the will most commonly has no part in it. It is exercised because we live in the midst ofmany excitements. We do not most often seek for the causes of general sensations; they are those that come and act upon us. On the contrary, the touch requires to be produced by an act of the will. It is exerted in consequence of the exercise of the other senses; it is because we have seen, heard or felt an object, that we touch it. We confirm or correct by this sense the notions, which the others have given us. Hence why it is, as it were, dependant on them. The more they are contracted, the less frequently is it exercised. The blind, the deaf, &c. have less desire to touch than him, who has all his sensitive gates open to the impression of external bodies.
4th. Most of the other senses require a peculiar structure as well as a peculiar sensibility in the organs which compose them. On the contrary, the touch only requires a particular form in its organs. Provided that these have on the one hand animal sensibility, and on the other can embrace by many points external objects, they can distinguish their tangible qualities. The touch will be obscure if we grasp bodies in one or two directions only; yet it will take place. Thus we touch with the hollow of the axilla, the bend of the arms, hams, &c. with the lips and with the tongue. Thus the elephant touches with his trunk, reptiles by twining themselves around bodies, most animals with their snouts, &c. But the more the points of contact are multiplied, the more perfectly is the sense exercised. The hand of man is in this respect the most advantageously formed; it proves that he is better adapted to communicate with what surrounds him than all other animals; that the empire of his animal life is naturally much more extended than that of theirs; that his sensations are more accurate, because they have a means of perfection that theirs have not; and that his intellectual faculties are destined to have an infinitely greater sphere, since they have an organ infinitely better than theirs to perfect them.
The sensibility of the skin resides essentially, as we have seen, in the papillary body; it is there that all the great phenomena relative to sensation take place. It is this portion of the skin that truly belongs to animal life, as the reticular body is, on account of the vascular plexus that forms it, the portion essentially dependant on organic life. The chorion being as it were passive, remains foreign to every kind of important function, and serves only for a covering.
The extremely acute sensibility of the papillary body requires a covering to defend it from strong impressions. This covering is the epidermis. When it is removed, every touch is painful; the impression of the air even is very much so; it is this removal of the epidermis that produces the smarting that is felt when a blister is taken off. Observe in fact that smarting is a very frequent kind of pain, which the animal sensibility of the skin occasions when more raised than usual. This term1is borrowed from burns, which, when they are only to a certain extent, acting nearly like blisters, lay the papillæ bare; now as it is always the skin which is exposed to the action of fire, we transfer to all burnt organs the ideas which we attach to the word smarting. But the pain is far from having the same character in the other systems; this peculiar one belongs only to the dermoid, in which it takes place from a burn, erysipelas, after a blister, &c. and during all inflammations that have their seat in the reticular body. No other system when inflamed gives us this sensation. The pain is throbbing in the cellular; it exhibits a wholly different modification in the muscular, when it is the seat of acute rheumatism, &c.
1In order to understand this sentence it should be observed that the word which I have translated smarting iscuisson, which means the action of fire upon animal bodies, and is also used for the painful sensation which this action produces.—Tr.
1In order to understand this sentence it should be observed that the word which I have translated smarting iscuisson, which means the action of fire upon animal bodies, and is also used for the painful sensation which this action produces.—Tr.
There is another kind of pain which is also peculiar to the cutaneous system; it is itching, which is the firstdegree of smarting. We remove it by a gentle friction, which exciting in the papillæ a different sensation, effaces that of which they are then the seat; but when this new sensation has passed off, the former one, which is occasioned by a permanent cause, is reproduced and requires a new friction; there happens then in a small way, what we observe in a large one, when a stronger pain makes us forget one that is weaker. No other system in the economy exhibits this kind of pain, so frequent in itch, herpes and many other cutaneous eruptions. In their tubercular inflammations, the serous membranes become the seat of white eruptions, analogous to many of those of the skin; the mucous surfaces are also often affected with many small pimples; now this sensation is never manifested in either of them.
There is also a sensation which appears to be the minimum of that pain of which smarting is the maximum; it is tickling, a mixed sensation, an hermaphrodite, as an author has called it, which is agreeable when carried to a certain degree and painful beyond it. Carry the fingers lightly over a mucous or serous surface, a muscle or a nerve laid bare; an analogous sensation will never arise from the contact.
The animal sensibility of the skin is, like that of the mucous surfaces, subjected to the essential influence of habit, which can transform successively into indifference or even into pleasure, what was at first painful. Every thing that surrounds us furnishes constant proof of this assertion. The air in the succession of the seasons, caloric in the numerous varieties of the atmosphere, in the sudden change from one temperature to another, water in a bath, in the moist vapours with which the medium is loaded in which we live, our garments of which some, as those of wool, are at first very painful, every thing which acts upon the skin by mere contact, produces sensations in it which habit continually modifies. Observe the modeof dress of different nations; in some, all the superior extremities are bare; in others, the fore-arm only appears; the inferior extremities, either in whole or part, are naked in others; in some, a more or less considerable portion of the trunk is left exposed to the air, and among the savages, nothing is covered. The portions which in each people remain naked, bear the contact of the air, without giving any painful sensation. Let them expose, on the contrary, parts usually covered, especially if it is cold, and at first pain will be the consequence of it; then the parts gradually becoming accustomed to this contact, will get to be insensible to it. There has been much said latterly of the danger of the Grecian costumes, of the nudity of females, &c. I do not speak of the morality of them; but every thing that is reprehensible physiologically is, that the progress of the fashion has been more rapid than that of the sensibility. If they had exposed at first the neck, then a little of the chest, then the bosom, &c. habit would by degrees have given a new modification to this property, and no accident would have resulted from it. But in going suddenly from a costume in which every part is covered, to that in which the superior half of the chest, either before or behind, remains naked, is it astonishing that colds, catarrhs, &c. should be the result of it?
Habit extends its empire, in relation to the skin, even to our manners themselves. Decency is in this respect a thing of comparison. An Indian woman, with nothing but a narrow cloth around the pelvis, would be with us an object at which the public modesty would be shocked. The habit of mankind serves her as a veil in her own country. A female savage transported entirely naked to the same country, would be indecent there; she is not so in her own. Observe our fashions in their rapid succession; a woman, who by not changing her costume, would have had two years since, that of a courtezan, would nowfind herself dressed with great modesty. Indecency in costume is that merely which shocks our habit. The female Indian, with the rag that covers only a quarter of her body, is more decent than the woman in whom a small opening separated the neck-handkerchief in our old fashions. The sight of the face shocks those people among whom females are veiled. Let us consider then habit as the type of the decency of costumes. Nature has wished in physiology, that the phenomena over which it presides, should be slowly connected; it is the same in morals. The woman who suddenly changes her dress from one that is close to one that is not, exposes herself to painful sensations, to catarrhal diseases, &c. and shocks the eyes of those who had been accustomed to see her in a different exterior. When the change is gradually and insensibly brought about, neither health nor morals are affected.
Habit does not modify the cutaneous sensibility which arises from an alteration of texture, from an inflammation, &c. Powerfully raised in this last state, it is much above its natural level. Then the least contact becomes extremely painful; thus the skin is no longer then in a state to exercise the sense of feeling. The touch itself does not distinguish general sensations. All bodies make a common and uniform impression, it is that of pain.
The animal sensibility of the skin sometimes diminishes and even disappears; paralysis is a proof of this. These affections, more rare than the loss of motion, often however take place. In the organs of the senses, it is the eye which most frequently loses the sensation; the ear comes next, then the skin, then the nostrils and finally the tongue, which is the sensitive organ that is always most rarely paralyzed, no doubt because it is that which is the most connected with the support of organic life, without which we could not exist. The others belong especially to animal life, which we can lose in part without ceasing to exist.
The whole skin is never at the same time paralyzed; there is rarely even hemiplegia in this respect; the feeling is not extinguished but in an insulated part. I would remark that the existence of these paralyses is also a proof of the want of nervous influence upon cutaneous exhalation and the capillary circulation, since both go on very well in this case as well as in paralysis of motion, as I have observed above. Cut the nerves of a limb of an animal, in order to render this limb insensible; if after this you apply an irritant, the skin will inflame as usual.
When the animal sensibility is in exercise, is there a kind of erection of the papillæ that they may feel more acutely? The same observation may here be made as was in regard to the mucous surfaces. This erection is an ingenious idea of some physicians, and not a fact which rests upon observation. I even think that this contradicts it; for examined with a glass the papillæ appear to be constantly in the same state. Why should not the skin feel like a nerve laid bare, like the eye, the ear, &c. in which these sorts of erections have never been imagined?
Animal contractility is wholly foreign to the cutaneous organ, which moves voluntarily only by the influence of its fleshy pannicle.
Organic sensibility and insensible contractility exist in the highest degree in the cutaneous organ. The external capillary system, which forms the reticular body, is, as I have said, especially the seat of these properties. They are in constant activity in order to preside, 1st, over the capillary circulation; 2d, over exhalation; 3d, over absorption; 4th, over the nutrition of the whole dermoid texture; 5th, over the secretion of the cutaneous oil, if the sebaceous glands exist. It is not astonishing thatthese properties should be so much developed in the skin, in which they have so many functions to support. Add to these considerations the constant action of external bodies, an action which keeps this organ in continual excitement, which incessantly stimulates its sensibility, which is to this sensibility what that of the bodies contained in the mucous surfaces is to the sensibility of these surfaces; the irritation is even more sensible, because the stimuli are oftener changed. A thousand agents of nature, of different density and composition continually succeed each other on the exterior of the body, and at the same time that they act upon the animal sensibility of the skin, to produce various sensations, they excite the organic sensibility in order to support the functions over which this sensibility presides.
Is it astonishing then that the greater number of cutaneous diseases supposes an alteration in this property and in the insensible organic contractility which is not separated from it? I divide these diseases into four classes, according to the structure we have distinguished in the skin.
1st. There are diseases of the papillæ; these are the paralyses and various kinds of increase of feeling, which reside only in the nerves. Women are especially subject to these last, which are so great in some nervous affections, that mere contact of the skin if considerably powerful produces convulsions. To this also should be referred the extreme susceptibility of some individuals in whom tickling produces a general revolution. It is necessary to distinguish these exaltations of animal sensibility, from those of which we have spoken above, and which depend upon inflammation. The organic sensibility is especially affected in these last; we might say that by its increase it is transformed into animal sensibility; whereas in the other case this last property alone is altered.
2d. There are diseases which have evidently their seat in the cellular texture which occupies the dermoid spaces; such are the inflammations of the cutaneous portion which covers a phlegmon, a bile, &c.
3d. There are diseases of the external capillary net-work, from which the exhalants arise. To this must be referred erysipelas, many species of herpes, measles, scarlatina and many acute cutaneous eruptions that are daily met with in practice.
4th. Finally, there are diseases in which the chorion is affected. Elephantiasis, and in general many chronic cutaneous diseases appear to me to be of this number, and I will even observe that the chorion never appears to be primarily affected in acute diseases. The obscurity of its vital forces, its dense and compact texture, and its comparative want of vessels prevent it from accommodating itself except to chronic affections. In phlegmonous erysi pelas, in biles, &c. it is only influenced, but it is not essentially diseased. Thus we have seen that all the affections of the osseous, cartilaginous, fibrous, fibro-cartilaginous systems, &c. are really slow and chronic, on account of the texture and the vital obscurity of these systems.
Now if we reflect on this division of cutaneous diseases, we shall see that except those of the first class, which are not numerous and which consist in greater or less alterations of animal sensibility, we shall see, I say, that all the others suppose a more or less considerable affection of the organic sensibility and of the corresponding insensible contractility. All are derived from an increase, a diminution or an alteration of these properties.
It is also to the different changes of these properties, that must be referred the more or less copious sweats and the various exudations of which the skin is the seat. In fact, the exhalant vessels remain always the same in relation to their structure. Why then do they admit a greateror less quantity of fluids? Why at certain times do they allow of the passage of substances, which they repel at others? It is because the modifications of their organic forces are changed. These forces are often weakened in an evident manner in diseases; they become languid and are prostrated. Then blisters are applied in vain; the organic sensibility no longer answers to the excitement that is made upon it. This is a striking phenomenon in ataxic fevers, and proves the independence of the phenomena of cutaneous exhalation, capillary circulation, &c. in regard to the cerebral nerves. In fact, whilst during the paroxysm the brain is in extreme excitement, the voluntary muscles are put by this excitement into a violent state of convulsion, and the energy of the whole of the animal life seems to be doubled before it ceases to exist, the organic is already in part exhausted; the functions of the portion of the skin which belongs to this life have already ceased.
The stimuli of cutaneous organic sensibility vary remarkably in their degree of intensity. 1st. The strongest are fire, cantharides, the alkalies, the acids sufficiently diluted by water not to act but upon the vital forces and not to alter the dermoid texture by the horny hardening, the juices of many acrid and corrosive plants, certain fluids even produced in the economy, as those of cancers, &c. All these stimuli redden the skin when they are applied to it. 2d. Most of the same stimuli, diminished in intensity, stimulate it but slightly. 3d. Finally, aqueous fluids, cataplasms and emollient fomentations seem to produce this excitement the least; they even rather weaken the cutaneous organic sensibility; they seem to act upon it like sedatives and moderate the kind of excitement it produces in inflammations. The same is true of most of the fatty substances; thus oils, butter, grease, &c. are in general not calculated to keep up the suppuration of blisters. It is requisite, in order to keep the skin atthe degree of organic sensibility, necessary for the purulent exudation that then takes place, to mix cantharides with fatty substances.
The skin does not appear to enjoy sensible organic contractility. Stimuli usually produce no other action upon it, than the contraction imperceptible to the eye, which composes insensible contractility, and which takes place especially in the small capillary vessels. There is however one circumstance in which this contraction is, to a certain extent, apparent; it is when cold acts briskly upon the skin, which it wrinkles into goose flesh, as it is called. I have pointed out above the mechanism of this contraction, of which the chorion is the seat, and which holds a medium, like many motions which I have already had occasion to notice, between the two species of organic contractility.
We shall still follow the division of the sympathies into active and passive, a division which is more remarkable here than in most of the other systems, because the sympathies are much more numerous.
The animal sensibility is very often brought into action in the skin, by the affections of the other systems. We know that the application of cold to the sole of the foot frequently produces affections of the head; that in many cases, the different species of itching, and even of smarting appear without an injury of the part where the pain is felt. It is useless to cite examples that are known to all physicians. I will confine myself to the sympathies of heat and cold alone, which have not yet been spoken of.
I call by this name the sensation that is experienced upon the skin, when there is not a superabundance or absence of caloric there. There is evidently a materialcause for the heat in inflammation and for the cold in the ligature of a great artery. On the contrary, in the cases of which I spoke, it is but an aberration of the internal sensitive principle, which resembles that which takes place when we refer the pain to the extremity of an amputated limb. This is what occurs in many cases of shivering, in which the internal sensitive principle refers to the skin a sensation of which the cause does not exist. By approaching the fire then we do not become warm, because we really were not cold; but we only destroy by a real sensation, the opposite sensation which is illusory that we experience, or rather we turn the perception from this sensation. We know that at the instant of the ejaculation of semen, a sudden and sympathetic chill often extends over the body. We know the cold of fear, which almost always arises, like the sweat produced by this passion, from the sympathetic action exerted upon the cutaneous organ by an epigastric organ affected by the passion.
Observe what takes place in the beginning of most acute local diseases, as in those of the serous and mucous surfaces, of the lungs, of the gastric viscera, &c. &c. The organ which is to be the seat of the disease is at first affected; immediately many sympathetic and irregular symptoms arise in all those which are sound; this is the affection that precedes. When the disease is once developed, and it follows its periods, a new order is established, as it were, in the economy. The relations of the organs seem to change. In the preternatural irregularity of the functions, a kind of regular assemblage of symptoms is manifested, it is this assemblage which characterizes the disease and distinguishes it from every other in which a different order of morbific relations is established between the functions; now the passage from the natural to the preternatural relation of functions is marked by a thousand vague symptoms, which should be attributed tosympathies, and among which appears particularly the kind of shiver in of which I have spoken.
In the beginning of digestion a kind of sympathetic cold is also referred to the skin, which is most often as warm as usual; it is an action exerted by the stomach upon the cutaneous sensibility, an action from which arises a particular sensation, different no doubt from that which the same viscus, when disordered, produces in the head, occasioning head-ache, but which is owing however to the same principle.
The heat is very often sympathetic in the cutaneous organ, less however, as I have observed, than in the mucous system. We know the flushes of heat that so often extend over the skin in an irregular manner, in different fevers, and which are not attended with a greater disengagement of caloric.
Our modern philosophers will not perhaps be able to understand, how it is that whilst in the greatest number of cases, the application of a degree of caloric superior or inferior to that of our temperature, is necessary to produce heat or cold, this sensation can arise in a part though it may not have experienced an increase or diminution of this principle. But in the greatest number of cases has not pain a material cause? And yet all sympathies produce it without this cause. The vulgar, who stop at the diversity of the modifications of feeling, believe that an insulated principle presides over each. Let us disregard all these modifications, in order to see but a single principle in the irregularities as in the regular course of sensibility. That this property, sympathetically altered, gives us the sensation of heat or cold as in the skin, of pulling as in the nerves, of lassitude as in the muscles in the beginning of a disease, &c.; these are but varieties of a single cause, one, of which we are ignorant, but which evidently exists. In general, the sympathies of animal sensibility put into action in each system the sensation which is usual there. The sympathy which, acting upon the skin, creates there a sensation of heat or of cold, would have produced that of lassitude if it had acted upon a muscle.
In order to form an exact idea of heat and cold considered as sensations, let us recollect that they may arise from different causes. 1st. From the increase or diminution of the caloric of the atmosphere. 2d. From the disengagement or the want of disengagement of this fluid in a part of the economy, as in a phlegmon or after the ligature of an artery of a limb. 3d. Sometimes without previous inflammation more caloric is disengaged in the whole body; there is a general increase of temperature; we then feel an internal and external heat; or caloric is disengaged locally in a part of the skin, and the patient feels a heat there as he does who applies his hand upon this place. 4th. Finally, there are sympathies of heat and cold. Some other parts, besides the mucous surfaces and the skin, feel these sympathies; we know the sensation of coldness that is felt to arise from the abdomen to the thorax, &c.
The organic properties of the skin are also frequently put into action by sympathies. The sweat on the skin is suppressed in a moment, if a cold body is taken into the stomach. The entrance of teas into this viscus, and an increased cutaneous exhalation, are two phenomena that take place almost at the same instant; so that we cannot refer the second to the absorption of the drink, then to its passage into the black blood through the lungs, and afterwards into the red blood. The production of sweat is then here analogous to its suppression in the preceding case; it resembles that of fear, and that of phthisis in which the lungs being affected act upon the skin. Shall I speak of the innumerable varieties of this organ in diseases, of its dryness, its moisture, its copious sweats, &c. phenomena for the most part sympathetic, and whicharise from the relations which connect this sound organ with the diseased parts? I have pointed out those which exist between it and the mucous surfaces. The membrane of the stomach is the one with which it especially sympathizes. The digestive phenomena are a proof of this. It would be necessary to treat of all diseases in order to speak of the sympathetic influences exerted upon the skin. These influences are often chronic. How in many organic diseases, do different tumours form upon the skin? Precisely as petechiæ, miliary eruptions, &c. are produced in acute fevers; the difference is only in the duration of the sympathetic phenomena.
Animal and sensible organic contractility cannot be evidently put into action in the passive sympathies of the skin, since it is not endowed with these properties.
The four classes of cutaneous affections of which we have spoken, occasion many sympathetic phenomena, the following are some of them.
1st. Whenever the papillæ are strongly excited, as in the tickling of very sensitive people, various organs feel it sympathetically; sometimes it is the heart; hence the syncopes that then take place; sometimes it is the stomach; thus I knew two persons who could be made to vomit by tickling them; sometimes it is the brain, as when in very irritable people, tickling is carried so far as to produce convulsions, which is not very rare in nervous women. Who is ignorant of the influence which the organs of generation receive from the skin, when stimulated in different parts?
Physicians are often astonished at the extraordinary effects which some mountebanks produce in the economy, who know how to profit by their knowledge of the cutaneous sympathies produced by tickling. But why should we be more astonished at these phenomena, than at thevomitings produced by an affection of the womb, at the diseases of the liver arising from an injury of the brain, or at hemicrania the seat of which is in the gastric viscera? The only difference is that we can in the first instance, produce to a certain extent those sympathetic phenomena, which we only observe in the other. Why do we not oftener make use in medicine of the influence which the skin when tickled exerts upon the other organs? In hemiplegia, in adynamic, ataxic fevers, &c. who knows if the excitement of the sole of the foot, which is so sensible, as every one knows, if that of the hypochondrium, which is not less so in some people, &c. would not be better, if repeated ten or twenty times a day, than the application of a blister, the irritation of which soon passes off? Besides you would never obtain by a blister, rubefacients, &c. means which act as much and more upon the organic than the animal sensibility, an effect as striking, an affection as general in the sensitive system, as by the tickling of certain parts, a means, which acting only upon this last species of sensibility, produces phenomena exclusively nervous; whilst the exhalant system and the capillary with red blood are especially affected by the others. Certainly there are cases in which one of these means is preferable to the other. I propose to ascertain these cases.
We have not yet sufficiently analyzed the different kinds of excitement in diseases; we have not endeavoured to profit enough by what observation has taught us, upon the sympathies we can produce at will. Might we not however say, that nature has established certain relations between very remote organs, that we may be able to make use of these relations in our means of cure? The charlatan, who employs external tickling for certain nervous affections, is often more rational, without knowing it, than the physician with all his pharmaceutical means.
2d. Whenever the cutaneous exhalants or the external capillary system from which they arise, are affected in any manner, many other parts feel it, and this is a second order of the active sympathies of the skin. Here are referred a great number of phenomena, of which the following are a part.
A bath which acts upon the skin during digestion, affects sympathetically the stomach, and disturbs this function. When this viscus is agitated by spasmodic motions, oftentimes the influence which it receives from it suddenly calms it, and brings it to its ordinary state. Not long since in my evening visit at the Hôtel Dieu, I saw a woman who was vomiting continually from a sudden suppression of her catamenia. I directed sedatives which were useless. The next evening she was in the same state; I had her put into a bath; every thing was calmed the moment she came out of it, and yet the catamenia did not return. Few organs are more dependant on the skin than the stomach.
The action of cold upon the cutaneous organ produces many sympathetic effects, especially when this action takes place while we are sweating. The term repercussion of transpiration is not proper to express what then takes place; it gives a very inaccurate idea. Let us suppose that a pleurisy arises from cold suddenly applied, the following is what happens; the organic sensibility of the skin being immediately altered, that of the pleura is sympathetically altered. By it the exhalants become in relation with the blood; they admit it instead of the serum which they before received, and inflammation supervenes. Thus this phenomenon is the same as that in which the application of a cold body upon the skin suddenly arrests uterine, nasal hemorrhage, &c. &c.; the result only differs. Now in this last case, no one ever supposed that there was a repercussion of fluid. The suppression of the transpiration is a thing purely accessoryand foreign to the internal inflammation which takes place. When the skin sweats in summer, the vital forces are more raised by the caloric which penetrates it; in this state, it is more capable of acting sympathetically upon the forces of the other systems. Hence why all strong stimulants that act upon it are more to be feared then. It is so true that it is not the suppression of the sweat which is dangerous, but the alteration of the vital forces of the skin which sweats, that many kinds, as the sweat of phthisis, are not so injurious when they cease for a time; they are checked even with much more difficulty, because they are not produced by a cause acting immediately upon the skin. Now if there was a repercussion of the transpiration, every species of sweat that was suppressed would be injurious. We never hear of a peripneumony arising from a suppression of sweat produced by fear, rheumatism, &c. There would be then also a repercussion of mucous matter, when a pleurisy arises from swallowing a glass of cold water. Men judge only by that which is striking. The suppression of the sweat is an effect like inflammation of the pleura, but it is not the cause of it. If there was no sweat the instant the cold was applied to the skin, inflammation would nevertheless come on. In wounds of the head, with abscesses of the liver, &c. there is no repercussion of fluids.
The trembling of which the voluntary muscles become the seat, the debility of the pulse which the weakness of the action of the heart produces, &c. are phenomena which the influence of the skin affected by cold alone causes. In fact, only this organ, the commencement of the mucous surfaces and all of that of the bronchia, are made cold by the external air; all the others remain at their usual temperature.
We know the innumerable phenomena which arise from the disappearance of herpes, the itch, &c. imprudently produced; in all these cases it does not appear that themorbific matter is carried to the other organs, though I do not pretend that this never happens. It is the vital forces of these which are raised and which then occasion different accidents; now as these forces vary in each system, these accidents will be essentially different; thus the same morbific cause disappearing from the skin, will produce vomiting if thrown upon the stomach, in which the sensible organic contractility predominates; pains, if it goes to the nerves which are especially characterized by animal sensibility; derangements of sight, hearing and smell, if it affects the respective viscera of these senses; hemorrhage, catarrhs, phthisis, tubercular inflammation, &c. if it attacks the mucous surfaces, the lungs, the serous membranes, &c. in which the organic sensibility is much raised. Now, if the same morbific matter carried upon these different organs, produced these accidents, they ought to be uniform. Do not their varieties, and especially the constant analogy which they have with the predominant vital forces of the organs in which they appear, prove, that they depend upon the cause which I have pointed out?
We know that the serous surfaces and the cellular texture on the one part, and the skin on the other, are often in opposition in diseases. There is no sweat when dropsies are formed; the dryness of the skin is often even more remarkable than the small quantity of urine, &c.
3d. When the cellular texture contained in the dermoid spaces is inflamed, as in phlegmonous inflammation, in biles, in some malignant pustules, &c. there comes on many sympathies which can be referred to those of the general cellular system, which have been already noticed.