Besides the red colour of the deeper portions, can, like that of the muscles, be removed by repeated washing and frequently changing the water. Yet the water in which they have been washed is not as red as that used for the muscles.
The instant a mucous surface is plunged into boiling water, however red it may be, as that of the intestines and the stomach, it instantly whitens. The action of the nitric, sulphuric and muriatic acids produces in it also a sudden whiteness.
This colour of the mucous surfaces acquires a remarkable intensity in inflammation. The redness becomes then extremely deep on account of the quantity of blood that is accumulated in the capillary system. It is particularly in dysentery that the internal surface of the intestines exhibits this phenomenon in a striking degree. I ought however to observe to those who open dead bodies, that they never should lose sight of the original tinge of the portion of the mucous system they examine, since each of the divisions of this system exhibits in its shades remarkable differences. If the membrane of the bladder, the rectum, &c. is found as red as that of the stomach in its natural state, then pronounce that there had been inflammation; if the redness of the sinusesequals that which is natural to the bladder and the rectum, decide that inflammation had existed in them. There is, as I have said, a scale of colour for the mucous system. It is then essential to have an accurate knowledge of this scale, a type to which we can refer the inflammatory state in the examination of dead bodies.
Does exhalation take place upon the mucous surfaces? The analogy of the skin seems to indicate it; for it is well proved that the sweat is not a transudation through the inorganic pores of the cutaneous surface, but a real transmission by vessels of a peculiar nature and continuous with the arterial system.
It appears at first that the pulmonary perspiration which takes place upon the mucous surface of the bronchia, which has so much relation with that of the skin, which increases and diminishes according as this diminishes or increases, and the matter of which is probably of the same nature; it appears, I say, that the pulmonary perspiration is made at least in great part by the system of exhalant vessels, and that if the combination of the oxygen of the air with the hydrogen of the blood contributes to produce it, during the act of respiration, it is but in very small quantity, and it is the portion that is purely aqueous. Besides, this last hypothesis of modern chemists, contradictory to the production of all the other fluids thrown out by the mucous surfaces, appears to me ill adapted to explain the formation of this. When the same phenomenon is produced in many places, and the explanation that is given of it is applicable only to one, we should be suspicious of this explanation.
It should be observed in regard to the pulmonary perspiration, that the solution of the mucous fluid which lubricates the bronchia, in the air constantly inspired and expired, furnishes a considerable portion of this vapourwhich, insensible in summer, is very evident in winter, on account of the condensation of the air. The mucous juices are dissolved like every other fluid; for wherever there is atmospheric air, heat and moisture, there is evaporation. Here this evaporation is even a means which nature employs to rid herself, as I have said, of the mucous juices. If they are too abundant, as in a cold, then the quantity of air which serves as a vehicle to them, not increasing in proportion, it is necessary that there should be another mode of evacuation; this is expectoration which compensates for what the air cannot remove by solution.
The intestinal juice which Haller has especially considered, but which appears to be in much less quantity than he thought it, the œsophagean and gastric juices, particularly this last which has been supposed to be distinct from the mucous juices, are probably deposited by exhalation upon their respective mucous surfaces. But in general it is very difficult to distinguish with precision what belongs in these organs to the exhalant system, from that which is furnished by the system of mucous glands, which, as we have said, are everywhere subjacent to them. Thus we constantly see the mucous fluids of the œsophagus, the stomach and the intestines, mixing with the œsophagean, gastric and intestinal fluids.
As on the one hand the blood vessels ramify almost naked on the mucous surfaces, and as on the other these vessels are always the origin of the exhalants, it is evident, that these have but a short course to run to arrive at their surfaces; they are rather pores than distinct vessels. Hence why no doubt the blood has so great a tendency to escape by the exhalants; why consequently hemorrhages without rupture are so frequent in the mucous system; why this affection can be classed in the diseases of this system, &c. &c. No other, by the arrangement of the arteries, offers to the exhalants so short acourse between their origin and termination. Often even, as I have said, we make the blood of these vessels ooze in the dead body through their exhalants.
The absorption of the mucous membranes is evidently proved, 1st, by those of chyle and of drinks on the intestinal surfaces, of the venereal virus upon the glans penis and the canal of the urethra, of the variolous when the gums are rubbed with it, of the serous portion of the bile, the urine and the semen, when they remain in their respective reservoirs. 2d. When, in the paralysis of the fleshy fibres that terminate the rectum, substances are accumulated at the extremity of this intestine, these substances often become hard, an effect probably of an absorption of the soft parts. 3d. There have been various cases in which the urine has been almost wholly absorbed by the mucous surface of the bladder, where there have been insurmountable obstacles in the urethra. 4th. If we respire, by means of a tube, the air of a large vessel filled with the exhalations of turpentine, so that these vapours can only act upon the mucous surface of the bronchia, the urine has the peculiar odour that always arises from the use of this substance, the exhalations from which have been introduced into the blood by the means of absorption, &c.
Whatever may be the mode of this absorption, it appears that it does not take place in a constant and uninterrupted manner, like those of the serous membranes, in which the exhalant and absorbent systems are in a regular and continual alternation of action. There is scarcely any but the chylous absorption, that of drinks, and that of the aqueous portion of the secreted fluids remaining in a reservoir as they come from their glands, that constantly take place. Nothing is more variable than the other absorptions. Under the same influence, the glans takes upor leaves the venereal virus; the internal surface of the bronchia sometimes admits and sometimes refuses admittance to contagious miasmata. There are more cases of retention in which the urine is not absorbed entirely, than there are where this absorption takes place, &c. &c. The innumerable varieties of the vital forces of the mucous membranes, varieties produced by those of the stimuli with which they are in contact, explain these phenomena. If these forces are raised or diminished a little, the absorption is altered, even that which is natural, as that of the chyle. Take a purgative; it contracts, shuts even the mouth of the absorbents of the intestinal canal; as long as the irritation continues, all the drinks that are taken pass off by the anus; at the end of four or five hours, the absorbents gradually recover their natural tone and absorption recommences. In these cases, the first discharges are only the intestinal matters, the others are the copious drinks that have been taken. There are many diseases in which, the sensibility of the chylous absorbents being too much raised, they are no longer in relation with the aliments, they take up with difficulty the residue of them, &c. Deficiency of action produces the same phenomenon; in absorption in fact it is a middle degree of sensibility of the organ which produces it, a degree below or above which it cannot take place.
All the mucous absorbents appear to go to the thoracic duct.
I would remark that at all the origins of the mucous system, where the animal sensibility is very great and where it places us, like the skin, in relation with external bodies, cerebral nerves are distributed. The pituitary and palatine membranes, the conjunctiva, the mucous surface of the rectum, the glans penis, the prepuce, &c. exhibit this fact very evidently. There are hardly any nervousfilaments coming from the ganglions in these different places.
On the contrary, this last species of nerves is the predominant one in the intestines, in all the excretories, in the reservoirs of the secreted fluids, &c. places where the organic sensibility is the most evident.
Extensibility and contractility are much less in this system than they at first appear to be, on account of the numerous folds which it exhibits in the hollow organs during their contraction, folds which are developed only during extension, as we have seen. Yet these two properties become very evident in some cases. The excretories are capable of taking a size much larger than is natural to them. This is seen in the ureters in particular, which are sometimes found as large as an intestine. The ductus choledochus and the pancreatic duct have often also these dilatations. The urethra and the salivary ducts appear to be less extensible than the others. If they have ever so little obstacles from strictures, contractions, &c. they break rather than stretch; hence various urinary and salivary fistulas.
Hence there is, as we see, many varieties in the degrees of the extensibility of the mucous system; it is the same with regard to the contractility of texture. These twoproperties are besides capable of being put rapidly into action. We know that the stomach, the intestines, the bladder, &c. pass in an instant from a great size to extreme contraction. Their functions even suppose this rapidity, without which they could not be performed. The palatine membrane which lines the cheeks, exhibits the same phenomenon when the mouth is filled with air, aliments, &c. which are afterwards expelled from it.
When the usual fluids cease to pass through the mucous ducts, they remain in permanent contraction; this is what takes place in the intestines below a preternatural anus. I have seen in this case the cæcum and the rectum reduced to the size of a large quill. Yet there is never then an obliteration of their parietes, on account of the presence of the mucous juices, of which the patient always passes a certain quantity. The urethra, after the operations for stone in which the urine passes for a long time through the wound, and in the great fistulas in the perineum or above the pubis, the salivary ducts in wounds which affect them and through which the whole saliva is discharged, the nasal canal in fistulæ lachrymales, contract also more or less, but are never obliterated. We know that the vas deferens is often a very long time without having semen pass through it, and yet it remains open. This phenomenon distinguishes the mucous ducts from the arterial, which, when the course of blood is interrupted in them, change into ligaments in which every thing like a canal disappears. We ought not to lose sight of this phenomenon of all the mucous ducts; it proves the incorrectness of the practice of those who, thinking that at the end of some time it is impossible to re-establish, in fistulas, the natural way, think it necessary to make an artificial one.
The mucous tubes are not only not obliterated when they are empty, but when inflamed they do not even contract adhesions of their parietes, as so often happens in the serous cavities, in the cellular texture, &c. Observehow important this fact is to the great functions of life; what would indeed become of these functions, if in catarrhs of the intestines, the bladder, the stomach, the œsophagus, the excretories, &c. these adhesions were as frequent as they are in pleurisy, peritonitis, pericarditis, &c.
Few systems live in a more active manner than this; few exhibit the vital forces in a higher degree.
Constantly in relation, like the integuments, with external bodies, the mucous surfaces have occasion for a sensibility which would enable the mind to perceive these relations, especially at the origin of these surfaces. Thus the animal sensibility is very much developed there. It is even superior in it in many places to that of the cutaneous organ, in which no sensation is as acute as those which take place on the pituitary membrane from odours, upon the palatine from tastes, upon the surface of the vagina, the urethra, the glans penis during coition. But without speaking of these exaggerations of sensibility, if I may so express myself, all the natural phenomena of the mucous surfaces prove this property in an evident manner; it is unnecessary however to pause for these phenomena.
I would only observe that this sensibility, like that of the cutaneous organ, is essentially subjected to the powerful influence of habit, which tending constantly to blunt the acuteness of the sensation of which they are the seat, brings equally to indifference the pain and the pleasure they make us experience, and of which it is the medium, as we know. 1st. I say that habit brings to indifference the painful sensations arising upon the mucous membranes. The presence of a sound in the urethra for the first time,is distressing the first day, painful the second, inconvenient the third, and insensible the fourth. Pessaries introduced into the vagina, bougies into the rectum, tents fixed in the nasal fossæ, and a canula kept for a length of time in the nasal canal, exhibit in different degrees the same phenomena. It is upon this remark that is founded the possibility of the introduction of sounds into the wind-pipe to aid respiration, and into the œsophagus to produce an artificial deglutition. This law of habit can even transform into a pleasure an impression at first painful; the use of snuff for the pituitary membrane and different aliments for the palatine, furnish well known examples of this. 2d. I say that habit brings to indifference agreeable sensations arising on the mucous surfaces; the perfumer, placed in an odoriferous atmosphere, the cook, whose palate is constantly affected by delicious tastes, do not find in their professions the acute enjoyments they give to others. From habit can even arise the succession from pleasure to painful sensations, as in the preceding case it converts pain to pleasure.
I would however observe that this remarkable influence of habit is only exerted upon sensations produced by simple contact, and not upon those produced by real injuries, as the tearing, the forced stretching, the cutting or pinching of the mucous system; thus it does not mitigate the pains caused in the bladder by pressure and by the tearing a stone occasions, or on the surface of the womb, of the nasal fossæ, &c. by a polypus, on that of the œsophagus or the wind-pipe by a sharp and uneven body accidentally lodged there, &c. &c.
It is to this power of habit over the sensibility of the mucous system, that must be in part referred the gradual diminution of its functions, which accompanies age. Every thing is stimulant in infancy, every thing is blunted in old age. In one, the very active sensibility of the alimentary, biliary, urinary, salivary surfaces, &c. contributes principally to produce that rapidity with which the digestive and secretory phenomena succeed each other; in the other, this sensibility blunted by habitual contact, connects but slowly the same phenomena.
Is it not from the same cause that arises this remarkable modification of the sensibility of this system, viz. that at its origins, as upon the pituitary, the palatine membranes, the œsophagus, the glans penis, the opening of the rectum, &c. it gives us the sensation of the bodies with which it is in contact, and that it does not give this sensation in the very deep organs which it lines, as in the intestines, the excretories, the gall-bladder, &c.? In the interior of the organs, this contact is always uniform; the bladder only knows the contact of the urine, the gall-bladder that of the bile, the stomach that of the aliments masticated and reduced, whatever may be their diversity, to an uniform, pulpy mass. This uniformity of sensation produces no perception, because in order to perceive, it is necessary to compare, and here the two terms of comparison are wanting. Thus the fœtus has no sensation of the waters of the amnios; thus, the air, very irritating to a new born infant, becomes insensible to it. On the contrary, at the beginning of the mucous membranes, the stimulants vary every instant; the mind can then perceive the presence of them, because it can establish approximations between their different modes of action. What I say is so true, that if in the interior of the organs, the mucous membranes are in contact with a foreign body, different from that which they are accustomed to, they transmit the sensation of it to the mind. A catheter in the bladder, sounds introduced into the stomach, &c. are examples of this. Fresh air, in great heat of the atmosphere, suddenly introduced into the trachea, carries an agreeable sensation over the whole surface of the bronchia; but habit soon renders us insensible to itand we cease to have the perception of it. Yet it is to be observed that when the intestines come out in preternatural inversions of the anus, their sensibility never becomes so acute as that of the palatine, pituitary surfaces, &c. &c. The absence of cerebral nerves no doubt has an influence upon this phenomenon.
The sensibility of the mucous system is much raised in inflammations; acute catarrhs are, as we know, very painful. The contact of bodies is then not only felt, but is very disagreeable. I would observe however that the sensibility never rises so high as it does in the inflamed cellular, serous, fibrous systems, &c. A phlegmon, a pleurisy, &c. compared with a catarrh, are sufficient to convince us of this. We may say that the organs least accustomed to feel in the natural state, experience in diseases the most acute sensations.
There is no animal contractility in the mucous system.
Organic sensibility and insensible contractility are very evident in the mucous system. They are constantly put in action in it by four different causes; 1st, by the nutrition of this system; 2d, by the absorption that takes place in it, either naturally or accidentally; 3d, by its exhalation; 4th, by the constant secretion of its glands. These two properties are the original causes of all these functions, the increase and diminution of which are truly the indices of the state of these glands. As a thousand causes continually act upon the mucous surfaces, as a thousand different stimuli continually excite them, especially at their origin, this state is incessantly varying like the functions that result from it.
The mucous system differs then from most of the others; 1st, in this, that the organic sensibility and the insensible contractility are habitually more exalted in it,on account of the more numerous functions over which they preside; 2d, in this, that they incessantly vary, on account of the variety of the stimuli. Observe in fact that, in the osseous, fibrous, cartilaginous, muscular, nervous systems, &c. on the one hand, these properties are put in action only by nutrition; and on the other, no stimulant being in contact with these systems, they always remain at the same degree.
Hence it is not astonishing that the diseases which especially put in action the organic sensibility and the insensible contractility of the same species, should be so frequent in the mucous organs. All the catarrhal affections, both acute and chronic, all the hemorrhages, various and numerous tumours, polypi, fungi, &c. all kinds of excoriations, ulcers, &c. of which they are the seat, are derived from the various alterations of which their organic properties are susceptible.
It is also to these alterations that must be attributed a remarkable phenomenon, viz. the innumerable varieties the mucous fluids exhibit in diseases. Take for example those that are thrown off from the internal surface of the bronchia, those that are brought up by expectoration, and which we can examine better than others, because they are mixed with no foreign substance; observe how they differ, in the different affections of the chest; sometimes they have a yellowish and as it were bilious tinge; sometimes they are frothy in the vessel which receives them; sometimes they adhere to it with tenacity, and at others they are easily detached from it. Viscid or liquid, fetid or without odour, grey, white, green or even black in the morning, they have a thousand external appearances which evidently denote differences in their composition, differences which chemists have not yet explained to us. I do not speak of the cases where as in phthisis, hemoptysis, &c. foreign substances are mixed with these mucous juices. Now it is evident that all these varieties dependonly upon the varieties of the organic sensibility of the bronchial glands or of the membrane upon which they pour out their fluids. According as the property is differently altered in the mucous system, it is in relation with different substances, admits some and rejects others. The same organ, the same vessels can there, according to the state of the forces that animate them, separate from the mass of blood many different substances, rejecting one to-day and admitting it to-morrow, &c.
Do you wish for other proofs of the innumerable varieties which the different modifications of the organic sensibility of the mucous membranes produce in their functions? Observe the urethra; in the ordinary state it lets the urine pass freely; in the excitement in which its forces are in erection, its sensibility repels it and admits only the semen. Who does not know that in one species of epiphora, the mucous passages for the tears are open, and that the diminution only of their vital forces prevents this fluid from flowing in them? The sensibility of the mucous surfaces is oftentimes so altered that their glands refuse to admit every kind of fluid; this happens in the beginning of some peripneumonies, in which expectoration is entirely suppressed, it is always a serious beginning, and even an indication of death, if the state of the sensibility does not change, unless a relaxation, as it is commonly called, takes place.
In general, I think that there are but few systems which deserve, more than this of which we are treating, to fix the attention of physicians, on account of the innumerable alterations of which it is susceptible, alterations which almost always suppose those of the predominant vital properties of this system, as the alterations of the muscular, nervous systems, &c. most often put in action the properties which more particularly belong to them, viz. animal contractility for one, and the sensibility of the same species for the other.
The sensible organic contractility does not appear to be the attribute of the mucous system; yet there is often in it something more than the insensible oscillations which compose the other organic contractility. For example, in the emission of semen, in which there is no agent of impulse at the extremity of the urethra, as in the evacuation of urine, it is very probable that this is spasmodically contracted to produce the jet, oftentimes very strong, which then takes place. The following phenomenon which I have observed in myself appears to belong to the same cause. In gaping, there sometimes escapes from the mouth then wide open, a small jet of fluid, which coming from the lateral parts of this cavity that it passes over, is thrown at some distance; if a surface is then before the mouth, as when we read a book, this fluid is spread in small drops upon this surface; it is the saliva which the excretory duct of Steno throws out with force. Now on the one hand this duct is almost wholly mucous, and on the other it has not at its posterior part a muscular agent of impulse. Perhaps the excretories which pour out their fluids in the deep parts of the organs, exhibit the same phenomenon. We know that the milk is also sometimes subject to a kind of ejection, when it is very abundant, an ejection which supposes a powerful contraction of the lactiferous ducts. In general, these different motions analogous to that of the dartos, of the cellular texture, &c. appear to hold a middle place between those of tone and those of irritability.
There are few systems that sympathize more frequently with the others than this. Now in its sympathies, it sometimes influences and sometimes is influenced. The first Tissot calls the active mode of sympathy, the second the passive. Let us make use of this classification.
One point of the mucous system being inflamed, irritated or stimulated in any way, all the vital forces can enter separately into action in the other systems.
Sometimes it is the animal contractility that is brought sympathetically into action; thus the diaphragm, the intercostal and abdominal muscles contract to produce sneezing from irritation of the pituitary membrane, or cough from the irritation of the membrane of the bronchia, or from that even of the surface of the stomach, which produces stomachic coughs, which, as we know, have nothing to do with affections of the chest. We know the general spasm that seizes all the muscles the instant a foreign body passes between the mucous edges of the epiglottis. Stones of the bladder and the urethra, by making the cremaster contract sympathetically, produce retraction of the testicle. Physicians might, I think, profit by the knowledge of these mucous sympathies. In apoplexy, in which the bronchia is sometimes filled with mucus that the patient cannot evacuate, the action of ammonia upon the pituitary membrane produces the double effect, 1st, of stimulating the brain as blisters do; 2d, of freeing, by the cough it occasions, the surface of the bronchia, which being obstructed, is an obstacle to the passage of the air.
Sometimes it is the animal sensibility that is put into action by an affection of the mucous surfaces. The stone, that irritates that of the bladder, causes an itching at the end of the glans penis. That of the intestines being irritated by worms, an inconvenient itching is felt at the end of the nose. Whytt has seen a foreign body introduced into the ear, affect painfully the whole corresponding side of the head; an ulcer of the bladder, produce every time the patient passed water, a pain on the superior part of the thigh, &c. &c.
The sensible organic contractility is often sympathetically excited by the affections of the mucous system. I might at first refer to this subject what I have observed respecting the organic muscles, almost all of which move from an excitement of a contiguous mucous surface; but that is a natural phenomenon; there are many others that are preternatural. A stone that irritates the internal surface of the pelvis of the kidney produces vomiting, which is, as we know, produced any time at will by an irritation of the uvula. The instant the semen passes the urethra in coition, the action of the heart is commonly accelerated. Tissot speaks of a stone which, being entangled in the duct of Warton, produced a sympathetic discharge from the bowels. I saw at the Hôtel Dieu two women, who, whenever they menstruated, and the mucous surface of the womb was consequently in activity, could retain the urine but a short time in the bladder, which contracted involuntarily to expel it the moment it entered it. At ordinary times, there was nothing peculiar in the evacuation of this fluid.
As to the sympathies of insensible contractility and of organic sensibility, they take place when a mucous surface being irritated towards the extremity of an excretory duct, the gland of this duct is brought into action, when, for example, the saliva flows in greater abundance by the action of sialagogues upon the extremity of the Stenonian duct. Whenever there is a gastric derangement and the mucous surface of the stomach consequently suffers, the surface of the tongue is sympathetically affected; the glands situated under this surface increase their action and hence that white mucous coat, that is commonly called a foul tongue, which is a real sympathetic catarrh, but which can however exist idiopathically. Here also is to be referred the remarkable influence of the mucous system upon the cutaneous; thus during digestion, in which the mucous juices pour out abundantly from all sides intothe stomach and the intestines, and in which the mucous membranes of the gastric viscera are consequently in great action, the fluid of insensible transpiration is lessened remarkably, according to the observation of Sanctorius; it is in very small quantity three hours after the meal, so that the action of the cutaneous organ is evidently less energetic. Thus during sleep, in which all the internal functions become more evident and are exerted to their utmost, and in which the sensibility of the mucous membranes is consequently strongly developed, the skin seems to be struck with a species of atony; it becomes cold more easily, it allows less substances to escape from it, &c. To these sympathies also can be referred many phenomena of hemorrhages. We know with what facility the mucous surface ceasing, from any accidental cause, to throw out blood, as happens so often on that of the womb, another is immediately affected and discharges this fluid; hence hemorrhages from the nose, the stomach, the chest, &c. from the suppression of those of the uterus, &c.
In many cases, the other systems being irritated, the animal sensibility of this is brought into action. Among the numerous examples of this fact, the following is a remarkable one. In many diseases in which organs foreign to the mucous system are affected, we experience a sensation of burning heat in the mouth, the stomach, the intestines, &c. and yet the mucous surface, the seat of this sensation, does not disengage more caloric than usual; we may be convinced of this by placing the fingers in the mouth. This sensation is of the same nature as that which we refer to the glans penis when there is a stone in the bladder, as that which is experienced at the end of the nose from worms in the intestines, &c. There is no material cause of pain, and yet there is suffering. Thus in intermittent fevers we experience a cutaneous shivering, though the skin may be as warm as usual; I would observe in respect to this, that the mucous membranes are hardly ever the seat of an analogous sensation of sympathetic cold, but it is almost always a sensation of heat that the aberrations of the vital forces produce in them. Whence arises this difference between them and the cutaneous organs? I know not. I attribute also to a sympathy of animal sensibility the great thirst which takes place in all the severe affections of any part. In all great wounds, after severe operations, in experiments on living animals, &c. we observe this thirst which depends upon a sympathetic affection of the whole mucous surface that extends into the mouth, the stomach and the œsophagus.
Animal contractility cannot be put sympathetically into action in the mucous system, since it does not exist in it.
The same is true of the sensible organic contractility. It is possible that sometimes the kind of motion we have noticed, and which resembles this property, may be sympathetically excited; I know no example of it.
The insensible organic contractility is here very frequently in sympathetic activity. It is the skin especially which exercises by means of this property, a great influence upon the mucous system. 1st. In hemorrhages of the mucous surface of the womb, the nostrils, &c. a cold body applied to the skin in the neighbourhood, contracts this surface and stops the blood. 2d. Who does not know that the production of most catarrhs is often the sudden consequence of the action of cold on the cutaneous organ? 3d. In various affections of the mucous membranes, baths which relax and expand the skin, frequently produce happy effects. 4th. When the temperature of the atmosphere benumbs the cutaneous tone, that of the mucous system receives a remarkable increase ofenergy. Hence why in winter and in cold climates, in which the functions of the skin are very much diminished, all those of this system increase in proportion. Hence the more evident pulmonary exhalation, the more abundant internal secretions, a more active digestion, more quickly performed and consequently an appetite more easily excited. 5th. When on the contrary the heat of the climate and the season relax and expand the cutaneous surface, the mucous surface is in proportion contracted; in summer, at noon, &c. there is a diminution of the secretions, of that of the urine especially, a slowness in the digestive phenomena from a defect in the action of the stomach and intestines, an appetite slow to return, &c. 6th. In various general affections of the skin, certain portions of the mucous membranes are almost always affected. In scarlet fever, the throat most usually suffers sympathetically. This phenomenon is very common in small pox. 7th. In the latter periods of organic affections of the viscera, as in phthisis, diseases of the heart, enlargements of the liver, cancers of the womb, &c. the mucous membranes are affected like the serous surfaces. The kind of atony in which they then are, produces a more copious flow of mucous juices in them which are altered, become more fluid, &c.; hence the diarrhœas that are called colliquative, which are then to the mucous surfaces, what dropsies are to the serous ones; 8th. It is also to this atony that must be attributed the pectoral hemorrhages which so frequently take place in the last periods of organic diseases, in those of the heart especially. During the short time that I have been at the Hôtel Dieu, there has already died more than twenty patients whom I have opened, of these affections almost forgotten by all practitioners before the time of Corvisart; I have only observed four examples in which passive hemorrhage of the lungs was not the precursor of death.
From what we have thus far said, it is evident that the mucous system is one of those of the whole economy, in which life is the most active. Always in contact with substances that stimulate and irritate it, it is as it were like the skin, in continual action. Yet the life is not the same in all its parts; it undergoes in each remarkable modifications, which no doubt depend on those we have pointed out in the organization of this system, in the nature of its corion, in the arrangement of its papillæ, in the distribution of its vessels and its nerves, in that of its glands, &c.; for as we have seen, none of these essential bases of the mucous system is everywhere arranged in the same manner. There is an organization common to the system, and one peculiar to each of its divisions. It is the same in regard to its life; there is a life common to the system, and as many peculiar ones as there are parts to which it is extended. We know how much the animal sensibility of the pituitary membrane differs from that of the palatine, how powerfully the membrane of the glans penis and the urethra is stimulated by the passage of the semen which makes no impression upon any other mucous surface. The same is true in regard to the organic sensibility and the contractility of the same species. Each mucous surface, in relation with the fluid it is accustomed to, would bear the others with difficulty. The urine would be a stimulant for the stomach and the gastric juice for the bladder; the bile that remains in the gall-bladder would produce a catarrh upon the membrane of the nose, in the vesiculæ seminales, &c.
From these varieties in the vital forces of each division of the mucous system, it is not astonishing that the diseases of this system should also be very variable. Each has a general character, but this is modified in each mucous surface. There is an order of symptoms commonto all catarrhs; but each has its peculiar signs, each has its different products. The fluid from a pulmonary catarrh does not resemble that from a nasal one; that coming from a urethral, vesical catarrh, &c. is wholly different from that from an intestinal one. These fluids exhibit in their morbid changes the same differences that we have pointed out in their natural composition, differences which are derived like them, from the different vitality of each portion of the mucous system.
It is to these varieties of life and the vital forces that must be referred also those of the sympathies. Each portion of this system has a peculiar sympathetic action upon the other organs. The pituitary alone being irritated produces sneezing. You would excite in vain the extremity of the glans penis, the rectum, &c. you would never produce vomiting as you do by stimulating the uvula.
An important remark should here be made in regard to the stomach. We know that there is no organ which performs a more important part in the sympathies than this. The least affection of this important viscus, the least gastric derangement, spread over the whole animal economy a painful influence; all the other parts feel it. I do not believe even that there is any uneasiness more fatiguing and general than that which we then experience in certain cases. The general weakness which takes place in hunger almost instantaneously, is sympathetic; the alteration of nutrition has not had time to produce it. The same is true with regard to the sudden increase of the forces which results from the contact of the aliments upon the mucous surface of this viscus, an increase which cannot be attributed to the passage of the chyle into the blood, which has not yet had time to take place.
I think the stomach owes this important part in the sympathies principally to its mucous surface. In fact, 1st, its serous surface has no connexion with it, since it isthere of the same nature as in all the rest of the peritoneum, besides in what is called inflammation of the abdomen, and in which this serous surface is especially affected, we do not observe such numerous sympathetic relations. 2d. The fleshy coat appears to be the same as that of the whole intestinal canal; why then should it have different influences? 3d. As it respects blood-vessels and nerves of the ganglions, the stomach is nearly organized like the rest of the alimentary tube. 4th. It has besides the par vagum; but is this nerve alone capable of producing such numerous phenomena? It can contribute to them; but certainly the peculiar modifications which it experiences in the mucous surface, the peculiar nature of this membrane contribute also much to it. No membrane is organized like that of the stomach. Though we do not see perfectly at first view its organic differences, reflection is sufficient to convince us of them; thus on the one hand no one separates so great a quantity of fluid, and on the other none furnishes one of a nature analogous to that of the gastric juice.
The development of the mucous system follows in general the laws of that of the organs to which it belongs. Early in the gastric apparatus, later in the pulmonary andthat of generation, it seems in its growth rather to obey the impulse it receives, than to give one to what surrounds it, an arrangement common to almost all the systems which contribute to form the different apparatus. Observe in fact that there is always in the growth certain parts to which all the others refer; thus in the cerebral apparatus, the early size of the brain produces that of the bones of the cranium, of the dura-mater, the pia-mater, the arachnoides and the vessels; thus it is on account of the spinal marrow, that the vertebral canal is so evident in the fœtus; thus all the serous surfaces have a growth in proportion to that of their respective organs, &c. &c. I would remark however that the early growth of the systems which are only to follow that of the parts to which they are destined, is only in the dimensions of length, breadth, &c. The thickness most commonly does not correspond with these dimensions. Thus the bones of the cranium though broader in proportion than those of the pelvis in the fœtus, are not thicker. The extent of the dura-mater is in proportion greater than that of the albuginea which belongs to the same system; but the organization is no further advanced.
In the fœtus, the delicacy of the mucous texture is extreme, the papillæ are hardly perceptible. But by carrying the hand over a mucous surface, we feel there an extremely delicate velvet and such as is not equalled by the finest velvet. The redness of this system is not then as evident, because no doubt less blood penetrates it, as the various functions which are afterwards to take place upon these surfaces, as digestion, the excretions, respiration, &c. are but feeble or entirely wanting. At this age, the quantity of blood seems to be in an inverse ratio in the skin and in these surfaces. The mucous red is then like the muscular, of a very deep tinge, often even livid, on account of the nature of the blood circulating in the arteries. Then the adhesions of the mucous texture tothe subjacent cellular are less; those especially of this last with the surrounding parts are very slight; thus it is very easy to draw out whole the internal portion of the intestines of the fœtus, from the external covering that contains it, so as to see two cylindrical canals, one of which is muscular and serous, the other cellular and mucous. The stretching destroys in this experiment all the valvulæ conniventes, and the small intestines are as smooth on the interior as the large, in the canal artificially extracted. If we subject this canal to ebullition, much more scum arises from it than in the adult; this scum is white and never green. The crisping that takes place a little before the first boiling, diminishes more in proportion the length of the canal, and consequently appears to be stronger.
At birth, when respiration and digestion suddenly commence, the secretions increase, the mucous system acquires a remarkable degree of activity. It is instantly excited powerfully by the many new substances with which it is in contact. It is by it and by the cutaneous system that bodies foreign to ours then immediately stimulate it, and so much the more efficaciously, as the double surface which receives the excitement is not accustomed to it. Then the red blood which penetrates the mucous system, gives it an increase of energy and sensibility, which renders it still more proper to receive impressions. Thus the mucous juices which till then stagnated upon their respective surfaces, without fatiguing and irritating them, are suddenly for them, on account of their increase of sensibility, stimulants which excite them, and force the subjacent muscles to contract. Then the urine becomes for the bladder a cause that promotes the contraction of it. A few instants after birth, all the openings in which the mucous membranes begin, open and permit to escape the meconium, the urine and all the mucous juices. This internal and general shock that empties allthe mucous cavities, renders them fit to become the seat of the great functions which are soon to take place in them.
When all the internal functions are in activity, the mucous surfaces experience no more sudden changes, analogous to that of which I have spoken. They grow like the other viscera in a slow and insensible manner; they preserve for a long time their original softness, which is remarkable, especially in the nose, the stomach, &c. and which during lactation, is not adapted in the infant, to the solid substances with which the adult is nourished. Is this softness the cause of the mucous affections which are in general so common at that age? We know that then the mucous juices abound; the pituitary membrane is more moist; the stomach and intestines are frequently affected with a species of catarrh which is the cause of the looseness that we have so often to combat in infancy. The membrane of the bronchia is also frequently diseased. The two extreme ages of life resemble each other by the abundance of the mucous juices secreted upon their respective mucous surfaces.
In youth the mucous system is in very powerful action. The active hemorrhages of this system are very frequent at this age; those of the nose, the bronchia and even the stomach often take place; those of the portions of this system, subjacent to the diaphragm, are then less common. Observe that in man, hemorrhages of the gastro-pulmonary surface are infinitely more frequent than those of the genito-urinary surface, which on the contrary, are much more numerous in woman in whom one of them is natural to a part of this surface, viz. menstruation.
At the period of puberty, the development of the genital parts in both sexes, gives much activity to a part of the genito-urinary surface; then menstruation begins upon that of the womb; then the sensibility of the urethra is raised in order to feel acutely the passage ofthe semen. Observe that this increase of energy is not attended with a weakness of the other parts, as happens in many cases; on the contrary, all the systems, all the apparatus seem to borrow, from the force which the genital parts acquire, an increase of action.
In the years which succeed youth, the mucous system continues to grow, thicken and become firmer. Its vital energy seems still to predominate for some time, in the superior surfaces, as in the pituitary, the membrane of the bronchia, &c.; thus the affections of these parts are more frequent until the thirtieth year. But as we advance in age, the abdominal mucous surfaces appear to predominate over the others, as in general all the organs of this region do.
Besides, a thousand causes in the course of life, make the state of the mucous system vary. We do not find it in two subjects, with the same shade of colour, with the same density, with the same external appearance. By taking any surface upon many subjects, that of the stomach, for example, we easily see these differences, with which we must be struck if we have opened dead bodies but ever so little.
The redness of the mucous texture is very bright until the thirtieth year; after that, it begins to alter. This texture becomes more and more pale in old age; the blood enters it but in small quantity; it acquires more consistence and density. The fingers carried over it no longer perceive that softness, that velvet so remarkable in the first age. Its forces, which grow languid, render difficult, in the excretories, the exit of the fluids which pass through these tubes to be thrown out. Yet the mucous glands still secrete their fluids in very great abundance.Often even these fluids increase in proportion which constitutes the catarrhal affections, so common in old age. But these affections then have the same character as the functions of the whole system; secretion takes place slowly; the disease is always chronic; most often it terminates only with life.
The mucous absorption is, at this age, slow and difficult, like all the others; the various contagions are taken much less easily, either by the respiratory surfaces, or by the contact of contagious miasmata upon the neighbouring surfaces of the skin. The chyle slowly absorbed, makes the digestive periods longer.