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 vapour which, 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 a course 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.
_Absorbents._
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
up or 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.
_Nerves._
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 nervous filaments 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.
ARTICLE THIRD.
PROPERTIES OF THE MUCOUS SYSTEM.
I. _Properties of Texture._
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 two properties 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. Observe how 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.
II. _Vital Properties._
Few systems live in a more active manner than this; few exhibit the
vital forces in a higher degree.
_Properties of Animal Life._
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
it and 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.
_Properties of Organic Life._
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 depend only 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.
_Sympathies._
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.
_Active Sympathies._
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.