diseases as she is in a state of health, in which the solids elaborate
the fluids and are at the same time excited by them. There is a
reciprocal action, every thing succeeds each other, every thing is
connected together. Our abstractions hardly ever exist in nature. We
usually adopt a certain number of general principles in medicine, and
we accustom ourselves afterwards to deduce from these principles, as
necessary consequences, all the explanations of diseases. There is in
physical phenomena a regularity and uniformity which never deceive. In
morals even, there is a certain number of principles acknowledged by
all men, which direct them and regulate their actions; hence a constant
uniformity in our manner of considering moral and physical phenomena;
hence the habit of going always from the same principles in reasoning
upon them. We have carried this habit into the study of the living
economy, without considering that it incessantly varies its phenomena,
that under the same circumstances they are hardly ever the same, that
they are continually increased and diminished and have a thousand
different modifications. Nature seems at every instant to be irregular,
capricious and inconsequent in their production, because the essence of
the laws which preside over these phenomena, is not the same as that of
the physical laws.
I would observe that the experiments the result of which I have just
given for the secreted fluids, differ from those which I published
the last year, and in which these fluids have always been fatal, the
instant they were forced towards the brain by the carotid. This is a
phenomenon general to all the irritating fluids, whether drawn from the
economy, or foreign to it; they destroy life when they arrive at the
cerebral organ, by a direct injection and without having undergone any
alteration, whilst we can inject them with impunity into the veins,
as the experiments of the physicians of the last age have proved. We
can even without danger, as I have observed, introduce them into the
arterial system, on the side opposite to the brain, as in the crural
artery, for example. Do the fluids mixed with the black blood rid
themselves of some principles by respiration, before they arrive at the
brain, or is the preceding phenomenon owing to other causes? I know
not. I would only observe that every thing which is not arterial blood,
as the black blood and even serum, produces death when forced into the
carotid. Water alone is injected with impunity. When the irritating
principles are much diluted in this fluid, their contact is less
injurious. I have seen very light coloured urine not produce death.
_Structure of the Excretories._
All the excretories have an internal membrane which is mucous, and
which is a continuation of the mucous or cutaneous surfaces, upon which
they terminate. But besides this, they all exhibit an external covering
which forms the shell, as it were, of this mucous canal. This shell
is very thick in the vas deferens, in which it exhibits a texture but
little known. In the urethra it is of a spongy nature, containing much
blood and analogous to the glans of which it is a continuation. In the
ureters, in the hepatic, salivary ducts, &c. it is this extremely dense
and compact cellular texture of which we have spoken, which, by its
structure, resembles that of the arterial and venous cellular texture,
and which differs essentially from the ordinary cellular texture, as
from the intermuscular. It does not appear that there is in these ducts
a membrane differing from this dense texture and the mucous surface.
Each excretory has its vessels. The ureters evidently receive branches
from the renal, spermatic arteries, &c. &c. The hepatic gives them to
the ductus choledochus; the transverse artery of the face supplies
the duct of Steno. Various nerves coming from the ganglions accompany
the corresponding arteries and veins. Yet I have uniformly observed
that there is never around these ducts a plexus as evident as there is
around most of the arteries.
The excretories have principally the vital properties of the mucous
system which forms them in great part. Their sympathies are also nearly
of the same nature.
II. _Parts common to the Organization of the Glandular System. Cellular
Texture._
The glands differ much in the cellular texture which enters into their
structure. We may even, in this respect, divide them into two classes.
In all the salivary glands, in the lachrymal, in the pancreas, in all
the glands with a granulated and white parenchyma, it is very abundant.
Each glandular body is divided into lobes very distinctly separated
by grooves which this texture fills, and which produce the lobulated
appearance on the exterior of this species of gland; not only each
lobe, but each lobule, each glandular grain even, has also the cellular
texture for a boundary. In this respect, this sort of gland is truly
an assemblage of small distinct bodies, which, separated from each
other, would also perform well their functions. This is what is seen
in the parotids, in which different accessory glands are often found
in the course of the duct of Steno, and are perfectly independent of
the principal gland. Sometimes there is a continuity, sometimes there
is a separation between the sub-maxillary and the sub-lingual glands.
The cellular texture is often loaded with much fat in this species of
gland. This is especially remarkable in the mammæ, the size of which is
owing sometimes to the glandular texture, as in young people in whom
this texture predominates over the fat; sometimes to the predominance
of this fat, as we see after the fortieth year, when this gland
preserves a considerable size. The difference is easily perceived by
the touch by the softness and flaccidity of the organ in the second
case, and by its resistance and firmness in the first. In the age of
puberty often, it is also the fatty cellular texture which increases
the size of this organ. Hence why there is often but little milk from
a large breast, and a much greater quantity from a smaller one. In the
voluptuous sensations which we experience at the sight of this organ,
we distinguish very well, without being conscious of it, the breast
whose prominence is real, from that which is not, and in which the fat
only raises the skin of the breast. It is rare in the salivary glands,
the pancreas, &c. that the cellular texture predominates so much, that
the fat accumulates in them in so considerable a quantity. I have
however seen cases in which the parotid resembled a fatty muscle; but
there was no increase of size.
In the testicle, whose parenchymatous portions are separated as in the
preceding glands, the cellular texture is not the medium of union.
There is found between each grain species of threads which appear to be
excretories, and not real cellular laminæ.
In the glands with a compact parenchyma, as the liver, the kidney, the
prostate, the mucous glands, &c. &c. there is very little cellular
texture; by tearing them in different directions, they break without
exhibiting intermediate laminæ. Fat is never found accumulated in
their parenchyma. The fatty state of the liver which takes place in
many diseases, and which is not, as has been thought, an affection
necessarily attendant upon phthisis, exhibits a phenomenon wholly
different from the mammæ and the salivary glands when they have become
fatty. The fat enters then like an element into the texture of the
organ; it is in this respect like the colouring substance, whose place
it has as it were taken; it is not found in cells. Moreover much of
it can be extracted by ebullition, and I have observed that much of
it swims on the surface of the water in which livers of this kind are
boiled. The kidney also has fat in its interior; but it is around the
pelvis and not in its peculiar parenchyma. The amygdalæ, the prostate,
the mucous glands, &c. never have it. Serum is never effused into the
texture of the glands with a compact parenchyma. The most complete
leucophlegmasia leaves them sound in this respect.
Yet it cannot be doubted that the cellular texture exists in these
glands; maceration demonstrates it in them. In the fungous tumours
that grow out of them, there is much of it. It is principally around
the vessels that it is found; the capsule of Glisson is an example of
this. It often happens even, as I have been led to observe, that this
texture becomes diseased, whilst that of the gland remains sound. Thus
we see steatomatous tumours developed in the liver, serous cysts in the
kidney, hydatids in both, and various productions in the other glands,
without deranging the secretion in the least. It is upon the liver
especially that these observations are best made; its size is trebled,
even often quadrupled by internal tumours, without an increase of its
texture; this texture dilated forms between these tumours, species of
partitions in which the bile is secreted as usual. The same thing takes
place in the kidney, in which serous cysts are found. Sometimes these
cysts grow there till the whole glandular texture is destroyed, and
there remains only a large sac separated by membranous partitions, and
filled with serum. I have preserved three kidneys of this kind.
_Blood Vessels._
All the glands not covered by a membrane, receive their arteries from
all sides. Numerous branches coming from the neighbouring vessels,
penetrate the whole surface of the pancreas, the salivary and lachrymal
glands, &c. These arteries wind at first in the interstices between
the lobes, ramify afterwards between the smaller lobes and finally
penetrate the glandular grains. Each of them has its own artery;
all communicate together; so that those of the sub-maxillary and the
sub-lingual are filled by injection made by means of small tubes into
the sub-mental, the external maxillary or the lingual, as well as by an
injection of the trunk even of the external carotid.
In the glands surrounded by a membrane, as the liver, the kidney,
the testicle, &c. the arteries enter only at one side, usually in a
fissure, and by a single trunk which is very considerable, and which is
sometimes divided into many branches more or less large. This part of
the gland in which the artery enters is always the most distant from
the action of external bodies, a remark common to all the important
organs, as the lungs, the intestines, the spleen, &c. which always
present externally their convex surface, that on which the vessels are
the most ramified; so that the place where an injury can happen to
them is that where hemorrhage is the least to be feared. The principal
artery, after it has entered the gland, is soon divided into different
branches which separate and are subdivided as they approach the
convexity. They give off in their course many branches to the body of
the gland and then terminate by a great number of capillaries on the
convex part of the gland. They often even pierce the organ and ramify
between it and the membrane which covers it. For example, by injecting
the hepatic artery, if the liver is bare, many small blackish striæ
suddenly appear on its convexity, which are owing to this cause. The
best means of seeing the glandular arterial system, is to inject a
kidney with a solid substance, and afterwards destroy its parenchyma
by maceration or something else. The arterial system is then bare and
entirely by itself. Many of these preparations are found in anatomical
museums.
The great arterial trunks winding in the glands, communicate to them
an internal motion very favourable to their functions. This motion is
so much the more evident, as almost all these organs very near the
heart by their position in the trunk, are, if we may so say, under the
immediate jar of its contractions. The salivary glands, the mucous
ones of the mouth and the lachrymal on the one hand, the testicle,
the prostate and the mucous ones of the genital parts on the other,
exhibit the extremes of this position. Another cause which favours the
jar of the glands by the entrance of the blood, is that almost all
the arteries that go to them run but a very short course before they
enter them. The spermatic alone is an exception to this rule; thus,
every thing in the secretion of semen seems to be characterized by a
remarkable slowness. To this constant motion imparted to the glands by
the entrance of the blood, should be added that which is communicated
to them by the neighbouring organs, and which keeps them in a constant
excitement, which is more necessary to their secretion than to their
excretion. In considering the action of organs, the constant motions
with which they are agitated has been too much neglected. The example
of the brain ought however to fix the attention of physiologists upon
this point.
The veins, everywhere continuous with the arteries, follow the same
distribution in the glandular system, and accompany them almost
everywhere. We do not see superficial and deep-seated veins, as we do
in many other organs. The liver is the only example in which the red
blood enters at one side, and the black goes out at the opposite.
Most of the veins of the glandular system pour their blood into the
general system of black blood, and as many glands are very near the
heart, they feel the reflux which this system often experiences. This
phenomenon is particularly remarkable in the liver, as the hepatic
veins open but very little below the right auricle. Hence why whenever
this auricle is considerably distended, as in asphyxia and in death in
which the lungs being crowded present an obstacle to the blood, the
liver has a much greater quantity than usual. I have uniformly made
this observation. Weigh comparatively this organ when the auricle is
full and when it is empty in the dead body, after having first tied
all its vessels; you will find a very great difference. For the same
reason, you will observe a constant relation between the weight of the
liver and that of the lungs, provided a morbid alteration of texture
of one of them be not the cause of death. The veins of many glands, as
those of the mucous ones of the stomach and the intestines, as those of
the prostate, &c. pour their blood into the system of abdominal black
blood. There are hardly any in the system of which we are treating, but
these veins, those especially of the glands situated in the pelvis,
which become varicose. Varices of the prostate are frequent, as we know.
_Of the Blood of the Glands._
The quantity of blood that is constantly found in the glands varies
remarkably; they may even be divided in this respect into three
classes. 1st. In the pancreas, the salivary, lachrymal glands, &c.
there is found but very little. It does not furnish the colouring
matter to these organs, which are white, and which, when macerated,
tinge with red but two or three waters. 2d. In the mucous glands, the
prostate, the testicles, and the amygdalæ, there is found a little
more. 3d. The liver and the kidneys contain so great a quantity of
it, that there is not in this respect any proportion between them and
the rest of the glandular system. This is owing in a small degree in
the first to the cause pointed out above; thus it often contains more
than the second, but it is not the essential cause. After death by
hemorrhage in which there was no reflux, in the liver or the kidney
suddenly taken from a living animal, &c. we observe the same thing. In
macerating these glands, it is necessary to renew the water at least
a dozen times before it ceases to be bloody. Hence why when they are
preserved in alkohol on account of an organic disease of which they
were the seat, they must be first macerated for a long time; if not,
the liquor soon becomes turbid from the blood. It is this quantity of
blood which gives to these glands a greater weight in proportion than
that of the other parts. It is from this that their redness is derived,
a colour which no other part exhibits to the same degree, but which is
not more strongly inherent in their texture, than it is in the mucous
surfaces or the muscles. In fact, we remove it with the same ease by
repeated washing. Then the liver assumes a greyish appearance, which
appears to be the colour inherent in its texture, as white is that of
the fleshy fibre. The kidney seems a little less to derive its colour
from the blood. It remains in part red when macerated; the pulp even
which is the product of it, after remaining some months in water, that
has been often changed, still exhibits in some degree this colour, much
less however than in a natural state.
Does the state of the secretions make the quantity of the glandular
blood vary? Does more of this fluid enter the kidney when it furnishes
much urine, than when it secretes but little, or if the same quantity
is brought by the arteries, is less returned by the veins in the first
than the second case? This is an interesting subject for experiment.
Is the nature of the blood changed when it arrives at the glands? Has
it a peculiar composition before entering each of them? Much has been
said of this change necessary to secretion; but that this may take
place, there must be a cause to produce it; now what is this cause
here? Does not the blood circulate in the trunks which go to the
glands, as in the others? It would be necessary then that the gland
should be surrounded with an atmosphere which acts upon the blood at
a certain distance from the place where it is; a vague idea, which
has no solid foundation, and which is met with only in the books of
those who have never made experiments. I have drawn blood from the
carotid, spermatic, hepatic and renal arteries; it is equally red and
coagulable. In the same animal, it is impossible for the senses to
discover the least difference.
I would observe that secretion differs essentially from nutrition in
this, that it always draws the materials of its fluids from the red
blood, whereas the second often takes its own from the white fluids, as
we see in the tendons, the cartilages, the hair, &c.
_Nerves._
The glands receive two species of nerves. 1st. The cerebral are found
almost exclusively in the salivary and lachrymal glands, the amygdalæ,
&c. 2d. The testicles, the prostate gland and the liver receive them in
an almost equal proportion from the brain and the ganglions. 3d. The
kidneys and most of the mucous glands receive scarcely any but those
of the ganglions. What is now said of the nerves should be understood
only of those that are free and independent of the arteries; for each
arterial trunk that enters a gland, is surrounded by a nervous net-work
belonging to the system of the ganglions, which is very evident in the
great glands, as in the liver and the kidneys where this net-work comes
from the semilunar ganglion, in the salivary glands where it comes from
the superior cervical, in the testicles where it comes from the lumbar
ganglions, &c.
Compared with the size of the glands, the nerves are in small
proportion, notwithstanding what Bordeu has said. It is not necessary
in fact to judge of this proportion by those of the parotid and
sub-maxillary glands, which merely pass through these glands without
stopping in them, and leave only some branches there. For example,
there is certainly no organ in the economy, among those which receive
nerves, that, in proportion to its size, has so few as the liver.
Besides, the nerves enter the glands nearly in the same way as the
blood-vessels, that is to say, 1st, on all sides, in those that have no
membrane; 2d, by a groove only in those that are covered with one. They
divide and subdivide after entering it, and are soon lost sight of.
Ganglions never exist in the interior of the glands.
Have the nerves an influence upon secretion? It is probable they have,
as every gland is provided with them; but they by no means exert so
immediate an influence upon this function as many physicians have
pretended. 1st. It is said that the nerves of the parotid glands have
been cut, and that the secretion of the saliva has been suppressed.
This division is evidently impossible, since the gland must be
extirpated before removing its nerves. 2d. I have divided the nerves
of the testicle of a dog, the only gland in which this experiment can
be made. I could not obtain any result, because an inflammation of the
gland came on and it suppurated; but this suppuration even supposes
that the nervous influx is not actually necessary for secretion,
since suppuration is accomplished by a mechanism analogous to that of
this function. All physicians know that a paralyzed limb can inflame
and suppurate. 3d. Erection and the ejection of semen take place in
paralysis of the lower half of the body, in which at least the nerves
of the prostate gland are completely paralyzed. Mr. Ivan related to me
the case of a soldier who took gonorrhœa in this state. 4th. We know
that when the bladder is perfectly paralyzed and its nerves have no
longer any action, its mucous glands still continue to secrete their
fluid so as even to produce a catarrh. 5th. The nostril of the affected
side in hemiplegia is as moist as usual. The ear of this side has its
ordinary quantity of wax. 6th. In paralysis of the uvula, the action of
its glands continues. 7th. When the eighth pair of one side of a dog
is cut, the bronchia is found some days after to contain as much mucus
as common. 8th. During the convulsions of the different parts in which
there are glands, and when consequently the nerves of these glands are
more excited, their secretion is not increased. 9th. If we weigh the
proofs given by Bordeu of the influence of the nerves on secretions,
we shall see, that they either rest upon false facts, like those of
the section of the nerve, of sleep, &c. or upon vague data. In general
physicians attach no precise idea to the term _nervous influence_;
the habit of experimenting shows how much they have abused it. When a
nerve being cut, paralyzed or irritated in any manner, the organ which
receives it undergoes no derangement in its functions, we certainly
are unable to appreciate the nervous influence upon this organ. I do
not say that it does not exist, but I maintain that we know nothing
about it, and that we ought not to employ at hazard a word to which
we cannot attach any precise idea. What word will you employ then to
express the influence of the nerves upon the organs of the senses, upon
the voluntary muscles, &c. if the same one is used to express an action
which has no relation with this, and which perhaps even does not exist?
_Exhalants and Absorbents._
This kind of vessels is but little known in the interior of the glands,
where they perform only the purposes of nutrition.
ARTICLE THIRD.
PROPERTIES OF THE GLANDULAR SYSTEM.
I. _Properties of Texture._
These properties are in general very inconsiderable in this system,
which appears to me to be particularly owing to its non-fibrous
texture. In fact, in order to be elongated and afterwards contracted
and preserve their integrity, it is necessary that the particles of an
organ should possess a certain degree of adhesion and cohesion; now, it
is to the fibre that especially belongs this double attribute. Observe
also that the glandular system is subjected to much less frequent
causes of distension and contraction, than the systems with distinct
fibres. It is scarcely ever found distended except when purulent
deposits, serous, steatomatous collections, &c. are formed in its
interior, as often happens in the middle of the liver, kidney, &c.; now
in these cases it does not yield like the skin, the muscles, &c.; its
particles are separated; it is the cellular texture with which they are
surrounded that is uniformly dilated; the glandular texture is even
soon destroyed. It is very evident when the collections are formed near
the convexity of the glands; if the tumour be at all large the texture
of the organ disappears; there remains only a cellular and membranous
cyst. Hydatids so frequent on the exterior of the kidneys present us
with examples of it. If it is in the middle of the gland that the
cyst is formed, the destruction also takes place, but it is much less
evident.
A strong proof of the small degree of extensibility of the glands, is
what takes place in the liver in dead bodies. I have said above that
it is more or less loaded with blood, according as the system with
black blood had been more or less embarrassed in the last moments. Now
whatever may be the quantity of blood it contains, its size remains
nearly the same; only its texture is more or less compressed by the
vessels, whilst on the contrary the greater or less size of the lungs,
which is very apparent, always indicates its state of fulness or
vacuity. It is probable even that it is this difference which has made
all physicians neglect the infinitely various states of engorgement
in which the liver may be found at death, whilst they have had a
particular regard to the varieties of the lungs.