effects, especially when this action takes place while we are sweating.
The term repercussion of transpiration is not proper to express what
then takes place; it gives a very inaccurate idea. Let us suppose that
a pleurisy arises from cold suddenly applied, the following is what
happens; the organic sensibility of the skin being immediately altered,
that of the pleura is sympathetically altered. By it the exhalants
become in relation with the blood; they admit it instead of the serum
which they before received, and inflammation supervenes. Thus this
phenomenon is the same as that in which the application of a cold body
upon the skin suddenly arrests uterine, nasal hemorrhage, &c. &c.; the
result only differs. Now in this last case, no one ever supposed that
there was a repercussion of fluid. The suppression of the transpiration
is a thing purely accessory and foreign to the internal inflammation
which takes place. When the skin sweats in summer, the vital forces
are more raised by the caloric which penetrates it; in this state, it
is more capable of acting sympathetically upon the forces of the other
systems. Hence why all strong stimulants that act upon it are more to
be feared then. It is so true that it is not the suppression of the
sweat which is dangerous, but the alteration of the vital forces of
the skin which sweats, that many kinds, as the sweat of phthisis, are
not so injurious when they cease for a time; they are checked even
with much more difficulty, because they are not produced by a cause
acting immediately upon the skin. Now if there was a repercussion of
the transpiration, every species of sweat that was suppressed would be
injurious. We never hear of a peripneumony arising from a suppression
of sweat produced by fear, rheumatism, &c. There would be then also a
repercussion of mucous matter, when a pleurisy arises from swallowing
a glass of cold water. Men judge only by that which is striking. The
suppression of the sweat is an effect like inflammation of the pleura,
but it is not the cause of it. If there was no sweat the instant the
cold was applied to the skin, inflammation would nevertheless come on.
In wounds of the head, with abscesses of the liver, &c. there is no
repercussion of fluids.
The trembling of which the voluntary muscles become the seat, the
debility of the pulse which the weakness of the action of the heart
produces, &c. are phenomena which the influence of the skin affected by
cold alone causes. In fact, only this organ, the commencement of the
mucous surfaces and all of that of the bronchia, are made cold by the
external air; all the others remain at their usual temperature.
We know the innumerable phenomena which arise from the disappearance of
herpes, the itch, &c. imprudently produced; in all these cases it does
not appear that the morbific matter is carried to the other organs,
though I do not pretend that this never happens. It is the vital forces
of these which are raised and which then occasion different accidents;
now as these forces vary in each system, these accidents will be
essentially different; thus the same morbific cause disappearing from
the skin, will produce vomiting if thrown upon the stomach, in which
the sensible organic contractility predominates; pains, if it goes to
the nerves which are especially characterized by animal sensibility;
derangements of sight, hearing and smell, if it affects the respective
viscera of these senses; hemorrhage, catarrhs, phthisis, tubercular
inflammation, &c. if it attacks the mucous surfaces, the lungs, the
serous membranes, &c. in which the organic sensibility is much raised.
Now, if the same morbific matter carried upon these different organs,
produced these accidents, they ought to be uniform. Do not their
varieties, and especially the constant analogy which they have with the
predominant vital forces of the organs in which they appear, prove,
that they depend upon the cause which I have pointed out?
We know that the serous surfaces and the cellular texture on the one
part, and the skin on the other, are often in opposition in diseases.
There is no sweat when dropsies are formed; the dryness of the skin is
often even more remarkable than the small quantity of urine, &c.
3d. When the cellular texture contained in the dermoid spaces is
inflamed, as in phlegmonous inflammation, in biles, in some malignant
pustules, &c. there comes on many sympathies which can be referred to
those of the general cellular system, which have been already noticed.
4th. The affections of the chorion itself, all marked with a chronic
character, on account of the kind of vitality and structure of this
portion of the skin, occasion also sympathies which have the same
chronic character, but of which we know but little.
The organic contractility cannot be put sympathetically in action in
the skin, as it does not exist there.
_Characters of the Vital Properties. First Character. The Cutaneous
Life varies in each organ._
Though we have spoken in general of the vital properties of the skin,
they are far from being uniform or at the same degree in all the
regions.
1st. There is no doubt that the animal sensibility of the soles of
the feet and the palms of the hands is greater than that of the other
parts. Many persons are so sensible in the hypochondriac region, that
the least tickling there produces convulsions. The anterior and lateral
part of the trunk is always more sensible than the region of the back.
2d. The organic properties do not vary less. The extreme susceptibility
of the face to receive the blood, is a proof of it, as I have said. It
is generally known that some parts are more proper than others for the
application of blisters. Observe on this subject that the places where
the animal sensibility predominates, are not the same as those in which
the organic is in the greatest proportion. The soles of the feet and
the palms of the hands hold the first rank in relation to one, and the
face in relation to the other.
In diseases we also see these varieties. Who does not know that some
particular parts of the skin are especially the seat of some particular
cutaneous affections, and that when these affections are general, they
always predominate in certain places. We ought not to be astonished
at these varieties, since we have seen that the dermoid texture is
infinitely variable as it respects its papillæ, its reticular body, its
chorion, &c.
_Second Character. Intermission in one relation; continuity in another._
The life of the cutaneous system is essentially intermittent in
relation to animal sensibility. All the senses exhibit this phenomenon.
Thus when the eye has for a long time gazed upon objects, the ear heard
sounds, the nose received odours, and the mouth tastes, these different
organs become unfit to receive new sensations; they become fatigued,
and require rest to regain their forces. It is the same with regard to
feeling and the touch; wearied by the impression of surrounding bodies,
the skin requires an intermission of action to regain excitability
adapted to new impressions. We know that a short time before sleep,
external bodies produce but an obscure sensation upon it, and that
their contact has no effect in this state, in which animals seem
to lose half of their existence. The more powerfully the cutaneous
sensibility has been excited, the more profound is sleep; hence why
all painful exercises, great frictions, &c. are always followed by a
deep sleep. Yet this sense can sometimes exert itself, while the others
sleep; pinch the leg of a man asleep; he draws it away without waking,
and has afterwards no remembrance of the sensation. Thus somnambulists
often hear sounds, even eat, &c.; for, as I have said elsewhere, sleep
may affect but a very limited part of animal life, as it may the whole.
Under the relation of organic sensibility, the life of the cutaneous
system is essentially continuous. Thus the functions over which this
property presides have a character opposite to the preceding. The
insensible transpiration takes place continually, though there may be
some periods in which it is more active than in others. The oily fluid
is incessantly carried away and renewed; we might even say sometimes
that it is when the animal sensibility is interrupted, that the
organic is in the greatest exercise.
It is especially in diseases that they have made this observation,
which is besides generally applicable to organic life. All this life
is as active and even more so during the night than during the day.
Most of the diseases that attack the functions which belong to it, are
marked by an increase of activity during the night. All fevers which
particularly affect the circulation have their exacerbation towards
night. In diseases of the heart, the patients are more oppressed at
this period, &c. In phthisis which affects respiration, it is in the
night especially that there is hectic fever, sweats, &c. Pneumonia and
pleurisy, exhibit frequent exacerbations towards night. In glandular
diseases, either acute or chronic we make the same observation. It
would be necessary to refer to almost all the affections which alter
especially an organic function, in order to omit nothing upon this
point. On the contrary, observe hemiplegia, epilepsy, convulsions,
various paralysies of the different organs of sense, most mental
alienations, apoplexy and other affections which exert their influence
more particularly upon animal life, they have not, so often at least,
their exacerbations towards evening and during the night, no doubt
because in the natural state, this life is in the habit of becoming
drowsy and not of being raised like the other which seems to imprint
this character upon its alterations. Other causes no doubt have an
influence upon this phenomenon; but I believe this to be a real one.
_Third Character. Influence of the Sexes._
The sex has an influence upon the cutaneous life. In general the animal
portion of this life is more raised in women, in whom every thing that
belongs to the sensations is proportionally more marked than in man,
who predominates by the power of his locomotive muscles. The effects
of tickling are infinitely more powerful in females. All the arts which
require nicety and delicacy of touch are advantageously cultivated
by women. The peculiar texture of the chorion, a texture generally
more delicate, has no doubt an influence upon this phenomenon. As to
the organic portion of the cutaneous life, the difference is not very
great. Man appears to be superior in this respect; he generally sweats
more; his skin is more unctuous, which proves a greater secretion.
_Fourth Character. Influence of Temperament._
The temperament peculiar to each individual is not a less real cause
of differences in the skin. We know that the colour, roughness and
pliability of this organ vary according as individuals are sanguineous,
phlegmatic, &c. that these external attributes are even a character of
the temperaments. Varieties of structure no doubt coincide with these.
Is it then astonishing that the animal sensibility differs so much,
that the touch itself should be delicate in some and dull in others,
that some should be very ticklish, whilst others are not so at all,
&c.? Ought we to be astonished if the organic sensibility, which is
very variable, should determine, according to the individuals, many
varieties in the phenomena over which it presides; if in some, it
allows much blood to go to the face, and if it repels this fluid in
others who are always pale; if some men sweat much, whilst others have
the skin almost always dry; if the cutaneous oil varies in quantity;
if there are some skins much disposed to eruptions, either acute or
chronic, to pimples of different natures, and if others are almost
always free from them, even when the individuals expose themselves to
the contagion of these diseases; if superficial wounds, of the same
extent and made by the same instrument, are sometimes quicker and
sometimes slower in healing; if the cure of cutaneous diseases is also
very variable in its periods, &c. &c.?
ARTICLE FOURTH.
DEVELOPMENT OF THE DERMOID SYSTEM.
I. _State of this System in the Fœtus._
In the first periods after conception, the skin is but a kind of
glutinous covering, which seems to be gradually condensed, forms a
transparent envelope, through which we see in part the subjacent
organs, the vessels especially, and which is torn by the least jar.
This state continues for a month and a half or two months. The
consistence constantly increasing, soon gives to the skin an appearance
more nearly like that which it has in infants after birth. Its delicacy
is extreme at this period. It has not one quarter the thickness of
that of the adult. The moment in which it begins to lose its mucous
state appears to be that in which the fibres of the chorion are formed.
Until then the cellular texture and the vessels especially composed
it, and as the first is abundantly filled with juices during the early
periods, it is not astonishing that it should then give way under the
least pressure. But when the fibres are formed, the cellular texture
diminishes on the one hand, and is concentrated in the spaces that are
developed, and on the other the dermoid fibres, more dense than its
layers, increase the resistance.
We do not see upon the external surface of the skin of the fœtus most
of the wrinkles of which we have spoken above. Those of the face in
particular are not seen; the kind of immobility, in which the facial
muscles are, is evidently the reason of it. The forehead, the eyelids,
the edges of the lips, &c. are smooth. Besides, the abundance of fat
which then distends the integuments of the cheeks, prevents every
species of fold there. As the hands and the feet are found in part
bent at their articulations, by the attitude of the fœtus, different
wrinkles are already formed about these articulations, principally on
the hand, where however they appear less in proportion than afterwards.
The curved, papillary lines are not very evident on the foot and the
hand, even when the epidermis is removed.
The internal surface of the skin is remarkable for the slight adhesion
of the subjacent cellular texture, the cells of which filled with
fatty particles are removed with great ease, by scraping this surface
with the edge of a knife. We see then there the spaces already well
formed, and as distinct in proportion as afterwards. By pursuing their
dissection from within outwards, we insensibly lose sight of them
towards the external surface where the skin is condensed.
More blood enters the skin of the fœtus, than at any other period of
life. It is easy to observe this in small animals taken alive from
the womb of their mother; for in the fœtuses that are dead at birth,
or born prematurely, the cause which destroys life, increasing or
diminishing in the last moments the quantity of cutaneous blood,
prevents us from drawing any conclusion as to the ordinary state by an
inspection of them. The nerves are, as in all the other parts, more
evident; but the papillæ, though sensible, as I have said, have not a
proportionable increase.
The animal sensibility is not in exercise in the skin of the fœtus, or
at least it is very obscure there. This is owing to the absence of the
causes of excitement. These are the surrounding heat, the waters of
the amnios and the parietes of the womb, which can furnish materials
for sensations; but as these causes are always uniform, and have no
varieties, the fœtus can have but a very feeble perception, because
acuteness of sensation requires change of stimuli. We know that heat
long continued at the same degree becomes insensible, that a long
continuance in a bath takes away almost entirely the sensation of the
water, because habit is every thing as it respects sensation; nothing
but what is new affects us powerfully.
Is the organic sensibility of the skin in activity in the fœtus?
does it preside over the alternate exhalation and absorption of the
waters of the amnios? This is not the common opinion, it is not even a
probable one; but this question is far from being settled in so precise
a manner as many other points of physiology.
Besides, it cannot be doubted that there is a copious secretion of an
unctuous and viscid fluid, which covers the whole body of the fœtus,
but which is more abundant in some places than others, as behind the
ears, in the groin, the axilla, &c. either because it is secreted there
in greater quantity, or accumulated on account of the arrangement of
the parts. Accoucheurs have it wiped off after birth, and the females
of animals remove it by the repeated application of their tongues to
the surface of the body. This fluid appears to be to the skin of the
fœtus what the oily fluid is to that of the adult; it defends this
organ from the impression of the waters of the amnios. If the sebaceous
glands exist, it would appear that they furnish it, for it is certainly
from a different source from the sweat. When care has not been taken
to remove this covering, it irritates the skin, and may produce
excoriations, and a species of erysipelas. The air cannot remove it
by solution. Nothing similar oozes from the skin of the infant after
birth. Is it because the black blood alone is capable of furnishing the
materials of this substance?
II. _State of the Dermoid System during growth._
At the moment of birth the dermis experiences a sudden revolution.
Hitherto entered only by black blood, it is at the time the fœtus is
born, more or less coloured by it. Some fœtuses come wholly livid,
others are paler; there is a remarkable variety in this respect. But
all, shortly after they have respired, become more or less decidedly
red. It is owing to the arterial blood which is formed and succeeds
the venous blood that circulated in the cutaneous arteries. In this
respect the state of the skin is in general an index of what goes on
in the lungs. If an infant remains a long time of a violet colour, he
either does not breathe or breathes with difficulty. The extremities of
the hands and the feet in general become red the last. They are those
in which the lividity consequently continues the longest, when this
lividity is very evident. The blood which goes to the cutaneous organ,
enters it in general in a very uniform manner; the cheeks do not appear
to receive more of it in proportion. The sudden excitement it brings to
the organ, raises its vital forces and renders it more fit to receive
the impressions, which are new to it, of the surrounding bodies.
Observe in fact that a thousand different agents, the surrounding
temperature, the air, dress, the fluid in which the fœtus is washed,
the tongues of those quadrupeds who lick their young, carry to the skin
an excitement which is so much the more felt by the fœtus, as it is
not accustomed to it, and as there is an essential difference between
these stimuli, and those to which it had been previously subjected.
It is then that the remarkable sympathy which connects the skin with
all the other organs, becomes especially necessary. Every thing within
soon perceives the new excitements that are applied without. It is
these excitements, those of the mucous surfaces at their origin and
those of the whole of the bronchia, which especially bring into action
many organs hitherto inactive. There happens then, what is observed in
syncope, in which respiration, circulation, the cerebral action and
many functions suspended by the affection, are suddenly roused up by
external friction, by the irritation of the pituitary membrane, &c. The
phenomena are different, but the principles from which they are derived
in both cases are the same.
Then the organic sensibility is also raised. Transpiration is
established. The skin begins to be an emunctory of different
substances, which it did not before throw out; it becomes also capable
of absorbing different principles applied to its surface. The skin
of the fœtus is hardly ever the seat of any kind of eruptions; then
pimples of different kinds frequently appear.
All the parts of the cutaneous organ do not however appear to be raised
to the same degree of organic sensibility. For a long time after birth
the skin of the cranium appears to be the centre of a more active life;
it becomes the frequent seat of many eruptions, all of which denote an
excess of the vital forces. The different kinds of scurf with which
it is covered do not appear elsewhere. In this respect, the skin of
the cranium follows, like the bones of this part and the cerebral
membranes, the early development of the brain, which, on this account
is the seat of diseases in infancy more than at any other age.
The skin of the face seems to be sometimes in less activity. In the
first months after birth, it has not that bright colour which it will
afterwards have upon the cheeks, and which does not commence until the
development of the sinuses and dentition bring to this part more vital
activity for the nutritive work. It is also towards this period that
the eruptions of which this part of the cutaneous system is especially
the seat, like those of the small-pox, measles, &c. begin to take place.
For a long time after birth the skin still preserves a remarkable
degree of softness; a very great quantity of gelatine enters it; this
substance is obtained from it with great ease by ebullition, which,
continued for some time, finally melts this organ entirely. The fibrous
part noticed by Seguin, is in very small quantity. I think it is this
predominance of the gelatinous portion of the skin, which renders that
of young animals easy of digestion. We know that in calves’ heads,
roasted lamb, and small sucking pigs, prepared for our tables, it
presents an aliment which the digestive juices alter with the greatest
ease; whilst that of animals of mature age and especially old ones,
cannot be digested by them. The carnivorous species tear their prey,
feed upon its internal organs, the muscles especially, and leave the
skin. Now what is it that makes the skin of young animals differ from
that of old ones? It is because the gelatinous substance predominates
over the fibrous in the first, and the fibrous predominates in the
second.
The skin of children is gradually thickened; but it is not until the
thirtieth year that it acquires the thickness that it is always to have
afterwards. Till then the different ages are marked in this respect
by different degrees. Take a portion of skin at birth, at two, six,
ten, fifteen, twenty years, &c. you will see these differences in a
remarkable manner. The more its thickness increases the more compact
it becomes; it is because the fibrous substance tends constantly to
predominate over the gelatinous.
As we advance in age, the adhesion of the internal surface of the
dermis with the subjacent cellular texture becomes much greater. It is
more difficult to detach one from the other. On the external surface
the wrinkles of the face are gradually formed. Smiles and tears
agitate the face of the infant the most. One is the expression of the
happiness, the other of the uneasiness which all its passions produce
in its mind. Now the wrinkles which weeping occasions on the eyelids
are marked in rather a more permanent manner, either because weeping
is more frequent than smiling, or because continual winking adds to
the motion which weeping produces, or because less fat is found in
this place. As smiling is on the one hand more rare, and on the other
much fat puffs out the cheeks of the infant, the perpendicular wrinkles
formed by the muscles of the face, which in this motion separate
transversely the features from within outwards, are much slower in
forming. Besides, the nursing of the infant, which requires the
contraction of its face from without inwards, opposes their formation.
The wrinkles of the forehead are always very slow in forming, because
the motions which contract the eyebrow, and those which wrinkle the
forehead, are rare in the infant, who has hardly any of those dark
passions which these motions serve to depict.
The growth of the dermoid system has not remarkable revolutions like
that of most of the others; it goes on in an uniform manner. At the
period of the growth of the hairs, it does not change, because this
growth is absolutely foreign to it, these productions only passing
through it. At puberty it increases in energy like all the other
systems. Until then sweats had not been very copious; for, other things
being equal, we may say that children sweat less in general than
adults, and that the residue of their nutrition passes rather by the
urine, which is probably the reason why they are so remarkably disposed
to calculi. Beyond the twentieth year we begin to sweat more, and until
old age, especially in summer, the fluids appear to go out in this way.
III. _State of the Dermoid System after Growth._
After growth, the skin continues for a long time to have great
activity; the excess of life which animates it, renders it capable of
influencing with ease the other organs if it be but a little excited.
Hence the disposition to pneumonia, pleurisy, &c. from the action of
cold on the skin in sweat, a state in which it is more disposed to
exert an injurious influence upon the internal organs, because its
forces are more excited. As to the different affections which result
from this influence, they depend upon the internal organs upon which it
is directed; so that the same sympathetic irradiations going from the
skin, will produce sometimes an affection of the abdomen, sometimes a
disease of the thorax, according to the age in which the abdominal or
pectoral organs, predominating by their vitality, are more disposed to
answer to the influence directed in general upon the whole economy.