it appears that it has a true analogy with the reticular body of the
skin, and that, like it, it arises from two sorts of vessels, one in
which the colouring matter stagnates, the other which gives passage, in
some cases at least, to fluids, and in which there is consequently a
kind of circulation.
The colouring substance of the hairs has some analogy with that of
the skin. Thus we observe that the first, like the second, is blacker
in warm climates and nearer the equator than in colder ones; thus
red hair is frequently found with freckles which are more or less
abundantly spread upon the skin of some people, and which are evidently
seated in the reticular body, as I have ascertained in many patients
who had these marks, and in whom the epidermis was raised up either
by erysipelas or a blister. The acids however change the colour of
the hair more than they do that of the skin of negroes. The muriatic
whitens at first the hairs of the head which become yellow in drying;
the nitric yellows, and the sulphuric leaves them black.
That which especially interests us in the internal substance of the
hairs, is the real vitality which it enjoys, and which essentially
distinguishes it from the external covering. It is to this character
that must be referred the following phenomena.
1st. The different passions of the mind have a remarkable influence
upon the internal substance of the hairs. Often, in a very short time,
grief has changed the colour of it, and whitened it by occasioning no
doubt the reabsorption of the fluid contained in the small capillary
vessels. Many authors have related facts of this kind. Some, even
Haller, have doubted them. But I know at least five or six instances
in which a discoloration has taken place in less than eight days. The
hair of a person of my acquaintance became almost entirely white in
the course of a night upon the receipt of melancholy intelligence. In
these changes, the epidermoid covering remains the same, preserves its
texture, its nature and its properties; the internal substance only
is altered. It is said that terror can make the hair stand an end;
painters express it even by this external attribute; I know not to what
extent we should give belief to this phenomenon which I have never
seen; but it is an opinion too generally received not to have some real
foundation. Now if fear acts so powerfully upon the hair, if it can
give it a real motion, is it astonishing that grief and pain should
suddenly change the fluids that are found in it, and deprive it even of
these fluids?
2d. The plica polonica, of which I spoke just now, in which the hairs
of the head become, when they are cut or even when they are not, the
seat of a bloody exhalation, and in which they have a remarkable excess
of life, evidently resides in the internal substance; the epidermoid
covering has no connexion with it. Some authors even say that this
internal substance acquires sometimes a fleshy nature; then their
covering is raised up in scales.
3d. We know the danger of cutting the hair after many acute diseases. I
have already seen a melancholy instance of it. Many physicians, Lanoix
in particular, have related others. Now, to what are these accidents
owing? It is certainly not to the contact of the air, from which the
hair defends the head; for these accidents take place, though the head
may be covered. It can only be owing to this, that the growth of the
hairs that are cut, calls to these organs a vital activity which the
internal viscera soon sympathetically feel; hence the pains of the
head, the affections of the eyes, &c. observed in these cases. It is
a species of active sympathy exerted by the hair upon the viscera;
now, every organ which sympathizes has a real vitality, and enjoys
very distinct vital properties. The epidermis never takes part in
sympathies, because it is almost completely inert, is hardly organized,
is not at the level of the other organs, and cannot consequently
correspond with them. The danger of cutting the hair after severe
sickness, gives me opportunity to observe that it is often as dangerous
to remove suddenly the vermin from the heads of children during these
diseases. I have seen three or four instances of accidents from this
cause.
4th. The hairs not only influence other systems, but are also
influenced by them. This is what we often see after acute diseases,
in which the roots sympathetically affected, repel the fluids that
come to nourish them, die, and the hairs fall out. Observe that this
falling out of the hair very rarely takes place at the same time with
the desquamation of the epidermis; which proves, that the generally
admitted opinion of the origin of the external covering of the hairs is
entirely false, and that, though very analogous to the epidermis, this
covering does not arise from it, as I have said.
5th. Many animals lose at one season of the year their hairy covering,
which is afterwards reproduced; now the period of its regeneration
is often that of many diseases, and almost always that of a greater
weakness than at other times. We might say that the nutritive work
which then calls to the exterior much vital force, diminishes this
force in the other regions. Man is not subject to these annual renewals
of the external productions which cover his body, like birds, many
quadrupeds, reptiles, &c. It is a cause of less diseases. In fact,
a thousand different causes would no doubt have frequently deranged
these renewals in society, as a thousand causes disturb the menstrual
evacuation, &c.; hence the various diseases we escape by the want of
this renewal. Man is in general subjected to fewer causes of natural
revolutions, than most animals.
6th. Heat and cold have also oftentimes an influence upon the internal
substance of the hairs. We know that in some animals, as rabbits,
hares, &c. they become white in the winter and resume their original
colour in the summer.
7th. A short time after painting the hairs of the head black, a fashion
now more common in France than at the period in which they powdered
them, there is often experienced pains in the head and a swelling of
the hairy scalp, though the skin has been in no way concerned, has not
been pulled, and the hair only has been affected.
It follows from all we have just said, that the hairs analogous, by
their external covering, to the epidermis; foreign by means of it,
if we may so say, to life, belong to it much more particularly by
their internal substance, a substance whose nature is yet but little
known, as I have already said. What moreover evidently proves this
assertion, is that the phenomena of which I have just spoken, and to
which I could add many others, cease to be evident in persons, in
whom the hairs having become white, have no longer any thing but the
epidermoid covering, the internal substance having in part disappeared;
particular observation proves this. It may be however that in this case
that portion alone of this internal substance, corresponding to the
colour, is destroyed, whilst that which is the seat of the exhalations
continues to live as usual; and, in this respect, white hairs may
experience vital phenomena, of which, I believe, there are a few
examples. But all this is subordinate to the future experiments, which
will elucidate the pilous structure more than it now is.
ARTICLE THIRD.
PROPERTIES OF THE PILOUS SYSTEM.
The hairs experience but a slight degree of the horny hardening when
exposed to the action of caloric. They then turn in various directions,
curl and twist; but this arises from a cause entirely different from
that of the horny hardening of the other organs. The caloric then
removes the moisture with which the hairs are constantly penetrated,
and thus approximates their particles. Thus when the hair is moistened
by fog, a bath, &c. the curls disappear. The oily substances that
are used at the toilet, give a coat that is insoluble in water, and
preserve the curling, by preventing it from penetrating the hairs. Some
time after the head has been washed, they curl more, as we have had
occasion to observe since the Grecian head dresses have been in fashion
among us. This at first appears to be contradictory, but it is not
so. In fact by then rubbing the hairs much, the unctuous substance is
removed, which always surrounds them, or this substance combines with
the soap, if the water contains it, as is often the case; by this means
it easily penetrates the hairs, the pores of which remain open, and by
afterwards evaporating with the fluids that were already there, and
which the unctuous substance retained, it leaves these organs more dry
than they were, and consequently more disposed to curl.
A proof, that it is the epidermoid covering which thus imbibes the
moisture that it afterwards loses in the state which succeeds the
curling, is, that the detached epidermis can be curled with a hot iron,
and afterwards rendered supple by soaking it in water.
The contractility and extensibility of texture are very indistinct in
the hairs; it is their resistance which prevents their rupture; they
can hardly be stretched at all.
They have no animal sensibility when pulled; the pain that arises from
it has its seat especially in the skin through which they pass. Thus
when drawn opposite to their direction, we suffer much more than by
stretching them in the direction of their pores. I do not deny however
that these elongations, which fix their origin to the neighbouring
parts, may be also the seat of pain when the hairs are pulled. These
organs have no animal contractility.
The organic properties certainly exist in their internal substance.
The changes which this substance undergoes can only depend on the
different alterations which affect these properties. The organic
sensibility and the insensible contractility especially are raised in
it in a remarkable degree in the plica polonica; now in order to have
the degree of energy which they then do, they must have existed there
in a natural state. It is these two properties, that, the sympathies of
which we have spoken, put into action. The organic contractility is
nothing in the hairs.
Yet we cannot deny that in the natural state, these organs are, next
to the epidermis and the nails, those in which life is the least
active, those which have the least numerous relations with the other
organs. Whilst every thing is destroyed in most of the other systems by
diseases, this is most often unaffected by them; it grows as usual, and
appears to be in no wise disturbed; it has then a manner of being, of
existing, wholly different from the others.
In general, the external productions of animals, as the feathers, the
hair, the scales, &c. seem to form a separate class of organs, foreign
to the life of the internal organs; it is almost like the different
species of mosses that grow upon trees, without making essentially a
part of them.
ARTICLE FOURTH.
DEVELOPMENT OF THE PILOUS SYSTEM.
I. _State of this System in the First Age._
In the first months of the fœtus there are no hairs on the skin which
is then gelatinous. It is when the fibres of the dermoid texture are
formed, that there begins to appear on the head a light down, an
indication of the hairs which are afterwards to arise. This down is
whitish and concealed by that fatty and unctuous substance, which we
have said is deposited on the external surface of the skin at this age.
Soon this down, which appears to be but the external covering of the
hairs, which is then of extreme tenuity, begins to be coloured black
or flaxen, according to the tint that is afterwards to predominate;
it is the internal substance that forms it. The colour remains faint
until after birth. At this period the hairs are often more than half an
inch long. Upon all the rest of the body there is only the down, the
precursor of the hairs; the face especially has much of it. The hairs
of the head are then in advance at one period of the other hairs, in
their growth.
After birth the hairs grow much more rapidly than before. It is
precisely the reverse of most of the other parts, whose growth is
more rapid in the womb of the mother. During the whole of youth this
system has a tint less deep, than it is afterwards to have. The flaxen
becomes nearer the chesnut, and this nearer black, and the first tints
of the bright red grow many degrees darker towards the period from
the twenty-sixth to the thirtieth year. The light tints are to the
pilous system in youth, what the imperfectly developed forms are to
the muscular, cellular, &c. Oftentimes that which is to be afterwards
flaxen, approaches a whitish tint, which is owing only to the nature
of the internal substance, and not to its absence in old age. Thus the
white of the Albinos depends also upon the peculiar species of this
internal substance. Many hairs are wanting upon the body of the young
man.
II. _State of the Pilous System in the following Ages._
At puberty there is a remarkable revolution in this system which
becomes almost double. The hairs of the genital parts are formed; the
beard which is, as I have said, the characteristic attribute of the
male in the human species, is also then developed. We might say that
there was the same relation between the hairs of the neighbourhood
of the testicles and those of the beard, as between the testicles
themselves and the organs of the voice, between the womb and the mammæ.
The beard is, in this respect, the external sign of virility. Some time
before it comes out, we see under the skin the sac which contains the
origin of the hairs; it is already very evidently formed, and permits
the principle of the organ to be seen which it is to contain, as I have
oftentimes ascertained; thus the sac of the tooth exists a long time
before the tooth is cut.
At the same time the hairs of the axilla grow also; those of the trunk
and extremities, which were then almost in a state of down, become
larger, assume a determinate colour, and increase even much in number.
Why does puberty occasion this general growth in the pilous system?
This is asking the reason of all the other phenomena which appear at
this period. I would only observe that the hairs of the head, the
eyebrows, the eyelashes and the hairs at the openings of the body, are
those which are the least affected by this revolution. Besides, this
growth is gradual; it requires at least two or three years for the
beard to become what it is always to be.
In the following ages the hairs undergo but few changes; they grow in
proportion as they are cut in different parts, and are the seat of a
constant external work; now, observe that this work is more prompt, and
the growth of the hairs consequently more rapid, in summer in which the
cutaneous organ is especially in action, than in winter in which it is
contracted; an additional proof of the real vitality of the organic
forces of the internal substance of the hairs.
III. _State of the Pilous System in Old Age._
Towards the end of life, the pilous system is affected by the general
obliteration which takes place in almost all the external vessels;
it ceases at first to receive the colouring substance. The internal
substance dies, the epidermoid covering remains alone; the hairs become
white. The hairs of the head appear the first, and are the first to
die. The beard, the hairs of the genital parts and then those of all
the parts of the body afterwards die. Besides, there is a great variety
among men as it respects the period in which the hairs whiten; in some,
this phenomenon begins about the thirtieth year, and even sooner, in
others it is towards the fortieth, fiftieth or sixtieth. A thousand
causes arising from the passions of the mind, from diseases, aliments,
&c. can have an influence in society upon this premature death, so
common in many men, but which does not take place in animals, who are
not exposed from their kind of life, to the same revolutions, until the
last years.
The hairs, after remaining white for a longer or shorter time, finally
fall out; then the sac which covered the origin of them flattens down
and entirely disappears. I have examined many bald heads; the skin of
the cranium was perfectly smooth on its internal surface, though it
had been separated from the cellular texture. No trace is discoverable
there of the innumerable appendices which the canals form, after the
hairs they contain have been drawn inwards. I have also dissected a man
who after a putrid fever had become almost entirely bald. There were
all these little canals entire, and in the bottom of them could already
be seen the rudiments of new hairs. There is then this difference
between the falling out of the hairs of old people, and that which
is the consequence of diseases, that every thing dies in the first,
because the vessels which go to the root cease to transmit fluids to
it; whereas in the second case the hair alone falls out, and its sac
remains.
It is a pretty generally received opinion that the hair, the nails and
the epidermis continue to grow after death. We have, I think, but few
data respecting this singular phenomenon. I am however certain that I
observed a real elongation of the hairs of a chin of a head that had
been carefully shaved, and which I macerated eight days in a cellar.
An attendant of the dissecting room, who prepares many heads for
the bones, informed me that he had often made the same remark, when
putrefaction is prevented for some time. What is certain also is, that
the growth of the beard is not in the direct ratio of the vital forces;
in the diseases which affect these forces with a general prostration,
it grows as much as in those in which there is a general exaltation
of these forces. We remark this in hospitals where at the side of an
inflammatory fever, there is often found a putrid or slow nervous
one. Besides, why should there not be sufficient tonic forces left in
the hairs to grow some time after general death, as there is in the
lymphatics to absorb, &c.?
The different phenomena which the hair, the epidermis, the skin, and
in general all the external organs experience in the successive ages,
are wholly owing, like those of the internal organs, to the laws of
nutrition, and not to the action of surrounding bodies. This is an
essential difference between organic and inorganic bodies. The latter
are gradually altered in two ways by the contact of external bodies
which act upon them, 1st, mechanically by friction, tearing, &c. &c.;
2d, chemically, by combining with them, as for example, the air whose
different principles undergo many combinations which change its nature
and that of the bodies with which it is in contact. In this respect
all inorganic bodies grow old. At the end of some time, they have no
longer the exterior which characterized them in the beginning. Observe
monuments, pictures, engravings, earths, metals, stones, &c. &c. every
thing which in the arts, commerce, sciences, in the uses of life or
in the phenomena of nature is formed of any inert bodies, whether
these bodies have never lived, or having lived, have not been able to
preserve themselves after death, as the solid portions of vegetables,
the bones, the horns, the hair of animals, &c. every thing finally has
the indelible stamp of time; every thing grows old; every thing loses
its freshness, every thing changes on the exterior of inert, as well
as on that of organic bodies; but as in the first surrounding bodies
alone have acted, the internal part is still young, whilst the external
is old, if I may be allowed to use two very improper words. Thus the
rock whose surface is blackened by the lapse of years, is the same in
the interior as when it was created. On the contrary in animals and
vegetables, the internal organs are worn out, as well as the exterior.
Time is marked upon the viscera, as well as upon the forehead of the
aged. Surrounding bodies act upon us, wear out life, if we may so say;
but it is as stimuli that they exert their action; it is by exhausting
the sensibility and contractility, and not by combination, mechanical
contact or friction. Language ought to express this difference. We do
not use the term _young_ when viewing the exterior of a new building,
a new garment, or a picture recently painted; why do we say an _old_
monument, an _old_ piece of cloth, &c.? if it is a metaphor, very well;
but this word cannot express a state analogous in its nature, to that
of an old animal, an old plant, &c.
IV. _Preternatural Development._
There are three principal cases in which the hairs are preternaturally
developed in the economy.
1st. Sometimes they are formed on the internal surface of the mucous
membranes; they have been seen in the bladder, the stomach and the
intestines; many authors have given cases of them. I have found them
upon the calculi of the kidney. I have seen in the gall-bladder at one
time a dozen of nearly an inch in length, and which were evidently
implanted in its surface.
2d. There is often seen on the skin preternatural collections of
them, which are usually a defect from birth. These collections are
particularly observed upon some of those productions or irregular
excrescences, that are called nævi materni. There was exhibited at
Paris, six years since, an unfortunate person, who had from his birth
his face covered with hairs almost like those of a wild boar; and to
whom there came on at the age of thirty-six years, that particular
species of elephantiasis, in which the skin of the face increased in
size, exhibits, if we may so say, the features of the lion, a species
which I have since had occasion to observe upon a natural skin. This
double circumstance gave to the face of this man an air of ferocity
which it is impossible to describe. Many of the stories circulated by
the vulgar concerning men with the heads of wild boars, bears, &c. are
nothing but these nævi in the face, with a growth of hair upon them.
3d. Hairs are often preternaturally developed in cysts, in those of the
ovaria especially. A great many instances have been related. Haller in
particular has collected many; I have seen two. The following is what
they exhibit; a considerable large sac contained many very distinct
small balls, analogous to those of the dung of sheep, formed by a
fat, unctuous, whitish substance, very different in its appearance
from ordinary fat. On the internal surface of this sac were implanted
many hairs, which the least force could remove, because they hardly
penetrated below the surface. These hairs were black. Many already
detached were found crossed in different directions, in the small balls
of fatty matter, which was like spermaceti; for it very much resembled
the substance into which the fat is changed by maceration.
END OF THE LAST VOLUME.
ANALYTICAL TABLE OF CONTENTS.
VOLUME FIRST.
PAGE.
Preface by the Translator. 5
Preface by the Author. _ib._
GENERAL OBSERVATIONS.
Of Animate and Inanimate Beings.—Of their Laws.—Of the Sciences which
treat of their Phenomena. 9
I. _General Remarks upon the Physiological and Physical Sciences._
The differences between these sciences are derived from the properties
which preside over the phenomena.—The necessity of always connecting
the second with the first.—Periods at which this progress commenced in
the physical sciences. False applications made to the physiological
sciences.—The necessity of following in these the same course as in
the others. 9
II. _Of the Vital Properties, and their influence upon the phenomena
of the Physiological and Physical Sciences._
Vital properties considered in the series of living beings.—Of those
which animate plants.—Consequences in regard to their diseases.—Of
those which belong to animals.—Consequences in regard to their
diseases.—Examination of each vital property under the relation
of the diseases over which it presides.—Necessity of referring to
these properties the action of medicines.—Uncertainty of the Materia
Medica.—Each vital property has a particular class of medicines which
act upon it.—Proofs.—Inconveniences of describing morbid phenomena
and those of medicines in too general a manner.—Consequences of the
preceding remarks. 13
III. _Characters of the Vital Properties, compared with the characters
of the Physical Properties._