GENERATION IN BRUTE BODIES AND LIVING BODIES. SPONTANEOUS GENERATION.
Protoplasm a substance which continues—Case of the
crystal—Characteristics of generation in the living being—Property of
growth—Supposed to be confined to the living being—Fertilization of
micro-organisms—Fertilization of crystals—Sterilization of crystalline
and living media—Spontaneous generation of crystals—Metastable and
labile zones—Glycerine crystals—Possible extinction of a crystalline
species—Conclusion.
We have not yet exhausted the analogies between a crystal and the
living being. The possession of a specific form, the tendency to
re-establish it by redisintegration and the existence of a kind of
nutrition are not sufficient to constitute complete similarity. It
still lacks a fundamental character, that of generation. Chauffard
some time ago, in an attack which he made upon the physiological ideas
of his day, aptly exhibited this weak point. “Let us disregard,”
he said, “those interesting facts relative to the acquisition of a
typical form—facts that are common to the mineral world as well as
to living beings. It is none the less true that the crystalline type
is in no way derived from other pre-existing types, and that nothing
in crystallization recalls the actions of ascendants and the laws of
heredity.”
This gap has since been filled. The work of Gernez, of Violette, of
Lecoq de Boisbaudran, the experiments of Ostwald and of Tammann, the
observations of Crookes and of Armstrong—all this series of researches,
so lucidly summarized by M. Leo Errera in his essays in botanical
philosophy, had for their result the establishment of an unsuspected
relation between the processes of crystallization and those of
generation in animals and plants.
_Protoplasm is a Substance which Continues. The Case of the
Crystal._—Under present conditions a living being of any kind springs
from another living being similar to itself.
Its protoplasm is always a continuation of the protoplasm of an
ancestor. It is an atavic substance of which we do not see the
beginning; we only see it continue. The anatomical element comes from a
preceding anatomical element, and the higher animal itself comes from
a pre-existing cell of the material organism, the ovum. The ladder of
filiation reaches back indefinitely into the past.
We shall see that there is something analogous to this in certain
crystals. They are born of a preceding individual; they may be
considered as the posterity of the antecedent crystal. If we speak of
the matter of a crystal as the matter of a living being is spoken of,
in cases of this kind we would say that the crystalline substance is an
atavic substance of which we see only the continuation, as in the case
of protoplasm.
_Characters of Generation in the Living Being._—Growth of the living
substance, and consequently of the being itself, is the fundamental
law of vitality. Generation is the necessary consequence of growth (p.
210).
Living elements or cells cannot subsist indefinitely without increasing
and multiplying. The time must come when the cell divides, either
directly or indirectly; and then, instead of one cell, there are
two. This is the method of generation for the anatomical element.
In a complex individual it is a more or less restricted part of the
organism, usually a simple sexual cell, that takes on the formation
of the new being, and assures the perpetuity of the protoplasm, and
therefore of the species.
_Property of Growth. Its Supposed Restriction to Living Beings._—At
first it would appear that nothing like this occurs in inanimate
nature. The physical machine, if we furnish it matter and energy, could
go on working indefinitely, without being compelled to increase and
reproduce. Here, then, there is an entirely new condition peculiar to
the organized being, a property well adapted, it would seem—and this
time without any possible doubt—for separating living matter from brute
matter. It is not so.
It would not be impossible to imagine a system of chemical bodies
organized like the animal or vegetable economy, so that a destruction
would be compensated for by a growth. The only thing impossible is to
suppose, with M. le Dantec, a destruction that would at the same time
be an analysis. And an additional perplexity occurs when he supposes
that in the successive acts exchanges of material may occur.
There is no necessity for making this impossible chemistry a
characteristic of the living being. The chemistry of the living being
is general chemistry. Lavoisier and Berthelot enforced this view. We
should not lose sight of the teachings of the masters.
Let us return to generation, properly so called, and find in it the
characteristics of brute bodies and of crystals.
_The Sowing of Micro-organisms._—When a microbiologist wishes to
propagate a species of micro-organisms, he places in a culture medium
a few individuals (one is all that is actually necessary), and soon
observes their rapid multiplication. Usually, if only the ordinary
microbes in atmospheric dust are wanted, the operator need not trouble
to charge the culture; if the culture tube remains open and the medium
is suitably chosen, some germ of a common species will fall in and the
liquid will become colonized. This has the appearance of spontaneous
generation.
_The Sowing of Crystals._—Concentrated solutions of various substances,
supersaturated solutions of sodium magnesium sulphate, and sodium
chlorate are also wonderful culture media for certain mineral organic
units—certain crystalline germs. Ch. Dufour, experimenting with water
cooled below 0° C., its point of solidification; Ostwald, with salol
kept below 39°.5, its point of fusion; Tammann, with betol, which
melts at 96°; and, before them, Gernez, with melted phosphorus and
sulphur—all these physicists have shown that liquids in superfusion are
also media specially appropriate for the culture and propagation of
certain kinds of crystalline individuals.
Some of these facts have become classic. Lowitz showed in 1785 that a
solution of sodium sulphate could be concentrated by evaporation so
as to contain more salt than was conformable with the temperature,
without, however, depositing the excess. But if a solid fragment, a
crystal of salt, is thrown into the liquor, the whole of the excess
immediately passes into the state of a crystallized mass. The first
crystal has engendered a second similar to itself; the latter has
engendered a third, and so on from one to the other. If we compare
this phenomenon with that of the rapid multiplication of a species of
microbes in a suitable culture medium, no difference will be perceived.
Or perhaps we may note one unimportant difference—the rapidity of
the propagation of the crystalline germs as opposed to the relative
slowness of the generation of the micro-organisms.
Again, the propagation of crystallization in a supersaturated
or superfused liquid may be delayed by appropriate devices. The
crystalline individual gives birth, then, to another individual that
conforms to its own type, or even to varieties of that type when such
exist. Into the right branch of a U tube filled with sulphur in a state
of superfusion Gernez dropped octahedric crystals of sulphur, and into
the left branch prismatic crystals. On either side were produced new
crystals conforming to the type that had been sown.
_Sterilization of Crystalline Media and Living Media._—Ostwald varied
these experiments by using salol. He melted the substance by heating
it above 39∙5°C.; then, protecting it from crystals of any kind, he
let the solution stand in a closed tube. The salol remained liquid
indefinitely—until it was touched with a platinum wire that had been
in contact with solid salol—_i.e._, until a crystalline germ was
introduced. But if the platinum wire has been previously sterilized by
passing it, as the bacteriologists do, through a flame, it can then be
introduced into the liquor with impunity.
_The Dimensions of Crystalline Germs Comparable to those of
Microbes._—We may dilute the solid salol with inert powder—lactin,
for example—dilute the first mixture with a second, the second with a
third, and so on; then, throwing into the solution of surfused salol
a tenth of a milligram from one of these various mixtures, we find
that the production of crystals will not take place if the fragment
thrown in weighs less than a millionth of a milligram, or measures
less than ten thousandths of a millimetre in length. It would seem,
then, that these are the dimensions of the crystalline particle or
crystallographic molecule of salol. In the same way Ostwald satisfied
himself that the crystalline germ of hyposulphite of soda weighs
about a thousand-millionth of a milligram, and measures a thousandth
of a millimetre; that of chlorate of soda weighs a ten-millionth of
a milligram. These dimensions are entirely comparable with those of
microbes.
All these phenomena have been studied with a detail into which it
is impossible to enter here, and which clearly shows more and more
intimate analogies between the formation of crystals and the generation
of micro-organisms.
_Extension and Propagation of Crystallization. Optimum Temperature
of Incubation._—Crystallization which has commenced around a germ is
propagated more or less rapidly, and ends by invading the whole of the
liquor.
The rapidity of this movement of extension depends upon the conditions
of the medium, especially upon its temperature. This is shown very
well by Tammann’s experiments with betol. This body, the salicylic
ester of naphthol, fuses at 96° C. If it is melted in tubes sealed
at a temperature of 100° C., it may be cooled to lower and lower
temperatures—to + 70°, to + 25°, to + 10°, to-5° without solidifying.
Let us suppose that by some combination of circumstances a few centres
of crystallization—that is to say, of crystalline germs—have appeared
in the solution. Solidification will extend slowly at the ordinary
temperature, at 20° to 25° and thereabouts. On the other hand, it will
be propagated with great rapidity if the liquor is kept at about 70°.
This point—70°—is the thermal optimum for the propagation of germs.
It is the most favourable temperature for what may be called their
incubation. As soon as the germs find themselves in a liquor at 70°
they increase, multiply, and show that they are in the best conditions
for growth.
_Spontaneous Generation of Crystals. Optimum Temperature for the
Appearance of Germs._—If we consider various supersaturated solutions
or liquids in superfusion, we shall soon discover that they can be
arranged in two categories. Some remain indefinitely liquid under
given conditions unless a crystalline germ is introduced into them.
Others solidify spontaneously without artificial intervention, and such
crystallization may even be propagated very rapidly under determinate
conditions. This implies that these are conditions favouring the
spontaneous appearance of germs.
This distinction between substances of crystalline generation by
filiation and substances of spontaneous crystalline generation is not
specific. The same substance may present the two methods of generation
according to the conditions in which it is placed. Betol furnishes a
good example of this. Liquefy it at 100° in a sealed tube and keep
it by means of a stove above 30°, and it will remain liquid almost
indefinitely. On the other hand, lower its temperature and leave it
for one or two minutes at 10°, and germs will appear in the liquor;
prolong the exposure to this degree of heat and the number of these
spontaneously appearing germs, appearing in isolation, will rapidly
increase. On the other hand, you will observe that propagation by
filiation—that is to say, by extension from one to another—is almost
absent. The temperature of 10° is not favourable to that method of
generation; and we have just seen, in fact, that it is at a temperature
of about 70° that extension of crystallization from one to another
is best accomplished. The temperature of 70° was the optimum for
propagation by filiation. Inversely, the temperature of 10° is the
optimum for spontaneous generation. Above and below this optimum the
action is slower. We may count the centres of crystallization, which
slowly extend further and further, as in a microbic culture one counts
the colonies corresponding to the germs primitively formed. To sum
up, if there is an optimum for the formation of crystals, there is a
different optimum for their rapid extension.
_The Metastable and Labile Zones._—This phenomena is general. There
is for each substance a set of conditions (temperature, degree of
concentration, volume of the solution) in which the crystalline
individuals can be produced only by germs or by filiation. This is what
occurs for betol above the temperature of 30°. The body is then in what
Ostwald has called a _metastable_ zone. There is, however, for the same
body another set of circumstances more or less complete, in which its
gems appear simultaneously. This is what happens for betol at about the
temperature of 10°. These circumstances are those of the _labile zone_
or zone of spontaneous generation.
_Crystals of Glycerine._—We may go a step further. Let us suppose, with
L. Errera, that we have a liquid in a state of metastable equilibrium,
whose labile equilibrium is as yet unknown. This is what actually
occurs for a very widely known body, glycerine. We do not know under
what conditions glycerine crystallizes spontaneously. If we cool it,
it becomes viscous; we cannot obtain its crystals in that way. It was
not found in crystals until 1867. In that year, in a cask sent from
Vienna to London during winter, crystallised glycerine was found,
and Crookes showed these crystals to the Chemical Society of London.
What circumstances had determined their formation? We knew not then,
and we know not now. It may be observed that this case of spontaneous
generation of the crystals of glycerine has not remained the solitary
instance. M. Henninger has noted the accidental formation of glycerine
crystals in a manufactory in St. Denis.
It may be remarked that this crystalline species appeared, as living
species may have done, at a given moment in an environment in which a
favourable chance combined the necessary conditions for its production.
It is also quite comparable to the creation of a living species;
for having once appeared we have been able to perpetuate it. The
crystalline individuals of 1867 have had a posterity. They have been
sown in glycerine in a state of superfusion, and there they reproduced
themselves. These generations have been sufficiently numerous to
spread the species throughout a great part of Europe. M. Hoogewerf
showed a great flask full to the Dutch biologists who met at Utrecht
in 1891. M. L. Errera presented others in June 1899, to the Society of
Medical and Natural Sciences at Brussels. To-day the great manufactory
of Sarg & Co., of Vienna, is engaged in their production on a large
scale for industrial purposes.
Thus we are able to study this crystalline species of glycerine and to
determine with precision the conditions of its continued existence. It
has been shown that it does not resist a temperature of 18°, so that
if precautions were not taken to preserve it, a single summer would
suffice to annihilate all the crystalline individuals existing on the
surface of the globe, and thus the species would be extinguished.
_Possible Extinction of a Crystalline Species._—As these crystals
melt at 18°, this temperature represents the point of fusion of solid
glycerine or the point of solidification of liquid glycerine. But the
liquor does not solidify at all if its temperature falls below 18° C.,
as we well know, for it is at that temperature we use it. Nor does it
solidify at zero, nor even at 18° below zero; at 20°, for instance, it
merely thickens and becomes pasty. We only know glycerine, then, in a
state of superfusion, a fact which chemists have not learned without
amazement. Under these conditions, so analogous to the appearance of
a living species, to its unlimited propagation and to its extinction,
the mineral world offers a quite faithful counterpart to the animal
world. The living body illustrates here the history of the brute body
and facilitates its exposition. Inversely, the brute body in its
turn throws remarkable light on the subject of the living body, and
on one of the most serious problems relative to its origin, that of
spontaneous generation.
_Conclusion._—These facts lead to one conclusion. Until the concourse
of propitious circumstances favourable to their spontaneous generation
was brought about, crystals were obtained only by filiation. Until the
discovery of electro-magnetism, magnets were made only by filiation,
by means of the simple or double application of a pre-existing magnet.
Before the discovery which fable attributes to Prometheus, every new
fire was produced only by means of a spark from a pre-existing fire.
We are at the same historical stage as regards the living world,
and that is why, up to the present, there has never been formed a
single particle of living matter except by filiation, except by the
intervention of a pre-existing living organism.
BOOK V.
SENESCENCE AND DEATH.
Chap. I. The different points of view from which death may
be regarded.—Chap. II. Constitution of the organisms—Partial
death—Collective death.—Chap. III. Physical and chemical
characteristics of cellular death—Necrobiosis.— Chap. IV. Apparent
perennity of complex individuals.—Chap. V. Immortality of the protozoa
and of slightly differentiated cells.
We grow old and we die. We see the beings which surround us grow old
and disappear. At first we see no exceptions to this inexorable law,
and we consider it as a universal and inevitable law of nature. But
is this generalization well founded? Is it true that no being can
escape the cruel fate of old age and death, to which we and all the
representatives of the higher animality are exposed? Or, on the other
hand, are any beings immortal? Biology answers that, in fact, some
beings are immortal. There are beings to whose life no law assigns a
limit, and they are the simplest, the least differentiated and the
least perfect. Death thus appears to be a singular privilege attached
to organic superiority, the ransom paid for a masterly complexity.
Above these elementary, monocellular, undifferentiated beings,
which are protected from mortality, we find others, higher in their
organization, which are exposed to it, but with whom death seems but
an accident, avoidable in principle if not in fact. The anatomical
elements of this higher animal are a case in point. Flourens once tried
to persuade us that the threshold of old age might be made to recede
considerably, and there are biologists in the present day who give us
some glimpse of a kind of vague immortality. We may, therefore, ask our
readers to follow us in our examination of these re-opened if not novel
questions, and we shall explain the views of contemporary physiology as
to the nature of death, its causes, its mechanisms, and its signs.
CHAPTER I.
VARIOUS WAYS OF REGARDING DEATH.
Different meanings of the word death—Physiological distinction between
elementary and general death—Non-scientific opinions—The ordinary
point of view—Medical point of view.—The signs of death are prognostic
signs.
_Different Meanings of the Word Death._—An English philosopher has
asserted that the word we translate by “cause” has no less than
sixty-four different meanings in Plato and forty-eight in Aristotle.
The word “death” has not so many meanings in modern languages, but
still it has many. Sometimes it indicates an action which is taking
place, the action of dying, and sometimes a state, the state which
succeeds the action of dying. The phenomena it connotes are in the eyes
of many biologists quite different, according as we watch them in an
animal of complex organization, or on the other hand, in monocellular
beings, protozoa and protophytes.
_Physiological Distinction between Elementary Death and General
Death._—We distinguish the death of the anatomical elements,
_elementary death_, from the death of the individual regarded as
a whole, _general death_. Hence we recognize an _apparent death_,
which is an incomplete and temporary suspension of the phenomena of
vitality, and a _real death_, which is a final and total arrest of
these phenomena. When we consider it in its essential nature (assumed,
but not known) we look on it as the _contrary of life_, as did the
Encyclopædia, Cuvier, and Bichat; or we regard it with others either as
the consequence of life, or simply as the end of life.
_Non-scientific Opinions._—What is death to those outside the realm of
science? First of all we find the consoling solution given by those
who believe death to be the commencement of another life. We next find
ourselves involved in a confused medley, an infinite diversity of
philosophical doubt and superstition. “A leap into the unknown,” says
one. “Dreamless and unconscious night,” says another. And again, “A
sleep which knows no waking.” Or, with Horace, “the eternal exile,” or
with Seneca, annihilation. _Post mortem nihil; ipsaque mors nihil._
The idea which is constantly supervening in the midst of this conflict
of opinion is that of the _breaking up_ of the elements, the union
of which forms the living being. It has, as we shall see, a real
foundation which may perhaps receive the support of science. We shall
not find that the best way of defining death is to say that it consists
of the “dissolution of the society formed by the anatomical elements,
or again, in the dissolution of the consciousness that the individual
possesses of himself—_i.e._, of the existence of this society.” It is
the rupture of the social bond. The old idea of dispersion is a variant
of the same notion. But the ancients evidently could not understand,
as we do, the nature of these elements which are associated to form
the living being, and which are liberated or dispersed by death.
We, as biologists, can see microscopical organic unity with a real
objective existence. The ancients were thinking of spiritual elements,
of principles, of entities. To the Romans, who may be said to have held
that there are three souls, death was produced by their separation
from the body. The first, the breath, the _spiritus_, mounting towards
celestial regions (_astra petit_); the second, the _shade_, regaining
on the surface of the earth and wandering around the tombs; the third,
the _manes_, descending to the lower regions. The belief of the Hindoos
was slightly different. The body returned to the earth, the breath to
the winds, the fire of the glance to the sun, and the ethereal soul to
the world of the pure. Such were the ideas of mortal dispersion formed
by ancient humanity.
Modern science takes a more objective point of view. It asks by
what facts, by what observable events death is indicated. Generally
speaking, we may say that these facts interrupt an interior state of
things which was life and to which they put an end. Thus death is
defined by life. It is the cessation of the events and of the phenomena
which characterize life. We must, therefore, know what life is to
understand the meaning of death. How wise was Confucius when he said to
his disciple, Li-Kou:—“If we do not know life, how can we know death?”
According to biology there are two kinds of death because there are two
kinds of life; elementary life and death correspond just as general
life and death do, and this is where scientific opinion diverges from
commonly received opinion.
What cares the man who reasons as most human beings do, about this life
of the anatomical elements of his body, the existence and the silent
activity of which are in no way revealed to him. What does their death
matter to him? To him there is but one poignant question, that of being
separated or not being separated from the society of his fellows. Death
is no longer to feel, no longer to think; it is the assurance that one
will never feel, one will never think again. Sleep, dreamless sleep,
is already in our eyes a kind of transient death; but, when we fall
asleep we are sure of waking again. There is no awaking from the sleep
of death. But that is not all. Man knows that death, this dreamless
sleep that knows no waking, will be followed by the dissolution of his
body. And what a dissolution will there be for the body, the object
of his continual care! Remember the description of Cuvier—the flesh
that passes from green to blue and from blue to black, the part which
flows away in putrid venom, the other part which evaporates in foul
emanations, and finally, the few ashes that remain, the tiny pinch of
minerals, saline or earthy, which are all that is left of that once
animated masterpiece.
_The Popular View._—To the man afraid of death it seems, in the
presence of so great a catastrophe, that the patient analysis of the
physiologist scrupulously noting the succession of phenomena and
explaining their sequence is uninteresting. He will only attach the
slightest importance to knowing that vestiges of vitality remain in
this or that part of his body, if they do not re-establish in every
part the _status quo ante_. He cares not to hear that a certain time
after the formal declaration of his death his nails and his hair will
continue to grow, that his muscles will still have the useless faculty
of contraction, that every organ, every tissue, every element, will
oppose a more or less prolonged resistance to the invasion of death.
_Medical View._—It is, however, these very facts and details, this
why and wherefore, which interest the physiologist. The state of
mind of the doctor in this respect, again, is different. When, for
instance, the doctor declares that such and such a person is dead,
he is really making not so much a statement of fact as a prediction.
How many elements are still living and will be capable of new birth
in this corpse that he has before his eyes? That is not what he asks
himself, nor is it what we should ask of him. He knows, besides, that
all these partial survivals will be extinguished and will never find
the conditions necessary to reviviscence, and that the organization
will never be restored to its primal activity; and this is what he
affirms. The fear of premature burial which haunts so many imaginations
is the fear of an error in the prediction. It is to avoid this that
practical medicine has devoted so much of its attention to the
discovery of a _certain_—and early—sign of death. By this we understand
the discovery of a _certain prognostic sign of general death_. We want
a prognostic sign enabling us to assert that the life of the brain is
now extinguished and will never be reanimated. And yet there are in
that organism many elements which are still alive. Many others even
may be born anew if we could give them suitable conditions which they
no longer meet with in the animal machine now thrown out of gear.
What finer example could we give than the experiment of Kuliabko, the
Russian physiologist, who kept a man’s heart working and beating for
eighteen hours after the official verification of his death.
CHAPTER II.
THE PROCESS OF DEATH.
Constitution of organisms.—Partial lives.—Collective life.—The
rôle of apparatus.—Death by lesion of the major apparatus.—The
vital tripod.—Solidarity of the anatomical elements.—Humoral
solidarity.—Nervous solidarity.—Independence and subordination of the
anatomical elements.
_Partial Lives._ _Collective Life._—With the exception of the
physiologist, no one, neither he who is ignorant nor he who is
intellectual, nor even the doctor, troubles his head about the life
or the death of the element, although this is the basis, the real
foundation, of the activity manifested by the social body and by its
different organs. The life of the individual, of the animal, depends
on these elementary partial lives just as the existence of the State
depends upon that of its citizens. To the physiologist, the organism
is a federation of cellular elements unified by close association.
Goethe compared them to a “multitude”; Kant to a “nation”; and others
have likened them to a populous city the anatomical elements of which
are the citizens, and which possesses an individuality of its own. So
that the activity of the federated organism may be discussed in each
of its parts, and then it is _elementary life_, or in its totality,
and then it is _general life_. Paracelsus and Bordeu had a glimpse
of this truth when they considered a life appropriate to each part
(_vita propria_) and a collective life, the life of the whole (_vita
communis_). In the same way we must distinguish the _elementary death_,
which is the cessation of the vital phenomena in the isolated cell,
from the _general death_, which is the disappearance of the phenomena
which characterised the collectivity, the totality, the federation, the
nation, the city, the whole in so far as it is a unit.
These comparisons enable us to understand how general life depends on
the partial lives of each anatomical citizen. If all die, the nation,
the federation, the total being clearly ceases to exist. This city
has an enormous population—there are thirty trillion cellules in the
body of man; it is peopled with absolutely sedentary citizens, each
of which has its fixed place, which it never leaves, and in which
it lives and dies. It must possess a system of more or less perfect
arrangements to secure the material life of each inhabitant. All have
analogous requirements: they feed very much the same; they breathe in
the same way; each in fact has its profession, industry, talents, and
aptitudes by which it contributes to social life, and on which, in its
turn, it depends. But the process of alimentation is the same for all.
They must have water, nitrogenous materials and analogous ternaries;
the same mineral substances, and the same vital gas, oxygen. It is no
less necessary that the wastes and the egesta, very much alike in every
respect, should be carried off and borne away in discharges arranged so
as to free the whole system from the inconvenience, the unhealthiness,
and the danger of these residues.
_Secondary Organization in Organs._—That is why, as we said above, the
secondary organizations of the economy exist:—the digestive apparatus
which prepares the food and enables it to pass into the blood, into the
lymph, and finally into the liquid medium which bathes each cell and
constitutes its real medium; the respiratory apparatus which imports
the oxygen and exports the gaseous excrement, carbonic acid; the heart
and the circulatory system which distributes through the system the
internal medium, suitably purified and recuperated. The organization
is dominated by the necessities of cellular life. This is the law of
the city, to which Claude Bernard has given the name of the _law of the
constitution of organisms_.
_Death by Lesion of the Major Organs. Vital Tripod._—Thus we understand
what life is, and at the same time what is the death of a complex
living being. The city perishes if its more or less complicated
mechanisms which look after its revictualling and its discharge are
seriously affected at any point. The different groups may survive for
a more or less lengthy period, but progressively deprived of the means
of food or of discharge, they are finally involved in the general
ruin. If the heart stops, there is a universal famine; if the lungs
are seriously injured, we are asphyxiated; if the principal organ of
discharge, the kidney, ceases to perform its allotted task, there is a
general poisoning by the used-up and toxic materials retained in the
blood.
We understand how the integrity of the major organs,—the heart, the
lungs, the kidney,—is indispensable to the maintenance of existence. We
understand that their lesion, by a series of successive repercussions,
involves universal death. We always die, said the doctors of old,
because of the failure of one of these three organs, the heart, the
lungs, or the brain. Life, they said in their inaccurate language,
depends upon these as upon three supports. Hence the idea of the _vital
tripod_. But it is not only this trio of organs which maintain the
organism; the kidney and the liver are no less important. In different
degrees each part exercises its action on the rest. Life is based in
reality on the immense multitude of living cells associated for the
formation of the body; on the thirty trillion anatomical elements,
each part is more or less necessary to all the rest, according as the
bond of solidarity is drawn more or less closely in the organism under
consideration.
_Death and the Brain._—There are indeed more noble elements charged
with higher functions than the rest. These are the nervous elements.
Those of the brain preside over the higher functions of animality,
sensibility, voluntary movement, and the exercise of the intellect. The
rest of the nervous system forms an instrument of centralization which
establishes the relations of the parts one with the other and secures
their solidarity. When the brain is stricken and its functions cease,
man has lost the consciousness of his existence. Life seems to have
disappeared. We say of a man in this plight that he no longer lives,
thus confusing general life with the cerebral life which is its highest
manifestation. But the man or the animal without a brain lives what may
be called a vegetative life. The human anencephalic foetus lives for
some time, just as the foetus which is properly formed. Observation
always shows that this existence of the other parts of the body cannot
be sustained indefinitely in the absence of that of the brain. By a
series of impulses due to the solidarity of the grouping of the parts,
the injury received by the brain affects by repercussion the other
organs, and leads in the long run to the arrest of elementary life in
all the anatomical elements. The death of the whole is then complete.
Doctors have therefore a two-fold reason for saying that the brain
may cause death. The death of the brain suppresses the highest
manifestation of life, and, in the second place, by a more or less
remote counter stroke, it suppresses life in all the rest of the system.
_Death is a Process._—Besides, the fact is general. The death of one
part always involves the death of the rest—_i.e._, universal death. A
living organism cannot be at the same time alive and a cemetery. The
corpses cannot exist side by side with the living elements. The dead
contaminates the living, or in some other way involves it in its ruin.
Death is propagated; it is a progressive phenomenon which begins at one
point and gradually is extended to the whole. It has a beginning and a
duration. In other words, the death of a complex organism is a process.
And further, the end of a simple organism, of a protozoan, of a cell,
is itself a process infinitely more shortened.
The very perfection of the organism is therefore the cause of its
fragility. It is the degree of solidarity of the parts one with another
which involves the one set in the catastrophe of the rest, just as in
a delicate piece of mechanism the derangement of a wheel brings nearer
and nearer the total breakdown. The important parts, the lungs, the
heart, the brain, suffer no serious alteration without the reflex being
felt throughout. But there are also wheels less evident, the integrity
of which is scarcely less necessary.
_The Solidarity of the Anatomical Elements._—The cause of the mortal
process—_i.e._, of the extension and the propagation of an initial
destruction—is therefore to be found in the solidarity of the parts
of the organism. The closer it is the greater do the chances of
destruction become, for the accident which has happened to one will by
repercussions affect the others.
Now the solidarity of the parts of the organism may be carried out in
two ways; there is a _humoral solidarity_ and a _nervous solidarity_.
_Humoral Solidarity._—Humoral solidarity is realized by the mixture
of humours. All the liquids of the organism which have lodged in the
interstices of the elements and which soak the tissues, are in contact
and in relation of exchange one with another, and through the permeable
wall of the small vessels they are in relation with the blood and the
lymph.
All the liquid atmospheres which surround the cells and form their
ambient medium have intercommunication. A change having taken place in
one cellular group, and therefore in the corresponding liquid, modifies
the medium of the further or nearer groups, and therefore these groups
themselves.
_Nervous Solidarity._—But the real instrument of the solidarity of the
part is the nervous system. Thanks to it in the living machine the
component activities of the cellular multitude restrain and control
one another. Nervous solidarity makes of the complex being not a mob
of cells, but a connected system, an individual in which the parts are
subordinated to the whole and the whole to the parts; in which the
social organism has its rights just as the individual has his rights.
The whole secret of the vital functional activity of the complex
being is contained in these two factors:—the independence and the
subordination of the elementary lives. General life is the harmony of
the elementary lives, their symphony.
_Independence and Subordination of the Anatomical Elements._—The
independence of the anatomical elements results from the fact that
they are the real depositaries of the vital properties, the really
active components. On the other hand the subordination of the parts
to the whole is the very condition of the preservation of form in
animals and plants. The architecture which is characteristic of
them, the morphological plan which they realize in their evolutive
development which they are ever preserving and repairing, form a
striking proof of this. This dependence in no way contradicts the
autonomy of the elements. For when with Claude Bernard and Virchow
we study the circumstances we see that the element accommodates
itself to the organic plan without violence to its nature. It behaves
in its natural place as it would behave elsewhere, if elsewhere it
were to meet around it the same liquid medium which at once is a
stimulant and a food. This at least is the conclusion we may draw from
experiments on transplanting, or on animal and vegetable grafting.
Neither the neighbouring elements, nor the whole system act on it at
a distance by a kind of mysterious induction, according to the ideas
of the vitalists, in order to regulate the activity of the element.
They contribute solely to the composition of the liquid atmosphere
which bathes it. They intervene in order to provide it with a
certain environment whose very characteristic physical and chemical
constitution regulates its activity. This constitution may be some day
imitated by the devices of experiment. When that result is achieved
the anatomical element will live in isolation exactly as it lives in
the organic association, and the mysterious bond which causes its
solidarity with the rest of the economy will become intelligible. In
fact, we may defer more or less the maturity of this prophecy, but
there is no doubt that we are daily nearing its fulfilment.
The general life of the complex being is therefore the more or less
perfect synergy, the _ordered process_ of elementary lives. General
death is the destruction of these partial lives. The nervous system,
the instrument of this harmony of the parts, represents the social
bond. It keeps most of the partial elements under its sway, and is
thus the intermediary of their relations. The closer this dependence,
the higher the development of the nervous apparatus, and the better,
also, is assured the universal solidarity and therefore the unity of
the organism. Cellular federation assumes the characteristic of a
unique individuality in proportion to the development of this nervous
centralization. With an ideal perfect nervous system the correlation
of the parts would also attain perfection. As Cuvier said: “None could
experience change without a change in the rest.”
But no animal possesses this extreme solidarity of the parts of the
living economy. It is a philosopher’s dream. It is the dream of Kant,
to whom the perfect organism would be “a teleological system,” a system
of reciprocal ends and means, a sum total of parts each existing for
and by the rest, for and by the whole. An organism so completely
connected would be unlikely to live. In fact, living organisms show
a little more freedom in the interplay of their parts. Their nervous
apparatus fortunately does not attain this imaginary perfection; their
unity is not so rigorous. The idea of individuality, of individual
existence, is therefore not absolute but relative. There are all
degrees of it according to the development of the nervous system. What
the man in the street and the doctor himself understand by death is the
situation created by the stopping of the general wheels, the brain, the
heart, and the lungs. If the breath leaves no trace on the glass held
to the mouth, if the beating of the heart is no longer perceptible by
the hand which touches or the ear which listens, if the movement and
the reaction of sensitiveness have ceased to be manifest, these signs
make us conclude that it is death. But this conclusion, as we have said
before, is a prognostic rather than a judgment of fact. It expresses
the belief that the subject will certainly die, and not that it is from
this moment dead. To the physiologist the subject is only on the way to
die. The process has started. The only real death is when the universal
death of all the elements has been consummated.
CHAPTER III.
PHYSICAL AND CHEMICAL CHARACTERS OF CELLULAR DEATH. NECROBIOSIS.
GROWING OLD.
Characteristic of elementary life—Changes produced by death in the
composition and the death of the cell—Schlemm; Loew; Bokorny; Pflüger;
A. Gautier; Duclaux—The processive character of death—Accidental
death—Necrobiosis—Atrophy—Degeneration—So-called natural
death—Senescence—Metchnikoff’s theory of senescence—Objections.
Elementary death is nothing but the suppression in the anatomical
elements of all the phenomena of vitality.
_Characteristics of Elementary Life._—The characteristic features of
elementary life have been sufficiently fixed by science. First of
all, there is _morphological unity_. All the living elements have
an identical morphological composition. That is to say that life is
only accomplished and sustained in all its fulness in organic units
possessing the anatomical constitution of the cell, with its cytoplasm
and its nucleus, constituted on the classical type. In the second
place, there is _chemical unity_. The constituent matter, the matter of
which the cell is built up, diverges but little from a chemical type—a
proteid complex, with a hexonic nucleus, and from a physical model
which is an emulsion of granulous, immiscible liquids, of different
viscosities. The third character consists in the possession of a
_specific form_ acquired, preserved, and repaired by the element.
The fourth character, and perhaps the most essential of all, is _the
property of growth_ or _nutrition_ with its consequence, namely, a
relation of exchanges with the external medium, exchanges in which
oxygen plays considerable part. Finally, there is a last property,
that of _reproduction_, which in a certain measure is a necessary
consequence of the preceding,—_i.e._, of growth.
These five vital characters of the elements are most in evidence
in cells living in isolation, in microscopical beings formed of a
single cell, protophytes and protozoa. But we find them also in
the associations formed by the cells among one another—_i.e._, in
ordinary plants and animals, multicellular complexes, called for this
reason metaphytes and metazoa. Free or associated, the anatomical
elements behave in the same way—feed, grow, breathe, digest in the
same manner. As a matter of fact, the grouping of the cells, the
relations, proximity and contiguity, which they assume, introduce
some variants into the expression of the common phenomena; but these
slight differences cannot disguise the essential community of the vital
processes.
The majority of physiologists, following Claude Bernard, admit as
valent and convincing the proof that the illustrious experimenter
furnished of this unity of the vital processes. There are, however, a
few voices crying in the wilderness. M. Le Dantec is one. In his new
theory of life he amplifies and exalts the differences which exist
between the elementary life of the proteids and the associated life of
the metazoa. In them he can see nothing but contrasts and deviations.
If this is elementary life, let us ask what is _elementary
death_—_i.e._, the death of the cell. And in this connection let us
ask the questions which we have to examine in the case of animals high
in organization, and of man himself. What are the characteristics
of elementary death? When the cell dies, is its death preceded by a
growing old or senescence? What are the preliminary signs and the
acknowledged symptoms?
_Changes Produced by Death._—The state of death is only truly realized
when the fundamental properties of living matter enumerated above have
entirely disappeared. We must follow step by step this disappearance in
all the anatomical elements of the metazoan.
Now the properties of the cell are connected with the physical and
chemical organization of living matter. For them to disappear entirely,
this organization must be destroyed as far as all that is essential in
it is concerned. We cannot admit with the vitalists that there is any
material difference between the dead and the living, and that only an
immaterial principle which has escaped into the air distinguishes the
corpse from the animated being. In fact, the external configuration may
be almost preserved, and the corpse may bear the aspect and the forms
of the preceding state. But this appearance is deceptive. Something in
reality has changed. The structure, the chemical composition of the
living substance, have undergone essential changes. What are these
changes?
_Physical Changes._—Certain physiologists have endeavoured to determine
them. Klemm, a botanist, pointed out in 1895 the physical changes
which characterize the death of vegetable cells—loss of turgescence,
fragmentation of the protoplasm, the formation of granules, and the
appearance of vacuoles.
_Chemical Changes._—O. Loew and Bokorny laid great stress in 1886 and
1896 on the chemical changes. The living protoplasm according to them
is an unstable proteid compound. A slight change would detach from the
albuminoid molecule a nucleus with the function of aldehyde, and at the
same time would transform an amido-group into an amido-group. This
would suffice for the transition of the protoplasm from the living to
the dead state. This theory is based on the fact that the compounds
which exercise a toxic action on the living cell, without acting
chemically on the dead albumin, are easily fixed by the aldehydes; and
on the fact that many of them, which attack simultaneously the living
albuminoids and the dead albumin, easily combine with the amido-group.
E. Pflüger, a celebrated German scientist, has considered living matter
as an albumin spontaneously decomposable, the essential nucleus of
which is formed by cyanogen. Its active instability would be due to the
penetration into the molecule of the oxygen which fixes on the carbon
and separates it from the nitrogen. Armand Gautier has not confirmed
this view. Duclaux (1898) has stated that the difference between the
living and the dead albumin would be of a stereochemical order.
_Progressive Character of Death. Accidental Death._—We have seen that
in general the disappearance of the characteristics of vitality is not
instantaneous, at least in the natural course of things, in complex
organisms. It is the end of a more or less rapid process. But death
is not instantaneous in the isolated anatomical element any more than
it is in the protozoan or protophyte. We must have recourse to very
violent devices of destruction to kill the cell at a blow, to leave
absolutely nothing of its organization existing. The protoplasm of
yeast when violently crushed by Büchner still possessed the power of
secreting soluble ferments. A powerful action, a very high temperature,
is necessary to obtain the result. _A fortiori_, the difficulty
increases in the case of complex organisms, all of whose living
elements cannot be attacked at the same moment by the destructive
cause. A mechanical action, capable of destroying at one blow all the
living parts of a complex being, of an animal, of a plant, must be of
almost inconceivable power. The blow of a Nasmyth hammer would not be
strong enough.
The chemical alteration produced by a very toxic substance distributed
throughout the blood, and thus brought into contact with each element,
would produce a disorganization which, however rapid it were, could not
be called instantaneous. And the same holds good of physical agents.
But these are not the processes of nature under normal circumstances.
They are accidents or devices. We shall leave on one side their
consideration and we shall only deal here with the natural processes of
the organism.
Imagine it placed in a medium appropriate to its needs and following
out without intervening complications the evolution assigned to it by
its constitution. Experiment tells us that this natural evolution in
every case known to us ends in death. Death supervenes sooner or later.
For beings higher in organization, which we can bring into closer
and closer resemblance to man, we find that they die of disease,
by accident, or of old age. And as disease is an accident, we may
naturally ask if what we call old age is not also a disease.
However that may be, the mortal process, being never instantaneous, has
a duration, a beginning, a development, an end—in a word, a history.
It constitutes an intermediary phase between perfect life and certain
death.
_Necrobiosis._ _Atrophy._ _Degeneration._—The process according to
the circumstances may be shortened or prolonged. When death is the
result of violence events are precipitated. The physical and chemical
transformations of the living matter constitute a kind of acute
alteration called by Schultze and Virchow _necrobiosis_. According
to the pathologists, there are two kinds of _necrobiosis_:—that by
_destruction_, by _simple atrophy_, which causes the anatomical
elements to disappear gradually without undergoing appreciable
modifications; and _necrobiosis by degeneration_, which transforms the
protoplasm into fatty matter into calcareous matter, into granulations
(fatty degeneration, calcification, granulous degeneration). There is
no disagreement as to the causes of this necrobiosis. They are always
accidental; they originate in external circumstances:—the insufficiency
of the alimentary materials, of water, of oxygen; the presence in the
medium of real poisons destroying the organized matter; the violent
intervention of physical agents, heat, electricity; the reflex on the
composition of the cellular atmosphere of a violent attack on some
essential organ, the heart, the lungs, the kidneys.
_Senescence._ _Old Age._—In a second category we must place the
mortal processes, slow in their movement, in which we cannot see the
intervention of clearly accidental and abnormal disturbing agents.
Death appears to be the termination of a breaking-up proceeding by
insensible degrees in consequence of the progressive accumulation
of very small inappreciable perturbations. This slow breaking up
is adequately expressed by the term—growing old, or senescence.
The alterations by which it is betrayed in the cell are especially
_atrophic_, but they are also accompanied, however, by different
forms of degeneration. An extremely important question arises on this
subject, and that is whether the phenomena of senility have their cause
in the cell itself, if they are inevitably found in its organization,
and therefore if old age and death are natural and necessary phenomena.
Or, on the other hand, should we consider them as due to a progressive
alteration of the medium, the character of which would be accidental
although frequent or habitual? This, in a word, is the problem which
has so often engaged the attention of philosophical biologists. Are old
age and death natural and inevitable phenomena?
The recent experiments of Loeb and Calkins, and all similar
observations, tend to attribute to the phenomenon of growing old the
character of a remediable accident. But the remedy has not been found,
and the animal finally succumbs to these slow transformations of its
anatomical elements. We then say that it _dies of old age_.
_Metchnikoff’s Theory of Senescence. Objections._—Metchnikoff has
proposed a theory of the mechanism of this general senescence. The
elements of the conjunctive tissue, phagocytes, macrophages, which
exist everywhere around the specialized and higher anatomical elements
would destroy and devour them as soon as their vitality diminishes,
and would take their place. In the brain, for example, it would be the
phagocytes which, attacking the nervous cellules, would disorganize the
higher elements, incapable of defending themselves. This substitution
of the conjunctive tissue, which only possesses vegetative properties
of a low order, for the nervous tissues, which possesses very high
vegetative properties, results in an evident breaking-up. The gross
element of violent and energetic vitality stifles the refined and
higher element.
This expulsion is a very real fact. It constitutes what is called
senile sclerosis. But the active _rôle_ attributed to it by Metchnikoff
in the process of degeneration is not so certain. An expert observer
in the microscopic study of the nervous system, M. Marinesco, does not
accept this interpretation as far as the senescence of the elements of
the brain is concerned. Diminution of the cell, the decrease in the
number of its stainable granulations, chromatolysis, the formation of
inert, pigmented substances—all these phenomena which characterize the
breaking-up of the cerebral cells would be accomplished, according to
this observer, without the intervention of the conjunctive elements,
the phagocytes.
The characteristic of extensive and progressive process presented
by death necessitates in a complex organism, which is a prey to it,
the existence side by side of living and dead cells. Similarly, in
the organism which is growing old, there are young elements and
elements of every age side by side with senile elements. As long as
the disorganization of the last has not gone too far, they may be
rejuvenated. All we have to do is to restore to them an appropriate
ambient medium. The whole question is one of knowing and being able
to realize, for this or that part which we wish to reanimate and to
rejuvenate, the very special or very delicate conditions that this
medium must fulfil. As we have said, success is attained in this
respect as far as the heart is concerned, and this is why we are able
to reanimate and to revive the heart of a dead man. It is hoped that
ideas along these lines will extend with the progress of physiology.
After this sketch of the conditions and of the varieties of cellular
death we must return to the essential problem which is engaging the
curiosity of biologists and philosophers. Is death unavoidable,
inevitable? Is it the necessary consequence of life itself, the
inevitable issue, the inevitable end?
There are two ways of endeavouring to solve this question of the
inevitability of death. The first is to examine popular observation,
practised, so to speak, unintelligently and without special
precautions. The second is to analyze everything we know relative to
the conditions of elementary life.
CHAPTER IV.
THE APPARENT PERENNITY OF COMPLEX INDIVIDUALS.
Millenary trees—Plants with a definite rhizome—Vegetables
reproduced by cuttings—Animal colonies—Destruction due to extrinsic
causes—Difficulty of interpretation.
Popular opinion teaches us that living beings have only a transient
existence, and as a poet has said: “Life is but a flash between two
dark nights.” But, on the other hand, simple observation shows us, or
appears to show us, beings whose duration of existence is far longer,
and practically illimitable.
_Millenary Trees._—We know of trees of venerable antiquity. Among these
patriarchs of the vegetable world there is a chestnut tree on Mount
Etna which is ten centuries old, and an ivy in Scotland which is said
to be thirty centuries old. Trees of 5000 years old are not absolutely
unknown. We may mention among those of that age the famous dragon
tree[21] at Orotava, in the island of Teneriffe. Two other examples are
known in California—the pseudo-cedar, or _Tascodium_, at Sacramento,
and a _Sequoïa gigantea_. We know that the olive tree may live 700
years. There are cedars 800 years old and oaks of the age of 1,500
years.
[21] Lately destroyed in a storm. [Tr.]
_Plants with a Rhizome._—Vegetable species of almost unlimited
duration of life are known to botanists. Such, for instance, are plants
with a definite rhizome, such as colchicum. Autumnal colchicum has a
subterranean root, the bulb of which pushes out every year fresh axes
for a new bloom; and as each of these new axes stretches out an almost
constant length, a botanist once set himself the singular problem of
discovering how long it would take such a foot, if suitably directed,
to travel round the world.
_Vegetables Reproduced by Cuttings._—Vegetables reproduced by slips
furnish another example of living beings of indefinite duration. The
weeping willows which adorn the banks of sheets of water in the parks
and gardens throughout the whole of Europe have sprung, directly or
indirectly, from slips of the first _Salix Babylonica_ introduced to
the West. May it not be said that they are the permanent fragments of
that one and the same willow?
_Animal Colonies._—These examples, as well as those furnished to
zoologists by the consideration of the polypi which have produced by
their slow growth the reefs, or _atolls_, of the Polynesian seas,
do not, however, prove the perennity of living beings. The argument
is valueless, for it is founded upon a confusion. It turns on the
difficulty that biologists experience in defining the individual. The
oak and the polypus are not simple individuals, but associations of
individuals, or, to use Hegel’s expression, the nations of which we see
the successive generations. We give to this succession of generations
a unique existence, and our reasoning comes to this, that we confer on
each present citizen of this social body the antiquity which belongs to
the whole.
_Destruction of the Social Individual due to Extrinsic Causes._—As
for the destruction, the death of this social individual, of this
hundred-year-old tree, it seems indeed that there is no ground for
considering it a natural necessity. We find the sufficient reason of
its usual end in the repercussion on the individual of external and
contingent circumstances. The cause of the death of a tree, of an oak
many centuries old, is to be found in the ambient conditions, and not
in some internal condition. Cold and heat, damp and dryness, the weight
of the snow, the mechanical action of the rain, of hail, of winds
unchained, of lightning; the ravages of insects and parasites—these are
what really work its ruin. And further, the new branches, appearing
every year and increasing the load the trunk has to bear, increase the
pressure of the parts, and make more difficult the motion of the sap.
But for these obstacles, external, so to speak, to the vegetable being
itself, it would continue indefinitely to bloom, to fructify, and as
each spring returned to show fresh buds.
_Difficulty of Interpretation._—In this as in all other examples we
must know the nature of the beings that we see lasting on and braving
the centuries. Is it the individual? Is it the species? Is it a living
being, properly so called, having its unity and its individuality,
or is it a series of generations succeeding one another in time and
extending in space? In a word, the question is one of knowing if we
have to do with a real tree or with a genealogical tree. We are just
as uncertain when we deal with animals. What is the being that lasts
on—a series of generations or an individual? This doubt forbids us to
draw any conclusion from the observation of complex beings. We must
therefore return from them to the _elementary being_; and we must
examine it from the point of view of perennity or of vital decay. Let
us then ask the questions that we have already examined with reference
to animals high in organization and to man himself. Is the death of the
cell an inevitable characteristic? Are there any cells, protophytes,
protozoa, which are immortal?
CHAPTER V.
THE IMMORTALITY OF THE PROTOZOA.
Impossibility of life without evolution—Law of increase and
division—Immortality of the protozoa—Death, a phenomenon of adaptation
which has appeared in the course of the ages—The infusoria—The
death of the infusoria—Two kinds of reproduction—The caryogamic
rejuvenescence of Maupas—Calkins on rejuvenescence—Causes of
senescence—Impossibility of life without evolution.
We take into account, _a priori_, the conditions that must be fulfilled
by the monocellular being in order to escape the inevitability of
evolution, of the succession of ages, of old age, and of death. It must
be able indefinitely to maintain itself in a normal régime, without
changing, without increasing, maintaining its constant morphological
and chemical composition, in an environment vast enough for it to
be unaltered by the borrowings or the spendings resulting from its
nutrition—_i.e._, it must remain constant in the presence of the
constant being. We might conceive of a nutrition perfect enough, of
exchanges exact enough, and regular enough, for the state of things to
be indefinitely maintained. This would be absolute permanence realized
in the vital mobility.
_The Law of Growth and Division._—This model of a perfect and
invariable machine does not exist in nature. Life is incompatible with
the absolute permanence of the dimensions and the forms of the living
organism.
In a word, it is a rigorous law of living nature that the cell can
neither live indefinitely without growth, nor grow indefinitely without
division.
Why is this so? Why is there this impossibility of a regular régime in
which the cell would be maintained in magnitude without diminution or
increase? Why has nutrition as a necessary consequence the growth of
the element? This is what we do not positively know.
Things are so. It is an irreducible fact, peculiar to the protoplasm, a
characteristic of the living matter of the cell. It is the fundamental
basis of the property of generation. That is all we can say about it.
Real living beings have therefore inevitably an evolution. They are not
unchangeable. In its simple form this evolution consists in the fact
that the cell grows, divides, and diminishes by this division, begins
the upward march which ends in a new division. And so on.
_Immortality of the Protozoa._—It may happen, and it does happen
in fact, that this series of acts is repeated indefinitely at any
rate unless an accidental cause should interrupt it. The animal thus
describes an indefinite curve, constituted by a series of indentations,
the highest point of which corresponds to the maximum of size, and the
lowest point to the diminution which succeeds the division. This state
of things has no inevitable end if the medium does not change. The
being is immortal.
In fact, the compound beings of a single cell, protophytes and
protozoa, the algae and the unicellular mushrooms, at the minimum stage
of differentiation, escape the necessity of death. They have not, as
Weismann remarks, the real immortality of the gods of mythology, who
were invulnerable. On the contrary, they are infinitely vulnerable,
fragile, and perishable; myriads die every moment. But their death is
not inevitable. They succumb to accidents, never to old age.
Imagine one of these beings placed in a culture medium favourable to
the full exercise of its activities, and, moreover, wide enough in
its extent to be unaffected by the infinitely small quantities of
material which the animal may take from it or expel into it. Suppose,
for example, it is an infusorian in an ocean. In this invariable medium
the being lives, increases, and grows continually. When it has reached
the limits of a size fixed by its specific law, it divides into two
parts, which are indistinguishable the one from the other. It leaves
one of its halves to colonize in its neighbourhood, and it begins its
evolution as before. There is no reason why the fact should not be
repeated indefinitely, since nothing is changed, either in the medium
or in the animal.
To sum up. The phenomena which take place in the cell of the protozoan
do not behave as a cause of check. The medium allows the organism
to revictual and to discharge itself in such a way and with such
perfection that the animal is always living in a regular régime, and,
with the exception of its growth and later on of its division, there is
nothing changed in it.
_Death a Phenomenon of Adaptation—It appeared in the Course of the
Ages._—This immortality belongs in principle to all the protista which
are reproduced by simple and equal division. If it be remarked that
these rudimentary organisms endowed with perennity are the first living
forms which have shown themselves on the surface of the globe, and
that they have no doubt preceded many others—the multicellular, for
instance, which are liable, on the contrary, to decay—the conclusion
is obvious:—Life has long existed without death. Death has been a
phenomenon of adaptation which has appeared in the course of the ages
in consequence of the evolution of species.
_The Death of Infusoria._—We may ask ourselves at what moment in the
history of the globe, at what period of the evolution of its fauna,
this novelty, death, made its appearance. The celebrated experiments of
Maupas on the senescence of the infusoria seem to authorize us to give
a precise answer to this question. By means of these experiments we are
led to believe that death must have appeared at the same time as sexual
reproduction. Death became possible when this process of generation was
established, not in all its plenitude, but in its humblest beginnings,
under the rudimentary forms of unequal division and of conjugation.
This happened when the infusoria began to people the waters.
_The Two Modes of Multiplication._—Infusoria are, in fact, capable of
multiplication by simple division. It is true to say that in addition
to this resource, the only one which interests us here, because it
is the only one which confers immortality, they possess another.
They present and exercise under certain circumstances a second mode
of reproduction, caryogamic conjugation. It is a rather complicated
process in its detail, but it is definitively summed up as the
temporary pairing of two individuals, which are otherwise very much
alike, and which cannot be distinguished as male and female. They
become closely united on one of their faces; they reciprocally exchange
a semi-nucleus which passes into the conjoint individual; and then
they separate. But infusoria can be prevented from this conjunction by
regularly isolating them immediately after their birth. Then they grow,
and are constrained after a lapse of time to divide according to the
first method.
Maupas has shown that the infusoria could not accommodate themselves
to this régime indefinitely; they could not go on dividing for ever.
After a certain number of divisions they show signs of degeneration
and of evident decay. The size diminishes, the nuclear organs become
atrophied, all the activities fail, and the infusorian perishes.
It succumbs to this kind of senile atrophy unless it is given an
opportunity of conjugation with another infusorian in the same plight.
In this act it then derives new strength, it grows larger, attains its
proper size, and builds up its organs once more. Conjugation gives it
life, youth, and immortality.
_Alimentary Rejuvenescence._—Recent observations due to Mr. G. N.
Calkins, an American biologist, and confirmed by other investigators,
have shown that this method of rejuvenescence is not the only one,
and is not even the most efficacious. Conjugation has no mysterious,
specific virtue. The infusoria need not be married in order to be
rejuvenated. It is sufficient to improve their food. In the case of
the “tailed” paramecium we may substitute beef broth and phosphates
for conjugation. Calkins observed 665 consecutive generations without
blemish, without exhaustion, and without any sign of old age. Plenty of
food and simple drugs have successfully resisted senility and the train
of atrophic degenerations which it involves.
_Causes of Senescence._—As for the causes of senescence which have
been remedied with such success, they are not exactly known. Calkins
thinks that senescence results from the progressive losses to the
organism of some substance essential to life. Conjugation or intensive
alimentation would act by building up again this necessary compound.
G. Loisel believes on the contrary that it is a matter of the
progressive accumulation of toxic products due to a kind of alimentary
auto-intoxication.
CHAPTER VI.
LETHALITY OF THE METAZOA AND OF DIFFERENTIATED CELLS.
Evolution and death of metazoa.—Possible rejuvenescence of the
differentiated cells by the conditions of the medium.—Conditions of
the medium for immortal cells.—The immortal elements of metazoa.—The
element in accidental and remediable death.—Somatic cells and sexual
cells.
_Evolution and Death of Metazoa._—We have seen that the infusoria
are no longer animals in which material exchanges take place with
sufficient perfection, and in which cellular division, the consequence
of growth, is produced with sufficient precision and equality for
life to be carried on indefinitely in a perfect equilibrium in the
appropriate medium without alteration or check. _A fortiori_ we no
longer find the perfect regularity of nutritive exchange in the classes
above them. In a word, starting from this inferior group, there are
no animated beings in the state of existence which Le Dantec calls
“condition Iº of manifested life?” Living matter, instead of being
continually kept identical in conditions of identical media, is
modified in the course of existence. It becomes dependent on time. It
describes a declining trajectory; it experiences evolution, decay,
and death. Thus the fundamental condition of invariable youth and of
immortality fails in all metazoa. The vital wastes accumulate in all
through the insufficiency or the imperfection of nutritive absorption
or of excretion. Life decays; the organism progressively alters, and
thus is constituted that state of decrepitude by atrophy or chemical
modification which we call senescence, and which ends in death. To sum
up, old age and death may be attributed to cellular differentiation.
_Possible Alimentary Rejuvenescence of the Differentiated
Cells—Conditions of Medium._—We must add, however—as the teaching
of experiments in general and in particular as the teaching of the
experiments of Loeb and of Calkins—that a slight change of the
environment, made at the right time, is capable of re-establishing
equilibrium and of completely rejuvenating the infusorian. Senescence
has not in this case a definitive any more than an intrinsic character;
a modification in the composition of the alimentary medium will
successfully resist it. If we are allowed to generalize this result, it
may be said that senescence, the declining trajectory, the evolution
step by step down to death, are not for the cells considered in
isolation an inevitable and essentially inherent in the organism, and
a rigorous consequence of life itself. They preserve an accidental
character. In senescence and death there is no really natural, internal
cause, inexorable, and irremediable, as was claimed in the past by J.
Müller, and more recently by Cohnheim in Germany and Sedgwick Minot in
America.
_Conditions of the Medium for Immortal Cells._—As for the cells which
are less differentiated, the protophytes and the protozoa situated
one degree lower in the scale than the infusoria, we must admit the
possibility of that perfect and continuous equilibrium which would
save them from senile decrepitude. And it is quite understood that
this privilege remains subordinated to the perfect constancy of the
appropriate medium. If the latter changes, the equilibrium is broken,
the small insensible perturbations of nutrition accumulate, vital
activity decays, and in sole consequence of the imperfection of the
extrinsic conditions or of the medium, the living being finds itself
once more dragged down to decay and to death.
_Immortal Elements of the Metazoa._—All the preceding facts and
considerations refer to isolated cells, to monocellular beings.
But, and this is what makes these truths so interesting, they may
be extended to all cells grouped in collectivity—i.e., to all the
animals and living beings that we know. In the complicated edifice
of the organism, the anatomical elements, at any rate the least
differentiated, would have a continual brevet of immortality. Generally
speaking, this would be the case for the egg, for the sexual elements,
and perhaps, too, for the white globules of the blood, the leucocytes.
And, further, around each of these elements must be realized the
invariably perfect medium which is the necessary condition. This does
not take place.
_Elements in Accidental and Remediable Death._—As for the other
elements, they are like the infusoria, but without the resource of
conjugation. The ambient medium becomes exhausted and intoxicated
around each cell, in consequence of the accidents which happen to the
other cells. Each therefore undergoes progressive decay, and finally
they perish—the decay and destruction being perhaps in principle
accidental, but, in fact, they are the rule.
The different anatomical elements of the organism are more or less
sensitive to those perturbations which cause senescence, necrobiosis,
and death. There are some more fragile and more exposed. Some are more
resisting, and finally, there are some which are really immortal. We
have just said that the sexual cell, the ovum, is one. It follows that
the metazoan, man for instance, cannot entirely die. Let us consider
one of these beings. Its ancestors, so to speak, have not entirely
disappeared; each has left the fertile egg, the surviving element from
which has issued the being of which we speak; and when it in its turn
has developed, part of that ovum has been placed in reserve for a new
generation. The death of the elements is not therefore universal. The
metazoan is divided from the beginning into two parts. On the one
hand are the cells destined to form the body, _somatic_ cells. They
will die. On the other hand are the _reproductive_, or _germinal_, or
_sexual_ cells, capable of living indefinitely.
_Somatic and Sexual Cells._—In this sense we may say with Weismann
that there are two things in the animal and in man—the one mortal,
the _soma_ the body, the other immortal, the _germen_. These germinal
cells, as in the case of the protozoa we mentioned above, possess a
conditional immortality. They are imperishable, but on the contrary,
are fragile and vulnerable. Millions of ova are destroyed and are
disappearing every moment. They may die by accident, but never of old
age.
We now understand that if the protistae are immortal, it is because
these living beings, reduced to a single cell, accumulate in it the
compound characters of the somatic cell and germinal cell, and enjoy
the privilege which is attached to the latter.
CHAPTER VII.
MAN. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH.
The miseries of humanity: 1. Disease; 2. Old age.—Old age considered
as a chronic disease.—Its occasional cause.—3. The disharmonies of
human nature; 4. The instinct of life and the instinct of death.
Man’s unhappy plight is the constant theme of philosophies and
religions. Without referring to its moral basis, it has a physical
basis due to four causes—the physical imperfection or disharmony of
nature, disease, old age, and death—or rather of three, for what we
call old age is perhaps a simple disease. These are the great sorrows
of man, the sources of all his woes. Disease attacks him, old age
awaits him, and death must tear him from all the ties which he has
formed. All his pleasures are poisoned by the certain knowledge that
they last but for a moment, that they are as precarious as his health,
his youth, and his life itself.
§ 1. DISEASE.
Disease, frequent, constant, and inevitable as it is, is, however,
nothing but a fact outside the natural order. Its character is clearly
accidental, and it interrupts the normal cycle of evolution. Medical
observation teaches us, on the other hand, that the health of the body
reacts on that of the mind; and therefore man as a whole, moral and
physical, is affected by disease. Bacon described a diseased body as a
jailer to the soul, and the healthy body as a host. Pascal recognized
in diseases a principle of error. “They spoil our judgment and our
senses.”
I am not expressing a chimerical hope when I predict that science will
conquer disease. Medicine has at last issued from the contemplative
attitude of so many centuries; it has engaged in the struggle, and
signs of victory are already appearing. Disease is no longer the
mysterious power which it was impossible to escape. Pasteur gave to it
a body. The microbe can be caught. In the words of Schopenhauer, an
alteration of the atmosphere so slight that it is impossible to detect
it by chemical analysis may bring on cholera, yellow fever, the black
plague, diseases which carry off thousands of men; and a slightly
greater alteration might endanger all life. The at once mysterious
and terrifying spectacle of the cholera at Berlin in 1831 had such
an effect on the philosopher that he fled in terror to Frankfort. It
has been said that this was the origin of his pessimism, and that
but for this he would have continued to teach idealistic philosophy
in some Prussian university. L. Hartmann, another celebrated leader
of contemporary pessimism, has also said that disease will always be
beyond the resources of medicine. Facts have given the lie to these
sombre prognostics. The microbic origin of most infectious diseases has
been recognized. The discovery of attenuated poisons and serums has
diminished their gravity. An exact knowledge of methods of contagion
has enabled us to erect against them impregnable barriers. Cholera,
yellow fever, the plague knock in vain at our doors. Diphtheria,
dreaded by every mother, has partially lost its deadly character.
Puerperal fever and blindness of the new-born child are tending to
disappear. Legend tells us that Buddha in his youth, frightened at
the sight of a sick man, expressed in his father’s presence the wish
to be always in perfect health and sheltered from disease. The King
answered: “My son! you are asking the impossible.” But it is towards
the realization of this impossibility that we are on our way. Science
is repelling the attacks of disease.
§ 2. OLD AGE.
Old age is another sorrow of humanity. The stage of existence in
which the strength grows less and never grows greater, and in which
a thousand infirmities appear, is not, however, a stage universal in
animals. Most of them die without our perceiving in them any apparent
signs of senile weakness. On the other hand, some vegetables exhibit
these signs. Some trees are old; but it is in birds and mammals that
this decay, with the train of evils which accompanies it, becomes a
very marked phase of existence. In man to debility is added a bodily
shrinkage, grey hairs, withered skin, and the wearing out and loss of
teeth. The exhausted and atrophied organism offers a favourable field
to all intercurrent diseases and to every cause of destruction. It is
this discrepitude which makes old age so hateful. All desire to be old,
said Cicero; and when they are old, they say that old age has come
quicker than they expected. La Bruyère expresses it in an apothegm,
“We want to grow old, and we fear old age.” One would like longevity
without old age.
But can life be prolonged without senility diminishing its value?
Metchnikoff thinks it can. He more or less clearly catches a glimpse
of a normal evolution of existence which would make it longer and
nevertheless exempt from senile decay.
It is remarkable that we have so few scientific data on the old age of
man, and we have still fewer on that of animals. The biologist knows
no more than the layman. The old age of the dog is betrayed by its
gait. Its coat loses its lustre, just as in disease. The hair whitens
around the forehead and the muzzle. The teeth grow blunt and drop out.
The character loses its gaiety and becomes gloomy; the animal becomes
indifferent. He ceases to bark, and often becomes blind and deaf.
It is admitted that senile degeneration is due to an alteration
affecting most of the tissues. The cells, the special anatomical
elements of the liver, the kidney, and the brain are reduced by atrophy
and degeneration. At the same time, the conjunctive woof which serves
them as a support develops, on the contrary, at the expense in a
measure of the higher elements. For this reason the tissues harden.
We know that the flesh of old animals is tough. We know in pathology
that this is happening to the tissues. It is due to growth, to injury
to the active and important elements, to the elements of support of
the organs. They form a tissue sometimes called packed tissue, to
show its secondary rôle with reference to the elements which are
deposited in it. This kind of degeneration of the organs is known as
sclerosis. It constitutes the characteristic lesion of a certain number
of chronic diseases; and these diseases are serious, for the stifling
of the characteristic elements by the less important elements of the
conjunctive or packed tissue results in the more or less complete
reduction or suppression of the function.
The blood vessels also undergo this transformation, and what we
may call universal trouble and danger ensue. This sclerosis of the
arteries, this arterio-sclerosis, not only deprives the walls of the
blood vessels of the suppleness and elasticity which are necessary for
the proper irrigation of the organs, but it makes them more fragile.
Thus it becomes a cause of hemorrhage, which is a very serious matter
as far as the brain and lungs are concerned.
It is remarkable that the alteration of the tissues during old age
should be exactly similar to this. This is inferred from the few
researches that have been made on the subject—from those of Demange in
1886, of Merkel in 1891, and finally from the researches of Metchnikoff
himself. It is a generalized sclerosis. As its consequence we have
the lowering of the proper activity of the organs and the danger of
cerebral hemorrhage created by arterio-sclerosis. The transformations
of the tissues in old men are therefore summed up in the atrophy of the
important and specific elements of the tissues, and their replacement
by the hypertrophied conjunctive tissue. This sclerosis is comparable
to that of chronic diseases; it is a pathological condition. Thus old
age, as we understand it, is a chronic disease and not a normal phase
of the vital cycle.
On the other hand, if we ask ourselves what is the origin of the
scleroses which engender chronic diseases, we find that they are due
to the action of various poisons, among which syphilitic poison and
the immoderate use of alcohol take the first place. These are also the
usual causes of senile degeneration. But there must be some other,
some very general cause to explain the universality of the process of
senescence. Metchnikoff thinks that he has found this cause in the
microbes which swarm in man’s digestive tube, particularly in the
large intestine. Their number is enormous. Strassburger has given
an approximate calculation, but words fail to express it. We have
to imagine a figure followed by fifteen zeros. This microbic flora
is composed of “bacilli” and of “cocci,” and comprises a third of
the rejected matter. It produces slow poisons, which, being at once
reabsorbed, pass into the blood and provoke the constant irritation
from which results arterio-sclerosis and the universal sclerosis of old
age. Instead of enjoying a healthy and normal old age, in which the
faculties of ripening years are preserved, we drag out a diminished
life, a kind of chronic disease, which is ordinary old age. This is
due, according to Metchnikoff, to the parasitism and the symbiosis
of microbic flora, lodged in a part of the economy in which it finds
all the conditions favourable to its prolific expansion. Such is the
specious theory, held to the verge of intrepidity, by which this
investigator explains the misery of our old age, and which inspires him
with the idea of a remedy. For his observations conclude with a régime,
a series of prescriptions by which the author fancies that life may be
lengthened and the evils of old age swept from our path. The dangerous
flora must be transformed into a cultivated and selected flora.
Although the organ in question may be of doubtful utility, and although
its existence, the legacy of atavic heredity, must be considered as
a disharmony of human nature, Metchnikoff does not go so far as to
propose that it should be cut away, and that we should call in surgery
to assist in making mankind perfect! But the rational means he proposes
will be endorsed by the most judicious students of hygiene; and their
effect, if it is not as wonderful as one hopes for, cannot fail to
ameliorate the conditions of old age and make it more vigorous.
§ 3. DISHARMONIES IN HUMAN NATURE.
Another misery in the condition of man is due to the dissidencies
of his nature—that is to say, to his physical imperfections and the
discordancies which exist between the physiological functions and the
instincts which should regulate them.
This discordance reigns throughout the physical organism. The body of
man is not the perfect masterpiece it was once supposed to be. It is
encumbered with annoying inutilities, with rudimentary organs that have
neither rôle nor function, unfinished sketches which nature has left
in the different parts of his body. Such are the lachrymal caruncle, a
vestige of the third eyebrow in mammals; the extrinsic muscles of the
ear; the pineal gland of the brain, which is only the rudiment of an
ancestral organ; the third eye, or the Cyclopean eye of the saurians.
The list is interminable. Wiedersheim has counted in man 107 of these
abortive hereditary organs, the useless vestiges of organs useful
to our remote animal ancestors, atrophied in the course of ages in
consequence of modifications that have taken place in the external
medium.
These rudimentary organs are not only useless; they are often
positively harmful.
But the most serious discordance is that which exists between the
physiological functions and the instincts which regulate them. In a
well-regulated organism slowly developed by adaptation the instincts
and the organs alike should be in relation with the functions. All
really natural acts are solicited by an instinct, the satisfaction
of which is at once a need and a pleasure. The maternal instinct is
awakened at the proper moment in animals, and it disappears as soon as
the offspring requires no more assistance. A craving for milk is shown
in all newborn children, and often disappears at an early age.
Nature has endowed man as well as the other animals with peculiar
instincts, destined to preside over the different functions and to
ensure their accomplishment. And, at the same time, it has enabled him
in a measure to deceive those instincts and to satisfy them by other
means than the execution of the physiological acts with a view to which
they exist. Love and the instinct of reproduction exist in man before
the age of puberty. Canova felt the spur of love at the age of five.
Dante was in love with Beatrice at nine; and Byron, then scarcely
seven, was already in love with Maria Duff. On the other hand, puberty
has no necessary relation to the general maturity of the organism.
The family instinct is subject to the same aberrations. Man limits
the number of his children. The Turks of to-day follow the ancient
Greeks in the practice of abortion. Plato approved of the custom, and
Aristotle sanctioned its general prevalence. In the province of Canton
the Chinese of the agricultural classes kill two-thirds of their girl
children, and the same is done at Tahiti. All these customs co-exist
with the perfect love and tender care of the living children.
Because of these different discordancies the physical life of man is
insufficiently regulated by nature. Neither the physiological instinct,
nor the family instinct, nor the social instinct is, in general,
sufficiently imperative and precise. Hence, since the internal impulse
has not sufficient power, the necessity arises for a rule of conduct
exercising its influence from without. Philosophies, religions, and
legislation have provided for this. They have regulated man’s hygiene
and the carrying out of his different physiological functions. Their
control has, moreover, had its hygienic side. The scientific hygiene of
to-day has inherited their rôle.
The idea of the fundamental perversity of human nature is born of our
cognizance of its discordancies, unduly amplified and exaggerated. Soul
and body have been considered as distinctly discordant and hostile
elements. The body, the shroud of the soul, the temporary host, the
prison, the present source of miseries, has been subjected to every
kind of mortification. Asceticism has treated the body and all the
innate instincts as our mortal foes.
This suspicion, this depreciation of human nature was the great
error of the mystics. This view was as fatal as the inverse view
of pagan antiquity. The model of the perfect life according to
Greek philosophy is a life in conformity with nature. To aim at the
harmonious development of man was the precept of the ancient Academy,
formulated by Plato. The Stoics and the Epicureans had adopted the
same principle. Physical nature is considered as good. It gives us
the type, the rule, and the measure. The moral rule itself is exactly
appropriate to the physical nature. We may say that pagan morality was
hygiene, the hygiene of the soul and the body alike; the _mens sana in
corpore sano_ gave individual and social direction. The Rationalists,
the philosophers of the eighteenth century, such as Baron d’Holbach
and later W. Von Humboldt, Darwin, and Herbert Spencer, have adopted
analogous views. If these views have been contested, it is because of
the imperfections or aberrations of the natural instincts of man. Also,
if we wish to base individual family or social morality on the natural
instincts of man, it must be specified that these instincts are to be
regularized. We must necessarily appeal from the imperfect instincts of
the present to the perfected instincts of the future. Their perfection,
moreover, will only be a more exact approximation to the real nature of
man, and he, having avoided by the aid of science the accidents which
cause disease and senile decrepitude, will enjoy a healthy youth and an
ideal old age.
The reason of the discrepancies between instinct and function in man is
given by the natural history of his development. We know that man has
within him original sin—his long atavism. He has sprung, according to
the transformists, from a simian stock. He is a cousin, the successful
relation, of a type of antinomorphic monkeys, the chimpanzees. He
has “arrived,” they have remained undeveloped. Probably he had a
common ancestor with them, some dryopithecan of an extinct species.
From that type sprang a new type already on the way to progress, the
_Pithecanthropus erectus_. Finally, the anthropoid ancestor became
one fine day the father of a scion, clearly superior to himself, a
miraculously gifted being, man. Here, then, is no sign of the slow
evolution and gradual progress, which is the doctrine held at present
by Transformists. The Dutch botanist De Vries has shown us, in fact,
that nature does leap: _natura facit saltus_. There would thus be
crises, as it were, in the life of species. At certain critical epochs
considerable differences of a specific value appear in their offspring.
It is at one of these critical periods in the simian life that man
has appeared as the phenomenal child of an anthropoid. He was born
with a brain and an intellect superior to those of his humble parents;
and on the other hand, he has inherited from them an organization
which is only inadequately adapted to the new conditions of existence
created by the development of his sensitiveness and his brain power.
This intellect is not proportioned to his organization, which has not
developed at the same rate; it protests against the discordances which
adaptation has not yet had time to efface. But it will efface them in
the future.
§ 4. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH.
The greatest discrepancy of this kind is the knowledge of inevitable
death without the instinct which makes it longed for.
There are immortal animals. Man is not of the number. He belongs,
like all highly organized beings, to the class of beings which have
an end. They die from accident or from disease. They perish in the
struggle with other animals, or with microbes, or with external
conditions. There are certainly very few, if there are any, which die a
really natural death. And so it is with man. We see old men gradually
declining who appear to doze gently off into the last sleep, and become
extinguished without disease, like a lamp whose oil is exhausted. But
this is in most cases only apparently so. Besides the fact that the old
age to which they seemed to succumb is really a disease, a generalized
sclerosis, autopsy always reveals some lesion more or less directly
responsible for the fatal issue.
Man, like all the higher animals, is therefore subject to the law
of lethality. But while animals have no idea of death and are not
tormented by the sentiment of their inevitable end, man knows and
understands this destiny. He has with the animals the instinct of
self-preservation, the instinct of life, and at the same time the
knowledge and the fear of death. This contradiction, this discordance,
is one of the sources of his woes.
Whether it be an accident or the regular term of the normal cycle,
death always comes too soon. It surprises the man at a time when he
has not yet completed his physiological evolution; hence the aversion
and the terror it inspires. “We cannot fix our eyes on the sun or on
death,” said La Rochefoucauld. The old man does not regard death with
less aversion than the young man. “He who is most like the dead dies
with most regret.” Man knows that he is not getting his full measure.
Further, all the really natural acts are solicited by an instinct, the
satisfaction of which is a need and a joy. The need of death should
therefore appear at the end of life, just as the need of sleep appears
at the end of the day. It would appear, no doubt, if the normal cycle
of existence were fulfilled, and if the harmonious evolution were not
always interrupted by accident. Death would then be welcomed and longed
for. It would lose its horror. The instinct of death would replace at
the wished for moment the instinct of life. Man would pass from the
banquet of life with no other desire. He would die without regret,
“being old and full of days,” according to the expression used in the
Bible in the case of Abraham, Isaac, and Jacob. No doubt there are some
analogies to this in the insects which only assume the perfect form
for the purpose of procreation and immediately perish in their full
perfection. In these animals the approach of death is blended with the
intoxication of hymen. Thus we see some of them, the ephemerae, lose at
that moment the instinct of life and the instinct of self-preservation.
They allow themselves to be approached, taken, and seized, and make no
effort at flight.
But what is this full measure of life which is imparted to us?
Metchnikoff holds that the ages attributed to several persons in the
Bible are very probable. Abraham lived 175 years, Ishmael 137, Joseph
110, Moses 120. Buffon believed in the existence of a ratio between the
longevity of animals and the duration of their growth. He fixed it at
7:1. The animal whose development lasts two years would thus have 14
years of life. This law would give us 140 years, but the figure is too
high, and Flourens has reduced the ratio to that of 5:1, which would
still give us 100 years. Plato died in the act of conversation at 81;
Isocrates wrote his _Panathenaïcus_ at 94; Gorgias died in the full
possession of his intellect at 107.
To reach the end of the promised longevity we must neither count on the
elixir of life nor on the potable gold of the alchemists, nor on the
stone of immortality which did not prevent its inventor, Paracelsus,
from dying at the age of 58, nor on transfusion, nor on Graham’s
celestial bed, nor on King David’s gerocomy, nor on any nostrum or
remedy. _Contra vim mortis non est medicamen in hortis_, said the
Salernian school. What Feuchtersleben said is most true, “The art of
prolonging life consists in not cutting it short,” and it is a hygiene,
but a brilliant hygiene, such as that of which Metchnikoff traces us
the future lines, which will realize the desires of nature.
And now shall we find that physiology has solved the enigma proposed by
the Sphinx, and that it has answered these poignant questions:—Whence
do we come? whither do we go? what is the end of life? The end of life
is, to the physiologist as well as to Herbert Spencer, the tendency
towards an existence as full and as long as possible, towards a life
in conformity with real nature freed from the discordancies which
still remain; it is the accomplishment of the harmonious cycle of our
normal evolution. This ideal human nature, without discordancies, no
longer vitiated as it is at present but improved, will be the work of
time and science. Realized at last it will serve as a solid basis for
individual, family, and social morality. Healthy youth fit for action;
prolonged, adult age, the symbol of strength; normal old age, wise in
council, these would have their natural places in harmonious society.
“Great actions,” said one of old, “are not achieved by exertions
of strength, or speed, or agility, but rather by the prudence, the
authority, and the judgment which are found in a higher degree in old
age.” The old age of which Cicero here speaks is the ideal old age,
regular and normal, and not the premature, deformed, incapable and
egoistic old age which results from a pathological condition. At the
end of this full life, the old man being full of days, will crave for
the eternal sleep and will resign himself to it with joy....
Death, then, “the last enemy that shall be destroyed,” to use the
expression of St. Paul, will yield to the power of science. Instead of
being “the king of terrors,” it will become after a long and healthy
life, after a life exempt from morbid accidents, a natural and longed
for event, a satisfied need. Then will be realized the wish of the
fabulist:—
“_I should like to leave life at this age, just as one leaves a
banquet, thanking the host, and departing._”
Has this physiological solution of the problem of death the virtue
attributed to it by Metchnikoff? Is it as optimistic as he thinks
it is? The instinct of death supervening at the end of a normal and
well-filled cycle will no doubt facilitate to the aged their departure
on the great voyage. The wrench will no longer exist for the dead.
Will it not exist for those who are left behind? And since the instinct
of death can only exist about the time at which death is expected,
will the young man and the man of ripened years look with less horror
than to-day at the law which cannot be escaped, when they are in full
possession of the instinct of life, but warned of the inevitability of
death?
INDEX OF AUTHORS.
Altmann, 258
Anaxagoras, 34
Aquinas, St. Thomas, 3, 19, 248
Aristotle, 3, 15, 18, 143, 146, 307
Armstrong, 295
Atwater, 137
Bacon, vi., 35, 346
Baker, 233
Balbiani, 161, 165, 191, 206-7, 257
Bang, d’Yvor, 179
Barthez, 3, 19, 24
Beclard, 121
Becquerel, 278
Beijerinck, 193
Benoit, 271
Bernard, Claude, vi., 17, 27, 29, 32, 48, 50-4, 107, 109, 112, 119,
148, 150-1, 171, 190-2, 194, 197, 204, 210, 214-218, 220 _et seq._,
310, 318
Bernoulli, John, 35, 73
Bert, Paul, 194
Berthelot, 91, 98, 128-130, 152, 204, 296
Berthollet, 82
Berzelius, 117
Bichat, 3, 6, 20, 22, 27-30, 35, 55, 158, 170, 198, 308
Blumenbach, 46
Boë, Sylvius Le, 35-6
Boerhaave, 35, 147, 245
Bohr, 29-30
Bokorny, 324
Boltzmann, 265
Bonnet, 23, 49
Bordeu, 3, 10, 19, 22, 24, 312
Borelli, 35
Boscovitch, 37, 248
Bose, 264
Bossuet, 11
Bouasse, 73, 264-5
Boullier, 12
Bourdeau, 237, 242
Boussingault, 149
Brandt, 257
Bravais, 282
Brillouin, 264, 273
Brown, 266 _et seq._
Brücke, 44
Büchner, 325
Buffon, 46, 254, 357
Bunge, von, 3, 14
Burdon, Sanderson, 176
Busquet, 175
Bütschli, 161-2, 175
Cabanis, 245, 246
Cailletet, 272
Calkins, 327, 338
Calvert, 271
Candolle, 20
Cardan, 261
Carnot, 72-3, 89, 92 _et seq._, 101, 114, 121
Charpy, 237, 271
Chauffard, 3, 10, 11, 294
Chauveau, 75, 103, 108, 123, 130, 145, 213
Chevreul, 32
Chossat, 152
Cicero, 347, 359
Clausius, 67, 88
Cohn, 191, 252
Cohnheim, 341
Colding, 58 _note_, 90
Colin, 52
Comte, 189-190, 310
Confucius, 309
Coulomb, 76, 264, 273
Crookes, 295, 302
Cuvier, 3, 6, 27-8, 105, 120, 152, 190, 198, 308, 310, 319
D’Alembert, 20, 59 _note_, 90, 92
Dantec, Le, 48, 52, 55 _note_, 110, 148, 173, 198, 201, 203, 213, 216,
220, 223 _et seq._, 231, 246, 261, 285, 296, 340
D’Arsonval, 126
Darwin, 3, 46, 167, 258, 354
Dastre, A., 192, 198 _note_
Davy, Sir Humphry, 61, 80
Delafosse, 282
Delage, 208
Demange, 349
Democritus, 34, 146
Descartes, 3, 9, 35, 37, 40, 73, 91, 98
Despretz, 126
Diderot, 245, 246
Drechsel, 183
Dressel, 20
Dubois-Reymond, 44, 58 _note_, 253
Duclaux, 119, 137, 184, 324
Dufour, 297
Duguet, 264
Duhem, 62, 264, 265
Dulong, 126
Dumas, 115, 149, 151-2
Epicurus, 35, 146
Ehrlich, 176
Errera, 52, 193-4, 237, 153, 295, 302 _et seq._
Euclid, v.
Faye, 260
Feuchterslehen, 358
Flemming, 161
Flourens, 20-1, 152, 208, 306, 358
Fouillée, 242
Fromann, 161
Fuerth, 183
Galen, 25, 55, 143
Galeotti, 180
Galileo, 73, 91, 98, 197, 241, 260
Gardair, 19, 248
Gautier, A., 3, 32, 36, 39, 176, 233, 324
Gernez, 237, 288, 295 _et seq._
Glisson, 27
Goethe, 170, 312
Gouy, 266, 268
Grimaud, 19
Gruber, 165, 206, 257
Guignard, 161
Guillaume, 237, 262, 264, 271, 277
Guillemin, 237
Guldberg, 83
Harbermann, 183
Haeckel, 3, 46, 164, 167, 246, 251
Hales, 43
Haller, 27
Hamilton, Sir W. Rowan, 67
Hammarsten, 180
Hartmann, 276, 346
Harvey, 43, 160
Haüy, 282
Hegel, 170, 331
Heidenhain, 3, 29, 30-1
Heitzmann, 161
Helmholtz, 44, 56, 58, 67, 90, 97, 99, 252
Helmont, van, 3, 21, 26, 33, 146, 250
Henninger, 302
Heraclitus, 34
Hertwig, 167
Hertz, 88
Hess, 91, 98
Hippocrates, 146
Hirn, 126
His, 46
Hlasitwetz, 183
Holbach, d’, 354
Hoogewerf, 303
Hopkinson, 271
Humboldt, W. von, 354
Ingenhousz, 115
Izolet, 247
Joule, 53 _note_, 90-1, 93, 133 _et seq._, 143, 152
Kant, 312, 319
Kaup, 213
Kaufmann, 126
Kelvin, Lord, 63, 67, 90, 92, 251-2, 264;
and the idea of energy, 66
Kepler, 29, 241
Klemm, 323
Koelliker, 160
Kossel, 174, 179, 130-1, 136 _et seq._
Kuhne, 45
Kuhm, 216
Kuliabko, 23, 311
Kunstler, 157, 161-2, 175
Kuppfer, 161
Lammettrie, 147
Lamarck, 46
Lapparent, 284
Lapicque, 140, 145
Langley, 216
Laplace, 43, 63, 126, 260
Laulanié, 103
Laurie, 271
La Rochefoucauld, 356
Lavoisier, 3, 28, 30, 36, 43, 65, 117, 121, 126, 128, 143, 176, 296
Lea, 216
Le Châtelier, 85, 92
Lechatelier, H. and A., 271
Lecocq de Boisbaudran, 295
Leeuwenhoek, 232
Lefèvre, 126
Legallois, 21
Leydig, 161-2
Liebermeister, 136
Liebig, 26, 53 _note_, 117
Lilienfeld, 179, 247
Locke, 23
Lodge, 271
Loeb, 43, 167, 327, 341
Loew, 324
Loisel, 339, 341
Lorry, 21
Longet, 52
Lowitz, 297
Loye, 192
Ludwig, 44, 215
Mach, 41, 62
Magendie, 43, 143
Magy, 37
Malgaigne, 153
Mallard, 284
Marinesco, 231, 328
Markel, 349
Maspero, 3, 234
Matthiesson, 271
Maupas, 337
Maxwell, 88
Mayer, R., 56, 58, 89, 90, 97, 99, 101
Mering, von, 133, 136
Metchnikoff, 327 _et seq._
Miescher, 174, 179
Milne-Edwards, 152, 195
Minot, 341
Miura, 137
Mori, 145
Müller, 20, 27, 341
Murato, 45
Naegeli, 168
Needham, 46
Newton, 58 _note_, 70, 90-1, 93
Noorden, van, 129, 137, 140, 210
Nussbaum, 165, 206, 215, 217
Obermeyer, 271
Osmond, 237, 271
Ostwald, 41, 62, 67, 85, 104, 237, 258, 289, 295 _et seq._
Paracelsus, 26, 146, 312
Pascal, 74, 161
Pasteur, 53, 191, 222 _et seq._, 237, 250, 288, 346
Payen, 151
Persoz, 152
Petit, 180
Pettenkofer, 210
Pfeffer, 175, 193
Pflüger, 12, 56, 135, 144, 176, 210, 213
Philpotts, 46
Pictet, 233
Pitcairn, 35
Plato, 35, 307
Plosz, 180
Poincaré, 62
Poisson, 63
Preyer, 192, 252 _et seq._
Priestley, 115
Ptolemy, v.
Pythagoras, 18
Rauber, 237, 288
Raulin, 191
Regnault, 117
Reinke, 3, 32
Renan, 240
Ribbert, 208
Ribot, 247
Riche, 271
Richet, 50, 126, 140
Richter, 252
Rindfleisch, 4
Roberts-Austen, 237, 271-2
Robin, 62, 177
Rosenthal, 126
Rouvier, 160
Roux, 46, 165
Rubner, 129, 130, 140 _et seq._, 210
Rumford, 80
Sabatier, 242
Sachs, 161, 194
Salles-Guyon, 252
Sanderson, Burdon, 176
Scaliger, 241
Schleiden, 159
Schopenhauer, 346
Schwartz, 162
Schultze, 160, 326
Schultzenberger, 174, 162 _et seq._
Secchi, 88
Seguin, 58 _note_, 90
Senebier, 115
Siven, 145
Spallanzani, 43, 233
Spencer, Herbert, 46, 247, 354, 358
Spring, 272
Stahl, 3, 9, 12, 35, 146
Stammreich, 137
Stead, 237
Stohmann, 129, 130, 140
Strassburger, 161, 350
Swann, 159
Swift, 262
Tait, 53 _note_, 66
Tammann, 237, 253, 295 _et seq._
Thales, 34
Thomson, Sir J. J., 279
Tissot, 12
Tomlinson, 264
Trembley, 22, 206
Tsuboï, 145
Tylor, 8
Verworn, 206, 252, 257
Violette, 295
Virchow, 318, 326
Voit, 119, 133 _et seq._, 210
Vries, de, 46, 258, 355
Vulpian, 24
Waage, 83
Waller, 47, 206
Wallerant, 282-3
Warburg, 264
Watt, 76
Weismann, 46, 167, 336, 343
Wertheim, 264
Whitman, 46
Widersheim, 351
Wiedermann, 264
Wiesner, 167
Willis, 36, 147
Winternitz, 126
Yung, 233
Zuntz, 133, 136, 210
INDEX OF SUBJECTS.
Activity, functional and vital, 106 _et seq._, 217 _et seq._
Aerobia, 193
Age, old, Book v.
Albumin, 178
Albuminoids, 178
Alcohol, 136
Alimentation, 116 _et seq._
Alloys, structure of, 273
Anærobia, 193
Animism, 6, 7, Chap. ii., _passim_
Annealing, 275
Apposition, 291
Archeus, the, 25, 26, 33
Arginin, 187
Assimilation, law of functional, 110, 213
Atomicities, satisfied, 185
Atrophy, 326
Attraction, energy of position, 64
Balance, sheet, nutritive, 118
Beliefs, primitive, 239
Bioblasts, 253
Biophors, 167
Blas, the, 25, 33
Blood, lavage of, 192
Brain, and death, 315
Butylic ferments, 193
Butyric ferments, 193
Calorie, 125 _note_
Calorimeter, ice, 126;
bomb, 128
Caprice, of Nature, 45
Cause, final, 45
Cells, 48, 147;
somatic and sexual, 343
Cellular theory, 158 _et seq._
Centrosome, 163
Chromosome, 165
Cicatrization, 287
Complex, homogeneity of the, 245
Conductibility, 26
Consciousness, in brute bodies, 244 _et seq._
Continuity, principle of, 242, 247
Contractility, 26
Contraction, energy of static and dynamic, 75
Conservation, of energy, 58;
of force, 58
Crystals, 200 _et seq._, 237 _et seq._, 281 _et seq._
Cytoplasm, 161 _et seq._
Death, apparent, 232;
senescence of, 305 _et seq._;
cellular, 321 _et seq._
Decentralization, 24
Degeneration, 326
Destruction, functional, 106;
organic, 211;
of living matter, 213
Determinism, 49
Digestion, of plants and animals, 152 _et seq._
Direction, idea of, 16
Dominants, 33, 39, 45
Dyne, the, 71
Effort, of force, 71
Electrolysis, 272
Energetics, 39, 56;
laws of biological, 105 _et seq._, 229;
alimentary, 116 _et seq._
Energy, 37, Book ii., _passim_;
origin of idea of, 57;
theory of, 62;
the only objective reality, 64-5;
and kinetic conception, 67;
mechanical, 69, 73;
of contraction, 75;
kinetic, 76, 83;
potential, 76, 83;
virtual, 77;
of motion and position, 79;
thermal, and its measurements, 80-2;
chemical, and its measurements, 81-2;
chemical and potential, 83;
materialization of, 84;
transformations of, 85 _et seq._;
luminous, 86 _et seq._;
conservation of, 90 _et seq._;
capacity of conversion of, 93;
in biology, 97;
in living beings, 99 _et seq._;
physical, 99 _et seq._;
vital, 99 _et seq._
Ether, 89
Equivalence, law of, 91
Excitability, 26-7
Fatigue, of metals, 264
Ferments, butylic and butyric, 193
Filiation, 250
Finalism, 43
Food, a source of energy, 118 _et seq._;
thermogenic and biothermogenic types of, 131 _et seq._;
dynamogenic type of, 143;
nitrogenous, 143;
of animals and plants, 153 _et seq._
Force, directive, 16 _et seq._, 32, 39, 48;
vital, 45;
an anthromorphic notion, 71;
and work, 74;
measurement of, 71;
plastic, 143;
plastic and morphoplastic forces, 208
Form, specific, 199 _et seq._, 281
Fruits, acids of, 136
Gemmules, 167, 258
Generation, spontaneous, 249 _et seq._, 294 _et seq._
Globulin, 178
Glycerine, crystals of, 302
Glycogen, 108, 153 _et seq._
Gramme, 71
Heat, a mode of motion, 61;
rôle of animal heat, 122;
mechanical equivalent of, 81;
an excretum, 114;
a degraded form of energy, 88;
converted into work, 92
Heterogeneity, 38, 61
Histones, 179, 182 _et seq._
Horse-power, 75
Hyaloplasm, 161
Iatro-chemistry and mechanics, 34-5
Idioblasts, 167
Infusoria, death of, 337
Instability, 188 _et seq._
Instinct, of life and death, 345 _et seq._
Intussusception, 291
Invariant, mass the first, 63
Irreversibility, of vital energies, 104
Irritability, 27, 196 _et seq._
Isodynamism, 142
Isomorphism, 286
Ka, the, 8
Kilogrammetre, 72, 75;
per second, 75
Kilowatt, 76
Kinetic theory, 39, 62
Knot, the vital, 21
Leucines, 183
Leucites, 163
Life, defined, 28;
latent, 233;
physico-chemical theory of, 36;
elementary, 321
Linin, 163
Mass, and matter, 63
Materialism, 34
Matter, 37, 60, 62;
and mass, 63;
two kinds of, 63;
life of, 236 _et seq._;
brute and living, 249 _et seq._;
organization and constitution of, 255 _et seq._;
defined as extension, 64;
conservation of, 65
“Memory,” of metals, etc., 265
Merotomy, 47
Metabolism, 117
Metazoa, evolution and death of, 340 _et seq._
Meteoric cosmozoa, 252
Micellar theory, 166 _et seq._
Microcosms, 163
Micro-organisms, culture of, 297
Mitomes, 169
Mobility of stars, 260
Modality, twofold, of soul, 12
Molecules, organic, 254
Monism, 34, Chap. iv. _passim_, 63
Montpellier, the school of, 35
Motion, cause of, 71;
kinetic conception of molecular, 263
Morphogenesis, idea of, 46
Movements, internal of bodies, 262;
Brownian, 266 _et seq._
Mutability, 80, 188 _et seq._;
of living matter, 259 _et seq._;
of brute bodies, 259 _et seq._
Necrobiosis, 326
Neo-vitalism, 15, 29, 32
Neurility, 27
Nickel, steels, 277
Nisus _formativus_, 46
Nous, the, 18, 239
Nucleins, 179, 180 _et seq._
Nucleo-albuminoids, 178;
-proteids, 177 _et seq._
Nucleus, 163 _et seq._;
hexonic, 186
Nutrition, directed, 205, 209 _et seq._, 227 _et seq._, 290 _et seq._
Organogenesis, 282
Organs, organization of, 314;
death of, 315;
perfect, 319
Pangenes, 167
Panspermia, 252
Parameter, mass the mechanical, 63
Phenomena, vital, 44, 51, 189;
modes of motion, 61
Photography, colour, 277
Physiology, general, 56;
cellular, 56
Plants, and immortality, 330
Plasomes, 167
Plurivitalism, 25
Power, 70, 75
Principle, vital, 15 _et seq._
Properties, vital, 25, 103
Proteids, 178
Protoplasm, 109 _et seq._, 175 _et seq._, 231 _et seq._;
life in crushed, 257 _et seq._
Protozoa, immortality of, 352 _et seq._
Psyche, 239
Pyrozoa, 253
Regeneration, normal, 205;
accidental, 206
Reparation, mechanism of, 288
Repose, functional, 109, 217 _et seq._
Reserve stuff, 106 _et seq._, 212, 230 _et seq._
Rachidian, soul, 12
Senescence, 305 _et seq._
Sensibility, in brute bodies, 244
Solidarity, of anatomical elements, humoral and nervous, 317
Soul, the, 7 _et seq._
Space, 69
Specificity, vital, 48
Spireme, 165
Spongioplasm, 162
States, initial and final, 128
Swelling, 167
Synthesis, organizing, 109
Tagmata, 169, 175
Teleology, 43
Tetanus, bacteria of, 193
Thermogenesis, 140
Time, 69
Tonus, muscular, 119
Trees, and immortality, 330 _et seq._
Tripod, vital, 2, 314
Turgescence, 168
Universe, the, mechanical explanation of, 60;
the end of the, 95
Unity, chemical, of living beings, 173 _et seq._, 321;
morphological, 321
Vacuoles, 113
Vibrion, septic, 193
Vis viva, 73
Vital properties, theory of, 29 _et seq._
Vitalism, 6, 7, Chap. iii. _passim_;
physico-chemical, 29
Vitality, phenomena of, 216
Vortex, vital, 105, 120, 229 _et seq._
Vulcans, 26-7
Weight, energy of position, 64;
conservation of, 65;
movement under action of, 271 _et seq._
Work, 70, 72;
and force, 74, 77;
converted into heat, 92;
physiological, 103
Xanthic bases, 180
Zones, metastable and labile, 301
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