Aristotle
384-322 B.C.E. - Wrote in Greek
On Youth and Old Age,
On Life and Death,
On Breathing
Written 350 B.C.E
Translated by G. R. T. Ross
On Youth and Old Age,
On Life and Death,
On Breathing
By Aristotle
Section 1
Part 1
We must now treat of youth and old age and life and death. We must probably
also at the same time state the causes of respiration as well, since in
some cases living and the reverse depend on this.
We have elsewhere given a precise account of the soul, and while
it is clear that its essential reality cannot be corporeal, yet manifestly
it must exist in some bodily part which must be one of those possessing
control over the members. Let us for the present set aside the other divisions
or faculties of the soul (whichever of the two be the correct name). But
as to being what is called an animal and a living thing, we find that in
all beings endowed with both characteristics (viz. being an animal and
being alive) there must be a single identical part in virtue of which they
live and are called animals; for an animal qua animal cannot avoid being
alive. But a thing need not, though alive, be animal, for plants live without
having sensation, and it is by sensation that we distinguish animal from
what is not animal.
This organ, then, must be numerically one and the same and yet
possess multiple and disparate aspects, for being animal and living are
not identical. Since then the organs of special sensation have one common
organ in which the senses when functioning must meet, and this must be
situated midway between what is called before and behind (we call 'before'
the direction from which sensation comes, 'behind' the opposite), further,
since in all living things the body is divided into upper and lower (they
all have upper and lower parts, so that this is true of plants as well),
clearly the nutritive principle must be situated midway between these regions.
That part where food enters we call upper, considering it by itself and
not relatively to the surrounding universe, while downward is that part
by which the primary excrement is discharged.
Plants are the reverse of animals in this respect. To man in particular
among the animals, on account of his erect stature, belongs the characteristic
of having his upper parts pointing upwards in the sense in which that applies
to the universe, while in the others these are in an intermediate position.
But in plants, owing to their being stationary and drawing their sustenance
from the ground, the upper part must always be down; for there is a correspondence
between the roots in a plant and what is called the mouth in animals, by
means of which they take in their food, whether the source of supply be
the earth or each other's bodies.
Part 2
All perfectly formed animals are to be divided into three parts,
one that by which food is taken in, one that by which excrement is discharged,
and the third the region intermediate between them. In the largest animals
this latter is called the chest and in the others something corresponding;
in some also it is more distinctly marked off than in others. All those
also that are capable of progression have additional members subservient
to this purpose, by means of which they bear the whole trunk, to wit legs
and feet and whatever parts are possessed of the same powers. Now it is
evident both by observation and by inference that the source of the nutritive
soul is in the midst of the three parts. For many animals, when either
part-the head or the receptacle of the food-is cut off, retain life in
that member to which the middle remains attached. This can be seen to occur
in many insects, e.g. wasps and bees, and many animals also besides insects
can, though divided, continue to live by means of the part connected with
nutrition.
While this member is indeed in actuality single, yet potentially
it is multiple, for these animals have a constitution similar to that of
Plants; plants when cut into sections continue to live, and a number of
trees can be derived from one single source. A separate account will be
given of the reason why some plants cannot live when divided, while others
can be propagated by the taking of slips. In this respect, however, plants
and insects are alike.
It is true that the nutritive soul, in beings possessing it, while
actually single must be potentially plural. And it is too with the principle
of sensation, for evidently the divided segments of these animals have
sensation. They are unable, however, to preserve their constitution, as
plants can, not possessing the organs on which the continuance of life
depends, for some lack the means for seizing, others for receiving their
food; or again they may be destitute of other organs as
well.
Divisible animals are like a number of animals grown together,
but animals of superior construction behave differently because their constitution
is a unity of the highest possible kind. Hence some of the organs on division
display slight sensitiveness because they retain some psychical susceptibility;
the animals continue to move after the vitals have been abstracted: tortoises,
for example, do so even after the heart has been removed.
Part 3
The same phenomenon is evident both in plants and in animals, and
in plants we note it both in their propagation by seed and in grafts and
cuttings. Genesis from seeds always starts from the middle. All seeds are
bivalvular, and the place of junction is situated at the point of attachment
(to the plant), an intermediate part belonging to both halves. It is from
this part that both root and stem of growing things emerge; the starting-point
is in a central position between them. In the case of grafts and cuttings
this is particularly true of the buds; for the bud is in a way the starting-point
of the branch, but at the same time it is in a central position. Hence
it is either this that is cut off, or into this that the new shoot is inserted,
when we wish either a new branch or a new root to spring from it; which
proves that the point of origin in growth is intermediate between stem
and root.
Likewise in sanguineous animals the heart is the first organ developed;
this is evident from what has been observed in those cases where observation
of their growth is possible. Hence in bloodless animals also what corresponds
to the heart must develop first. We have already asserted in our treatise
on The Parts of Animals that it is from the heart that the veins issue,
and that in sanguineous animals the blood is the final nutriment from which
the members are formed. Hence it is clear that there is one function in
nutrition which the mouth has the faculty of performing, and a different
one appertaining to the stomach. But it is the heart that has supreme control,
exercising an additional and completing function. Hence in sanguineous
animals the source both of the sensitive and of the nutritive soul must
be in the heart, for the functions relative to nutrition exercised by the
other parts are ancillary to the activity of the heart. It is the part
of the dominating organ to achieve the final result, as of the physician's
efforts to be directed towards health, and not to be occupied with subordinate
offices.
Certainly, however, all saguineous animals have the supreme organ
of the sensefaculties in the heart, for it is here that we must look for
the common sensorium belonging to all the sense-organs. These in two cases,
taste and touch, can be clearly seen to extend to the heart, and hence
the others also must lead to it, for in it the other organs may possibly
initiate changes, whereas with the upper region of the body taste and touch
have no connexion. Apart from these considerations, if the life is always
located in this part, evidently the principle of sensation must be situated
there too, for it is qua animal that an animal is said to be a living thing,
and it is called animal because endowed with sensation. Elsewhere in other
works we have stated the reasons why some of the sense-organs are, as is
evident, connected with the heart, while others are situated in the head.
(It is this fact that causes some people to think that it is in virtue
of the brain that the function of perception belongs to
animals.)
Part 4
Thus if, on the one hand, we look to the observed facts, what we
have said makes it clear that the source of the sensitive soul, together
with that connected with growth and nutrition, is situated in this organ
and in the central one of the three divisions of the body. But it follows
by deduction also; for we see that in every case, when several results
are open to her, Nature always brings to pass the best. Now if both principles
are located in the midst of the substance, the two parts of the body, viz.
that which elaborates and that which receives the nutriment in its final
form will best perform their appropriate function; for the soul will then
be close to each, and the central situation which it will, as such, occupy
is the position of a dominating power.
Further, that which employs an instrument and the instrument it
employs must be distinct (and must be spatially diverse too, if possible,
as in capacity), just as the flute and that which plays it-the hand-are
diverse. Thus if animal is defined by the possession of sensitive soul,
this soul must in the sanguineous animals be in the heart, and, in the
bloodless ones, in the corresponding part of their body. But in animals
all the members and the whole body possess some connate warmth of constitution,
and hence when alive they are observed to be warm, but when dead and deprived
of life they are the opposite. Indeed, the source of this warmth must be
in the heart in sanguineous animals, and in the case of bloodless animals
in the corresponding organ, for, though all parts of the body by means
of their natural heat elaborate and concoct the nutriment, the governing
organ takes the chief share in this process. Hence, though the other members
become cold, life remains; but when the warmth here is quenched, death
always ensues, because the source of heat in all the other members depends
on this, and the soul is, as it were, set aglow with fire in this part,
which in sanguineous animals is the heart and in the bloodless order the
analogous member. Hence, of necessity, life must be coincident with the
maintenance of heat, and what we call death is its destruction.
Part 5
However, it is to be noticed that there are two ways in which fire
ceases to exist; it may go out either by exhaustion or by extinction. That
which is self-caused we call exhaustion, that due to its opposites extinction.
[The former is that due to old age, the latter to violence.] But either
of these ways in which fire ceases to be may be brought about by the same
cause, for, when there is a deficiency of nutriment and the warmth can
obtain no maintenance, the fire fails; and the reason is that the opposite,
checking digestion, prevents the fire from being fed. But in other cases
the result is exhaustion,-when the heat accumulates excessively owing to
lack of respiration and of refrigeration. For in this case what happens
is that the heat, accumulating in great quantity, quickly uses up its nutriment
and consumes it all before more is sent up by evaporation. Hence not only
is a smaller fire readily put out by a large one, but of itself the candle
flame is consumed when inserted in a large blaze just as is the case with
any other combustible. The reason is that the nutriment in the flame is
seized by the larger one before fresh fuel can be added, for fire is ever
coming into being and rushing just like a river, but so speedily as to
elude observation.
Clearly therefore, if the bodily heat must be conserved (as is
necessary if life is to continue), there must be some way of cooling the
heat resident in the source of warmth. Take as an illustration what occurs
when coals are confined in a brazier. If they are kept covered up continuously
by the so-called 'choker', they are quickly extinguished, but, if the lid
is in rapid alternation lifted up and put on again they remain glowing
for a long time. Banking up a fire also keeps it in, for the ashes, being
porous, do not prevent the passage of air, and again they enable it to
resist extinction by the surrounding air by means of the supply of heat
which it possesses. However, we have stated in The Problems the reasons
why these operations, namely banking up and covering up a fire, have the
opposite effects (in the one case the fire goes out, in the other it continues
alive for a considerable time).
Part 6
Everything living has soul, and it, as we have said, cannot exist
without the presence of heat in the constitution. In plants the natural
heat is sufficiently well kept alive by the aid which their nutriment and
the surrounding air supply. For the food has a cooling effect [as it enters,
just as it has in man] when first it is taken in, whereas abstinence from
food produces heat and thirst. The air, if it be motionless, becomes hot,
but by the entry of food a motion is set up which lasts until digestion
is completed and so cools it. If the surrounding air is excessively cold
owing to the time of year, there being severe frost, plants shrivel, or
if, in the extreme heats of summer the moisture drawn from the ground cannot
produce its cooling effect, the heat comes to an end by exhaustion. Trees
suffering at such seasons are said to be blighted or star-stricken. Hence
the practice of laying beneath the roots stones of certain species or water
in pots, for the purpose of cooling the roots of the
plants.
Some animals pass their life in the water, others in the air, and
therefore these media furnish the source and means of refrigeration, water
in the one case, air in the other. We must proceed-and it will require
further application on our part-to give an account of the way and manner
in which this refrigeration occurs.
Part 7
A few of the previous physical philosophers have spoken of respiration.
The reason, however, why it exists in animals they have either not declared
or, when they have, their statements are not correct and show a comparative
lack of acquaintance with the facts. Moreover they assert that all animals
respire-which is untrue. Hence these points must first claim our attention,
in order that we may not be thought to make unsubstantiated charges against
authors no longer alive.
First then, it is evident that all animals with lungs breathe,
but in some cases breathing animals have a bloodless and spongy lung, and
then there is less need for respiration. These animals can remain under
water for a time, which relatively to their bodily strength, is considerable.
All oviparous animals, e.g. the frog-tribe, have a spongy lung. Also hemydes
and tortoises can remain for a long time immersed in water; for their lung,
containing little blood, has not much heat. Hence, when once it is inflated,
it itself, by means of its motion, produces a cooling effect and enables
the animal to remain immersed for a long time. Suffocation, however, always
ensues if the animal is forced to hold its breath for too long a time,
for none of this class take in water in the way fishes do. On the other
hand, animals which have the lung charged with blood have greater need
of respiration on account of the amount of their heat, while none at all
of the others which do not possess lungs breathe.
Part 8
Democritus of Abdera and certain others who have treated of respiration,
while saying nothing definite about the lungless animals, nevertheless
seem to speak as if all breathed. But Anaxagoras and Diogenes both maintain
that all breathe, and state the manner in which fishes and oysters respire.
Anaxagoras says that when fishes discharge water through their gills, air
is formed in the mouth, for there can be no vacuum, and that it is by drawing
in this that they respire. Diogenes' statement is that, when they discharge
water through their gills, they suck the air out of the water surrounding
the mouth by means of the vacuum formed in the mouth, for he believes there
is air in the water.
But these theories are untenable. Firstly, they state only what
is the common element in both operations and so leave out the half of the
matter. For what goes by the name of respiration consists, on the one hand,
of inhalation, and, on the other, of the exhalation of breath; but, about
the latter they say nothing, nor do they describe how such animals emit
their breath. Indeed, explanation is for them impossible for, when the
creatures respire, they must discharge their breath by the same passage
as that by which they draw it in, and this must happen in alternation.
Hence, as a result, they must take the water into their mouth at the same
time as they breathe out. But the air and the water must meet and obstruct
each other. Further, when they discharge the water they must emit their
breath by the mouth or the gills, and the result will be that they will
breathe in and breathe out at the same time, for it is at that moment that
respiration is said to occur. But it is impossible that they should do
both at the same time. Hence, if respiring creatures must both exhale and
inhale the air, and if none of these animals can breathe out, evidently
none can respire at all.
Part 9
Further, the assertion that they draw in air out of the mouth or
out of the water by means of the mouth is an impossibility, for, not having
a lung, they have no windpipe; rather the stomach is closely juxtaposed
to the mouth, so that they must do the sucking with the stomach. But in
that case the other animals would do so also, which is not the truth; and
the water-animals also would be seen to do it when out of the water, whereas
quite evidently they do not. Further, in all animals that respire and draw
breath there is to be observed a certain motion in the part of the body
which draws in the air, but in the fishes this does not occur. Fishes do
not appear to move any of the parts in the region of the stomach, except
the gills alone, and these move both when they are in the water and when
they are thrown on to dry land and gasp. Moreover, always when respiring
animals are killed by being suffocated in water, bubbles are formed of
the air which is forcibly discharged, as happens, e.g. when one forces
a tortoise or a frog or any other animal of a similar class to stay beneath
water. But with fishes this result never occurs, in whatsoever way we try
to obtain it, since they do not contain air drawn from an external source.
Again, the manner of respiration said to exist in them might occur in the
case of men also when they are under water. For if fishes draw in air out
of the surrounding water by means of their mouth why should not men too
and other animals do so also; they should also, in the same way as fishes,
draw in air out of the mouth. If in the former case it were possible, so
also should it be in the latter. But, since in the one it is not so, neither
does it occur in the other. Furthermore, why do fishes, if they respire,
die in the air and gasp (as can be seen) as in suffocation? It is not want
of food that produces this effect upon them, and the reason given by Diogenes
is foolish, for he says that in air they take in too much air and hence
die, but in the water they take in a moderate amount. But that should be
a possible occurrence with land animals also; as facts are, however, no
land animal seems to be suffocated by excessive respiration. Again, if
all animals breathe, insects must do so also. many of them seem to live
though divided not merely into two, but into several parts, e.g. the class
called Scolopendra. But how can they, when thus divided, breathe, and what
is the organ they employ? The main reason why these writers have not given
a good account of these facts is that they have no acquaintance with the
internal organs, and that they did not accept the doctrine that there is
a final cause for whatever Nature does. If they had asked for what purpose
respiration exists in animals, and had considered this with reference to
the organs, e.g. the gills and the lungs, they would have discovered the
reason more speedily.
Part 10
Democritus, however, does teach that in the breathing animals there
is a certain result produced by respiration; he asserts that it prevents
the soul from being extruded from the body. Nevertheless, he by no means
asserts that it is for this purpose that Nature so contrives it, for he,
like the other physical philosophers, altogether fails to attain to any
such explanation. His statement is that the soul and the hot element are
identical, being the primary forms among the spherical particles. Hence,
when these are being crushed together by the surrounding atmosphere thrusting
them out, respiration, according to his account, comes in to succour them.
For in the air there are many of those particles which he calls mind and
soul. Hence, when we breathe and the air enters, these enter along with
it, and by their action cancel the pressure, thus preventing the expulsion
of the soul which resides in the animal.
This explains why life and death are bound up with the taking in
and letting out of the breath; for death occurs when the compression by
the surrounding air gains the upper hand, and, the animal being unable
to respire, the air from outside can no longer enter and counteract the
compression. Death is the departure of those forms owing to the expulsive
pressure exerted by the surrounding air. Death, however, occurs not by
haphazard but, when natural, owing to old age, and, when unnatural, to
violence.
But the reason for this and why all must die Democritus has by
no means made clear. And yet, since evidently death occurs at one time
of life and not at another, he should have said whether the cause is external
or internal. Neither does he assign the cause of the beginning of respiration,
nor say whether it is internal or external. Indeed, it is not the case
that the external mind superintends the reinforcement; rather the origin
of breathing and of the respiratory motion must be within: it is not due
to pressure from around. It is absurd also that what surrounds should compress
and at the same time by entering dilate. This then is practically his theory,
and how he puts it.
But if we must consider that our previous account is true, and
that respiration does not occur in every animal, we must deem that this
explains death not universally, but only in respiring animals. Yet neither
is it a good account of these even, as may clearly be seen from the facts
and phenomena of which we all have experience. For in hot weather we grow
warmer, and, having more need of respiration, we always breathe faster.
But, when the air around is cold and contracts and solidifies the body,
retardation of the breathing results. Yet this was just the time when the
external air should enter and annul the expulsive movement, whereas it
is the opposite that occurs. For when the breath is not let out and the
heat accumulates too much then we need to respire, and to respire we must
draw in the breath. When hot, people breathe rapidly, because they must
do so in order to cool themselves, just when the theory of Democritus would
make them add fire to fire.
Part 11
The theory found in the Timaeus, of the passing round of the breath
by pushing, by no means determines how, in the case of the animals other
than land-animals, their heat is preserved, and whether it is due to the
same or a different cause. For if respiration occurs only in land-animals
we should be told what is the reason of that. Likewise, if it is found
in others also, but in a different form, this form of respiration, if they
all can breathe, must also be described.
Further, the method of explaining involves a fiction. It is said
that when the hot air issues from the mouth it pushes the surrounding air,
which being carried on enters the very place whence the internal warmth
issued, through the interstices of the porous flesh; and this reciprocal
replacement is due to the fact that a vacuum cannot exist. But when it
has become hot the air passes out again by the same route, and pushes back
inwards through the mouth the air that had been discharged in a warm condition.
It is said that it is this action which goes on continuously when the breath
is taken in and let out.
But according to this way of thinking it will follow that we breathe
out before we breathe in. But the opposite is the case, as evidence shows,
for though these two functions go on in alternation, yet the last act when
life comes to a close is the letting out of the breath, and hence its admission
must have been the beginning of the process.
Once more, those who give this kind of explanation by no means
state the final cause of the presence in animals of this function (to wit
the admission and emission of the breath), but treat it as though it were
a contingent accompaniment of life. Yet it evidently has control over life
and death, for it results synchronously that when respiring animals are
unable to breathe they perish. Again, it is absurd that the passage of
the hot air out through the mouth and back again should be quite perceptible,
while we were not able to detect the thoracic influx and the return outwards
once more of the heated breath. It is also nonsense that respiration should
consist in the entrance of heat, for the evidence is to the contrary effect;
what is breathed out is hot, and what is breathed in is cold. When it is
hot we pant in breathing, for, because what enters does not adequately
perform its cooling function, we have as a consequence to draw the breath
frequently.
Part 12
It is certain, however, that we must not entertain the notion that
it is for purposes of nutrition that respiration is designed, and believe
that the internal fire is fed by the breath; respiration, as it were, adding
fuel to the fire, while the feeding of the flame results in the outward
passage of the breath. To combat this doctrine I shall repeat what I said
in opposition to the previous theories. This, or something analogous to
it, should occur in the other animals also (on this theory), for all possess
vital heat. Further, how are we to describe this fictitious process of
the generation of heat from the breath? Observation shows rather that it
is a product of the food. A consequence also of this theory is that the
nutriment would enter and the refuse be discharged by the same channel,
but this does not appear to occur in the other instances.
Part 13
Empedocles also gives an account of respiration without, however,
making clear what its purpose is, or whether or not it is universal in
animals. Also when dealing with respiration by means of the nostrils he
imagines he is dealing with what is the primary kind of respiration. Even
the breath which passes through the nostrils passes through the windpipe
out of the chest as well, and without the latter the nostrils cannot act.
Again, when animals are bereft of respiration through the nostrils, no
detrimental result ensues, but, when prevented from breathing through the
windpipe, they die. Nature employs respiration through the nostrils as
a secondary function in certain animals in order to enable them to smell.
But the reason why it exists in some only is that though almost all animals
are endowed with the sense of smell, the sense-organ is not the same in
all.
A more precise account has been given about this elsewhere. Empedocles,
however, explains the passage inwards and outwards of the breath, by the
theory that there are certain blood-vessels, which, while containing blood,
are not filled by it, but have passages leading to the outer air, the calibre
of which is fine in contrast to the size of the solid particles, but large
relatively to those in the air. Hence, since it is the nature of the blood
to move upwards and downwards, when it moves down the air rushes in and
inspiration occurs; when the blood rises, the air is forced out and the
outward motion of the breath results. He compares this process to what
occurs in a clepsydra.
Thus all things outwards breathe and in;- their flesh has
tubes
Bloodless, that stretch towards the body's outmost
edge,
Which, at their mouths, full many frequent channels
pierce,
Cleaving the extreme nostrils through; thus, while the gore Lies
hid, for air is cut a thoroughfare most plain. And thence, whenever
shrinks away the tender blood,
Enters the blustering wind with swelling billow
wild.
But when the blood leaps up, backward it breathes. As
when
With water-clock of polished bronze a maiden sporting, Sets on her
comely hand the narrow of the tube
And dips it in the frail-formed water's silvery sheen; Not then
the flood the vessel enters, but the air, Until she frees the crowded
stream. But then indeed Upon the escape runs in the water meet.
So also when within the vessel's deeps the water
Remains, the opening by the hand of flesh being
closed,
The outer air that entrance craves restrains the flood At the gates
of the sounding narrow, upon the surface pressing,
Until the maid withdraws her hand. But then in contrariwise
Once more the air comes in and water meet flows
out.
Thus to the to the subtle blood, surging throughout the limbs, Whene'er
it shrinks away into the far recesses Admits a stream of air rushing
with swelling wave,
But, when it backward leaps, in like bulk air flows
out.
This then is what he says of respiration. But, as we said, all
animals that evidently respire do so by means of the windpipe, when they
breathe either through the mouth or through the nostrils. Hence, if it
is of this kind of respiration that he is talking, we must ask how it tallies
with the explanation given. But the facts seem to be quite opposed. The
chest is raised in the manner of a forge-bellows when the breath is drawn
in-it is quite reasonable that it should be heat which raises up and that
the blood should occupy the hot region-but it collapses and sinks down,
like the bellows once more, when the breath is let out. The difference
is that in a bellows it is not by the same channel that the air is taken
in and let out, but in breathing it is.
But, if Empedocles is accounting only for respiration through the
nostrils, he is much in error, for that does not involve the nostrils alone,
but passes by the channel beside the uvula where the extremity of the roof
of the mouth is, some of the air going this way through the apertures of
the nostrils and some through the mouth, both when it enters and when it
passes out. Such then is the nature and magnitude of the difficulties besetting
the theories of other writers concerning respiration.
On Youth and Old Age,
On Life and Death,
On Breathing
By Aristotle
Section 2
Part 14
We have already stated that life and the presence of soul involve a certain
heat. Not even the digesting process to which is due the nutrition of animals
occurs apart from soul and warmth, for it is to fire that in all cases
elaboration is due. It is for this reason, precisely, that the primary
nutritive soul also must be located in that part of the body and in that
division of this region which is the immediate vehicle of this principle.
The region in question is intermediate between that where food enters and
that where excrement is discharged. In bloodless animals it has no name,
but in the sanguineous class this organ is called the heart. The blood
constitutes the nutriment from which the organs of the animal are directly
formed. Likewise the bloodvessels must have the same originating source,
since the one exists for the other's behoof-as a vessel or receptacle for
it. In sanguineous animals the heart is the starting-point of the veins;
they do not traverse it, but are found to stretch out from it, as dissections
enable us to see.
Now the other psychical faculties cannot exist apart from the power
of nutrition (the reason has already been stated in the treatise On the
Soul), and this depends on the natural fire, by the union with which Nature
has set it aglow. But fire, as we have already stated, is destroyed in
two ways, either by extinction or by exhaustion. It suffers extinction
from its opposites. Hence it can be extinguished by the surrounding cold
both when in mass and (though more speedily) when scattered. Now this way
of perishing is due to violence equally in living and in lifeless objects,
for the division of an animal by instruments and consequent congelation
by excess of cold cause death. But exhaustion is due to excess of heat;
if there is too much heat close at hand and the thing burning does not
have a fresh supply of fuel added to it, it goes out by exhaustion, not
by the action of cold. Hence, if it is going to continue it must be cooled,
for cold is a preventive against this form of extinction.
Part 15
Some animals occupy the water, others live on land, and, that being so,
in the case of those which are very small and bloodless the refrigeration
due to the surrounding water or air is sufficient to prevent destruction
from this cause. Having little heat, they require little cold to combat
it. Hence too such animals are almost all short-lived, for, being small,
they have less scope for deflection towards either extreme. But some insects
are longer-lived though bloodless, like all the others), and these have
a deep indentation beneath the waist, in order to secure cooling through
the membrane, which there is thinner. They are warmer animals and hence
require more refrigeration, and such are bees (some of which live as long
as seven years) and all that make a humming noise, like wasps, cockchafers,
and crickets. They make a sound as if of panting by means of air, for,
in the middle section itself, the air which exists internally and is involved
in their construction, causing a rising and falling movement, produces
friction against the membrane. The way in which they move this region is
like the motion due to the lungs in animals that breathe the outer air,
or to the gills in fishes. What occurs is comparable to the suffocation
of a respiring animal by holding its mouth, for then the lung causes a
heaving motion of this kind. In the case of these animals this internal
motion is not sufficient for refrigeration, but in insects it is. It is
by friction against the membrane that they produce the humming sound, as
we said, in the way that children do by blowing through the holes of a
reed covered by a fine membrane. It is thus that the singing crickets too
produce their song; they possess greater warmth and are indented at the
waist, but the songless variety have no fissure there.
Animals also which are sanguineous and possess a lung, though that
contains little blood and is spongy, can in some cases, owing to the latter
fact, live a long time without breathing; for the lung, containing little
blood or fluid, can rise a long way: its own motion can for a long time
produce sufficient refrigeration. But at last it ceases to suffice, and
the animal dies of suffocation if it does not respire-as we have already
said. For of exhaustion that kind which is destruction due to lack of refrigeration
is called suffocation, and whatsoever is thus destroyed is said to be
suffocated.
We have already stated that among animals insects do not respire,
and the fact is open to observation in the case of even small creatures
like flies and bees, for they can swim about in a fluid for a long time
if it is not too hot or too cold. Yet animals with little strength tend
to breathe more frequently. These, however, die of what is called suffocation
when the stomach becomes filled and the heat in the central segment is
destroyed. This explains also why they revive after being among ashes for
a time.
Again among water-animals those that are bloodless remain alive
longer in air than those that have blood and admit the sea-water, as, for
example, fishes. Since it is a small quantity of heat they possess, the
air is for a long time adequate for the purposes of refrigeration in such
animals as the crustacea and the polyps. It does not however suffice, owing
to their want of heat, to keep them finally in life, for most fishes also
live though among earth, yet in a motionless state, and are to be found
by digging. For all animals that have no lung at all or have a bloodless
one require less refrigeration.
Part 16
Concerning the bloodless animals we have declared that in some
cases it is the surrounding air, in others fluid, that aids the maintenance
of life. But in the case of animals possessing blood and heart, all which
have a lung admit the air and produce the cooling effect by breathing in
and out. All animals have a lung that are viviparous and are so internally,
not externally merely (the Selachia are viviparous, but not internally),
and of the oviparous class those that have wings, e.g. birds, and those
with scales, e.g. tortoises, lizards, and snakes. The former class have
a lung charged with blood, but in the most part of the latter it is spongy.
Hence they employ respiration more sparingly as already said. The function
is found also in all that frequent and pass their life in the water, e.g.
the class of water-snakes and frogs and crocodiles and hemydes, both sea-
and land-tortoises, and seals.
All these and similar animals both bring forth on land and sleep
on shore or, when they do so in the water, keep the head above the surface
in order to respire. But all with gills produce refrigeration by taking
in water; the Selachia and all other footless animals have gills. Fish
are footless, and the limbs they have get their name (pterugion) from their
similarity to wings (pterux). But of those with feet one only, so far as
observed, has gills. It is called the tadpole.
No animal yet has been seen to possess both lungs and gills, and
the reason for this is that the lung is designed for the purpose of refrigeration
by means of the air (it seems to have derived its name (pneumon) from its
function as a receptacle of the breath (pneuma)), while gills are relevant
to refrigeration by water. Now for one purpose one organ is adapted and
one single means of refrigeration is sufficient in every case. Hence, since
we see that Nature does nothing in vain, and if there were two organs one
would be purposeless, this is the reason why some animals have gills, others
lungs, but none possess both.
Part 17
Every animal in order to exist requires nutriment, in order to
prevent itself from dying, refrigeration; and so Nature employs the same
organ for both purposes. For, as in some cases the tongue serves both for
discerning tastes and for speech, so in animals with lungs the mouth is
employed both in working up the food and in the passage of the breath outwards
and inwards. In lungless and non-respiring animals it is employed in working
up the food, while in those of them that require refrigeration it is the
gills that are created for this purpose.
We shall state further on how it is that these organs have the
faculty of producing refrigeration. But to prevent their food from impeding
these operations there is a similar contrivance in the respiring animals
and in those that admit water. At the moment of respiration they do not
take in food, for otherwise suffocation results owing to the food, whether
liquid or dry, slipping in through the windpipe and lying on the lung.
The windpipe is situated before the oesophagus, through which food passes
into what is called the stomach, but in quadrupeds which are sanguineous
there is, as it were, a lid over the windpipe-the epiglottis. In birds
and oviparous quadrupeds this covering is absent, but its office is discharged
by a contraction of the windpipe. The latter class contract the windpipe
when swallowing their food; the former close down the epiglottis. When
the food has passed, the epiglottis is in the one case raised, and in the
other the windpipe is expanded, and the air enters to effect refrigeration.
In animals with gills the water is first discharged through them and then
the food passes in through the mouth; they have no windpipe and hence can
take no harm from liquid lodging in this organ, only from its entering
the stomach. For these reasons the expulsion of water and the seizing of
their food is rapid, and their teeth are sharp and in almost all cases
arranged in a saw-like fashion, for they are debarred from chewing their
food.
Part 18
Among water-animals the cetaceans may give rise to some perplexity,
though they too can be rationally explained.
Examples of such animals are dolphins and whales, and all others
that have a blowhole. They have no feet, yet possess a lung though admitting
the sea-water. The reason for possessing a lung is that which we have now
stated [refrigeration]; the admission of water is not for the purpose of
refrigeration. That is effected by respiration, for they have a lung. Hence
they sleep with their head out of the water, and dolphins, at any rate,
snore. Further, if they are entangled in nets they soon die of suffocation
owing to lack of respiration, and hence they can be seen to come to the
surface owing to the necessity of breathing. But, since they have to feed
in the water, they must admit it, and it is in order to discharge this
that they all have a blow-hole; after admitting the water they expel it
through the blow-hole as the fishes do through the gills. The position
of the blow-hole is an indication of this, for it leads to none of the
organs which are charged with blood; but it lies before the brain and thence
discharges water.
It is for the very same reason that molluscs and crustaceans admit
water-I mean such animals as Carabi and Carcini. For none of these is refrigeration
a necessity, for in every case they have little heat and are bloodless,
and hence are sufficiently cooled by the surrounding water. But in feeding
they admit water, and hence must expel it in order to prevent its being
swallowed simultaneously with the food. Thus crustaceans, like the Carcini
and Carabi, discharge water through the folds beside their shaggy parts,
while cuttlefish and the polyps employ for this purpose the hollow above
the head. There is, however, a more precise account of these in the History
of Animals.
Thus it has been explained that the cause of the admission of the
water is refrigeration, and the fact that animals constituted for a life
in water must feed in it.
Part 19
An account must next be given of refrigeration and the manner in
which it occurs in respiring animals and those possessed of gills. We have
already said that all animals with lungs respire. The reason why some creatures
have this organ, and why those having it need respiration, is that the
higher animals have a greater proportion of heat, for at the same time
they must have been assigned a higher soul and they have a higher nature
than plants. Hence too those with most blood and most warmth in the lung
are of greater size, and animal in which the blood in the lung is purest
and most plentiful is the most erect, namely man; and the reason why he
alone has his upper part directed to the upper part of the universe is
that he possesses such a lung. Hence this organ as much as any other must
be assigned to the essence of the animal both in man and in other
cases.
This then is the purpose of refrigeration. As for the constraining
and efficient cause, we must believe that it created animals like this,
just as it created many others also not of this constitution. For some
have a greater proportion of earth in their composition, like plants, and
others, e.g. aquatic animals, contain a larger amount of water; while winged
and terrestrial animals have an excess of air and fire respectively. It
is always in the region proper to the element preponderating in the scheme
of their constitution that things exist.
Part 20
Empedocles is then in error when he says that those animals which
have the most warmth and fire live in the water to counterbalance the excess
of heat in their constitution, in order that, since they are deficient
in cold and fluid, they may be kept in life by the contrary character of
the region they occupy; for water has less heat than air. But it is wholly
absurd that the water-animals should in every case originate on dry land,
and afterwards change their place of abode to the water; for they are almost
all footless. He, however, when describing their original structure says
that, though originating on dry land, they have abandoned it and migrated
to the water. But again it is evident that they are not warmer than land-animals,
for in some cases they have no blood at all, in others
little.
The question, however, as to what sorts of animals should be called
warm and what cold, has in each special case received consideration. Though
in one respect there is reason in the explanation which Empedocles aims
at establishing, yet his account is not correct. Excess in a bodily state
is cured by a situation or season of opposite character, but the constitution
is best maintained by an environment akin to it. There is a difference
between the material of which any animal is constituted and the states
and dispositions of that material. For example, if nature were to constitute
a thing of wax or of ice, she would not preserve it by putting it in a
hot place, for the opposing quality would quickly destroy it, seeing that
heat dissolves that which cold congeals. Again, a thing composed of salt
or nitre would not be taken and placed in water, for fluid dissolves that
of which the consistency is due to the hot and the dry.
Hence if the fluid and the dry supply the material for all bodies,
it is reasonable that things the composition of which is due to the fluid
and the cold should have liquid for their medium [and, if they are cold,
they will exist in the cold], while that which is due to the dry will be
found in the dry. Thus trees grow not in water but on dry land. But the
same theory would relegate them to the water, on account of their excess
of dryness, just as it does the things that are excessively fiery. They
would migrate thither not on account of its cold but owing to its
fluidity.
Thus the natural character of the material of objects is of the
same nature as the region in which they exist; the liquid is found in liquid,
the dry on land, the warm in air. With regard, however, to states of body,
a cold situation has, on the other hand, a beneficial effect on excess
of heat, and a warm environment on excess of cold, for the region reduces
to a mean the excess in the bodily condition. The regions appropriate to
each material and the revolutions of the seasons which all experience supply
the means which must be sought in order to correct such excesses; but,
while states of the body can be opposed in character to the environment,
the material of which it is composed can never be so. This, then, is a
sufficient explanation of why it is not owing to the heat in their constitution
that some animals are aquatic, others terrestrial, as Empedocles maintains,
and of why some possess lungs and others do not.
Part 21
The explanation of the admission of air and respiration in those
animals in which a lung is found, and especially in those in which it is
full of blood, is to be found in the fact that it is of a spongy nature
and full of tubes, and that it is the most fully charged with blood of
all the visceral organs. All animals with a full-blooded lung require rapid
refrigeration because there is little scope for deviation from the normal
amount of their vital fire; the air also must penetrate all through it
on account of the large quantity of blood and heat it contains. But both
these operations can be easily performed by air, for, being of a subtle
nature, it penetrates everywhere and that rapidly, and so performs its
cooling function; but water has the opposite characteristics.
The reason why animals with a full-blooded lung respire most is
hence manifest; the more heat there is, the greater is the need for refrigeration,
and at the same time breath can easily pass to the source of heat in the
heart.
Part 22
In order to understand the way in which the heart is connected
with the lung by means of passages, we must consult both dissections and
the account in the History of Animals. The universal cause of the need
which the animal has for refrigeration, is the union of the soul with fire
that takes place in the heart. Respiration is the means of effecting refrigeration,
of which those animals make use that possess a lung as well as a heart.
But when they, as for example the fishes, which on account of their aquatic
nature have no lung, possess the latter organ without the former, the cooling
is effected through the gills by means of water. For ocular evidence as
to how the heart is situated relatively to the gills we must employ dissections,
and for precise details we must refer to Natural History. As a summarizing
statement, however, and for present purposes, the following is the account
of the matter.
It might appear that the heart has not the same position in terrestrial
animals and fishes, but the position really is identical, for the apex
of the heart is in the direction in which they incline their heads. But
it is towards the mouth in fishes that the apex of the heart points, seeing
that they do not incline their heads in the same direction as land-animals
do. Now from the extremity of the heart a tube of a sinewy, arterial character
runs to the centre where the gills all join. This then is the largest of
those ducts, but on either side of the heart others also issue and run
to the extremity of each gill, and by means of the ceaseless flow of water
through the gills, effect the cooling which passes to the
heart.
In similar fashion as the fish move their gills, respiring animals
with rapid action raise and let fall the chest according as the breath
is admitted or expelled. If air is limited in amount and unchanged they
are suffocated, for either medium, owing to contact with the blood, rapidly
becomes hot. The heat of the blood counteracts the refrigeration and, when
respiring animals can no longer move the lung aquatic animals their gills,
whether owing to discase or old age, their death ensues.
Part 23
To be born and to die are common to all animals, but there are
specifically diverse ways in which these phenomena occur; of destruction
there are different types, though yet something is common to them all.
There is violent death and again natural death, and the former occurs when
the cause of death is external, the latter when it is internal, and involved
from the beginning in the constitution of the organ, and not an affection
derived from a foreign source. In the case of plants the name given to
this is withering, in animals senility. Death and decay pertain to all
things that are not imperfectly developed; to the imperfect also they may
be ascribed in nearly the same but not an identical sense. Under the imperfect
I class eggs and seeds of plants as they are before the root
appears.
It is always to some lack of heat that death is due, and in perfect
creatures the cause is its failure in the organ containing the source of
the creature's essential nature. This member is situate, as has been said,
at the junction of the upper and lower parts; in plants it is intermediate
between the root and the stem, in sanguineous animals it is the heart,
and in those that are bloodless the corresponding part of their body. But
some of these animals have potentially many sources of life, though in
actuality they possess only one. This is why some insects live when divided,
and why, even among sanguineous animals, all whose vitality is not intense
live for a long time after the heart has been removed. Tortoises, for example,
do so and make movements with their feet, so long as the shell is left,
a fact to be explained by the natural inferiority of their constitution,
as it is in insects also.
The source of life is lost to its possessors when the heat with
which it is bound up is no longer tempered by cooling, for, as I have often
remarked, it is consumed by itself. Hence when, owing to lapse of time,
the lung in the one class and the gills in the other get dried up, these
organs become hard and earthy and incapable of movement, and cannot be
expanded or contracted. Finally things come to a climax, and the fire goes
out from exhaustion.
Hence a small disturbance will speedily cause death in old age.
Little heat remains, for the most of it has been breathed away in the long
period of life preceding, and hence any increase of strain on the organ
quickly causes extinction. It is just as though the heart contained a tiny
feeble flame which the slightest movement puts out. Hence in old age death
is painless, for no violent disturbance is required to cause death, and
there is an entire absence of feeling when the soul's connexion is severed.
All diseases which harden the lung by forming tumours or waste residues,
or by excess of morbid heat, as happens in fevers, accelerate the breathing
owing to the inability of the lung to move far either upwards or downwards.
Finally, when motion is no longer possible, the breath is given out and
death ensues.
Part 24
Generation is the initial participation, mediated by warm substance,
in the nutritive soul, and life is the maintenance of this participation.
Youth is the period of the growth of the primary organ of refrigeration,
old age of its decay, while the intervening time is the prime of
life.
A violent death or dissolution consists in the extinction or exhaustion
of the vital heat (for either of these may cause dissolution), while natural
death is the exhaustion of the heat owing to lapse of time, and occurring
at the end of life. In plants this is to wither, in animals to die. Death,
in old age, is the exhaustion due to inability on the part of the organ,
owing to old age, to produce refrigeration. This then is our account of
generation and life and death, and the reason for their occurrence in
animals.
Part 25
It is hence also clear why respiring animals are suffocated in
water and fishes in air. For it is by water in the latter class, by air
in the former that refrigeration is effected, and either of these means
of performing the function is removed by a change of
environment.
There is also to be explained in either case the cause of the cause
of the motion of the gills and of the lungs, the rise and fall of which
effects the admission and expulsion of the breath or of water. The following,
moreover, is the manner of the constitution of the organ.
Part 26
In connexion with the heart there are three phenomena, which, though
apparently of the same nature, are really not so, namely palpitation, pulsation,
and respiration.
Palpitation is the rushing together of the hot substance in the
heart owing to the chilling influence of residual or waste products. It
occurs, for example, in the ailment known as 'spasms' and in other diseases.
It occurs also in fear, for when one is afraid the upper parts become cold,
and the hot substance, fleeing away, by its concentration in the heart
produces palpitation. It is crushed into so small a space that sometimes
life is extinguished, and the animals die of the fright and morbid
disturbance.
The beating of the heart, which, as can be seen, goes on continuously,
is similar to the throbbing of an abscess. That, however, is accompanied
by pain, because the change produced in the blood is unnatural, and it
goes on until the matter formed by concoction is discharged. There is a
similarity between this phenomenon and that of boiling; for boiling is
due to the volatilization of fluid by heat and the expansion consequent
on increase of bulk. But in an abscess, if there is no evaporation through
the walls, the process terminates in suppuration due to the thickening
of the liquid, while in boiling it ends in the escape of the fluid out
of the containing vessel.
In the heart the beating is produced by the heat expanding the
fluid, of which the food furnishes a constant supply. It occurs when the
fluid rises to the outer wall of the heart, and it goes on continuously;
for there is a constant flow of the fluid that goes to constitute the blood,
it being in the heart that the blood receives its primary elaboration.
That this is so we can perceive in the initial stages of generation, for
the heart can be seen to contain blood before the veins become distinct.
This explains why pulsation in youth exceeds that in older people, for
in the young the formation of vapour is more abundant.
All the veins pulse, and do so simultaneously with each other,
owing to their connexion with the heart. The heart always beats, and hence
they also beat continuously and simultaneously with each other and with
it.
Palpitation, then, is the recoil of the heart against the compression
due to cold; and pulsation is the volatilization of the heated
fluid.
Part 27
Respiration takes place when the hot substance which is the seat
of the nutritive principle increases. For it, like the rest of the body,
requires nutrition, and more so than the members, for it is through it
that they are nourished. But when it increases it necessarily causes the
organ to rise. This organ we must to be constructed like the bellows in
a smithy, for both heart and lungs conform pretty well to this shape. Such
a structure must be double, for the nutritive principle must be situated
in the centre of the natural force.
Thus on increase of bulk expansion results, which necessarily causes
the surrounding parts to rise. Now this can be seen to occur when people
respire; they raise their chest because the motive principle of the organ
described resident within the chest causes an identical expansion of this
organ. When it dilates the outer air must rush in as into a bellows, and,
being cold, by its chilling influence reduces by extinction the excess
of the fire. But, as the increase of bulk causes the organ to dilate, so
diminution causes contraction, and when it collapses the air which entered
must pass out again. When it enters the air is cold, but on issuing it
is warm owing to its contact with the heat resident in this organ, and
this is specially the case in those animals that possess a full-blooded
lung. The numerous canal-like ducts in the lung, into which it passes,
have each a blood-vessel lying alongside, so that the whole lung is thought
to be full of blood. The inward passage of the air is called respiration,
the outward expiration, and this double movement goes on continuously just
so long as the animal lives and keeps this organ in continuous motion;
it is for this reason that life is bound up with the passage of the breath
outwards and inwards.
It is in the same way that the motion of the gills in fishes takes
place. When the hot substance in the blood throughout the members rises,
the gills rise too, and let the water pass through, but when it is chilled
and retreats through its channels to the heart, they contract and eject
the water. Continually as the heat in the heart rises, continually on being
chilled it returns thither again. Hence, as in respiring animals life and
death are bound up with respiration, so in the other animals class they
depend on the admission of water.
Our discussion of life and death and kindred topics is now practically
complete. But health and discase also claim the attention of the scientist,
and not mercly of the physician, in so far as an account of their causes
is concerned. The extent to which these two differ and investigate diverse
provinces must not escape us, since facts show that their inquiries are,
to a certain extent, at least conterminous. For physicians of culture and
refinement make some mention of natural science, and claim to derive their
principles from it, while the most accomplished investigators into nature
generally push their studies so far as to conclude with an account of medical
principles.
THE END
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