softness of voice) except by the large and small amount of the air
put in motion? If then height and depth are to be decided in
accordance with the distinction postulated, the result will be that
the same animals will be deep-and loud-voiced, and the same will be
high-and not loud-voiced; but this is false.
The reason of the difficulty is that the words 'great' and
'small', 'much' and 'little' are used sometimes absolutely,
sometimes relatively to one another. Whether an animal has a great
(or loud) voice depends on the air which is moved being much
absolutely, whether it has a small voice depends on its being little
absolutely; but whether they have a deep or high voice depends on
their being thus differentiated in relation to one another. For if
that which is moved surpass the strength of that which moves it, the
air that is sent forth must go slowly; if the opposite, quickly. The
strong, then, on account of their strength, sometimes move much air
and make the movement slow, sometimes, having complete command over
it, make the movement swift. On the same principle the weak either
move too much air for their strength and so make the movement slow, or
if they make it swift move but little because of their weakness.
These, then, are the reasons of these contrarieties, that neither
are all young animals high-voiced nor all deep-voiced, nor are all the
older, nor yet are the two sexes thus opposed, and again that not only
the sick speak in a high voice but also those in good bodily
condition, and, further, that as men verge on old age they become
higher-voiced, though this age is opposite to that of youth.
Most young animals, then, and most females set but little air in
motion because of their want of power, and are consequently
high-voiced, for a little air is carried along quickly, and in the
voice what is quick is high. But in calves and cows, in the one case
because of their age, in the other because of their female nature, the
part by which they set the air in motion is not strong; at the same
time they set a great quantity in motion and so are deep-voiced; for
that which is borne along slowly is heavy, and much air is borne along
slowly. And these animals set much in movement whereas the others
set but little, because the vessel through which the breath is first
borne has in them a large opening and necessarily sets much air in
motion, whereas in the rest the air is better dispensed. As their
age advances this part which moves the air gains more strength in each
animal, so that they change into the opposite condition, the
high-voiced becoming deeper-voiced than they were, and the deep-voiced
higher-voiced, which is why bulls have a higher voice than calves
and cows. Now the strength of all animals is in their sinews, and so
those in the prime of life are stronger, the young being weaker in the
joints and sinews; moreover, in the young they are not yet tense,
and in those now growing old the tension relaxes, wherefore both these
ages are weak and powerless for movement. And bulls are particularly
sinewy, even their hearts, and therefore that part by which they set
the air in motion is in a tense state, like a sinewy string
stretched tight. (That the heart of bulls is of such a nature is
shown by the fact that a bone is actually found in some of them, and
bones are naturally connected with sinew.)
All animals when castrated change to the female character, and utter
a voice like that of the females because the sinewy strength in the
principle of the voice is relaxed. This relaxation is just as if one
should stretch a string and make it taut by hanging some weight on
to it, as women do who weave at the loom, for they stretch the warp by
attaching to it what are called 'laiai'. For in this way are the
testes attached to the seminal passages, and these again to the
blood-vessel which takes its origin in the heart near the organ
which sets the voice in motion. Hence as the seminal passages change
towards the age at which they are now able to secrete the semen,
this part also changes along with them. As this changes, the voice
again changes, more indeed in males, but the same thing happens in
females too, only not so plainly, the result being what some call
'bleating' when the voice is uneven. After this it settles into the
deep or high voice of the succeeding time of life. If the testes are
removed the tension of the passages relaxes, as when the weight is
taken off the string or the warp; as this relaxes, the organ which
moves the voice is loosened in the same proportion. This, then, is the
reason why the voice and the form generally changes to the female
character in castrated animals; it is because the principle is relaxed
upon which depends the tension of the body; not that, as some suppose,
the testes are themselves a ganglion of many principles, but small
changes are the causes of great ones, not per se but when it happens
that a principle changes with them. For the principles, though small
in size, are great in potency; this, indeed, is what is meant by a
principle, that it is itself the cause of many things without anything
else being higher than it for it to depend upon.
The heat or cold also of their habitat contributes to make some
animals of such a character as to be deep-voiced, and others
high-voiced. For hot breath being thick causes depth, cold breath
being thin the opposite. This is clear also in pipe-playing, for if
the breath of the performer is hotter, that is to say if it is
expelled as by a groan, the note is deeper.
The cause of roughness and smoothness in the voice, and of all
similar inequality, is that the part or organ through which the
voice is conveyed is rough or smooth or generally even or uneven. This
is plain when there is any moisture about the trachea or when it is
roughened by any affection, for then the voice also becomes uneven.
Flexibility depends on the softness or hardness of the organ, for
what is soft can be regulated and assume any form, while what is
hard cannot; thus the soft organ can utter a loud or a small note, and
accordingly a high or a deep one, since it easily regulates the
breath, becoming itself easily great or small. But hardness cannot
be regulated.
Let this be enough on all those points concerning the voice which
have not been previously discussed in the treatise on sensation and in
that on the soul.
8
With regard to the teeth it has been stated previously that they
do not exist for a single purpose nor for the same purpose in all
animals, but in some for nutrition only, in others also for fighting
and for vocal speech. We must, however, consider it not alien to the
discussion of generation and development to inquire into the reason
why the front teeth are formed first and the grinders later, and why
the latter are not shed but the former are shed and grow again.
Democritus has spoken of these questions but not well, for he
assigns the cause too generally withou
t investigating the facts in all
cases. He says that the early teeth are shed because they are formed
in animals too early, for it is when animals are practically in
their prime that they grow according to Nature, and suckling is the
cause he assigns for their being found too early. Yet the pig also
suckles but does not shed its teeth, and, further, all the animals
with carnivorous dentition suckle, but some of them do not shed any
teeth except the canines, e.g. lions. This mistake, then, was due to
his speaking generally without examining what happens in all cases;
but this is what we to do, for any one who makes any general statement
must speak of all the particular cases.
Now we assume, basing our assumption upon what we see, that Nature
never fails nor does anything in vain so far as is possible in each
case. And it is necessary, if an animal is to obtain food after the
time of taking milk is over, that it should have instruments for the
treatment of the food. If, then, as Democritus says, this happened
about the time of reaching maturity, Nature would fail in something
possible for her to do. And, besides, the operation of Nature would be
contrary to Nature, for what is done by violence is contrary to
Nature, and it is by violence that he says the formation of the
first teeth is brought about. That this view then is not true is plain
from these and other similar considerations.
Now these teeth are developed before the flat teeth, in the first
place because their function is earlier (for dividing comes before
crushing, and the flat teeth are for crushing, the others for
dividing), in the second place because the smaller is naturally
developed quicker than the larger, even if both start together, and
these teeth are smaller in size than the grinders, because the bone of
the jaw is flat in that part but narrow towards the mouth. From the
greater part, therefore, must flow more nutriment to form the teeth,
and from the narrower part less.
The act of sucking in itself contributes nothing to the formation of
the teeth, but the heat of the milk makes them appear more quickly.
A proof of this is that even in suckling animals those young which
enjoy hotter milk grow their teeth quicker, heat being conducive to
growth.
They are shed, after they have been formed, partly because it is
better so (for what is sharp is soon blunted, so that a fresh relay
is needed for the work, whereas the flat teeth cannot be blunted but
are only smoothed in time by wearing down), partly from necessity
because, while the roots of the grinders are fixed where the jaw is
flat and the bone strong, those of the front teeth are in a thin part,
so that they are weak and easily moved. They grow again because they
are shed while the bone is still growing and the animal is still young
enough to grow teeth. A proof of this is that even the flat teeth grow
for a long time, the last of them cutting the gum at about twenty
years of age; indeed in some cases the last teeth have been grown in
quite old age. This is because there is much nutriment in the broad
part of the bones, whereas the front part being thin soon reaches
perfection and no residual matter is found in it, the nutriment
being consumed in its own growth.
Democritus, however, neglecting the final cause, reduces to
necessity all the operations of Nature. Now they are necessary, it
is true, but yet they are for a final cause and for the sake of what
is best in each case. Thus nothing prevents the teeth from being
formed and being shed in this way; but it is not on account of these
causes but on account of the end (or final cause); these are
causes only in the sense of being the moving and efficient instruments
and the material. So it is reasonable that Nature should perform
most of her operations using breath as an instrument, for as some
instruments serve many uses in the arts, e.g. the hammer and anvil
in the smith's art, so does breath in the living things formed by
Nature. But to say that necessity is the only cause is much as if we
should think that the water has been drawn off from a dropsical
patient on account of the lancet, not on account of health, for the
sake of which the lancet made the incision.
We have thus spoken of the teeth, saying why some are shed and
grow again, and others not, and generally for what cause they are
formed. And we have spoken of the other affections of the parts
which are found to occur not for any final end but of necessity and on
account of the motive or efficient cause.
-THE END-
.
350 BC
ON THE MOTION OF ANIMALS
by Aristotle
translated by A. S. L. Farquharson
1
ELSEWHERE we have investigated in detail the movement of animals
after their various kinds, the differences between them, and the
reasons for their particular characters (for some animals fly, some
swim, some walk, others move in various other ways); there remains
an investigation of the common ground of any sort of animal movement
whatsoever.
Now we have already determined (when we were discussing whether
eternal motion exists or not, and its definition, if it does exist)
that the origin of all other motions is that which moves itself, and
that the origin of this is the immovable, and that the prime mover
must of necessity be immovable. And we must grasp this not only
generally in theory, but also by reference to individuals in the world
of sense, for with these in view we seek general theories, and with
these we believe that general theories ought to harmonize. Now in
the world of sense too it is plainly impossible for movement to be
initiated if there is nothing at rest, and before all else in our
present subject- animal life. For if one of the parts of an animal
be moved, another must be at rest, and this is the purpose of their
joints; animals use joints like a centre, and the whole member, in
which the joint is, becomes both one and two, both straight and
bent, changing potentially and actually by reason of the joint. And
when it is bending and being moved one of the points in the joint is
moved and one is at rest, just as if the points A and D of a
diameter were at rest, and B were moved, and DAC were generated.
However, in the geometrical illustration, the centre is held to be
altogether indivisible (for in mathematics motion is a fiction, as the
phrase goes, no mathematical entity being really moved), whereas in
the case of joints the centres become now one potentially and
divided actually, and now one actually and divided potentially. But
still the origin of movement, qua origin, always remains at rest
when the lower part of a limb is moved; for example, the elbow
joint, when the forearm is moved, and the shoulder, when the whole
arm; the knee when the tibia is moved, and the hip when the whole leg.
Accordingly it is plain that each animal as a whole must have within
itself a point at rest, whence will be the ori
gin of that which is
moved, and supporting itself upon which it will be moved both as a
complete whole and in its members.
2
But the point of rest in the animal is still quite ineffectual
unless there be something without which is absolutely at rest and
immovable. Now it is worth while to pause and consider what has been
said, for it involves a speculation which extends beyond animals
even to the motion and march of the universe. For just as there must
be something immovable within the animal, if it is to be moved, so
even more must there be without it something immovable, by
supporting itself upon which that which is moved moves. For were
that something always to give way (as it does for mice walking in
grain or persons walking in sand) advance would be impossible, and
neither would there be any walking unless the ground were to remain
still, nor any flying or swimming were not the air and the sea to
resist. And this which resists must needs be different from what is
moved, the whole of it from the whole of that, and what is thus
immovable must be no part of what is moved; otherwise there will be no
movement. Evidence of this lies in the problem why it is that a man
easily moves a boat from outside, if he push with a pole, putting it
against the mast or some other part, but if he tried to do this when
in the boat itself he would never move it, no not giant Tityus himself
nor Boreas blowing from inside the ship, if he really were blowing
in the way painters represent him; for they paint him sending the
breath out from the boat. For whether one blew gently or so stoutly as
to make a very great wind, and whether what were thrown or pushed were
wind or something else, it is necessary in the first place to be
supported upon one of one's own members which is at rest and so to
push, and in the second place for this member, either itself, or
that of which it is a part, to remain at rest, fixing itself against