and 'moulting'. The cause of the condition is deficiency of hot
moisture, such moisture being especially the unctuous, and hence
unctuous plants are more evergreen. (However we must elsewhere
state the cause of this phenomena in plants, for other causes also
contribute to it.) It is in winter that this happens to plants
(for the change from summer to winter is more important to them than
the time of life), and to those animals which hibernate (for
these, too, are by nature less hot and moist than man); in the latter
it is the seasons of life that correspond to summer and winter.
Hence no one goes bald before the time of sexual intercourse, and at
that time it is in those naturally inclined to such intercourse that
baldness appears, for the brain is naturally the coldest part of the
body and sexual intercourse makes men cold, being a loss of pure
natural heat. Thus we should expect the brain to feel the effect of it
first, for a little cause turns the scale where the thing concerned is
weak and in poor condition. Thus if we reckon up these points, that
the brain itself has but little heat, and further that the skin
round it must needs have still less, and again that the hair must have
still less than the skin inasmuch as it is furthest removed from the
brain, we should reasonably expect baldness to come about this age
upon those who have much semen. And it is for the same reason that the
front part of the head alone goes bald in man and that he is the
only animal to do so; the front part goes bald because the brain is
there, and man is the only animal to go bald because his brain is much
the largest and the moistest. Women do not go bald because their
nature is like that of children, both alike being incapable of
producing seminal secretion. Eunuchs do not become bald, because
they change into the female condition. And as to the hair that comes
later in life, eunuchs either do not grow it at all, or lose it if
they happen to have it, with the exception of the pubic hair; for
women also grow that though they have not the other, and this
mutilation is a change from the male to the female condition.
The reason why the hair does not grow again in cases of baldness,
although both hibernating animals recover their feathers or hair and
trees that have shed their leaves grow leaves again, is this. The
seasons of the year are the turning-points of their lives, rather than
their age, so that when these seasons change they change with them
by growing and losing feathers, hairs, or leaves respectively. But the
winter and summer, spring and autumn of man are defined by his age, so
that, since his ages do not return, neither do the conditions caused
by them return, although the cause of the change of condition is
similar in man to what it is in the animals and plants in question.
We have now spoken pretty much of all the other conditions of hair.
4
But as to their colour, it is the nature of the skin that is the
cause of this in other animals and also of their being uni-coloured or
vari-coloured); but in man it is not the cause, except of the hair
going grey through disease (not through old age), for in what is
called leprosy the hairs become white; on the contrary, if the hairs
are white the whiteness does not invade the skin. The reason is that
the hairs grow out of skin; if, then, the skin is diseased and white
the hair becomes diseased with it, and the disease of hair is
greyness. But the greyness of hair which is due to age results from
weakness and deficiency of heat. For as the body declines in vigour we
tend to cold at every time of life, and especially in old age, this
age being cold and dry. We must remember that the nutriment coming
to each part of the body is concocted by the heat appropriate to the
part; if the heat is inadequate the part loses its efficiency, and
destruction or disease results. (We shall speak more in detail of
causes in the treatise on growth and nutrition.) Whenever, then,
the hair in man has naturally little heat and too much moisture enters
it, its own proper heat is unable to concoct the moisture and so it is
decayed by the heat in the environing air. All decay is caused by
heat, not the innate heat but external heat, as has been stated
elsewhere. And as there is a decay of water, of earth, and all such
material bodies, so there is also of the earthy vapour, for instance
what is called mould (for mould is a decay of earthy vapour). Thus
also the liquid nutriment in the hair decays because it is not
concocted, and what is called greyness results. It is white because
mould also, practically alone among decayed things, is white. The
reason of this is that it has much air in it, all earthy vapour
being equivalent to thick air. For mould is, as it were, the
antithesis of hoar-frost; if the ascending vapour be frozen it becomes
hoar-frost, if it be decayed, mould. Hence both are on the surface
of things, for vapour is superficial. And so the comic poets make a
good metaphor in jest when they call grey hairs 'mould of old age' and
For the one is generically the same as greyness, the other
specifically; hoar-frost generically (for both are a vapour),
mould specifically (for both are a form of decay). A proof that this
is so is this: grey hairs have often grown on men in consequence of
disease, and later on dark hairs instead of them after restoration
to health. The reason is that in sickness the whole body is
deficient in natural heat and so the parts besides, even the very
small ones, participate in this weakness; and again, much residual
matter is formed in the body and all its parts in illness, wherefore
the incapacity in the flesh to concoct the nutriment causes the grey
hairs. But when men have recovered health and strength again they
change, becoming as it were young again instead of old; in consequence
the states change also. Indeed, we may rightly call disease an
acquired old age, old age a natural disease; at any rate, some
diseases produce the same effects as old age.
Men go grey on the temples first, because the back of the head is
empty of moisture owing to its containing no brain, and the 'bregma'
has a great deal of moisture, a large quantity not being liable to
decay; the hair on the temples however has neither so little that it
can concoct it nor so much that it cannot decay, for this region of
the head being between the two extremes is exempt from both states.
The cause of greyness in man has now been stated.
5
The reason why this change does not take place visibly on account of
age in other animals is the same as that already given in the case
of baldness; their brain is small and less fluid than in man, so
that the heat required for concoction does not altogether fail.
Among them it is most clear in horses of all animals that we know,
because the bone about the brain is thinner in them than in others
in proportion to their size. A sign of this is that a blow to this
spot is fatal to them, wherefore Home
r also has said: 'where the first
hairs grow on the skull of horses, and a wound is most fatal.' As then
the moisture easily flows to these hairs because of the thinness of
the bone, whilst the heat fails on account of age, they go grey. The
reddish hairs go grey sooner than the black, redness also being a sort
of weakness of hair and all weak things ageing sooner. It is said,
however, that cranes become darker as they grow old. The reason of
this would be, if it should prove true, that their feathers are
naturally moister than others and as they grow old the moisture in the
feathers is too much to decay easily.
Greyness comes about by some sort of decay, and is not, as some
think, a withering. (1) A proof of the former statement is the fact
that hair protected by hats or other coverings goes grey sooner
(for the winds prevent decay and the protection keeps off the winds),
and the fact that it is aided by anointing with a mixture of oil and
water. For, though water cools things, the oil mingled with it
prevents the hair from drying quickly, water being easily dried up.
(2) That the process is not a withering, that the hair does not whiten
as grass does by withering, is shown by the fact that some hairs
grow grey from the first, whereas nothing springs up in a withered
state. Many hairs also whiten at the tip, for there is least heat in
the extremities and thinnest parts.
When the hairs of other animals are white, this is caused by nature,
not by any affection. The cause of the colours in other animals is the
skin; if they are white, the skin is white, if they are dark it is
dark, if they are piebald in consequence of a mixture of the hairs, it
is found to be white in the one part and dark in the other. But in man
the skin is in no way the cause, for even white-skinned men have
very dark hair. The reason is that man has the thinnest skin of all
animals in proportion to his size and therefore it has not strength to
change the hairs; on the contrary the skin itself changes its colour
through its weakness and is darkened by sun and wind, while the
hairs do not change along with it at all. But in the other animals the
skin, owing to its thickness, has the influence belonging to the
soil in which a thing grows, therefore the hairs change according to
the skin but the skin does not change at all in consequence of the
winds and the sun.
6
Of animals some are uni-coloured (I mean by this term those of
which the kind as a whole has one colour, as all lions are tawny;
and this condition exists also in birds, fish, and the other classes
of animals alike); others though many-coloured are yet whole-coloured
(I mean those whose body as a whole has the same colour, as a bull is
white as a whole or dark as a whole); others are vari-coloured.
This last term is used in both ways; sometimes the whole kind is
vari-coloured, as leopards and peacocks, and some fish, e.g. the
so-called 'thrattai'; sometimes the kind as a whole is not so, but
such individuals are found in it, as with cattle and goats and,
among birds, pigeons; the same applies also to other kinds of birds.
The whole-coloured change much more than the uniformly coloured,
both into the simple colour of another individual of the same kind
(as dark changing into white and vice versa) and into both colours
mingled. This is because it is a natural characteristic of the kind as
a whole not to have one colour only, the kind being easily moved in
both directions so that the colours both change more into one
another and are more varied. The opposite holds with the uniformly
coloured; they do not change except by an affection of the colour, and
that rarely; but still they do so change, for before now white
individuals have been observed among partridges, ravens, sparrows, and
bears. This happens when the course of development is perverted, for
what is small is easily spoilt and easily moved, and what is
developing is small, the beginning of all such things being on a small
scale.
Change is especially found in those animals of which by nature the
individual is whole-coloured but the kind many-coloured. This is owing
to the water which they drink, for hot waters make the hair white,
cold makes it dark, an effect found also in plants. The reason is that
the hot have more air than water in them, and the air shining
through causes whiteness, as also in froth. As, then, skins which
are white by reason of some affection differ from those white by
nature, so also in the hair the whiteness due to disease or age
differs from that due to nature in that the cause is different; the
latter are whitened by the natural heat, the former by the external
heat. Whiteness is caused in all things by the vaporous air imprisoned
in them. Hence also in all animals not uniformly coloured all the part
under the belly is whiter. For practically all white animals are
both hotter and better flavoured for the same reason; the concoction
of their nutriment makes them well-flavoured, and heat causes the
concoction. The same cause holds for those animals which are
uniformly-coloured, but either dark or white; heat and cold are the
causes of the nature of the skin and hair, each of the parts having
its own special heat.
The tongue also varies in colour in the simply coloured as
compared with the vari-coloured animals, and again in the simply
coloured which differ from one another, as white and dark. The
reason is that assigned before, that the skins of the vari-coloured
are vari-coloured, and the skins of the white-haired and dark-haired
are white and dark in each case. Now we must conceive of the tongue as
one of the external parts, not taking into account the fact that it is
covered by the mouth but looking on it as we do on the hand or foot;
thus since the skin of the vari-coloured animals is not uniformly
coloured, this is the cause of the skin on the tongue being also
vari-coloured.
Some birds and some wild quadrupeds change their colour according to
the seasons of the year. The reason is that, as men change according
to their age, so the same thing happens to them according to the
season; for this makes a greater difference to them than the change of
age.
The more omnivorous animals are more vari-coloured to speak
generally, and this is what might be expected; thus bees are more
uniformly coloured than hornets and wasps. For if the food is
responsible for the change we should expect varied food to increase
the variety in the movements which cause the development and so in the
residual matter of the food, from which come into being hairs and
feathers and skins.
So much for colours and hairs.
7
As to the voice, it is deep in some animals, high in others, in
others again well-pitched and in due proportion between both extremes.
Again, in some it is loud, in others small, and it differs in
smoothness and roughness, flexibility and inflexibility. We must
inquire
then into the causes of each of these distinctions.
We must suppose then that the same cause is responsible for high and
deep voices as for the change which they undergo in passing from youth
to age. The voice is higher in all other animals when younger, but
in cattle that of calves is deeper. We find the same thing also in the
male and female sexes; in the other kinds of animals the voice of
the female is higher than that of the male (this being especially
plain in man, for Nature has given this faculty to him in the
highest degree because he alone of animals makes use of speech and the
voice is the material of speech), but in cattle the opposite obtains,
for the voice of cows is deeper than that of bulls.
Now the purpose for which animals have a voice, and what is meant by
'voice' and by 'sound' generally, has been stated partly in the
treatise on sensation, partly in that on the soul. But since lowness
of voice depends on the movement of the air being slow and its
highness on its being quick, there is a difficulty in knowing
whether it is that which moves or that which is moved that is the
cause of the slowness or quickness. For some say that what is much
is moved slowly, what is little quickly, and that the quantity of
the air is the cause of some animals having a deep and others a high
voice. Up to a certain point this is well said (for it seems to be
rightly said in a general way that the depth depends on a certain
amount of the air put in motion), but not altogether, for if this
were true it would not be easy to speak both soft and deep at once,
nor again both loud and high. Again, the depth seems to belong to
the nobler nature, and in songs the deep note is better than the
high-pitched ones, the better lying in superiority, and depth of
tone being a sort of superiority. But then depth and height in the
voice are different from loudness and softness, and some high-voiced
animals are loud-voiced, and in like manner some soft-voiced ones
are deep-voiced, and the same applies to the tones lying between these
extremes. And by what else can we define these (I mean loudness and