The milk collects in the upper part of the body and the breasts because of the original plan of the organism. For the part above the hypozoma is the part that [5] controls life, while that below is concerned with nourishment and residual matter, in order that all animals which move about may contain within themselves nourishment enough to make them independent when they move from one place to another. From this upper part also is produced the generative secretion for the reason mentioned in the opening of our discussion. But both the secretion of the male and [10] the menses of the female are of a sanguineous nature, and the first principle of this blood and of the blood-vessels is the heart, and the heart is in this part of the body. Therefore it is here that the change of such a secretion must first become plain. This is why the voice changes in both sexes when they begin to bear seed (for the first [15] principle of the voice resides there, and is itself changed when its moving cause changes). At the same time the parts about the breasts are raised visibly even in males but still more in females, for the region of the breasts becomes empty and spongy in them because so much material is drained away below. This is so also in [20] those animals which have the breasts low down.
This change in the voice and the parts about the breasts is plain even in other creatures to those who have experience of each kind of animal, but is most remarkable in man. The reason is that in man the production of secretion is greatest [25] in both sexes in proportion to their size as compared with other animals. [I mean menstruation in women and the emission of semen in men.]6 When, therefore, the embryo no longer takes up the secretion in question but yet prevents its being discharged from the mother, it is necessary that all the residual matter should [30] collect in all those empty parts which are set upon the same passages. And such is the position of the breasts in each kind of animals for both causes; it is so both for the sake of what is best and of necessity.
It is here, then, that the nourishment in animals is now formed and becomes concocted. As for the cause of concoction, we may take that already given, or we may take the opposite, for it is a reasonable view also that the embryo being larger [777a1] takes more nourishment, so that less is left over about this time, and the less is concocted more quickly.
That milk has the same nature as the secretion from which each animal is formed is plain, and has been stated previously. For the material which nourishes is [5] the same as that from which nature forms the animal in generation. Now this is the sanguineous liquid in the sanguinea, and milk is blood concocted (not corrupted; Empedocles either mistook the fact or made a bad metaphor when he wrote that [10] milk ‘on the tenth day of the eighth month comes into being, a white pus’,7 for putrefaction and concoction are opposite things, and pus is a kind of putrefaction but milk is concocted). While women are suckling children menstruation does not occur according to nature, nor do they conceive; if they do conceive, the milk dries [15] up. This is because the nature of the milk and of the menses is the same, and nature cannot be so productive as to supply both at once; if the secretion is diverted in the one direction it must needs cease in the other, unless some violence is done contrary to the general rule. But this is as much as to say that it is contrary to nature, for in [20] all cases where it is not impossible for things to be otherwise than they generally are but where they may so happen, still what is the general rule is what is according to nature.
The time also at which the young animal is born has been well arranged. For when the nourishment coming through the umbilical cord is no longer sufficient for the foetus because of its size, then at the same time the milk becomes useful for the coming nourishment and the blood-vessels round which the so-called umbilical cord [25] lies as a coat collapse as the nourishment is no longer passing through it; for these reasons it is at that time also that the young animal enters into the world.
9 · The natural birth of all animals is head-foremost, because the parts above the umbilical cord are larger than those below. The body then, being suspended [30] from the cord as in a balance, inclines towards the heavy end, and the larger parts are the heavier.
10 · The period of gestation is, as a matter of fact, determined generally in each animal in proportion to the length of its life. For it is reasonable that the development of the long-lived animals should take a longer time. Yet this is not the cause of it, but the correspondence holds for the most part; for though the larger and [777b1] more perfect sanguinea do live a long time, yet the larger are not all longer-lived. Man lives a longer time than any animal of which we have any credible experience except the elephant, and yet the human kind is smaller than that of the bushy-tailed [5] animals and many others. The real cause of long life in any animal is its being tempered in a manner resembling the environing air, along with certain other circumstances of its nature, of which we will speak later; but the cause of the time of gestation is the size of the offspring. For it is not easy for large masses to arrive at [10] their perfection in a small time, whether they be animals or, one may say, anything else whatever. That is why horses and animals akin to them, though living a shorter time than man, yet carry their young longer; for the time in the former is a year, but in the latter ten months at the outside. For the same reason also the time is long in [15] elephants; they carry their young two years on account of their excessive size.
We find, as we might expect, that in all animals the time of gestation and development and the length of life aim naturally at being measured periods. By a period I mean, e.g., a day and night, a month, a year, and the times measured by these, and also the periods of the moon, that is to say, the full moon and her [20] disappearance and the halves of the times between these, for it is by these that the moon’s orbit fits in with that of the sun, the month being a period common to both.
The moon is a first principle because of its connexion with the sun and its participation in its light, being as it were a second smaller sun, and therefore she [25] contributes to all generation and development. For heat and cold varying within certain limits make things to come into being and after this to perish, and it is the motions of the sun and moon that fix the limit both of the beginning and of the end [30] of these processes. Just as we see the sea and all bodies of water settling and changing according to the movement or rest of the winds, and the air and winds again according to the course of the sun and moon, so also the things which grow out of these or are in these must follow suit. For it is reasonable that the periods of the [778a1] less important should follow those of the more important. For in a sense a wind, too, has a life and birth and death.
As for the revolutions of the sun and moon, they may perhaps depend on other principles.
It is the aim, then, of nature to count the coming into being and the end of [5] animals by the numbers of these higher periods, but nature does not bring this to pass accurately because matter cannot be easily brought under rule and because there are many principles which hinder generation and decay from being according to nature, and often cause things to fall out contrary to nature.
We have now spoken of the nourishment of animals within the mother and of [10] their birth into the world, both of each kind separately and of all in common.
BOOK V
1 · We must now investigate the qualities by which the parts of animals differ. I mean such qualities of the parts as blueness and blackness of the eyes, height and depth of pitch in the voice, and differences in colour and in hair or [20] feathers. Some such qualities are found to characterize the whole of a kind of animals sometimes, while in other kinds they occur at random, as is especially the case in man. Further, in connexion with the changes in the time of life, all animals are alike in some points, but are opposed in others as in the case of the voice and the colour of the hair, for some do not grow grey visibly in old age, while man is subject [25] to this more than any other animal. And some of these affections appear immediately after birth, while others become plain as age advances or in old age.
Now we must no longer suppose that the
cause of these and all such phenomena is the same. For whenever things are not the product of nature in [30] general nor yet characteristic of each separate kind, then none of these things is such as it is or is so developed for the sake of anything. The eye for instance exists for a final cause, but it is not blue for a final cause unless this condition be characteristic of the kind of animal. In fact in some cases this condition has no connexion with the account of the animal’s essence, but we must refer the causes to [778b1] the material and the motive principle on the view that these things come into being by necessity. For, as was said originally in the outset of our discussion, when we are dealing with definite and ordered products of nature, we must not say that each is of a certain quality because it becomes so, rather that they become so and so because [5] they are so and so, for the process of becoming attends upon being and is for the sake of being, not vice versa.
Past students of nature, however, took the opposite view. The reason for this is that they did not see that the causes were numerous, but only saw the material and efficient and did not distinguish even these, while they made no inquiry at all into [10] the formal and final causes.
Everything then exists for a final cause, and all those things which are included in the definition of each animal, or which either are for the sake of some end or are ends in themselves, come into being both through this cause and the rest. But when we come to those things which come into being without falling under the heads just [15] mentioned, their cause must be sought in the movement or process of coming into being, on the view that the differences which mark them arise in the actual formation of the animal. An eye, for instance, the animal must have of necessity (for an animal is supposed to be of such a sort), but it will have an eye of a particular kind of necessity in another sense, not the sense mentioned just above, because it is its nature to act or be acted on in this or that way.
[20] These distinctions being drawn let us speak of what comes next in order. As soon then as the offspring of all animals are born, especially those born imperfect, they are in the habit of sleeping, because they continue sleeping also within the mother when they first acquire sensation. But there is a difficulty about the earliest period of development, whether the state of wakefulness exists in animals first, or [25] that of sleep. Since they plainly wake up more as they grow older, it is reasonable to suppose that the opposite state, that of sleep, exists in the first stages of development. Moreover the change from not being to being must pass through the intermediate condition, and sleep seems to be in its nature such a condition, being as [30] it were a boundary between living and not living, and the sleeper being neither altogether non-existent nor yet existent. For life most of all appertains to wakefulness, on account of sensation. But on the other hand, if it is necessary that the animal should have sensation and if it is then first an animal when it has acquired sensation, we ought to consider the original condition to be not sleep but only something resembling sleep, such a condition as we find also in plants, for indeed at [779a1] this time animals do actually live the life of a plant. But it is impossible that plants should sleep, for there is no sleep which cannot be broken, and the condition in plants which is analogous to sleep cannot be broken.
It is necessary then for the animal to sleep most of the time because the growth [5] and the weight lie on the upper part of the body (and we have stated elsewhere that such is the cause of sleep). But nevertheless they are found to wake even in the womb (this is clear in dissections and in the ovipara), and then they immediately fall into a sleep again. This is why after birth also they spend most of their time in [10] sleep.
When awake infants do not laugh, but while asleep they both laugh and cry. For animals have sensations even while asleep, not only what are called dreams but also others besides dreams, as those persons who arise while sleeping and do many [15] things without dreaming. For there are some who get up while sleeping and walk about seeing just like those who are awake; these have perception of what is happening, and though they are not awake, yet this perception is not like a dream. So infants presumably have sense-perception and live in their sleep owing to [20] previous habit, being as it were without knowledge of the waking state. As time goes on and their growth is transferred to the lower part of the body, they now wake up more and spend most of their time in that condition. Children continue asleep at first more than other animals, for they are born in a more imperfect condition than other animals that are produced in a perfect state, and their growth has taken place [25] more in the upper part of the body.
The eyes of all children are bluish immediately after birth; later on they change to the colour which is to be theirs permanently. But in the case of other animals this is not visible. The reason for this is that the eyes of other animals are more apt to have only one colour; e.g. cattle are dark-eyed, the eye of all sheep is [30] pale, of others again the whole kind is blue or grey-eyed, and some are yellow as the majority of goats themselves, whereas the eyes of men happen to be of many colours, for they are blue or grey or dark in some cases and yellow in others. Hence, [779b1] as the individuals in other kinds of animals do not differ from one another in the colour, so neither do they differ from themselves, for they are not of a nature to have more than one colour. Of the other animals the horse has the greatest variety of colour in the eye, for some of them actually have eyes of different colour; this [5] phenomenon is not to be seen in any of the other animals, except in some men.
Why then is it that there is no visible change in the other animals if we compare their condition when newly born with their condition at a more advanced age, but that there is such a change in children? We must consider just this to be a sufficient cause, that the part concerned has only one colour in the former but several colours in the latter. And the reason why the eyes of infants are bluish and [10] have no other colour is that the parts are weaker in the newly born and blueness is a sort of weakness.
We must also gain a general notion about the difference in eyes, for what reason some are blue, some grey, some yellow and some dark. To suppose that the [15] blue are fiery, as Empedocles says, while the dark have more water than fire in them, and that this is why the former, the blue, have not keen sight by day, viz. owing to deficiency of water in their composition, and the latter are in like condition by night, viz. owing to deficiency of fire—this is not well said if indeed we are to assume sight to be connected with water, not fire, in all cases. Moreover it is [20] possible to render another account of the cause of the colours, but if indeed the fact is as was stated before in the treatise on the senses, and still earlier than that in the investigations concerning soul1—if this sense organ is composed of water and if we were right in saying for what reason it is composed of water and not of air or [25] fire—then we must assume the water to be the cause of the colours mentioned. For some eyes have too much liquid to be adapted to the movement, others have too little, others the due amount. Those eyes therefore in which there is much liquid are [30] dark because much liquid is not transparent, those which have little are blue; (so we find in the sea that the transparent part of it appears light blue, the less transparent watery, and the unfathomable water is dark or deep-blue on account of its depth). When we come to the eyes between these, they differ only in degree.
We must suppose the same cause also to be responsible for the fact that blue [780a1] eyes are not keen-sighted by day nor dark eyes by night. Blue eyes, because there is little liquid in them, are too much moved by the light and by visible objects in respect of their liquidity as well as their transparency, but sight is the movement of this part in so far as it is transparent, not in so far as it is liquid. Dark eyes are less [5] moved because of the quantity of liquid in them. For the nocturnal light is weak; at the same time also liquid is in general hard to move in the night. But if the eye is to see, it must neither not be moved at all nor yet more than in so far as it is transparent, for the stronger movement drives out the weaker. Hence it is that on [10] changing fro
m strong colours, or on going out of the sun into the dark, men cannot see, for the motion already existing in the eye, being strong, stops that from outside, and in general neither a strong nor a weak sight can see bright things because the liquid is acted upon and moved too much.
The same thing is shown also by the morbid affections of each kind of sight. [15] Cataract attacks the blue-eyed more, but what is called night-blindness the dark-eyed. Now cataract is a sort of dryness of the eyes and therefore it is found more in the aged, for this part also like the rest of the body gets dry towards old age; [20] but night-blindness is an excess of liquidity and so is found more in the younger, for their brain is more liquid.
The sight of the eye which is intermediate between too much and too little liquid is the best, for it has neither too little so as to be disturbed and hinder the movement of the colours, nor too much so as to cause difficulty of movement.
[25] Not only the above-mentioned facts are causes of seeing keenly or the reverse, but also the nature of the skin upon what is called the pupil. This ought to be transparent, and it is necessary that the transparent should be thin and white and even, thin that the movement coming from without may pass straight through it, [30] even that it may not cast a shadow by wrinkling (for this also is a reason why old men have not keen sight, the skin of the eye like the rest of the skin wrinkling and becoming thicker in old age), and white because black is not transparent, for that is just what is meant by ‘black’, what is not shone through, and that is why lanterns [780b1] cannot give light if they be made of black skin. It is for these reasons then that the sight is not keen in old age nor in the diseases in question, but it is because of the small amount of liquid that the eyes of children appear blue at first.
The Complete Works of Aristotle Page 210
