by Aristotle
The reason why the parts may be multiplied contrary to nature is the same as the cause of the birth of twins. For the reason exists already in the embryo, whenever more material gathers than is required by the nature of the part. The [15] result is then that either one of its parts is larger than the others, as a finger or hand or foot or any of the other extremities or limbs; or again if the embryo is cleft there may come into being more than one, as eddies do in rivers; as the water in these is carried along with a certain motion, if it dash against anything two systems come [20] into being out of one, each retaining the same motion; the same thing happens also with the embryos. They generally are attached near one another, but sometimes at a distance because of the movement taking place in the embryo, and especially because of the excess of material returning to that place whence it was taken away while retaining the form of that part whence it arose as a superfluity. [25]
In certain cases we find a double set of generative organs [one male and the other female].5 When such duplication occurs the one is always functional but not the other, because it is always insufficiently supplied with nourishment as being contrary to nature; it is attached like a tumour (for such growths also receive nourishment though they are a later development than the body proper and [30] contrary to nature). If the formative power prevails, both are similar; if it is altogether vanquished, both are similar; but if it prevail here and be vanquished there, then the one is female and the other male. (For whether we consider the reason why the whole animal is male or female, or why the parts are so, makes no difference.)
[35] When we meet with deficiency in such parts, e.g. an extremity or one of the other limbs, we must assume the same cause as when the embryo is altogether aborted (abortion of embryos happens frequently).
[773a1] Outgrowths differ from the production of many young in the manner stated before; monsters differ from these in that most of them are due to embryos growing together. Some however are also of the following kind, when the monstrosity affects [5] greater and more sovereign parts, as for instance some monsters have two spleens or more than two kidneys. Further, the parts may migrate, the movements being diverted and the material changing its place. We must decide whether the monstrous animal is one or is composed of several grown together by considering the vital principle; thus, if the heart is a part of such a kind then that which has one [10] heart will be one animal, the multiplied parts being mere outgrowths, but those which have more than one heart will be two animals grown together through their embryos having been confused.
It also often happens even in many animals that do not seem to be defective and whose growth is now complete, that some of their passages may have grown [15] together or others may have been diverted from the normal course. Thus in some women before now the os uteri has remained closed, so that when the time for menstruation has arrived pain has attacked them, till either the passage has burst open of its own accord or the physicians have removed the impediment; some such cases have ended in death if the rupture has been made too violently or if it has been [20] impossible to make it at all. In some boys, on the other hand, the end of the penis has not coincided with the end of the passage where the urine is voided, but the passage has ended below, so that they crouch sitting to void it, and if the testes are drawn up they appear from a distance to have both male and female generative organs. The [25] passage of the solid food also has been closed before now in sheep and some other animals; there was a cow in Perinthus which passed fine matter, as if it were sifted, through the bladder, and when the anus was cut open it quickly closed up again nor could they succeed in keeping it open.
[30] We have now spoken of the production of few and many young, and of the outgrowth of superfluous parts and also of monstrosities.
5 · Superfoetation does not occur at all in some animals but does in others; of the former some are able to bring the later formed embryo to birth, while others can only do so sometimes. The reason why it does not occur in some is that they produce [773b1] only one young one, for it is not found in solid-hoofed animals and those larger than these, as owing to their size the secretion is all used up for the one embryo. For all these have large bodies, and when an animal is large its foetus is large in proportion, [5] e.g. the foetus of the elephant is as big as a calf. But superfoetation occurs in those which produce many young because the production of more than one at a birth is itself a sort of superfoetation, one being added to another. Of these all that are large, as man, bring to birth the later embryo, if the second impregnation takes [10] place soon after the first, for such an event has been observed before now. The reason is that given above, for even in a single act of intercourse the semen discharged is more than enough for one embryo, and this being divided causes more than one child to be born, the one of which is later than the other. But when the embryo has already grown to some size and it so happens that copulation occurs again, superfoetation sometimes takes place, but rarely, since the uterus generally closes in women during the period of gestation. If this ever happens (for this also has [15] occurred) the mother cannot bring the second embryo to perfection, but it is cast out in a state like what are called abortions. For just as, in those animals that bear only one, all the secretion of the female is converted to the first formed embryo because of its size, so it is here also; the only difference is that in the former case this happens [20] at once, in the latter when the foetus has attained to some size, for then they are in the same state as those that bear only one. In like manner—since man naturally would produce many young, and since the size of the uterus and the quantity of the female secretion are both greater than is necessary for one embryo, only not so much so as to bring to birth a second—therefore women and mares are the only [25] animals which admit the male during gestation, the former for the reason stated, and mares both because of the barrenness of their nature and because their uterus is of superfluous size, too large for one but too small to allow a second embryo to be brought to perfection by superfoetation. And the mare is naturally inclined to sexual intercourse because she is in the same case as the barren among women; these latter are barren because they have no monthly discharge (which corresponds [30] to the act of intercourse in males) and mares have exceedingly little. And in all the vivipara the barren females are so inclined, because they resemble the males when the semen has collected in the testes but is not being got rid of. For the discharge of the menstrual fluids is in females an emission of semen, they being unconcocted [774a1] semen as has been said before. Hence it is that those women also who are incontinent in regard to such intercourse cease from their passion for it when they have borne many children, for, the seminal secretion being then drained off, they no [5] longer desire this intercourse. And among birds the hens are less disposed that way than the cocks, because the uterus of the hen-bird is up near the hypozoma; but with the cock-birds it is the other way, for their testes are drawn up within them so that, if any kind of such birds has much semen naturally, it is always in need of this [10] intercourse. In females then it encourages copulation to have the uterus low down, but in males to have the testes drawn up.
It has been now stated why superfoetation is not found in some animals at all, why it is found in others which sometimes bring the later embryos to birth and sometimes not, and why some such animals are inclined to sexual intercourse while [15] others are not.
Some of those animals in which superfoetation occurs can bring the embryos to birth even if a long time elapses between the two impregnations, if their kind is abundant in semen, if their body is not of a large size, and if they bear many young. For because they bear many their uterus is spacious, because they are abundant in [20] semen the generative discharge is copious, and because the body is not large but the discharge is in greater measure than is required for the nourishment wanted for the embryo, therefore they can not only form animals but also bring them to birth later [25] on. Further, the uterus in such animals does not close up because there is a quantity of the res
idual discharge left over. This has happened before now even in women, for in some of them the discharge continues during all the time of pregnancy. In women, however, this is contrary to nature, so that the embryo suffers, but in such [30] animals it is according to nature, for their body is so formed from the beginning, as with hares. For superfoetation occurs in these animals, since they are not large and they bear many young (for they have many toes and the many-toed animals bear many), and they abound in semen. This is shown by their hairiness, for the quantity [35] of their hair is excessive, these animals alone having hair under the feet and within the jaws. Now hairiness is a sign of abundance of residual matter, wherefore among [774b1] men also the hairy are given to sexual intercourse and have much semen rather than the smooth. In the hare it often happens that some of the embryos are imperfect while others of its young are produced perfect.
[5] 6 · Some of the vivipara produce their young imperfect, others perfect; the one-hoofed and cloven-footed perfect, most of the many-toed imperfect. The reason for this is that the one-hoofed produce one young one, and the cloven-footed either one or two generally speaking; now it is easy to bring the few to perfection. All the [10] many-toed animals that bear their young imperfect give birth to many. Hence, though they are able to nourish the embryos while newly formed, their bodies are unable to complete the process when the embryos have grown and acquired some size. So they produce them imperfect, like those animals which generate a grub; for some of them when born are scarcely brought into form at all, as the fox, bear, and [15] lion, and some of the rest in like manner; and nearly all of them are blind, as not only the animals mentioned but also the dog, wolf, and jackal. The pig alone produces both many and perfect young, and thus here alone we find any overlapping; it produces many as do the many-toed animals, but is cloven-footed or solid-hoofed (for there certainly are solid-hoofed swine). They bear, then, many [20] young because the nutriment which would otherwise go to increase their size is diverted to the generative secretion (for considered as a solid-hoofed animal the pig is not a large one), and also it is more often cloven-hoofed, striving as it were with the nature of the solid-hoofed animals. For this reason it produces sometimes only one, sometimes two, but generally many, and brings them to perfection before birth [25] because of the good condition of its body, being like a rich soil which has sufficient and abundant nutriment for plants.
The young of some birds also are hatched imperfect and blind; this applies to all small birds which lay many eggs, as crows, jays, sparrows, swallows, and to all those which lay few eggs without producing abundant nourishment along with the [30] young, as ring-doves, turtle-doves, and pigeons. Hence if the eyes of swallows while still young be put out they recover their sight again, for the birds are still developing, not yet developed, when the injury is inflicted, so that the eyes grow and sprout afresh. And in general the production of young before they are perfect is [35] owing to inability to continue nourishing them, and they are born imperfect because they are born too soon. This is plain also with seven-months children, for since they [775a1] are not perfected it often happens that even the passages, e.g. of the ears and nostrils, are not yet opened in some of them at birth, but only open later as they are growing, and many such infants survive.
In man males are more often born defective than females, but in the other animals this is not the case. The reason is that in man the male is much superior to [5] the female in natural heat, and so the male foetus moves about more than the female, and on account of moving is more liable to injury, for what is young is easily injured since it is weak. For this same reason also the female foetus is not perfected equally with the male in women (but they are so in the other animals, for in them [10] the female is not later in developing than the male). For while within the mother the female takes longer in developing, but after birth everything is perfected more quickly in females than in males; I mean, for instance, puberty, the prime of life, and old age. For females are weaker and colder in nature, and we must look upon the female character as being a sort of natural deficiency. Accordingly while it is [15] within the mother it develops slowly because of its coldness (for development is concoction, and it is heat that concocts, and what is hotter is easily concocted); but after birth it quickly arrives at maturity and old age on account of its weakness, for all inferior things come sooner to their perfection, and as this is true of works of art [20] so it is of what is formed by nature. For the reason just given also twins are less likely to survive in man if one be male and one female, but this is not at all so in the other animals; for in man it is contrary to nature that they should run an equal course, as their development does not take place in equal periods; but the male must [25] needs be too late or the female too early; in the other animals, however, it is not contrary to nature. A difference is also found between man and the other animals in respect of gestation, for animals are in better bodily condition most of the time, whereas in most women gestation is attended with discomfort. Their way of life is [30] partly responsible for this, for being sedentary they are full of more residual matter; among nations where the women live a laborious life gestation is not equally conspicuous and those who are accustomed to work bear children easily both there and elsewhere; for work consumes the residual matter, but those who are sedentary [35] have a great deal of it in them because not only is there no monthly discharge during pregnancy but also they do not work; therefore their travail is painful. But work exercises them so that they can hold their breath, upon which depends the ease or [775b1] difficulty of child-birth. These circumstances then, as we have said, contribute to cause the difference between women and the other animals in this state, but the most important thing is this: in some animals the discharge is small, and in some not [5] visible at all, but in women it is greater than in any other animal, so that when this discharge ceases owing to pregnancy they are troubled (for if they are not pregnant they are afflicted with ailments whenever the discharges do not occur); and they are more troubled as a rule at the beginning of pregnancy, for the embryo is able indeed [10] to stop the discharges but is too small at first to consume any quantity of the secretion: later on it takes up some of it and so alleviates the mother. In the other animals, on the contrary, the residual matter is but small and so corresponds with the growth of the foetus, and as the secretions which hinder nourishment are being [15] consumed by the foetus the mother is in better bodily condition than usual. The same holds good also with aquatic animals and birds. If it ever happens that the body of the mother is no longer in good condition when the foetus is now becoming [20] large, the reason is that its growth needs more nourishment than the residual matter supplies. (In some few women it happens that the body is in a better state during pregnancy; these are women in whose body the residual matter is small so that it is all used up along with the nourishment that goes to the foetus.)
[25] 7 · We must also speak of what is known as a ‘mole’, which occurs rarely in women but still is found sometimes during pregnancy. For they produce what is called a mole; it has happened before now to a woman, after she had had intercourse with her husband and supposed she had conceived, that at first the size of her belly [30] increased and everything else happened accordingly, but yet when the time for birth came on, she neither bore a child nor was her size reduced, but she continued thus for three or four years until dysentery came on, endangering her life, and she produced a lump of flesh which is called a mole. Moreover this condition may continue till old age and death. Such masses when expelled from the body become [35] so hard that they can hardly be cut through even by iron. Concerning the cause of this phenomenon we have spoken in the Problems; the same thing happens to the [776a1] embryo in the womb as to meats half cooked in roasting, and it is not due to heat, as some say, but rather to the weakness of the heat. (For their nature seems to be weak and unable to perfect or to put the last touches to the process of generation. Hence it [5] is that the mole remains in them till old age or at any rate for a long time, f
or in its nature it is neither perfect nor altogether a foreign body.) It is want of concoction that is the reason of its hardness, for half-cooking is also a sort of want of concoction.
A difficulty is raised as to why this does not occur in other animals, unless indeed it has entirely escaped observation. We must suppose the reason to be that [10] woman alone among animals is subject to troubles of the uterus, and alone has a superfluous amount of menstrual fluids and is unable to concoct them; when, then, the embryo has been formed of a liquid hard to concoct, then comes the so-called mole into being, and this happens naturally in women alone or at any rate more than in other animals.
[15] 8 · Milk is formed in the females of all internally viviparous animals, becoming useful for the time of birth. For nature has made it for the sake of the nourishment of animals after birth, so that it neither fails at this time at all nor yet is at all superfluous; this is just what we find happening, unless anything chance [20] contrary to nature. In the other animals the period of gestation does not vary, and so the milk is concocted in time to suit the moment, but in man, since there are several times of birth, it must be ready at the first of these; hence in women the milk is useless before the seventh month and only then becomes useful. That it is only [25] concocted at the last stages is what we should expect to happen also as being due to a necessary cause. For at first such residual matter when secreted is used up for the development of the embryo; now the nutritious part in all things is the sweetest and the most concocted, and thus when all such elements are removed what remains must become of necessity bitter and ill-flavoured. As the embryo is perfecting, the [30] residual matter left over increases in quantity because the part consumed by the embryo is less; it is also sweeter since the easily concocted part is less drawn away from it. For it is no longer expended on moulding the embryo but only on slightly increasing its growth, the embryo being now as it were stationary because it has reached perfection (for in a sense there is a perfection even of an embryo). [776b1] Therefore it comes forth from the mother and changes its mode of development, as now possessing what belongs to it; and no longer takes that which does not belong to it; and it is at this season that the milk becomes useful.