Aristotle · a new plain-English translation from the original language
1| On Youth and Old Age. On Life and Death. We must now speak about youth and old age, and about life and death; and at the same time it is probably necessary to state the causes connected with respiration, since for some animals living and not living turn on this. Now since soul has been determined in other works, and it is clear that its substance cannot be a body, yet it is plain that it exists in some part of the body, and in that part which is one of those having power among the parts. As for the other parts or powers of the soul—whichever way one ought to call them—let them be set aside for now. But of the things that are called animals and are said to live, in those that possess both of these (I mean both being an animal and living), it is necessary that it be the same and one part in virtue of which it lives and in virtue of which we call it an animal. For an animal, insofar as it is an animal, cannot fail to live; but insofar as a thing lives, it is not necessary that it be an animal on that account—for plants live but do not have perception, and it is by perceiving that we distinguish the animal from the non-animal. In number, then, this part must necessarily be one and the same, but in being it is several and different things,
2| for being an animal and living are not the same thing. Since, then, of the private senses there is some one common sense-organ, to which the perceptions in actuality must arrive, and this would be midway between what is called the front and the back (for we call front that toward which our perception is directed, and back what is opposite to it); and further, since the body of all living things is divided by up and down (for all things have an up and a down, so that even plants do), it is clear that the nutritive principle would have its seat midway between these. For the part by which nourishment enters we call up, looking to it in itself and not to the surrounding whole, and down is that by which it first releases the residue. This is the reverse in plants and in animals: for man, because of his upright posture, has this above all the other animals—that his upper part is turned toward the upper part of the universe, while in the other animals it is intermediate; but plants, being motionless and taking their nourishment from the earth, necessarily always have this part turned downward. For roots are analogous in plants to what is called the mouth in animals, the part through which some take their nourishment from the earth, others through themselves.
3| There being three parts into which all the complete animals are divided—one by which they receive nourishment, one by which they discharge the residue, and a third, the middle of these—this in the largest animals is called the chest, and in the others the analogous part, though it is more clearly articulated in some than in others. Those of them that are capable of locomotion have, in addition, parts serving this function, by which they will carry the whole trunk—legs and feet and whatever else has the same power as these. But the principle of the nutritive soul plainly lies in the middle of the three parts, both according to perception and according to reasoned account. For many animals, when either part is removed—the so-called head, or the receiver of nourishment—go on living with whichever part is the middle one. This is evident in the case of insects, such as wasps and bees; and many of the non-insects too, when divided, are able to live because of the nutritive part. Such a part is one in actuality, but several in potentiality, for it is constituted in the same way as plants: plants too, when divided, live apart, and many trees come to be from one starting point.
4| For what reason some things cannot live when divided, while others among plants can be propagated by cutting, will be a separate account. But plants and the class of insects are alike, at least in this respect. And it is necessary that the nutritive soul too be one in actuality in the things that have it, but several in potentiality; and likewise the perceptive principle, for the divided parts of these creatures evidently retain perception. But when it comes to preserving their nature, plants can do so, while these creatures cannot, because they do not have organs for self-preservation, and are deficient—some in what would take the nourishment, others in what would receive it, and others in both of these together. For such animals resemble many animals grown together into one; but the best-constituted animals do not undergo this, because their nature is, as far as possible, one. This is why some, when their parts are divided, produce a slight perception, because they have some affection of the soul in them: for when the entrails are separated they produce motion, as tortoises do when the heart has been removed.
5| Further, this is clear both in plants and in animals: in plants, if one examines the generation from seeds and both graftings and cuttings. For the generation of seeds occurs, in all cases, from the middle: since all seeds have two valves, joined where they have grown together, and the middle is common to each of the two parts; for from there both the stalk and the root grow out in the things that sprout, and the starting point is their middle. In graftings and cuttings this happens especially in connection with the nodes: for the node is in a way a starting point of the branch, and at the same time a middle, so that people either remove this or insert into this, so that either the branch or the roots may grow from it, on the ground that the starting point comes from the middle of stalk and root. And in the blooded animals the heart comes to be first. This is clear from what we have observed in cases where it is still possible to see the animal in the process of coming to be. So in the bloodless animals too the part analogous to the heart must come to be first. That the heart is the starting point of the veins has been stated earlier, in the works on the parts of animals;
6| and that blood is the final nourishment for the blooded animals, out of which the parts come to be. It is clear, then, that the power of the mouth performs one function with regard to nourishment, and that of the belly a different one. But the heart is the most authoritative, and puts the finishing touch on it. So it is necessary that the starting point of both the perceptive and the nutritive soul be in the heart, for the blooded animals: for the functions of the other parts concerning nourishment exist for the sake of this one's function. For the authoritative thing must persist with a view to that for the sake of which it exists, and not be counted among the things that exist for its sake—as a doctor exists for the sake of health, not the reverse. And indeed the authoritative element of the senses is in this part, for all the blooded animals: for it is necessary that the common sense-organ of all the sense-organs be in this. And we plainly see two senses converging there, taste and touch, so that the others must do so as well: for in the case of the other sense-organs it is possible for the motion to be produced elsewhere and then travel to this part, but taste and touch have no tendency toward the upper region at all. And apart from these considerations, if living resides in this part for all animals, it is clear that the perceptive principle must be there too;
7| for insofar as a thing is an animal, in that respect we also say it lives, and insofar as it is perceptive, in that respect we say the body is an animal. As for why some of the senses evidently converge on the heart while others are in the head (which is also why some think that animals perceive by means of the brain), the cause of this has been stated separately elsewhere. So then, from what has been said, it is clear on the evidence of the observed facts that in this part, and in the middle of the body's three parts, lies both the principle of the perceptive soul and that of the growth-producing and nutritive soul.
8| And by argument too, since we see nature in all things doing the finest thing possible from among the possibilities. Now since each of the two principles lies in the middle of the substance, each of the two parts will most fully perform its own work — the part that works up the ultimate nourishment and the part that receives it; for in this way it will be next to each of them, and the middle region of such a thing is the region of a ruler. Further, that which uses and that which is used must differ. And just as with the capacity, so it might be with the manner too — as with pipes and that which moves the pipes, namely the hand. If then the animal is defined by having a perceptive soul, then in blooded animals this principle must be in the heart, and in bloodless animals in the part analogous to it. Now all the parts, and the whole body of animals, have a certain connate natural heat; that is why, while living, they appear warm, but when they die and are deprived of life, the opposite holds. So the principle of this heat must necessarily be in the heart in blooded animals, and in the analogous part in bloodless ones; for it is by natural heat that all of them work up and concoct their nourishment, and above all the most sovereign part does. That is why, when the other parts are chilled, life still persists, but when the heat in this part is chilled, life is destroyed entirely, because the principle of heat for all the parts depends on this one, and the soul is, as it were, kindled as a fire within these parts — in the analogous part for bloodless animals, and in the heart for blooded ones. It is necessary, then, that being alive and the preservation of this heat hold together at once, and that what is called death be the destruction of this heat.
9| But indeed we observe two kinds of destruction of fire, wasting away and quenching. We call the one that comes about by the fire's own agency a wasting away, and the one that comes about at the hands of its opposites a quenching — the one by old age, the other by force. Now it turns out that both kinds of destruction come about through the same cause: for when the nourishment falls short, the heat being unable to take up nourishment, destruction of the fire results. For the opposite, by stopping the concoction, prevents the fire from being nourished; but sometimes a wasting away results because more heat is gathered together on account of there being no respiration and no cooling; for in this way too the heat, being gathered together in quantity, quickly uses up the nourishment, and it uses it up before the exhalation can arrive in its place. That is why not only does the lesser fire waste away next to the greater, but the very flame of a lamp, when placed within a larger flame, is itself burned up, just as anything else combustible is. And the cause is that the larger flame gets to the nourishment present in the flame first, before another supply can come to it, while the fire itself continues always coming to be and flowing like a river, though this escapes notice because of its speed. It is clear, then, that if the heat is to be preserved (and this is necessary, if the thing is going to live), some cooling of the heat in the principle must come about.
10| One can take as an example of this what happens with coals being smothered: for if they are continuously covered over by what is called a choke-pot, they are quickly extinguished; but if one repeatedly, close together, removes and replaces the cover, they remain aglow for a long time. Now burial in ash preserves the fire: for it is not prevented from breathing out on account of the porousness of the ash, and yet the ash also blocks off the surrounding air, so that it does not extinguish the fire by the abundance of the heat present within it. But concerning this cause — that the opposite result happens to fire that is buried in ash and to fire that is smothered outright (the one wastes away, the other persists for a longer time) — this has been discussed in the Problems.
11| Since every animal has soul, and soul does not exist without natural heat, as we have said, in plants the assistance that comes through their nourishment and through what surrounds them proves sufficient for the preservation of the natural heat. For nourishment, too, produces cooling as it enters, just as it does in human beings when they first take food; whereas fasting produces heat and causes thirst; for the air, being unmoved, is constantly being heated, but when the nourishment enters, it cools as it is set in motion, until it undergoes concoction. But if the surrounding air exceeds in coldness on account of the season, strong frosts occurring, the plant is dried out; or if in summer strong heat-waves occur and the moisture drawn up from the earth is unable to cool it, the heat is destroyed as it wastes away, and at these seasons the trees are said to become blighted and struck as if by a star. That is why people also place certain kinds of stones beneath the roots, and water in vessels, so that the roots of the plants may be cooled. And of animals, since some live in water and others make their dwelling in air, they procure their cooling from these media and by means of them, some by water and some by air. But in what manner and how this happens must be stated once we have applied our argument more closely to it.