by Aristotle
8 · Why is it more fatiguing to the arm if one casts with the hand empty than [881b1] with a stone in it? Is it because the movement is more spasmodic if the hand be empty, for the hand has nothing to rest upon, such as the thrower finds in the missile which he holds in his hand? Similarly the competitor in the pentathlon finds resistance in the weights which he holds, and the runner in his arms which he [5] swings; so the former jumps farther if he holds weights than if he does not, and the latter runs more quickly if he swings his arms than if he does not do so.
9 · Why is it that quick running causes a tendency to disease in the head both in man and in the other animals? Yet generally speaking running appears to draw [10] the excretions downwards, as does walking; for which reason also those who walk much grow fat in the legs, because both the nourishment and the excretions settle down from the upper into the lower parts. Is it true that while motion has the same effect, yet quick motion, owing to the strain and the holding of the breath which it involves, causes heat in the head and inflates the veins in it and renders them liable [15] to be affected by external influences, such as cold and heat, and by the contents of the trunk; and that if these can enter the head, disease is necessarily engendered in that region?
10 · Why is it more fatiguing to walk on level than on uneven ground, whereas one can walk more quickly on an even than on an uneven road? Is it [20] because it is less fatiguing if one does not move continually in the same position, and this is the case rather in traversing uneven ground? On the other hand one progresses more quickly the less one’s movement is contrary to nature. On even ground, therefore, the raising and planting of the foot is a slight but frequent movement, while the opposite occurs on uneven ground. Now to raise the foot is unnatural (for raising anything requires an effort); and the slight movement of [25] raising the foot at each step becomes considerable when repeated many times.
11 · Why is it more fatiguing to lie down on a flat than on a concave surface? Is it for the same reason that it is more fatiguing to lie on a convex than on a flat surface? For the weight being concentrated in one place in the sitting or [30] reclining position causes pain owing to the pressure. This is more the case on a convex than on a straight surface, and more on a straight than on a concave; for our body assumes curved rather than straight lines, and in such circumstances concave surfaces give more points of contact than flat surfaces. For this reason also couches and seats which yield to pressure are less fatiguing than those which do not do so. [35]
12 · Why are short walks fatiguing? Is it because they involve abrupt change, for they necessitate coming often to a standstill? Now frequent change from one extreme to another is fatiguing, for it does not allow one to become accustomed to either extreme, and this is tiring; and one cannot become accustomed [882a1] to both things at once.
13 · Why is it that those who ride on horseback water more freely at the eyes the quicker the horse goes? Is it because the stream of air which meets them is colder according as it is for a shorter time in contact with the body (as happens in [5] the case of naked runners), and it is the cold which makes the eyes water? Or is the reason the contrary of this, namely, that heat makes the eyes water (the sun, for instance), and movement engenders heat? Or is it due to the impact of the air? For as blasts of wind coming from an opposite direction trouble the eyes, so the air all [10] the more deals a gentle blow the quicker the horse is driven.
14 · Why is it that the other parts of the body become more fleshy when subjected to friction, but the stomach becomes leaner? Or is it true that the stomach does not become gradually leaner but solider? The flesh, however, is not similarly [15] affected, and this is the point of the problem; for, speaking generally, the stomach does become leaner as the result of exercise and exertion. The reason is that the fat parts, and those which naturally admit of more expansion, liquefy when heated. Now the skin naturally admits of expansion; but, because it very quickly fattens, it [20] always contains some fat, unless any disease is present. The reason for this is that it is near the nourishment. Since, therefore, generally speaking, fat is not natural but adventitious, and is not one of the necessary constituents of the body, as is the flesh, the movements set up by exercise and friction warm and melt it and distribute the [25] superfluous nourishment in the other portions of the body. It is for this reason that sitting still makes the stomach fat and the rest of the body thin; whereas movement and friction make the stomach thin and fill out the rest of the body.
15 · Why is it that after long and violent walking or running, if one stands on [30] tiptoe, the heels quiver and are hastily drawn1 down again? Is it because, owing to the continuity and violence of the movement, the quivering of the muscles in the man does not cease? For the mind often controls the body as a whole, but does not control certain parts of it, when they have been set in motion in a certain way, the [35] heart, for example, and the sexual organ. The reason is that a considerable quantity of breath is consumed by heat round the muscles, which does not cool off immediately a man comes to a standstill. This breath, therefore, is drawn down, making him quiver, as it were dragging him down by its movement, and leaves him little control over the most distant part of his body—in this case over his heels. A similar phenomenon occurs in the trembling of the lower lip in those who are angry.
[882b1] 16 · Why is it that those who are not running very hard respire rhythmically? Is it because every rhythm is measured by a definite movement, and the movement at regular intervals which occurs in running is of this nature? As soon, therefore, as they begin to run they respire; and so the respiration taking place at [5] equal intervals, because it is measured out by a uniform movement, creates a rhythm. Or is it because all respiration without exception takes place at intervals in those who respire naturally and do not hold their breath? The rhythm then is not obvious in those who are sitting or walking, because the movement of the body is [10] slight; and in those who are running vigorously we cannot get a complete view of the rhythm of the respiration, because our senses cannot follow the movement. But in those who are running moderately fast the movement allows the measure observed by the breathing to be perceptible, and so shows the rhythm.
17 · Why is it that, when we are running, the air seems to turn into breath? [15] Is it because, while we are moving in the act of running, we set in motion a stream of air continuous with our bodies, and this is breath? That is why the air not only seems to turn into breath, but actually does so. Or is it because in running we come into collision with the air, and, when this happens, we have a more acute perception of the air owing to the movement? It is only natural, therefore, that it should seem [20] to us to turn into breath; for the phenomenon occurs through the rush of our movement.
18 · Why is it that one is more liable to fall when running than when walking? Is it because in the former case one raises oneself higher before moving? For this is the difference between running and walking.
[25] 19 · Why is it that in ascending a slope our knees feel the strain, and in descending our thighs? Is it because when we ascend we throw the body upwards and the jerk of the body2 from the knees is considerable, and so we feel the strain in the knees? But in going downhill, because the weight is carried by the legs, we are supported by our thighs, and so they feel the strain. Furthermore, whatever is [30] unnatural causes strain and pain. Now it is natural for the knees to bend forwards and the thighs to bend backwards. In going uphill then the knees are bent backwards owing to one’s desire to support oneself, but in going downhill the thighs [35] are bent forwards because the body has a tendency to fall forwards.
20 · Why is it that on journeys the middle of the thigh is the part which feels the strain most? Is it because in anything that is prolonged and continuous and fixed the strain falls most upon the centre, and so it is most likely to break at that point? Now the thigh is of this nature, and so it is in the middle of it that we feel the strain [883a1] most.
21 · Why is it that persons of a moist temperament easily
choke as a result of exertion and through heat? Is it because their moisture when heated becomes air and the excess of it burns more fiercely? When, therefore, it cannot find its way out [5] owing to its abundance, the process of cooling does not take place; and so it quickly catches fire owing to the natural and adventitious heat. It is for this reason that perspiration induced by taking physical exercise, and by exerting oneself generally, and the emission of breath are beneficial; for breath is formed by the separation and rarefaction of moisture. [10]
22 · Why is it that bodies of an equable temperament often feel weariness but throw it off more easily? Is the cause the same in both cases? For that which is equable is uniform, and that which is uniform is the more subject to similar influences; so if any part suffers, the whole straightaway suffers in sympathy. But that which is not equable, being more disunited, is not sympathetically affected by [15] its parts. A body of equable temperament therefore often feels weariness, but throws it off more easily, because the whole body shares it; for the suffering, being distributed over a larger area, is weaker and therefore more easily got rid of. But a body which is not of an equable temperament, inasmuch as it has no communion with its members, is less often afflicted with weariness, but has greater difficulty in [20] shaking it off; for its suffering is acute.
23 · Why is it more fatiguing to walk on level than on uneven ground, whereas one can walk more quickly on an even than on an uneven road? Is it because it is least fatiguing if one does not move continually in the same position, and this is the case rather in traversing uneven ground?3 But one travels more [25] quickly when the foot has to be lifted less in any equal period of time. On level ground the raising of the foot is a slight but frequent movement, on uneven ground the reverse; but the slight4 movement of raising the foot at each step becomes considerable when repeated many times.
24 · Why is it that in descending a slope we feel the strain most in the thighs, [30] and in ascending in the legs? Is it because in ascending the strain is due to the raising of the body? For the whole body becomes a burden; and so the part upon which it all rests and with which we raise it (that is, the legs) feels the strain most. For the leg is an extremity, having length but not having width, as the foot has; consequently it is shaken. So we may cite in illustration the fact that we move [35] weights with the shoulder and rest them upon it, and therefore feel the strain most in the shoulder. But when we are descending, the strain is caused by the body falling downwards and thrusting us forward unnaturally, so that we feel the strain most in the part on which it falls most and which it shakes. Now the leg remains unaffected, and the trunk forms the weight; but it is the thigh which receives the weight and is [883b1] shaken, because it has extension and is forced from above into a bent position where the trunk presses on it.
25 · Why is it that a journey seems longer when we traverse it without [5] knowing its length than when we do know it, all other conditions equal? Is it because to know its length is to be able to connect a number with it, and the indeterminate is always more than the determinate? Just as, therefore, if one knows that a journey is a certain length, it must necessarily be finite, so, if one does not know, as though the proposition was convertible, the mind draws a false conclusion, and the distance appears infinite. Furthermore, a quantity is determinate, and that which is [10] determinate is a quantity; therefore when a thing appears not to be determinate, it appears to be as it were infinite, because that which is of a nature to be determined, if it is not so, is infinite; so that what appears not to be determined necessarily appears in a sense unlimited.
26 · Why is it that the thighs feel fatigue more than the legs? Is it because [15] they are nearer to the part of the body which contains the excrement, so that, when that part overflows with heat owing to the movement, the thighs contract more readily and to a greater extent? Or is it because the thighs are more closely connected by growth with one another, for they suffer considerably owing to the separation of what is really continuous? For indeed, if one feels fatigue when there [20] is no excrement in the body, even so it is the thighs and loins which suffer more than the other parts. Or is it because, just as swellings in the groin are caused, if one receives a blow, owing to the close connexion of the veins and sinews, so the thigh is similarly affected? For the thigh is nearer than the leg to the source of the veins. Or is it because the thigh remains more in the same position than the legs, and this is [25] more fatiguing? Or is it because the thigh is fleshy, and therefore the natural heat5 there is considerable?
27 · Why is it that in some people sores are formed as the result of exertion? Is it because, when the body contains impurities, movement heats it and causes other excretions to exude with the perspiration? These excretions, being thick and containing harmful humours of an acid, bitter, and salty nature, cannot be expelled [30] owing to their thickness, but swell up through the flesh and cause sores owing to the bitterness of the humour which they contain.
28 · Why is it that food is not given immediately after exercise and after medicine has been administered? It is because the body is still being purged and has not yet rested from its toil, and the excretions have not yet been expelled? [35]
29 · Why is it more difficult to run than to walk? Is it because the runner has a heavier burden, since, when he is raised in the air, he has his whole weight to support? But a man who is walking continues to put his weight on the part of him which is at rest, like a man leaning against a wall.
30 · Why is it that one does not feel hungry immediately after exercise? Is it [884a1] because liquefaction still remains until the concoction of anything is complete? Or is it owing to the breath which the exertion engenders from the moisture? Or is it owing to the thirst which is due to the heat caused by the exertion? All these possible causes are present. [5]
31 · Why is it that those who are fatigued and those who are suffering from phthisis are apt to emit semen during sleep? Is it because generally speaking those who are warm and moist are inclined to do so, since the semen naturally has these characteristics? Now such a thing is most likely to happen in persons in these conditions, when the heat engendered by sleep is added; for the body requires a [10] slight impulse only, which must be internal and not external. This condition is fulfilled in those who are suffering from phthisis and in those who are fatigued; the latter being full of hot liquid owing to their fatigue and movement, and the former owing to their state of flux and the heat engendered by their inflamed condition. [15]
32 · Why is it more difficult to apply prolonged friction oneself to the left leg than to the right? Is it because, though our right is the side which is capable of exertion, yet the rubbing of the left leg, since it involves a distorted attitude, is unnatural, and anything which is unnatural is difficult? The difficulty of rubbing the right side with the left hand is not obvious, because the left hand has no strength [20] whichever side it is applied to.
33 · Why is it healthy to reduce the amount of nourishment and to increase the amount of exercise? Is it because abundance of excretion is the cause of disease? Now this is due either to excess of nourishment or to lack of exercise. [25]
34 · Why should the flesh be made rare rather than dense in order to promote health? For just as a city or locality is healthy which is open to the breezes (and that is why the sea too is healthy), so a body is healthier in which the air can circulate. For either there ought to be no excrement present in the body, or else the [30] body ought to get rid of it as soon as possible and ought to be in such a condition that it can reject the excrement as soon as it receives it and be always in a state of motion and never at rest. For that which remains stationary putrefies (water, for example), and that which putrefies and does not move causes disease; but that which is [35] rejected passes away before it becomes corrupt. This then does not occur if the flesh is dense, the ducts being as it were blocked up, but it does happen if the flesh is rare. One ought not, therefore, to walk naked in the sun; for the flesh thereby solidifies and acquir
es an absolutely fleshy consistency, and the body becomes moister, for the internal moisture remains, but the surface moisture is expelled, a process which [884b1] also takes place in meat when it is roasted rather than boiled.6 Nor ought one to walk about with the chest bare; for then the sun draws the moisture out of the best constructed parts of the body, which least of all require to be deprived of it. It is rather the inner parts of the body which should be submitted to this process; for, because they are remote, it is impossible to produce perspiration from them except [5] by violent effort, but it is easy to produce it from the chest because it is near the surface.