Aristotle · a new plain-English translation from the original language
1| Book 37. Problems Concerning the Whole Body Why is it that although the body is always in a state of flux, and an efflux is constantly occurring from its residues, the body is not made lighter unless one sweats? Is it because the excretion that occurs is smaller? For when it changes from liquid into air it becomes greater from less, since what is separated out becomes more in bulk, so that the excretion takes a longer time.
2| But why is this so? Is it because the exit is through narrower passages? For what is viscous and sticky is excreted together with the liquid because of its admixture with it, but it cannot be excreted together with breath alone. And it is this viscous matter above all that causes distress. That is why vomiting relieves one more than sweating does, because it draws this substance out along with it, being thicker and more bodily in nature. Or is it also because this region, where the viscous and sticky matter is, is far from the flesh, so that it is a task to move it out, whereas it is near to the stomach cavity? For it either arises in the stomach or near it; that is also why it is otherwise hard to expel.
3| Why does rubbing the body make it fleshy? Is it because heat is the most productive of growth of all things in the body? For where heat is present, the bulks of things become greater, because it is always in motion and tends to move upward and to turn the liquids within us into breath, which is what happens in rubbing; but when heat is lacking, the body wastes and diminishes. Or is it because the flesh becomes more bulky than the nourishment on account of the heat? For everything hot draws moisture to itself, and the nourishment that is distributed into the flesh is moist, and the flesh receives the nourishment better because of its looseness; for becoming more porous it is better able to receive it, like a sponge. Now rubbing makes the flesh well-aerated and porous, and prevents congestions from forming in the body. And when this does not happen, wastings away do not occur either; for both undernourishments and wastings arise from things that have collected together. Bodies that become better-aerated, more porous, and more even are likely to grow in bulk more, since they become both more receptive of nourishment and more able to release excretions, because it is not proper for health to make the flesh dense, but rather to make it porous. For just as a city is healthy when it is well-aired, and a place well-aired (which is also why the sea is healthy), so too a body that is well-aired is healthier than one in the opposite condition.
4| For it is necessary either that nothing at all be present, or that one get rid of it as quickly as possible; and the body must be in such a state that as soon as it takes in the residue it excretes it, and that it be always in motion and never at rest. For what remains stationary putrefies, just as water that is not in motion does; and putrefying it produces disease; but what is excreted departs before it is corrupted. This, then, does not occur when the flesh is dense (for the passages are, as it were, blocked up), but it does occur when the flesh is porous. That is why one should not walk about naked in the sun (for the flesh contracts and becomes thoroughly stripped of its substance; for the moisture within remains, but the moisture on the surface departs by evaporation, just as roasted meats have more moisture within them than boiled ones do), nor should one walk about with the chest bared in the sun (for the sun takes away from the best-built parts of the body that which least needs to be taken away), but rather one should dry out the inner parts. From there, then, because it is far off, it is not possible to draw off sweat except with exertion; but from these outer parts, because they are readily accessible, it is easy to use up the moisture. Why is it that when we have been chilled we burn and feel pain more from the same degree of heat? Is it because, through its density, the flesh confines the heat that strikes it? That is why lead is hotter than wool. Or is it that the passage of the heat becomes forcible because the body has been made rigid by cold?
5| Why do dry rubbings make the flesh solid? Is it because, as the heat arises through the rubbing, the moisture is used up? In addition to this, the flesh becomes denser as it is rubbed; and everything that undergoes a great deal of rubbing becomes dense and solid. One can observe this in many cases: for dough, or clay, or anything else of this sort, if you pour water on it and work it, remains liquid and sloshing, but if you apply more rubbing to it, it quickly becomes dense and solid and sticky. Why do rubbings produce more flesh than running does? Is it because running chills the flesh all around and makes it unreceptive of nourishment, since some parts are shaken downward while others, as a great deal of the natural heat is expended, are thinned out completely and separated off into breath? But the palm, through rubbing, makes the flesh porous and receptive of nourishment. And the touch from outside, opposing the flow of matter through its compression, holds it together more, and produces a rebound of the flesh.