The origin of disease is plain, of course, to everybody. For seeing that there are four elements of which the body is compacted,—earth, fire, water and air,—when, contrary to nature, there occurs either an excess or a deficiency of these elements, or a transference thereof from their native region to an alien region; or again, seeing that fire and the rest have each more than one variety, every time that the body admits an inappropriate variety, then these and all similar occurrences bring about internal disorders and disease. For when any one element suffers a change of condition that is contrary to nature, all its particles that formerly were being cooled become heated, and the dry presently become moist, and the light heavy, and they undergo every variety of change in every respect. For, as we maintain, it is only the addition or subtraction of the same substance from the same substance in the same order and in the same manner and in due proportion which will allow the latter to remain safe and sound in its sameness with itself. But whatsoever oversteps any of these conditions in its going out or its coming in will produce alterations of every variety and countless diseases and corruptions. Again, in the structures which are naturally secondaryCf. 41 D ff. in order of construction, there is a second class of diseases to be noted by him who has a mind to take cognizance of them. For inasmuch as marrow and bone and flesh and sinew are compacted from the elements,—and blood also is formed from the same constituents, although in a different way,— most of the other maladies come about like those previously described, but the most severe of them have dangerous results for the reason following: whenever the production of these secondary substances proceeds in the reverse direction, then they are corrupted. For in the order of nature flesh and sinews arise from blood,Cf. 74 D. the sinew from the fibrine because of its kindred quality, and flesh from the coagulated substance which coagulates on its separation from the fibrine; and further, the substance which is derived from the sinews and flesh, being viscid and oily,i.e., the synovial fluid. not only glues the flesh to the substance of the bones but also feeds and increases the bone itself which encloses the marrow, while that which is formed of the purest kind of triangles, very smooth and very oily, filters through the density of the bones, and, as it oozes and drips from the bones, moistens the marrow. Now when each of these substances is produced in this order, health as a rule results; but if in the reverse order, disease. For whenever the flesh is decomposed and sends its decomposed matter back again into the veins, then, uniting with the air, the blood in the veins, which is large in volume and of every variety, is diversified by colors and bitter flavors, as well as by sharp and saline properties, and contains bile and serum and phlegm of every sort.

For when all the substances become reversed and corrupted, they begin by destroying the blood itself, and then they themselves cease to supply any nourishment to the body; for they move through the veins in all directions and no longer preserve the order of their natural revolutions, being at enmity with themselves because they have no enjoyment of themselves, and being at war also with the established and regular constitution of the body, which they corrupt and dissolve. Therefore all the oldest part of the flesh that is decomposed becomes tough and is blackened by the continued combustion; and because it is eaten away on every side it is bitter, and therefore dangerous in its attack on any part of the body that is not as yet corrupted. And at one time the black matter acquires a sharpness in place of its bitterness, when the bitter substance becomes more diluted; and at another time the bitter substance acquires a redder color through being dipped in blood, while if the black matter is blended with this it turns greenish; and again, whenever new flesh also is decomposed by the fire of the inflammation, a yellow matter is commingled with the bitter substance. To all these humors the general designation bile has been given,Cf. 71 B. either by certain physicians or by someone who was capable of surveying a number of dissimilar cases and discerning amongst them one single typeCf. 68 D. worthy to give its name to them all. All the rest that are counted as species of bile have gained their special descriptions in each case from their colors. Serum is of two kinds: one is the mild whey of the blood; the other, being derived from black and acid bile, is malignant whenever it is imbued with a saline quality through the action of heat; and this kind is termed acid phlegm. Another kind involves air and is produced by dissolution from new and tender flesh. And when this is inflated and enclosed by a fluid, and when as a result of this process bubblesCf. 66 B. are formed which individually are invisible because of their small size but in the aggregate form a mass which is visible, and which possess a color which appears white owing to the foam created,—then we describe all this decomposition of tender flesh intermixed with air as white phlegm. And the whey of phlegm that is newly formed is sweat and tears, and all other such humors as pour forth in the daily purgings of the body. And all these are factors in disease, whenever the blood is not replenished naturally from meats and drinks but receives its mass from opposite substances contrary to Nature’s laws.

Now, when the flesh in any part is being decomposed by disease, but the bases thereof still remain firm, the force of the attack is reduced by half, for it still admits of easy recovery; but whenever the substance which binds the flesh to the bonesCf. 82 D. becomes diseased and no longer separates itself at once from them and from the sinews, so as to provide food for the bone and to serve as a bond between flesh and bone, but becomes rough and saline instead of being oily and smooth and viscid, owing to its being starved by a bad regimen,—then, every such substance, as it undergoes these affections, molders away beneath the flesh and the sinews and withdraws from the bones; while the flesh falls away with it from the roots and leaves the sinews bare and full of saline matter, and by falling back itself into the stream of the blood it augments the maladies previously described. But although these bodily ailments are severe, still more grave are those which precede them, whenever the bone by reason of the density of the flesh fails to receive sufficient inspiration, and becoming heated because of its moldiness decays and does not admit its nutriment, but, on the contrary, falls back itself, as it crumbles, into its nutriment which then passes into flesh, and this flesh falling into, the blood causes all such maladies to be more violent than those previously described. And the most extreme case of all occurs whenever the substance of the marrow becomes diseased either from deficiency or from excess; for this results in the gravest of diseases and the most potent in causing death, inasmuch as the whole substance of the body, by the force of necessity, streams in the reverse direction. A third class of diseases takes place, as we must conceive, in three ways, being due partly to air, partly to phlegm, and partly to bile. Whenever the lungs, which are the dispensers of air to the body, fail to keep their outlets clean through being blocked up with rheums, then the air, being unable to pass one way while entering by another way in more than its proper volume, causes the parts deprived of respiration to rot, but forces and distorts the vessels of the veins, and as it thus dissolves the body it is itself shut off within the center thereof which contains the midriff; and as a result of this countless diseases of a painful kind are produced, accompanied by much sweating. And often, when the flesh is disintegrated, air which is enclosed in the body and is unable to pass out brings about the same pangs as those caused by the air that enters from without; and these pangs are most severe when the air surrounds the sinews and the adjacent veins and by its swelling up strains backwards the tendons and the sinews attached to them; hence it is actually from this process of intense strain that these maladies have derived their names of tetanus and opisthotonus.

Of these maladies the cure also is severe for what does most to relieve them is, in fact, an attack of fever. White phlegm, also, is dangerous when it is blocked inside because of the air in its bubbles; but when it has air-vents outside the body it is milder, although it marks the body with spots by breeding white scabs and tetters and the maladies akin thereto. And when this phlegm is blended with black bile and spreads over the revolutions of the head, which are the most divine, and perturbs them, its action is more gentle during sleep, but when it attacks persons who are awake it is harder to shake off; and because it is a disease of the sacred substance it is most justly termed the sacred disease.i.e., epilepsy; Cf. 916 A. Phlegm that is sharp and saline is the fount of all the maladies which are of the nature of catarrhs; and these have received all kinds of names because the regions into which they flow are of all varieties. All those diseases which are called inflammations, owing to the burning and inflaming of the body which they involve, are caused by bile. This, when it gains an external outlet, boils and sends up all kinds of eruptions; but when it is confined inside it produces many burning diseases; and of these the gravest occurs when the bile, being mixed with pure blood, displaces the matter of the fibrine from its proper position. For this fibrine is dispersed through the blood in order that the blood may have a due proportion of both rarity and density, and may neither flow out from the porous body through being liquefied by heat, nor yet prove immobile through its density and circulate with difficulty in the veins. Of these qualities the fibrine preserves the due amount owing to the nature of its formation.Cf. 82 D. Even when anyone collects together the fibrine of blood that is dead and in process of cooling, all the rest of the blood turns liquid; but if the fibrine is left alone as it is, it acts in combination with the surrounding cold and rapidly congeals the blood. As the fibrine, then, has this property, bile, which is naturally formed of old blood and dissolved again into blood from flesh, penetrates the blood gradually at first, while it is hot and moist, and is congealed by this property of the fibrine; and as it becomes congealed and forcibly chilled it causes internal cold and shivering.

But when the bile flows in with more volume, it overpowers the fibrine by the heat it contains, and shakes it into disorder by its boiling up; and should it be capable of thus overpowering the fibrine continuously, it penetrates to the substance of the marrow and loosens from thence, by burning, the mooring-ropes of the soul,Cf. 73 D, 81 D. as it were of a ship, and sets it free. But when the bile is in smaller quantity and the body resists dissolution, then the bile itself is overpowered, and either it is ejected over the whole surface of the body, or else it is forced through the veins into the lower or the upper belly, being ejected from the body like fugitives from a city in revolt; and it produces diarrhoea and dysentery and all suchlike maladies. When a body has become diseased mainly from an excess of fire, it produces constant inflammations and fevers; when from air, quotidian fevers; when from water, tertian fevers, because that element is more sluggish than air or fire; and when from earth, which is the fourth and most sluggish of the elements and is purged in four-fold periods of time,i.e., the fever recurs after an interval of two days. it causes quartan fevers and is cured with difficulty. Such is the manner in which diseases of the body come about; and those of the soul which are due to the condition of the body arise in the following way. We must agree that folly is a disease of the soulCf. . 571 D,. 228 A,689 A ff.; and of folly there are two kinds, the one of which is madness, the other ignorance. Whatever affection a man suffers from, if it involves either of these conditions it must be termed disease; and we must maintain that pleasures and pains in excess are the greatest of the soul’s diseases. For when a man is overjoyed or contrariwise suffering excessively from pain, being in haste to seize on the one and avoid the other beyond measure, he is unable either to see or to hear anything correctly, and he is at such a time distraught and wholly incapable of exercising reason. And whenever a man’s seed grows to abundant volume in his marrow,Cf. 73 C, 91 C. as it were a tree that is overladen beyond measure with fruit, he brings on himself time after time many pangs and many pleasures owing to his desires and the issue thereof, and comes to be in a state of madness for the most part of his life because of those greatest of pleasures and pains, and keeps his soul diseased and senseless by reason of the action of his body. Yet such a man is reputed to be voluntarily wicked and not diseased; although, in truth, this sexual incontinence, which is due for the most part to the abundance and fluidity of one substance because of the porosity of the bones, constitutes a disease of the soul. And indeed almost all those affections which are called by way of reproach incontinence in pleasure, as though the wicked acted voluntarily, are wrongly so reproached; for no one is voluntarily wicked,For this Socratic dictum Cf. . 345 D ff.,731 C ff. but the wicked man becomes wicked by reason of some evil condition of body and unskilled nurture, and these are experiences which are hateful to everyone and involuntary. And again, in respect of pains likewise the soul acquires much evil because of the body.