For that which takes place according to nature is
pleasant, but that which is contrary to nature is painful. And
thus death, if caused by disease or produced by wounds, is
painful and violent; but that sort of death which comes with old
age and fulfils the debt of nature is the easiest of deaths, and
is accompanied with pleasure rather than with pain.
Now every one can see whence diseases arise. There are four
natures out of which the body is compacted, earth and fire and
water and air, and the unnatural excess or defect of these, or
the change of any of them from its own natural place into
another, or-since there are more kinds than one of fire and of
the other elements-the assumption by any of these of a wrong
kind, or any similar irregularity, produces disorders and
diseases; for when any of them is produced or changed in a manner
contrary to nature, the parts which were previously cool grow
warm, and those which were dry become moist, and the light become
heavy, and the heavy light; all sorts of changes occur. For, as
we affirm, a thing can only remain the same with itself, whole
and sound, when the same is added to it, or subtracted from it,
in the same respect and in the same manner and in due proportion;
and whatever comes or goes away in violation of these laws causes
all manner of changes and infinite diseases and corruptions. Now
there is a second class of structures which are also natural, and
this affords a second opportunity of observing diseases to him
who would understand them. For whereas marrow and bone and flesh
and sinews are composed of the four elements, and the blood,
though after another manner, is likewise formed out of them, most
diseases originate in the way which I have described; but the
worst of all owe their severity to the fact that the generation
of these substances stances in a wrong order; they are then
destroyed. For the natural order is that the flesh and sinews
should be made of blood, the sinews out of the fibres to which
they are akin, and the flesh out of the dots which are formed
when the fibres are separated. And the glutinous and rich matter
which comes away from the sinews and the flesh, not only glues
the flesh to the bones, but nourishes and imparts growth to the
bone which surrounds the marrow; and by reason of the solidity of
the bones, that which filters through consists of the purest and
smoothest and oiliest sort of triangles, dropping like dew from
the bones and watering the marrow.
Now when each process takes place in this order, health
commonly results; when in the opposite order, disease. For when
the flesh becomes decomposed and sends back the wasting substance
into the veins, then an over-supply of blood of diverse kinds,
mingling with air in the veins, having variegated colours and
bitter properties, as well as acid and saline qualities, contains
all sorts of bile and serum and phlegm. For all things go the
wrong way, and having become corrupted, first they taint the
blood itself, and then ceasing to give nourishment the body they
are carried along the veins in all directions, no longer
preserving the order of their natural courses, but at war with
themselves, because they receive no good from one another, and
are hostile to the abiding constitution of the body, which they
corrupt and dissolve. The oldest part of the flesh which is
corrupted, being hard to decompose, from long burning grows
black, and from being everywhere corroded becomes bitter, and is
injurious to every part of the body which is still uncorrupted.
Sometimes, when the bitter element is refined away, the black
part assumes an acidity which takes the place of the bitterness;
at other times the bitterness being tinged with blood has a
redder colour; and this, when mixed with black, takes the hue of
grass; and again, an auburn colour mingles with the bitter matter
when new flesh is decomposed by the fire which surrounds the
internal flame-to all which symptoms some physician perhaps, or
rather some philosopher, who had the power of seeing in many
dissimilar things one nature deserving of a name, has assigned
the common name of bile. But the other kinds of bile are
variously distinguished by their colours. As for serum, that sort
which is the watery part of blood is innocent, but that which is
a secretion of black and acid bile is malignant when mingled by
the power of heat with any salt substance, and is then called
acid phlegm.
Again, the substance which is formed by the liquefaction of
new and tender flesh when air is present, if inflated and encased
in liquid so as to form bubbles, which separately are invisible
owing to their small size, but when collected are of a bulk which
is visible, and have a white colour arising out of the generation
of foam-all this decomposition of tender flesh when inter-mingled
with air is termed by us white phlegm. And the whey or sediment
of newly-formed phlegm is sweat and tears, and includes the
various daily discharges by which the body is purified. Now all
these become causes of disease when the blood is not replenished
in a natural manner by food and drink but gains bulk from
opposite sources in violation of the laws of nature.
