timaeus   

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.
When the several parts of the flesh are separated by disease, if the
foundation remains, the power of the disorder is only half as great,
and there is still a prospect of an easy recovery; but when that which
binds the flesh to the bones is diseased, and no longer being
separated from the muscles and sinews, ceases to give nourishment to
the bone and to unite flesh and bone, and from being oily and smooth
and glutinous becomes rough and salt and dry, owing to bad regimen,
then all the substance thus corrupted crumbles away under the flesh
and the sinews, and separates from the bone, and the fleshy parts fall
away from their foundation and leave the sinews bare and full of
brine, and the flesh again gets into the circulation of the blood
and makes the previously-mentioned disorders still greater. And if
these bodily affections be severe, still worse are the prior
disorders; as when the bone itself, by reason of the density of the
flesh, does not obtain sufficient air, but becomes mouldy and hot
and gangrened and receives no nutriment, and the natural process is
inverted, and the bone crumbling passes into the food, and the food
into the flesh, and the flesh again falling into the blood makes all
maladies that may occur more virulent than those already mentioned.
But the worst case of all is when the marrow is diseased, either
from excess or defect; and this is the cause of the very greatest
and most fatal disorders, in which the whole course of the body is
reversed.
There is a third class of diseases which may be conceived of as
arising in three ways; for they are produced sometimes by wind, and
sometimes by phlegm, and sometimes by bile. When the lung, which is
the dispenser of the air to the body, is obstructed by rheums and
its passages are not free, some of them not acting, while through
others too much air enters, then the parts which are unrefreshed by
air corrode, while in other parts the excess of air forcing its way
through the veins distorts them and decomposing the body is enclosed
in the midst of it and occupies the midriff thus numberless painful
diseases are produced, accompanied by copious sweats. And oftentimes
when the flesh is dissolved in the body, wind, generated within and
unable to escape, is the source of quite as much pain as the air
coming in from without; but the greatest pain is felt when the wind
gets about the sinews and the veins of the shoulders, and swells
them up, so twists back the great tendons and the sinews which are
connected with them. These disorders are called tetanus and
opisthotonus, by reason of the tension which accompanies them. The
cure of them is difficult; relief is in most cases given by fever
supervening. The white phlegm, though dangerous when detained within
by reason of the air-bubbles, yet if it can communicate with the
outside air, is less severe, and only discolours the body,
generating leprous eruptions and similar diseases. When it is
mingled with black bile and dispersed about the courses of the head,
which are the divinest part of us, the attack if coming on in sleep,
is not so severe; but when assailing those who are awake it is hard to
be got rid of, and being an affection of a sacred part, is most justly