d 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 intermingled 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 dispens