take place in regular order the body is in health.

But when the flesh wastes and returns into the veins there is discoloured
blood as well as air in the veins, having acid and salt qualities, from
which is generated every sort of phlegm and bile. All things go the wrong
way and cease to give nourishment to the body, no longer preserving their
natural courses, but at war with themselves and destructive to the
constitution of the body. The oldest part of the flesh which is hard to
decompose blackens from long burning, and from being corroded grows bitter,
and as the bitter element refines away, becomes acid. When tinged with
blood the bitter substance has a red colour, and this when mixed with black
takes the hue of grass; or again, the bitter substance has an auburn
colour, when new flesh is decomposed by the internal flame. To all which
phenomena some physician or philosopher who was able to see the one in many
has given the name of bile. The various kinds of bile have names answering
to their colours. Lymph or serum is of two kinds: first, the whey of
blood, which is gentle; secondly, the secretion of dark and bitter bile,
which, when mingled under the influence of heat with salt, is malignant and
is called acid phlegm. There is also white phlegm, formed by the
decomposition of young and tender flesh, and covered with little bubbles,
separately invisible, but becoming visible when collected. The water of
tears and perspiration and similar substances is also the watery part of
fresh phlegm. All these humours become sources of disease when the blood
is replenished in irregular ways and not by food or drink. The danger,
however, is not so great when the foundation remains, for then there is a
possibility of recovery. But when the substance which unites the flesh and
bones is diseased, and is no longer renewed from the muscles and sinews,
and instead of being oily and smooth and glutinous becomes rough and salt
and dry, then the fleshy parts fall away and leave the sinews bare and full
of brine, and the flesh gets back again into the circulation of the blood,