the soul; and if the release be according to
nature, she then flies away with joy. For the death which is natural is
pleasant, but that which is caused by violence is painful.

Every one may understand the origin of diseases. They may be occasioned
by the disarrangement or disproportion of the elements out of which the
body is framed. This is the origin of many of them, but the worst of all
owe their severity to the following causes: There is a natural order
in the human frame according to which the flesh and sinews are made of
blood, the sinews out of the fibres, and the flesh out of the congealed
substance which is formed by separation from the fibres. The glutinous
matter which comes away from the sinews and the flesh, not only binds
the flesh to the bones, but nourishes the bones and waters the marrow.
When these processes 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