rightly； will find that such wonderful phenomena are attributable to
the combination of certain conditions…the non…existence of a vacuum；
the fact that objects push one another round； and that they change
places； passing severally into their proper positions as they are
divided or combined
Such as we have seen； is the nature and such are the causes of
respiration…the subject in which this discussion originated。 For the
fire cuts the food and following the breath surges up within； fire and
breath rising together and filling the veins by drawing up out of
the belly and pouring into them the cut portions of the food； and so
the streams of food are kept flowing through the whole body in all
animals。 And fresh cuttings from kindred substances； whether the
fruits of the earth or herb of the field； which God planted to be
our daily food； acquire all sorts of colours by their inter…mixture；
but red is the most pervading of them； being created by the cutting
action of fire and by the impression which it makes on a moist
substance； and hence the liquid which circulates in the body has a
colour such as we have described。 The liquid itself we call blood；
which nourishes the flesh and the whole body； whence all parts are
watered and empty places filled。
Now the process of repletion and evacuation is effected after the
manner of the universal motion by which all kindred substances are
drawn towards one another。 For the external elements which surround us
are always causing us to consume away； and distributing and sending
off like to like； the particles of blood； too； which are divided and
contained within the frame of the animal as in a sort of heaven； are
compelled to imitate the motion of the universe。 Each； therefore； of
the divided parts within us； being carried to its kindred nature；
replenishes the void。 When more is taken away than flows in； then we
decay； and when less； we grow and increase。
The frame of the entire creature when young has the triangles of
each kind new； and may be compared to the keel of a vessel which is
just off the stocks； they are locked firmly together and yet the whole
mass is soft and delicate； being freshly formed of marrow and nurtured
on milk。 Now when the triangles out of which meats and drinks are
composed come in from without； and are comprehended in the body； being
older and weaker than the triangles already there； the frame of the
body gets the better of them and its newer triangles cut them up；
and so the animal grows great； being nourished by a multitude of
similar particles。 But when the roots of the triangles are loosened by
having undergone many conflicts with many things in the course of
time； they are no longer able to cut or assimilate the food which
enters； but are themselves easily divided by the bodies which come
in from without。 In this way every animal is overcome and decays；
and this affection is called old age。 And at last； when the bonds by
which the triangles of the marrow are united no longer hold； and are
parted by the strain of existence； they in turn loosen the bonds of
the soul； and she； obtaining a natural release； flies away with joy。
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。
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 dis