elements are disturbed, and the secondary substances which are formed out
of them, namely, blood, flesh, sinews, are generated in an inverse order.

Plato found heat and air within the human frame, and the blood circulating
in every part. He assumes in language almost unintelligible to us that a
network of fire and air envelopes the greater part of the body. This outer
net contains two lesser nets, one corresponding to the stomach, the other
to the lungs; and the entrance to the latter is forked or divided into two
passages which lead to the nostrils and to the mouth. In the process of
respiration the external net is said to find a way in and out of the pores
of the skin: while the interior of it and the lesser nets move alternately
into each other. The whole description is figurative, as Plato himself
implies when he speaks of a 'fountain of fire which we compare to the
network of a creel.' He really means by this what we should describe as a
state of heat or temperature in the interior of the body. The 'fountain of
fire' or heat is also in a figure the circulation of the blood. The
passage is partly imagination, partly fact.

He has a singular theory of respiration for which he accounts solely by the
movement of the air in and out of the body; he does not attribute any part
of the process to the action of the body itself. The air has a double
ingress and a double exit, through the mouth or nostrils, and through the
skin. When exhaled through the mouth or nostrils, it leaves a vacuum which
is filled up by other air finding a way in through the pores, this air
being thrust out of its place by the exhalation from the mouth and
nostrils. There is also a corresponding process of inhalation through the
mouth or nostrils, and of exhalation through the pores. The inhalation
through the pores appears to take place nearly at the same time as the
exhalation through the mouth; and conversely. The internal fire is in
either case the propelling cause outwards--the inhaled air, when heated by