. It is an
unceasing wonder how one man, even with a school of devoted students,
could have done so much.

(28) The "Good collector of qualities," Dioscorides,
Hippocrates, Avicenna, Galen and Averroes were the medical
members of the group. Dante, Inferno, canto iv.

Dissection--already practiced by Alcmaeon, Democritus, Diogenes and
others--was conducted on a large scale, but the human body was still
taboo. Aristotle confesses that the "inward parts of man are known
least of all," and he had never seen the human kidneys or uterus. In his
physiology, I can refer to but one point--the pivotal question of the
heart and blood vessels. To Aristotle the heart was the central organ
controlling the circulation, the seat of vitality, the source of
the blood, the place in which it received its final elaboration and
impregnation with animal heat. The blood was contained in the heart
and vessels as in a vase--hence the use of the term "vessel." "From the
heart the blood-vessels extend throughout the body as in the anatomical
diagrams which are represented on the walls, for the parts lie round
these because they are formed out of them."(29) The nutriment oozes
through the blood vessels and the passages in each of the parts "like
water in unbaked pottery." He did not recognize any distinction between
arteries and veins, calling both plebes (Littre); the vena cave is the
great vessel, and the aorta the smaller; but both contain blood. He did
not use the word "arteria" (arthria) for either of them. There was no
movement from the heart to the vessels but the blood was incessantly
drawn upon by the substance of the body and as unceasingly renewed by
absorption of the products of digestion, the mesenteric vessels taking
up nutriment very much as the plants take theirs by the roots from the
soil. From the lungs was absorbed the pneuma, or spiritus, which was
conveyed to the heart by the pulmonary vessels--one to the right,
and one to the left side. These vessels in the lungs, "through mutual
contact" with the branches of the trachea, took in the pneuma. A point
of interest is that the windpipe, or trachea, is called "arteria," both
by Aristotle and by Hippocrates ("Anatomy," Littre, VIII, 539). It was
the air-tube, disseminating the breath through the lungs. We shall see
in a few minutes how the term came to be applied to the arteries, as
we know them. The pulsation of the heart and arteries was regarded by
Aristotle as