The third part of the _Fabrica_, comprising sixty pages, is devoted to
the veins and arteries. Vesalius begins with the definition of a vein,
and describes the structure of these vessels in general. The term
“artery” is treated in like manner. He introduces several small
illustrations which serve to elucidate this part of the text. His first
large plate in this section is devoted to the venae portae. This is
followed by a full-page picture of the entire venous system. The
arterial system is fully described and elaborately illustrated. To these
is added another plate, in which both arteries and veins are represented
in their natural order. In other plates he shows the special
circulations—cerebral, portal, and pulmonary.
[Illustration: DISSECTION OF THE ABDOMEN BY VESALIUS
(From the “Fabrica”, 1543)]
Vesalius described the valve which guards the foramen ovale in the
foetus, and also noticed the valve-like fold which guards the entrance
of each hepatic vein into the inferior vena cava. He also gave an
admirable description of the vena azygos. Blinded by the ancient theory
of the movement of the blood—a sort of flux and reflux in the veins, he
overlooked the function of the venous valves. He described them as
eminences, or projections, or accidental rugosities, which in no way
interfere with the flux and reflux of the blood.
[Illustration: DISSECTION OF THE HEART BY VESALIUS
(From the “Fabrica”, 1543)]