e heart and brain.

Vesalius gives a good account of the sphenoid bone, with its large and
small wings and its pterygoid processes; and he accurately describes the
vestibule in the interior of the temporal bone. He shows the sternum to
consist, in the adult, of three parts and the sacrum of five or six. He
discovered the valve which guards the _foramen ovale_ in the f[oe]tus;
and he not only verified the observation of Etienne as to the valve-like
fold guarding the entrance of each hepatic vein into the inferior vena
cava, but he also fully described the _vena azygos_. He observed, too,
the canal which passes in the f[oe]tus between the umbilical vein and
vena cava, and which has since been known as the _ductus venosus_. He
was the first to study and describe the mediastinum, correcting the
error of the ancients, who believed that this duplicature of the pleura
contained a portion of the lungs. He described the omentum and its
connections with the stomach, the spleen, and the colon; and he
enunciated the first correct views of the structure of the pylorus,
noticing at the same time the small size of the caecal appendix in man.
His account of the anatomy of the brain is fuller than that of any of
his predecessors, but he does not appear to have well understood the
inferior recesses, and his description of the nerves is confused by
regarding the optic as the first pair, the third as the fifth, and the
fifth as the seventh. The ancients believed the optic nerve to be hollow
for the conveyance of the visual spirit, but Vesalius showed that no
such tube existed. He observed the elevation and depression of the brain
during respiration, but being ignorant of the circulation of the blood,
he wrongly explained the phenomenon.

Exclusively an anatomist, he makes but brief references in his great
work to the functions of the organs which he describes. Where he differs
from Galen on these matters he does so apologetically. He follows him in
regarding the heart as the seat of the emotions and passions--the
hottest of all the viscera and source of heat of the whole body;
although he does not, as Aristotle did, look upon the heart as giving
rise to the nerves. He considers the heart to be in ceaseless motion,
alternately dilating and contracting, but the diastole is in his opinion
the influential act of the organ. He knows that eminences or projections
are present in the veins, and indeed speaks of them as being analogous
to the valv