he recognized that it consisted of a diastole (expansion) and a systole
(contraction) with an interval after the diastole, and another after the
systole. Aristotle thought that arteries contained air, but Galen taught
that they contained blood, for, when an artery was wounded, blood gushed
out. He was not far from the discovery of the circulation. He described
the heart as having the appearance of a muscle, and considered it the
source of natural heat, and the seat of violent passions. He knew well
the anatomy of the human skeleton, and advised students to go to
Alexandria where they might see and handle and properly study the bones.
He recognized that inspiration is associated with enlargement of the
chest, and imagined that air passed inside the skull through the
cribriform plate of the ethmoid bone, and passed out by the same
channel, carrying off humours from the brain into the nose. But some of
this air remained and combined with the vital spirits in the anterior
ventricles of the brain, and finally exuded from the fourth ventricle,
the residence of the soul. Aristotle had taught that the heart was the
seat of the soul, and the brain relatively unimportant.

II.--WORKS ON DIETETICS AND HYGIENE.

Galen was a strong advocate of exercises and gymnastics, and eulogizes
hunting specially. He recommends cold baths for people in the prime of
life. As old age is "cold and dry," this is to be treated with hot baths
and the drinking of wine. He thought that wine was particularly suitable
for the aged, and that old people required three meals a day, others two
meals. He had a very high opinion of pork as an article of diet, and
said that the strength of athletes could not be maintained without this
form of food.

III.--ON PATHOLOGY.

Galen believed in the doctrine of the four elements, and his
speculations led him into a belief in a further subdivision. "Fire is
hot and dry; air is hot and moist; for the air is like a vapour; water
is cold and moist, and earth is cold and dry." He held that there were
three principles in man--spirits, solids, and humours--and eight
temperaments ranging between health and disease and compatible with
life. He retained a good deal of the teaching of the Pneumatic school,
and believed that the _pneuma_ was different from the soul, but the
vehicle for the interaction of soul and body. From his theory of the
action of the air through the nose on the contents of the ventricles of
the brain