t, however, remain for a
long period at Rome, and probably passed the greater part of the rest of
his life in his native country.

Although the date of his death is not positively known, yet it appears
from a passage[17] in his writings that he was living in the reign of
Septimius Severus; and Suidas seems to have reason for asserting that he
reached his seventieth year.

Galen's writings represent the common depository of the anatomical
knowledge of the day; what he had learnt from many teachers, rather than
the results of his own personal research. Roughly speaking, they deal
with the following subjects: Anatomy and Physiology, Dietetics and
Hygiene, Pathology, Diagnosis and Semeiology, Pharmacy and Materia
Medica, Therapeutics.

The only works of this voluminous writer at which we can here glance are
those dealing with Anatomy and Physiology. These exhibit numerous
illustrations of Galen's familiarity with practical anatomy, although it
was most likely comparative rather than human anatomy at which he
especially worked. Indeed, he seems to have had but few opportunities of
carrying on human dissections, for he thinks himself happy in having
been able to examine at Alexandria two human skeletons; and he
recommends the dissection of monkeys because of their exact resemblance
to man. To this disadvantage may, perhaps, be attributed the readiness,
which sometimes appears, to assume identity of organization between man
and the brutes. Thus, because in certain animals he found a double
biliary duct, he concluded the same to be the case in man, and in one
instance he proceeded to deduce the cause of disease from this erroneous
assumption.

He supposed that there were three modes of existence in man, namely--

(_a_) The nutritive, which was common to all animals and plants, of
which the liver was the source.

(_b_) The vital, of which the heart was the source.

(_c_) The rational, of which the brain was the source.

Again, he considered that the animal economy possessed four natural
powers--

(1) The attractive.

(2) The alterative or assimilative.

(3) The retentive or digestive.

(4) The expulsive.

Like his predecessors, he asserted that there were four humours, namely,
blood, yellow bile, black bile, and aqueous serum. He held that it was
the office of the liver to complete the process of sanguification
commenced in the stomach, and that during this process the yellow bile
was attracted