he arteries, but thought that the pulmonary veins
conveyed air from the lungs to the left side of the heart, and he
observed the lacteals without determining their function. Herophilus
operated upon the liver and spleen, and looked upon the latter as of
little consequence in the animal economy. He had a good knowledge of
obstetric operations. His ideas in relation to pathology did not proceed
much further than the belief that disease was due to corruption of the
humors. He was more scientific and accurate when he taught that
paralysis results from a defect in the nerves.

_Erasistratus_ studied under Chrysippos (or Chrysippus), and under
Metrodorus, the son-in-law of Aristotle. Herophilus had been a student
at Cos, Erasistratus at Cnidos, so that the teaching of the two great
Greek medical schools was introduced into Alexandria. Xenophon, of Cos,
one of the followers of Erasistratus, first resorted to the ligation of
vessels for the arrest of haemorrhage, although for many years in later
times this important practice was lost through the neglect of the study
of the history of medicine. Erasistratus and Herophilus, it is sad to
relate, considered that vivisection of human beings, as well as
dissection of the dead, was a necessary part of medical education, and
believed that the sufferings of a few criminals did not weigh against
the benefit likely to accrue to innocent people, who could be relieved
or cured of disease and suffering as the result of the knowledge gained
by dissection of the living. This cruel and nefarious practice was
followed "so that the investigators could study the particular organs
during life in regard to position, colour, form, size, disposition,
hardness, softness, smoothness, and superficial extent, their projection
and curvatures."

The followers of these teachers, unfortunately, became very speculative
and fond of discussions of a fruitless kind, and, according to Pliny, it
was easier "to sit and listen quietly in the schools than to be up and
wandering over the deserts, and to seek out new plants every day,"[9]
and so, in the third century before Christ, the school of _Empiricism_
was established, the system of which resembled the older Scepticism. It
rested upon the "Empiric tripod," namely, accident, history and analogy.
This meant that discoveries were made by accident, knowledge was
accumulated by the recollection of previous cases, and treatment adopted
which had been found suitable in