296 Chapter 16
Medicine: From Galen to Harvey
Mechanistic views would also triumph in medicine, but
the process by which they did so was more convoluted
than it had been in physics. Physicians moved from
mechanism to magic and back again in the course of
the sixteenth century. The works of the ancient Greek
anatomist Galen had long been known through Arabic
commentaries and translations. Galen’s views were
mechanistic in the sense that he was careful to relate
the form of organs to their function and had little use
for magic or for alchemical cures. The recovery andDOCUMENT 16.2
Newton: Gravity
In The Mathematical Principles of Natural Philoso-
phy,Sir Isaac Newton describes his revolutionary concept of
gravity and, in the process, sets forth some of his thoughts on
scientific method.Hitherto, we have explained the phenomena of
the heavens and of our sea by the power of gravity,
but have not yet assigned the cause of this power.
This is certain, that it must proceed from a cause
that penetrates to the very centers of the sun and
planets, without suffering the least diminution of
its force; that operates not according to the quan-
tity of the surfaces of the particles upon which it
acts (as mechanical causes used to do) but accord-
ing to the quantity of solid matter which they con-
tain, and propagates its virtue on all sides to
immense distances, decreasing always in the dupli-
cate portion of the distances....
Hitherto I have not been able to discover the
cause of those properties of gravity from the phe-
nomena, and I frame no hypothesis; for whatever
is not deduced from phenomena is to be called an
hypothesis; and hypothesis, whether metaphysical
or physical, whether of occult qualities or mechan-
ical, have no place in experimental philosophy. In
this philosophy particular propositions are inferred
from the phenomena, and afterward rendered gen-
eral by induction. Thus it was the impenetrability,
the mobility, and the impulsive force of bodies,
and the laws of motion and gravitation were dis-
covered. And to us it is enough that gravity does
really exist, and acts according to the laws that we
have explained, and abundantly serves to account
for all the motions of the celestial bodies, and of
our sea.
Newton, Isaac. The Mathematical Principles of Natural
Philosophy,book 3, vol. 2, p. 310, trans. Andrew Motte.
London, 1803, II.Illustration 16.3
A Diagram of the Veins.This diagram is from Andreas
Vesalius (1514–64), De humani corporis fabrica.The venous system
was especially important to physicians because drawing blood
was the primary treatment for many ailments. As impressive as
these drawings are, they contain anatomical errors. Vesalius did
not understand the circulation of the blood and based some of
his ideas on the dissection of animals (see the arrangement of
veins at the base of the neck). However, his work, with its mag-
nificent illustrations, is still a remarkable monument to the
anatomical revolution.