Page:The Harvard Classics Vol. 51; Lectures.djvu/105

Rh power and precision of scientific instruments and measurements.

This development of mechanics from Galileo to Newton is perhaps the best illustration of the method of scientific progress. Upon a vast basis of accurate descriptive knowledge, erected partly by Tycho Brahe and partly by earlier astronomers, observations with instruments of precision and high power, quantitative experiments, and finally mathematical calculations produced in little more than half a century a work which it taxes the highest powers of the specially trained human mind to understand, and which has withstood all criticism for two centuries, the most critical in history.

HARVEY AND THE CIRCULATION OF THE BLOOD

Only less important than that of mechanics was the development of biology in the seventeenth century. William Harvey, supported by the excellent work of anatomists that had begun with Vesalius, but held back by many vestiges of the old superstitious belief in authority and the garbled teachings of Hippocrates and Galen, in the early years of the century discovered the circulation of the blood. After long and most admirable investigations and self-criticism, in the year 1628 he gave this discovery to the world.

It is impossible to imagine a more illuminating contrast between the false learning of the Middle Ages and the sound positive knowledge of modern times than is presented in Harvey's book. For at almost every point the work of Harvey himself has quite as much the modern flavor as that of Newton. The introduction presents the old traditional views on the physiological functions of heart and lungs, and bewilders with its meaningless play with words. There follow upon this the simplest descriptions of observations and experiments, and the soundest reasoning from such positive knowledge, till one feels that he has passed from a dream into reality.

The work of Harvey, like so much of the work of great Englishmen, was isolated, and the full development of biology came somewhat later, in mid-century and thereafter. In this later growth, aided by the microscope and the principles of mechanics, the studies of Swammerdam, Grew, Malpighi, Redi, Borelli, Leeuwenhoek,