The two opponents named by Harvey were not his contemporaries, but worthies of the Renaissance who had written about one hundred years before the publication of his treatise On Generation and had died before he was born. The Italian physician Julius Cæsar Scaliger had written learned commentaries on Aristotle, as well as other works; and the Frenchman Jean Fernel, physician to King Henri II of France, had taught anatomy at Paris and had been a medical writer of importance. Each of these two authors was nearly sixty years of age in 1543, in which memorable year were first published the revolutionary writings of the aged astronomer Copernicus and of the young anatomist Vesalius, in the second year after the death of the hardy innovator Paracelsus. Such were the men against whose doctrines Harvey was impelled in his old age to launch his vigorous criticism, in order to clear the way for his own doctrine of the preëminence of the blood. What can we workers of to-day make of their opinions, which were living for Harvey but now are so deeply buried? Test-tube and balance, telescope, spectroscope, microscope, manometer, and the rest, have served their purpose so well since Harvey's time that even he, one of the foremost worthies of science, must seem merely to beat the air with words in his last message to us, unless we can recover his standpoint. Happily he himself shall attempt to clarify the meaning of his polemic by setting before us certain words of Aristotle, embodying far-reaching speculations as to body and soul in relation to the universe. Yet we shall find these not easy to understand. Let Harvey continue his criticism of his predecessors. He says:-- "But while they believe that there are found in animals spirits and ultimate or primitive nourishment, or something else, which acts beyond the powers of the elements more than does the blood, they do not seem to have a sufficient grasp of what it may be to 'act beyond the powers of the elements'; nor have they rightly interpreted the words of Aristotle where he says:[315] 'The virtue or potency of every soul[316] seems to be associated with a body[317] other than the so-called elements and more divine.'" And a little farther on:[318]--