In the foregoing have been described the two entirely contrasted natural systems which appeared independently in opposition to Aristoteleanism: the mechanical conception of nature, and the mystical view of life. As has been shown in the first part of this work, the foundations of the mechanical view of natural phenomena were laid by Harvey, who proved that the circulation of the blood, which had up to that time been regarded as an expression for certain vital spirits, goes on as a purely mechanical process. Although himself a convinced disciple of Aristotle, Harvey thereby laid the foundations of that modern scientific theory of the phenomena of life which follows the same methods in dealing with them as those applied to the investigation of phenomena in inorganic nature. This discovery of Harvey's created an immense sensation; during the immediately succeeding decades after its publication (in 1628) it was the one great question of the day and occasioned a vast quantity of literature both for and against it. Its overwhelming truth, however, soon silenced all opposition; the conservative adherents to the old system gradually died off and the young research-workers were easily won over to the new view and devoted themselves to gathering fresh proofs of its validity. How successful it was is best evidenced by the extraordinary stimulus given to the study of anatomy during the middle and latter half of the seventeenth century. This period, perhaps more than any other, can be regarded as one of brilliant anatomical achievement, to which the preceding era, beginning with Vesalius's revolutionary inventions in the field of technique and methods of observation, impresses one mostly as being a period of introduction. A comparison between these two epochs also produces a remarkable contrast of a national character; while during the Renaissance Italy was the sole centre of anatomical research, its range had now spread northwards: now for the first time England, Holland, and Scandinavia begin to make definite contributions to the development of biology. And simultaneously with this shifting of the centre of biological research we find another change appearing in its conditions, first in Italy and later the 142farther north we go. During the sixteenth century the natural philosophers were still mostly university teachers; such had been both Vesalius and Galileo. In the seventeenth century, on the other hand, and still more so in the eighteenth century, the universities cease to be the centres of scientific progress and become instead the seats of unproductive conservatism, mechanically repeating the formula: inherited from the Middle Ages; the real pioneer scientists are now private scholars. Descartes, Spinoza, Leibniz, as well as Harvey and van Helmont, all worked, as we have seen, independently of the universities, as we shall also find did several of the leading scientists among their successors, in both the seventeenth and the eighteenth centuries. A new type of bond of association between men of learning came to be established in connexion therewith — namely, the scientific societies. Such "academies" were founded during the seventeenth century all over Europe, earliest in Italy, afterwards in all countries north of the Alps. Princes and distinguished people allowed themselves to be nominated as patrons or to be elected honorary members, thereby acquiring an interest in the study of nature. To promote this study they established laboratories and made collections of natural objects — so-called "curiosity cabinets" — mostly, it is true, as the name implies, for their own amusement, but still in many cases for the benefit of science, owing to the possibilities they offered for research and the grants of money made by scientists in connexion therwith. All this naturally increased, as it were, the social reputation of science and in this respect offered a decided contrast to the Renaissance; whereas then the students of nature had to live in inferior positions, during the seventeenth and eighteenth centuries many of them held important posts in the community. The period now to be described was thus in all respects a brilliant one for natural science — a period which has no counterpart until we come to the latter half of the nineteenth century.