Harvey caught the experimental spirit in Italy, with brain, eye and hand as his only aids, but now an era opened in which medicine was to derive an enormous impetus from the discovery of instruments of precision. "The new period in the development of the natural sciences, which reached its height in the work of such men as Galileo, Gilbert and Kepler, is chiefly characterized by the invention of very important instruments for aiding and intensifying the perceptions of the senses, by means of which was gained a much deeper insight into the phenomena than had hitherto been possible. Such instruments as the earlier ages possessed were little more than primitive hand-made tools. Now we find a considerable number of scientifically made instruments deliberately planned for purposes of special research, and as it were, on the threshold of the period stand two of the most important, the compound microscope and the telescope. The former was invented about 1590 and the latter about 1608."(34) It was a fellow professor of the great genius Galileo who attempted to put into practice the experimental science of his friend. With Sanctorius began the studies of temperature, respiration and the physics of the circulation. The memory of this great investigator has not been helped by the English edition of his "De Statica Medicina," not his best work, with a frontispiece showing the author in his dietetic balance. Full justice has been done to him by Dr. Weir Mitchell in an address as president of the Congress of Physicians and Surgeons, 1891.(35) Sanctorius worked with a pulsilogue devised for him by Galileo, with which he made observations on the pulse. He is said to have been the first to put in use the clinical thermometer. His experiments on insensible perspiration mark him as one of the first modern physiologists. (34) Dannemann: Die Naturwissenschaften in ihrer Entwickelung..., Vol. II, p. 7, Leipzig, 1911. (35) See Transactions Congress Physicians and Surgeons, 1891, New Haven, 1892, II, 159-181.