Professor of Anatomy at the University of Leyden, Holland; Reignier de Graaf (1641–1673), a native of the Netherlands; and Thomas Willis (1622–1675) and William Cowper (1666–1709), both of them Englishmen. And, finally, it may be stated that all the leading anatomists of the sixteenth century devoted a great deal of time to the study of the manner in which the nerves are distributed throughout the body and to ascertaining the arrangement of the intracranial and intraspinal nervous structures. To give even the most superficial account of what these men accomplished would occupy far more space than can well be spared for this purpose. Kurt Sprengel is my authority for saying that, of all the workers in this particular field during the period in question, Fallopius is entitled to receive the greatest credit for what he accomplished. _The First Beginnings of Minute or Microscopic Anatomy._--The anatomy of the tissues--microscopic anatomy--begins with Marcello Malpighi (1628–1694), a native of Crevalcuore, near Bologna, Italy. It is not positively known who was the inventor of the compound microscope. First employed about the year 1620, the instruments of this type came into fairly general use toward the middle of the seventeenth century. But the early compound microscopes were not very satisfactory, and consequently preference was given, for a long time, to those of the simple type. Achromatic instruments were not purchasable until 1780, when the famous German physicist, Leonhard Euler, succeeded in overcoming the obstacles which had up to that time stood in the way of their successful manufacture. In 1661 Malpighi, who was in the habit of manufacturing his own microscopes, was able, by aid of one of these instruments, to exhibit the blood, loaded with its corpuscular bodies, passing rapidly from one capillary vessel to another in the frog’s lung. Then in 1683 Guillaume Molyneux, in 1690 Anton van Leeuwenhoek, and in 1697 William Cowper, witnessed the same phenomenon in warm-blooded animals. Among the other anatomists of this period who contributed in varying degrees to our knowledge of the minute anatomy of the different tissues and organs the following deserve to be mentioned: J. Riolan (1577–1657), Boselli of Naples (1608–1679), Lower of Oxford, England (1631–1691), Vesling of Minden, Germany (1598–1649), Regnier de Graaf of Delft, Holland (1641–1673), who gained so great distinction by his accurate description of the ovarian follicles (“Graafian follicles”); and James Douglas (1676–1742), the English anatomist, who ascertained and described the precise limits of the peritoneum.