Charles Daremberg (all his works); Rousselot, Études sur la philosophie dans le Moyen Age, 1840; Pattison, Casaubon, 1875; Meunier, Francis, Essai sur la vie et les ouvrages de Nicole Oresme, Paris 1857. Descartes, Epist. Cartes. 4to. Amst., 1668; Plumpius, Fundamenta Med. Fol. Lovan., 1652; Sylvii Op. Omn., 1679, p. 875; Haller, Elem. Physiol., 1757, I. 3; Tiedemann, Physiologie de l'homme, Paris 1831, I. 41; Delle Chiaja, Instituzione di Anatom. e Fis. Comp., 1832, I. 13. (The six last works are cited as being especially useful, among many others, to show the extent to which modern physiology, from Harvey onwards, is based upon vivisection; and that it could not have arisen or thriven otherwise. It was by the test of many vivisections that Plumpius was led to the honourable withdrawal of his opposition to Harvey.) INTRODUCTION[1]. In the many Harveian Orations which have been delivered since the death of the founder of modern physiology the direct aspects of his honour and of his work have been exhausted; of late years the orators have concerned themselves with indirect aspects. Some of my friends have said to me that they lack a perspective view of Harvey and his work; that even highly educated men have little sense of his relation to medieval thought, or of the evolution of medieval into modern thought. Of the several stars of the constellation—of Copernicus, Gilbert, Galileo, Harvey—they had some knowledge; but how came Harvey to be at Padua? how did science spring up in North Italy? did science arise out of the womb of medicine, or contrariwise? why did natural science not flourish in the thirteenth century, and was it not a great misfortune for Europe that it did not then flourish? what were the systems of thought which in the Middle Ages preceded, encouraged or thwarted the travail of the human mind, and what of good or ill do we owe to them? These and such questions it seemed not unfitting that a Harveian Orator of this latter day should consider. Now on the philosophy of the Middle Ages, and on its relation to the era of positive science of which Harvey was perhaps the chief pioneer, there lay in a drawer in my cabinet the confused and occasional notes of many years. An interest in this thorny subject, sown in my mind at first by accident, and reawakened by these enquiring friends, had for me the charms of an old fancy, and I trust some brief essay thereon may have a temporary service; if, that is, I can touch the imagination of my hearers, and after some broken fashion bring before them a vision of the nations swayed hither and thither upon the face of Europe by a thirst for knowledge of a kind different, both in its methods and in its aims, from our own.