his experiments; this was money most happily employed, since it made possible a number of important discoveries. It is said that Bacon knew the properties of convex and concave lenses, and was the first to conceive of the microscope and telescope; his astronomical knowledge led him to demand a reform in the calendar, which Gregory XIII carried out three centuries later; he had knowledge of gunpowder and its effects, and was, in fact, the wizard of his day; but his boldness and originality drew upon him the enmity of the church, by which he was persecuted and finally condemned to imprisonment for life upon a diet of bread and water, although he was ultimately released, in 1266, by Pope Clement IV. He wrote extensively, but only fragments of his works exist, since the friars believed{069} them tainted with witchcraft and prevented their publication. Before and during the time of Roger Bacon the philosophers were divided into two parties, which engaged in very unseemly and unphilosophic strife. One was termed the _Realist_, and believed, with Plato, that ideas are self-existent and independent of the mind,--in other words, veritable entities; the other, the _Nominalist_, held, with Aristotle, that general ideas are pure abstractions formed by the mind with the aid of sensations received from without, without which they could never exist,--that is, if a being could be imagined without sensibilities and the power of sensation, such being would be destitute of ideas. These two parties kept up a very active warfare, and enlisted the aid of both civil and ecclesiastical authorities, the result being persecution of each other, and that general unsatisfactory conflict into which theology and metaphysical speculation always force those who indulge in them. Now, regarding the condition of medical affairs in the Empire of the West: Down to the seventh century, in Rome, there were court-archiaters who were attached to the retinues of the nobles, and in each large city popular archiaters formed a college charged with sanitary matters, the instruction and examination of candidates, and gratuitous services to the poor. Although there is little definite information available, it is probable that after the ruin of Alexandria much the same medical organization obtained in those provinces as continued under the Greek Empire at Constantinople. Under Arab sway we know very little of what rules or regulations governed instruction in medicine and its practice; and, so soon as one of these countries fell under the rule of the Turks, all scientific institutions seem to have decayed or been discontinued,--or, as Renouard states it: "If we may judge by what still exists to-day in this unfortunate country (Turkey), consumed by the power of ignorance{070} and despotism, the most complete anarchy followed all older organizations."