Boyle's first major work which dealt extensively with medical problems was the _Usefulness of Experimental Philosophy_. This work, although published in 1663, had been written in two parts, the first much earlier than the second. Fulton[38] indicates it had been drafted around 1650, while Hall[39] ascribes it to the period 1647-1648. This first part has relatively little to do with medicine; the references are few and rather incidental, and have significance only for the light they throw on "natural philosophy" and "natural religion." The second part, however, written apparently not too long before publication, has a great deal to do with medicine and constitutes one of the important medical documents of the century. Deserving of mention is an earlier and minor work of Boyle, indeed, his first published writing, only recently identified. This work, apparently written in 1649, bore the title "An Invitation to a free and generous communication of Secrets and Receits in Physick," and appeared anonymously in 1655 as part of a volume entitled _Chymical, Medicinal and Chirurgical Addresses Made to Samuel Hartlib, Esquire_.[40] For our purposes, it is significant as emphasizing his early interest in medicine. Boyle seems to have acquired most of his medical knowledge between, say, 1649 and 1662. It is worth recalling some of the trends and conflicts that formed the medical environment during this period. Among the major trends, first place, perhaps, must be given to Galenic doctrine, which had come under progressively severe attack. Molière, who lived from 1622 to 1673, showed in his comedies the popular reaction to a system which, although dominant, was clearly crumbling. The cracks in the edifice even the layman could readily see. Nevertheless, Galenism had its strong supporters. Riverius, who lived from 1589 to 1655, was a staunch Galenist. An edition of his basic and clinical works[41] was translated into English in 1657, and Latin editions continued to be published well into the eighteenth century.[42] Galenism, of course, had to withstand the great new discoveries in anatomy and physiology made by Vesalius, Aselli, Sanctonius, Harvey, and others, not to mention the host of great investigators who were more strictly contemporaries of Boyle.