Besides these important advances in medicine made by him, and his great discovery of the identity of cowpox and smallpox, Dr. Jenner was an interesting observer of phenomena in all the biological sciences, and in geology and palaeontology. He was a great friend of Dr. John Hunter, who frequently suggested to him the making of such experiments and observations as were more likely to succeed in the country than in the city, and one cannot help but be struck with the determination evinced all his life to take nothing on authority, but to test everything by actual observation, and above all not to theorize where he did not have the actual data necessary for assured conclusions; and even where he thought he had them, his wonderful faculty for waiting until they had properly matured, and their true significance had become evident, stamped him for all time as a model for scientific investigators. Undoubtedly Jenner's greatest work was that of determining the value of vaccination. His patient investigation of this subject, the thorough conservatism with which he guarded himself from publishing his conclusions until he had tested them in every way, the absence of that haste to rush into print so characteristic of most present-day medical investigators, and which is the cause of so much disappointment in modern medicine, all distinguished this country physician as one of the greatest investigating geniuses that medicine has produced. His life is a mirror for the medical student and the investigating practitioner of medicine. His discovery was so complete when he finally announced it that but very little has been added to it since. His invention came from his mind as Minerva from the brain {91} of Jove fully armed for the conflict that was sure to come. In this Jenner resembled very much Laennec and the other investigating geniuses in medicine. As a matter of fact only one improvement has been made in the preparation of vaccine material since Jenner's time, and that is the incorporation of glycerin in very recent years, which gradually destroys any micro-organisms that may be present, leaving the vaccine virus itself unimpaired in its efficacy, though without the possibility of inflicting those secondary infections which for so long cast a shadow on vaccination. Dr. Edward Jenner was the third son of an Anglican clergyman, his mother being the daughter of a clergyman who had been at one time prebend in the cathedral of Bristol. The family held considerable property in Gloucestershire. He received his early education at Wotton-under-Edge and later at Cirencester, the old Roman town in Gloucestershire. While he acquired a good working knowledge of the classics, from his earliest years he was interested in natural history. Before he was nine he made a collection of the nests of the dormouse. The hours that other boys spent at play he devoted to searching for fossils or other interesting natural curiosities.