We now come to the important epoch in the life of this eminent man. On the 14th of May, 1796 (commemorated in Berlin as an annual festival), he made his first successful vaccination on a boy of the name of Phipps, eight years old, and announced the event in a letter to a friend named Gardner, in the following words: "But listen to the most delightful part of my story. The boy has since been inoculated for the small-pox, which, as I ventured to predict, produced no effect. I shall now pursue my experiments with redoubled ardour." In the year 1798 he made public the result of his continued observations and experiments, published during this year his work entitled an 'Inquiry into the Causes and Effects of the Variolæ Vaccinæ,' and henceforth the imperishable name of Jenner was to be identified with vaccination. Although Jenner announced his discovery thus late in life, his attention had been drawn forcibly towards the subject when quite a youth, while pursuing his professional education in the house of his master at Sudbury. During that time, a young countrywoman having come to seek advice, the subject of small-pox was mentioned in her presence; she immediately observed, "I cannot take that, for I have had the cow-pox." This incident rivetted the attention of Jenner, and he resolved to let no opportunity escape of procuring knowledge upon so interesting a subject. When, in 1770, he was prosecuting his studies in London, he mentioned the matter to Hunter, who told him not to _think_ but _try_, and above all to be patient and accurate. Hunter, however, from the great number of original and important pursuits, which fully engrossed his attention, was never so greatly impressed, as Jenner, with the probable consequences of the successful elucidation of the subject of cow-pox; while other surgeons and scientific men, to whom the subject was mentioned, ridiculed the idea; and even when Jenner had drawn up his 'Inquiry,' he was recommended not to send it to the Royal Society, lest it should injure the scientific reputation which he had formerly acquired with that body by his paper on the 'Natural History of the Cuckoo.' Undeterred by this want of sympathy, Jenner, during the time of his practice at Berkeley, patiently continued his investigations as to the nature of cow-pox, and, gradually struggling through the difficulties which he had to encounter on his way, eliminated the following facts: that there were certain people to whom it was impossible to give the small-pox by inoculation, and that these had all had the cow-pox; but that there were also others who had had cow-pox, and who yet received small-pox. This, after much labour, led him to the discovery that the cow was subject to a variety of eruptions, of which one only had the power of guarding from small-pox, and that this, the true cow-pox, as he called it, could, at only one period of its course, produce, by inoculation, such an