Music, the lighter kinds of literature, both as a reader and occasionally as an author, and the innocent recreations of society, which no one enjoyed more keenly than himself, were the means by which Jenner lightened the burden of his professional labours; but his chief amusement was natural history, including geology, a science then in its infancy, for the study of which his position in the vale of Gloucester afforded ample opportunity, the neighbourhood abounding with fossil remains, and exhibiting a great variety of terrestrial structure. Towards subjects of this nature he was led, not only by his original bias, but by his correspondence with Hunter, Banks, and Parry.
In 1778 he formed a medical society, which held its periodical meetings at Rodborough, for the purpose of communicating professional information and promoting a friendly feeling among the members. In furtherance of these objects, Jenner contributed several important and original papers, the substance of which is now embodied in medical science, without his property in them being generally known. Among these were essays on the nature and causes of Angina Pectoris, on a peculiar disease of the heart occurring in acute rheumatism, and on several of the more severe affections of the eye. He also belonged to another medical society, meeting at Alveston near Bristol, to the members of which, who were men of congenial dispositions with his own, he was personally much attached. Upon one topic, however, they did not agree; for it is said that he was in the habit of enlarging so frequently upon his favourite speculation of the cow-pox, that the subject was at length proscribed, and he was jestingly forbidden to renew it on pain of expulsion. This club was for many years a source of much enjoyment and advantage to him, and we may suppose that he was a very principal contributor to the diversion of the other members; for it ceased to exist in 1789, when other objects began to engross the time that he could spare from his practice. In March of the previous year, at the age of thirty-seven, he married Miss Catharine Kingscote, by whom he had several children. The choice appears to have been a very fortunate one for his domestic happiness.
In 1786 he had communicated to Mr. Hunter, in the form of an essay, the result of several years’ careful observation of the singular habits of the cuckoo, till then a mystery to naturalists. It was presented by Mr. Hunter to the Royal Society, and was printed entire in their Transactions in 1789, having been returned to Jenner in the mean time, in order that he might record some additional facts which he had ascertained. This tract has been considered as a very masterly performance, and was the occasion of the author being elected to the fellowship of the Royal Society. It is not a little remarkable that Mr. Hunter, like Jenner’s friends at Alveston, thought so doubtfully of his views on the subject of vaccination, that he cautioned him against publishing them, lest they should interfere with the fame he had acquired in the learned world by his ‘Essay on the Cuckoo.’ But the event proved that the caution, though well meant, was unnecessary. Jenner was not more disposed than his gifted master to admit any conclusion on merely collateral grounds, that might be put to the test of experiment. This, however, was too new and important a matter to be lightly or prematurely hazarded; and Jenner waited long and patiently for an opportunity of thus testing his opinions, losing in the mean time no occasion of collecting additional information. The idea, thus watchfully and laboriously improved, was first excited in his mind while he was an apprentice at Sodbury, by a remark accidentally dropped by a young countrywoman in his master’s surgery, who, overhearing a conversation about the small-pox, observed that she had no fear of catching that disease as she had taken the cow-pox. Jenner, who was always alive to any subject connected with natural history, was induced to make more particular inquiries into this complaint, of which he had never heard before; and the answers he received were such as to suggest the probability of substituting it with advantage for the inoculated small-pox. Of this theory he never lost sight till he established it on the clearest evidence, and with it his unrivalled claim to the perpetual gratitude of mankind.
The cow-pox is a disease of the eruptive kind, which is sometimes extensively prevalent among cattle in large dairy countries where they are herded together in numbers, but often disappears for a long time together. Though commonly mild, it is occasionally so severe as to terminate fatally; and it is believed, on strong grounds, to have been at different times even pestilential among them, and as such, to have been mentioned by various writers on rural economy, ancient and modern, as well as in medical and other histories. It is generally, however, a very mild disorder, appearing on the udder of the cow, at first in the form of vesicles much resembling those of small-pox; and it is sometimes, as in the instance which first attracted the attention of Jenner, communicated to the hands of milkers. In such cases, an eruption of similar vesicles takes place on the hands and arms, not without much swelling and inflammation, and occasionally with fever and disturbance of the health for some days. It has never been known to prove fatal when thus communicated, or to have left any unpleasant effects behind it, except a few indented marks in the situation occupied by the pustules. It is not communicable, like small-pox in the human subject, by the effluvia; but the matter, or lymph as it is called, contained in the vesicles, must be actually inserted under the skin, or applied to a raw or an absorbing surface. But the most important of its peculiarities is the security it affords against the infection of small-pox. This property was well known among the agricultural classes in the grazing districts before the time of Jenner, and it has been stated that individuals among them had turned their knowledge of it to account for the protection of their families, by inoculating them with the vaccine disease. But this circumstance, alleged on very scanty evidence by those who were opposed to Jenner’s claims, cannot lessen the merit of his independent discovery, of which each step was communicated in succession to a numerous circle of medical friends, and is recorded in the most authentic form. His reputation is, on the other hand, enhanced by the fact that, although the immunity conferred by the casual disease in milkers had frequently come under the notice of medical men from their failing in such persons to produce the small-pox by inoculation, yet the idea of introducing the disease of an animal into the human frame was so little in consonance with any former practice, that Jenner was the first among his brethren to conjecture that cow-pox, as the milder disease, might advantageously supersede the inoculated small-pox; and that, as the latter is rendered less virulent by inoculation, so the former introduced in the same way might be milder than the casual complaint, and yet retain its protecting power. He had even communicated this conjecture to Hunter, himself no mean innovator in medicine, so early as the year 1770; and Mr. Hunter was for many years in the habit of mentioning it in his public lectures coupled with Jenner’s name: but the proposed substitution was so distasteful, or appeared of such questionable propriety, that it obtained no favourable notice till it was forced by the inventor on the public attention, thirty years after it had first attracted his own.
It would be interesting to enter into a detail of the progress of Jenner’s discovery and of its introduction into general use, as well as to show its inestimable value to society by a reference to statistical facts. This, however, can only be done here in a very cursory manner.
The way in which the idea was first suggested to him has been already mentioned. After his return to Berkeley from London, he pursued the subject with great patience and sagacity for many years. In the course of these preliminary inquiries he found reason to believe that of several kinds of vesicular disease in the cow, but one had the property of securing from the small-pox, and that one exclusively, or at least with the greatest certainty, in its first stage. He also ascertained that the horse is subject to an eruption of similar vesicles, apparently arising without infection, and popularly known by the name of the grease. The matter issuing from these is sometimes conveyed to the cow by milkers engaged in farriery; and Jenner conceived it to be the original and only source of cow-pox among the herds. The opinion is not generally held at present to its full extent; but experiments by himself and others since the publication of his Inquiry have proved a fact much disputed at the time, that he was right in believing the diseases to be identical, whatever may be their origin.
It may be mentioned as a curious circumstance, that the first lymph transmitted in an active state to British India in 1802 by Dr. De Carro of Vienna, long the only source of vaccination in that country, had been furnished to him by Dr. Sacco of Milan, from genuine vesicles produced by direct inoculation from the horse, without passing through the cow; an intervention which, till about that period, Jenner had continued to think essential to the production of the true disease in man.
In addition to these and other curious results, laboriously collected during a period of twenty-six years, Dr. Jenner at length arrived at a rational conviction of the safety of the experiment he meditated, from observing the invariable harmlessness of the disease when casually taken: he determined therefore to put his long-cherished idea to the trial on the first opportunity.
This offered on the 14th of May, 1796, the anniversary of which is still kept as a festival at Berlin. On that day he inoculated a boy of the name of Phipps in the arm, from a pustule on the hand of a young woman who was infected by her master’s cows. The boy went favourably through the disease. On the 1st of July he was inoculated for the small-pox, and, as Jenner had predicted, without effect.
The feelings of the sanguine philanthropist may be conceived. They cannot be better described than they have been by himself in the following terms. “While the vaccine discovery was progressive, the joy I felt at the prospect before me of being the instrument destined to take away from the world one of its greatest calamities, blended with the fond hope of enjoying independence and domestic peace and happiness, was often so excessive, that in pursuing my favourite subject among the meadows, I have sometimes found myself in a reverie. It is pleasant to me to recollect that these reflections always ended in devout acknowledgments to that Being from whom this and all other mercies flow.”