Jenner was remarkable for the neatness and precision with which he made preparations of anatomy and natural history. His dissection of tender and delicate organs, his success in minute injections, and the taste he displayed in their arrangement are said to have been almost unrivalled. Hunter recommended him to Sir Joseph Banks, to prepare and arrange the various specimens brought home by the celebrated circumnavigator, Captain Cook, in his first voyage of discovery in 1771, and he was solicited to become the naturalist of the succeeding expedition in the year following; but Jenner's partiality to his native soil, and his desire of settling in the place of his birth, were too strong to admit of his being allured into such an appointment. He preferred the seclusion of a country village; and to this selection do we owe one of the greatest blessings ever bestowed upon mankind. It is not unreasonable to suppose that the subject by which he should afterward be known to the whole world, dwelt upon his mind with considerable force even at this early period, for the prophylactic powers of the cowpox were known, or rather rumored of, in a few districts, and the subject had been mentioned by Jenner to Hunter and others, though he had not been successful in directing their attention sufficiently to the importance of it. Indeed, he pressed this subject so much upon his professional brethren, that, at a medical club at Redborough to which he belonged, he was threatened to be expelled if he persisted in harassing them with a proposition which they then conceived had no foundation but in popular and idle rumor, and which had become so entirely distasteful to them. It remained, therefore, to Jenner to pursue the inquiry and to place the whole matter upon a proper physiological basis, by which it might be rendered permanently beneficial. This inquiry was perfected amid the labors and anxious toils attendant on the life of "a country surgeon," with few books to consult, and little leisure to devote to their perusal. Observation necessarily supplied the place of literary research; the book of nature was open to his view, and it was one he was well calculated to comprehend; it surpassed all others, and its contemplation amply repaid the student.
Of all classes of men with whom it has been the fortune of the writer of this sketch to associate, there is none, in his opinion, so generally and so truly amiable as the naturalists. The contemplation of nature seldom fails to produce an elevation of character; it also begets a sweetness of disposition flowing from a sense of what is beautiful in creation; and the evidences of beneficence, everywhere so abundant, soften the feelings and impart to the individual a sincere benevolence of heart. This disposition was strikingly manifested in Jenner, to whose affection, kindness, meekness, good-will, and benevolence so many have borne the most ample testimony. It was no uncommon thing for Jenner to be accompanied in his daily professional tour of many miles by friends, who have eagerly listened to the outpourings of his mind called forth by the beauties which in the vale of Gloucester surrounded him.
His observations on the structure and economy of the various objects of natural history were delivered with the most captivating simplicity and ingenuity. Full of information himself, he delighted to impart it, and was equally solicitous of obtaining a return from others. He was an enthusiast in his devotion to nature, and he anxiously desired that all should participate in the gratification which such a study never failed to afford. He united in an especial manner a talent for the most profound observations to a disposition most lively and ardent distinguished by mirth, playfulness, and wit. With these powers, it is not surprising that his society should have been much courted; and, fully engaged as he was by the duties of an extensive practice, he yet found time to cultivate an acquaintance with polite literature. Many little productions of his muse have appeared in print; they were addressed to some of his more favored correspondents, or occasionally read at convivial meetings, and display the turn of his mind, the benevolence of his disposition, and the liveliness of his imagination. His best poetical productions find their subjects in natural history. The Signs of Rain unites the accuracy of the naturalist with the fancy of the poet.
Jenner had nearly passed half a century before he made known to the world his experiments and investigations relative to the vaccine disease. His first successful vaccination was made May 14, 1769. His ardor from an early period had been noticed, and it took its rise from the following accidental circumstance. While a pupil with Mr. Ludlow, a young countrywoman applied for advice. The subject of smallpox was mentioned, upon which she observed, "I cannot take that disease, for I have had the cowpox." This was sufficient to excite the attention of Jenner, and the incident never escaped his recollection. It is easier to conceive than to express the emotions which would naturally spring from reflection on such a subject; his benevolent feelings were at once aroused to full activity; he pictured to himself all the horrors of that pestilential and most loathsome disease, disfiguring Nature's greatest work, slaying thousands upon thousands, and he was yet sufficiently young to recollect the severity of discipline to which he had himself submitted in the process preparatory to the practice of inoculation, which, to use his own words, in that day was no less than that of "bleeding till the blood was thin; purging till the body was wasted to a skeleton; and starving on vegetable diet to keep it so."
The patience manifested by Jenner in the prosecution of his inquiry into the cowpox, the scrutiny to which he subjected every appearance that presented itself, and the fortitude with which he withstood every untoward circumstance entitle him to all praise and show forth his great capabilities for conducting a philosophical investigation. He divested the subject of all its difficulties and obscurities, and gave to "vague, inapplicable and useless rumor the certainty and precision of scientific knowledge." The extent of his anticipations upon this truly momentous subject do not appear to have been fully stated until 1780, ten years subsequent to his mention of it to John Hunter. He then confidentially disclosed to his intimate friend, Edward Gardner—who gave evidence upon the subject before the committee of the House of Commons—the opinions he entertained upon the natural history of the cowpox; dated its origin from the diseased heel of a horse; alluded to the different diseases with which the hands of the milkers became affected from handling the infected cows; distinguished that which was calculated to afford security against the smallpox; and divulged the hope he entertained of being able finally to eradicate that disease from the face of the globe. Doctor Baron has recorded the remarkable words with which this important communication was made:
"I have intrusted a most important matter to you, which I firmly believe will prove of essential benefit to the human race. I know you, and should not wish what I have stated to be brought into conversation; for should anything untoward turn up in my experiments I should be made, particularly by my medical brethren, the subject of ridicule—for I am the mark they all shoot at."
Jenner's reasons for concealment did not arise from any selfish or unworthy motive. The publicity he had always given to the subject and the efforts he had made among his professional associates to pursue the inquiry exclude the possibility of entertaining such a suspicion. It arose from a dread of disappointment and the fear of failure should the matter be brought forward in a state other than that of a maturity sufficient to carry conviction immediately upon its promulgation. In the course of his researches he was led to conclude that swinepox, as well as cowpox, was only a variety of smallpox. He inoculated his eldest son with the matter of swinepox and produced a disease similar to a very mild smallpox. After this, the inoculation of variolous matter would produce no effect.
He ascertained that cowpox, as it was commonly termed by the milkers, would frequently fail in effecting a security against the smallpox. This led him to inquire more particularly into the variety of spontaneous eruptions to which the teats of the cow were liable, and to discriminate the different kinds of sores produced by them on the hands of the milkers, and to establish the character of those which possessed a specific power over the constitution, and those which had no such efficacy. He found that instances occurred in which the true cowpox failed in preventing smallpox; but nothing daunted by this apparently fatal discovery he set about ascertaining the causes of this deviation. He found the specific virtues of the virus to have been lost or deteriorated so that it was rendered capable only of producing a local affection and had no influence whatever upon the constitution; and by the greatest ingenuity and patience of observation of the analogies drawn from the virus of smallpox, aided by his knowledge of the laws of the animal economy, he discovered that it was only in a certain state of the vesicle that the virus was capable of affording its protecting agency, and that when taken under other conditions, or at other periods, it could produce a local disease, yet that it was not able to manifest any constitutional effect, or afford immunity from the invasions of the smallpox.
On May 14, 1796, Jenner inserted lymph taken from the hand of Sarah Nelmes who was infected with cowpox, into the arm of James Phipps, a healthy boy about eight years of age. This is the first instance of regular inoculation of the vaccine disease by Jenner. The boy went through the disorder, and on July 1st following he had the matter of smallpox introduced into his arm, but no effect followed. Jenner had not before seen the cowpox but as presented on the hands of the milkers, nor had it been transmitted from one human being to another. He was struck with its great resemblance to the smallpox pustule. The success of this case must necessarily have operated powerfully upon him, and have urged him to continue the research with increased energy.
His anticipations thus realized, his intentions accomplished, what must have been the feelings of such a man as Jenner? They were suited to the magnitude of the occasion, and mark the character of the philosopher, distinguished as it ever was by great simplicity, benevolence, and humility. "While," says he, "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 favorite subject among the meadows I have sometimes found myself in a kind of 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." Lord Bacon said that "it is Heaven upon earth to have a man's mind move in charity, rest in Providence, and turn upon the poles of truth." Jenner was a striking illustration of the truth of that remark.