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 accountfor 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 cowpox, 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 beenalready 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."

During the next two years many other equally successful trials were

made; and at length the discovery was published to the world in June, 1798, in a quarto pamphlet of seventy pages, which had been previously subjected to the most rigorous criticism and revision by a few chosen friends who met for that purpose at the house of Thomas Westfaling, Esq., at Rudhall, near Ross. It is entitled An Inquiry into the Causes and Effects of the Variola Vaccinæ; a disease discovered in some of the Western Counties of England, particularly Gloucestershire, and known by the name of the Cow-pox.' The pamphlet is enriched with the detail of sixteen cases of the casual, and seven of the inoculated disease, the latter including the case of one of the author's sons; and with coloured drawings of the appearances in both.

The style of this pamphlet, as well as of others which succeeded it from Jenner's pen in the course of a few years, is remarkably modest, and admirable in all respects, which probably contributed much to the early. favour it received. The facts were such as to defy contradiction, and the conclusions so just and mature, that the experience of nearly forty years has been able to add little more than its seal of confirmation to them. The few errors that have been detected relate chiefly to the degree of protection afforded by the cow-pox, which Jenner affirmed to be perfect: it is now however believed to be incomplete, perhaps in three instances out of every hundred; that small proportionate number passing, in general after the lapse of some years, through a very mild and modified small-pox, in which the per-centage of fatal cases is certainly not more, and probably much less, than five; being not more than three in 2000 of all vaccinated persons, while the rate of mortality even in inoculated small-pox is one in fifty, or forty in 2000. It should be borne in mind that small-pox itself sometimes occurs a second time even in a severe and fatal form, as in the case of Louis XV. Some constitutional peculiarity is probably the occasion of both these anomalies; and this supposition will also account for the oftenobserved fact, that small-pox after vaccination commonly affects several members of the same family almost simultaneously, thus giving an appearance of failure in a proportion much greater than the truth.

Another position advanced by Jenner in this pamphlet is too remarkable to be passed over. After stating his belief that the cow-pox originates from the horse in the way already mentioned, he proceeds to suggest that the small-pox may have been itself originally morbid matter of the same kind, aggravated into a malignant and contagious form by accidental circumstances. But this opinion, though plausible, is not considered by any means as established.

Favourably as his work was received, the author, who had come to

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London partly to superintend the publication, was unable to obtain an opportunity of displaying the disease in that city, which had been the chief object of his visit; and returned, much disappointed, to Cheltenham, where he now frequently resided, in the middle of July. He left, however, some vaccine lymph with Mr. Cline, who was the first surgeon in London that ventured to make a trial of it. The complete success of the experiment, which was publicly performed, so strongly interested the profession, that the new practice became quickly popular, in spite of a warm though partial opposition, which was put down in the summer of 1799 by a manifesto expressive of confidence in its efficacy and safety, signed by seventy-three of the most eminent medical men in the metropolis. In the same year some unfortunate occurrences took place in consequence of Dr. Woodville, the physician of the Small-pox Hospital, having incautiously used and distributed matter from persons whom he had inoculated with small-pox a few days after vaccination, before it had taken a sufficient hold. The mongrel lymph thus produced sometimes occasioned one, sometimes the other disease; their effects were confounded; and some deaths which ensued, as well as a general eruption of the skin which took place in many instances, were attributed to the cow-pox. This and other mistakes would probably have much retarded the general adoption of vaccination, but for the promptitude of Jenner to discover and expose the source of the error.

In 1802 a parliamentary inquiry into the value of the new method of preventing small-pox, including Jenner's claim to the discovery of it, was instituted, and a grant was voted to him of 10,000l. In 1807 he received an additional vote of 20,0007., which, considering that he had been the instrument of saving in England alone at least 45,000 lives annually, will seem by no means an extravagant mark of national gratitude and respect.

In 1803 the Royal Jennerian Society, for the encouragement of vaccination, was established in London under the superintendance of Dr. Jenner. In 1808 this society was merged by his advice in the National Vaccine Establishment, which still continues to dispense the blessings of the antidote at the public charge.

The growing interest in the public mind in favour of vaccination was of course everywhere extended to its author, who, in spite of several unworthy cabals, and attempts to deprive him of the credit of a discovery peculiarly his own, was received among all ranks with the highest distinction at home, and also gratified with various continental honours. If he had thought fit to settle in London, he might

undoubtedly have secured wealth in proportion to his reputation; but he preferred the quiet enjoyment of rural life and domestic happiness. His death took place at Berkeley, from a sudden attack of apoplexy, in February, 1823, in the seventy-fourth year of his age. The latter years of his life were spent between Berkeley and Cheltenham, and in occasional visits to London, in the zealous prosecution of his favourite subjects of research, and successful endeavours to diffuse the blessings of his discovery more widely in his own and other lands.

In England, however, these have not been so extensively felt as in some other countries where the form of government has given facilities for the enforcement of vaccination. The small-pox consequently prevails to a considerable extent in this country, and especially in London. Yet the annual number of deaths from small-pox within the bills of mortality is at present under 700; the largest number in one year since the general practice of vaccination having been 1299, in 1825. A century ago, when the population certainly did not reach half its present amount, the yearly average was 2000, the maximum being in 1796, when the mortality swelled to 3549. That this decrease is wholly due to vaccination cannot be doubted; the advantage, however, is partly indirect, and has arisen from the discontinuance of the practice of inoculating for the small-pox, which afforded security to individuals, but increased the general mortality by keeping alive a constant source of infection. But the most striking examples of the advantage derived from vaccination are to be found on the continent. Thus at Berlin, where the average annual amount of deaths from small-pox was 472 for the twenty years previous to 1802, and 1646 died in 1801, the mortality so speedily diminished after the enforcement of vaccination by law, that in 1821 and 1822 there was only one death in each year. These and similar instances which might be adduced from other countries, seem almost to warrant us in adopting the sanguine expectation of Jenner, that by means of his discovery this disgusting and dreadful malady, from which not four in a hundred of the human race wholly escaped, and which destroyed a tenth part of all that were born, and disfigured where it did not destroy, may yet be swept from the face of the earth.

The best books of reference on the subjects of this memoir are 'Baron's Life of Jenner,' Moore's History of the Cow-pox,' Dr. Gregory's admirable articles in the Encyclopædia of Medicine,' and the reports of various parliamentary committees, especially those of 1802 and 1833.