a history of science-4-第38章
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JENNER AND VACCINATION
All advances in science have a bearing； near or remote； on the welfare of our race； but it remains to credit to the closing decade of the eighteenth century a discovery which； in its power of direct and immediate benefit to humanity； surpasses any other discovery of this or any previous epoch。 Needless to say； I refer to Jenner's discovery of the method of preventing smallpox by inoculation with the virus of cow…pox。 It detracts nothing from the merit of this discovery to say that the preventive power of accidental inoculation had long been rumored among the peasantry of England。 Such vague； unavailing half…knowledge is often the forerunner of fruitful discovery。
To all intents and purposes Jenner's discovery was original and unique。 Nor； considered as a perfect method； was it in any sense an accident。 It was a triumph of experimental science。 The discoverer was no novice in scientific investigation； but a trained observer； who had served a long apprenticeship in scientific observation under no less a scientist than the celebrated John Hunter。 At the age of twenty…one Jenner had gone to London to pursue his medical studies； and soon after he proved himself so worthy a pupil that for two years he remained a member of Hunter's household as his favorite pupil。 His taste for science and natural history soon attracted the attention of Sir Joseph Banks； who intrusted him with the preparation of the zoological specimens brought back by Captain Cook's expedition in 1771。 He performed this task so well that he was offered the position of naturalist to the second expedition； but declined it； preferring to take up the practice of his profession in his native town of Berkeley。
His many accomplishments and genial personality soon made him a favorite both as a physician and in society。 He was a good singer； a fair violinist and flute…player； and a very successful writer of prose and verse。 But with all his professional and social duties he still kept up his scientific investigations； among other things making some careful observations on the hibernation of hedgehogs at the instigation of Hunter； the results of which were laid before the Royal Society。 He also made quite extensive investigations as to the geological formations and fossils found in his neighborhood。
Even during his student days with Hunter he had been much interested in the belief； current in the rural districts of Gloucestershire； of the antagonism between cow…pox and small…pox； a person having suffered from cow…pox being immuned to small…pox。 At various times Jenner had mentioned the subject to Hunter； and he was constantly making inquiries of his fellow…practitioners as to their observations and opinions on the subject。 Hunter was too fully engrossed in other pursuits to give the matter much serious attention； however； and Jenner's brothers of the profession gave scant credence to the rumors； although such rumors were common enough。
At this time the practice of inoculation for preventing small…pox； or rather averting the severer forms of the disease； was widely practised。 It was customary； when there was a mild case of the disease； to take some of the virus from the patient and inoculate persons who had never had the disease； producing a similar attack in them。 Unfortunately there were many objections to this practice。 The inoculated patient frequently developed a virulent form of the disease and died； or if he recovered； even after a mild attack； he was likely to be 〃pitted〃 and disfigured。 But； perhaps worst of all； a patient so inoculated became the source of infection to others； and it sometimes happened that disastrous epidemics were thus brought about。 The case was a most perplexing one； for the awful scourge of small…pox hung perpetually over the head of every person who had not already suffered and recovered from it。 The practice of inoculation was introduced into England by Lady Mary Wortley Montague （1690…1762）； who had seen it practised in the East； and who announced her intention of 〃introducing it into England in spite of the doctors。〃
From the fact that certain persons； usually milkmaids； who had suffered from cow…pox seemed to be immuned to small…pox； it would seem a very simple process of deduction to discover that cow…pox inoculation was the solution of the problem of preventing the disease。 But there was another form of disease which； while closely resembling cow…pox and quite generally confounded with it； did not produce immunity。 The confusion of these two forms of the disease had constantly misled investigations as to the possibility of either of them immunizing against smallpox； and the confusion of these two diseases for a time led Jenner to question the possibility of doing so。 After careful investigations； however； he reached the conclusion that there was a difference in the effects of the two diseases； only one of which produced immunity from small…pox。
〃There is a disease to which the horse； from his state of domestication； is frequently subject；〃 wrote Jenner； in his famous paper on vaccination。 〃The farriers call it the grease。 It is an inflammation and swelling in the heel； accompanied at its commencement with small cracks or fissures； from which issues a limpid fluid possessing properties of a very peculiar kind。 This fluid seems capable of generating a disease in the human body （after it has undergone the modification I shall presently speak of） which bears so strong a resemblance to small…pox that I think it highly probable it may be the source of that disease。
〃In this dairy country a great number of cows are kept； and the office of milking is performed indiscriminately by men and maid servants。 One of the former having been appointed to apply dressings to the heels of a horse affected with the malady I have mentioned； and not paying due attention to cleanliness； incautiously bears his part in milking the cows with some particles of the infectious matter adhering to his fingers。 When this is the case it frequently happens that a disease is communicated to the cows； and from the cows to the dairy…maids； which spreads through the farm until most of the cattle and domestics feel its unpleasant consequences。 This disease has obtained the name of Cow…Pox。 It appears on the nipples of the cows in the form of irregular pustules。 At their first appearance they are commonly of a palish blue； or rather of a color somewhat approaching to livid； and are surrounded by an inflammation。 These pustules； unless a timely remedy be applied； frequently degenerate into phagedenic ulcers； which prove extremely troublesome。 The animals become indisposed； and the secretion of milk is much lessened。 Inflamed spots now begin to appear on different parts of the hands of the domestics employed in milking； and sometimes on the wrists； which run on to suppuration； first assuming the appearance of the small vesications produced by a burn。 Most commonly they appear about the joints of the fingers and at their extremities； but whatever parts are affected； if the situation will admit the superficial suppurations put on a circular form with their edges more elevated than their centre and of a color distinctly approaching to blue。 Absorption takes place； and tumors appear in each axilla。 The system becomes affected； the pulse is quickened； shiverings； succeeded by heat； general lassitude； and pains about the loins and limbs； with vomiting； come on。 The head is painful； and the patient is now and then even affected with delirium。 These symptoms； varying in their degrees of violence； generally continue from one day to three or four； leaving ulcerated sores about the hands which； from the sensibility of the parts； are very troublesome and commonly heal slowly； frequently becoming phagedenic； like those from which they sprang。 During the progress of the disease the lips； nostrils； eyelids； and other parts of the body are sometimes affected with sores； but these evidently arise from their being heedlessly rubbed or scratched by the patient's infected fingers。 No eruptions on the skin have followed the decline of the feverish symptoms in any instance that has come under my inspection； one only excepted； and in this case a very
