Edward Jenner · An Inquiry into the Causes and Effects of the Variolæ Vaccinæ · London, 1798
The deviation of Man from the state in which he was originally placed by Nature seems to have proved to him a prolific source of Diseases. From the love of splendour, from the indulgences of luxury, and from his fondness for amusement he has familiarised himself with a great number of animals, which may not originally have been intended for his associates.
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There is a disease to which the Horse, from his state of domestication, is frequently subject. The Farriers have termed it the Grease. … Thus the disease makes its progress from the horse to the nipple of the cow, and from the cow to the human subject.
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Case XVII.
The more accurately to observe the progress of the infection I selected a healthy boy, about eight years old, for the purpose of inoculation for the cow-pox. The matter was taken from a sore on the hand of a dairymaid, who was infected by her master's cows, and it was inserted, on the 14th of May, 1796, into the arm of the boy by means of two superficial incisions, barely penetrating the cutis, each about half an inch long.
On the seventh day he complained of uneasiness in the axilla, and on the ninth he became a little chilly, lost his appetite, and had a slight headache. During the whole of this day he was perceptibly indisposed, and spent the night with some degree of restlessness, but on the day following he was perfectly well.
In order to ascertain whether the boy, after feeling so slight an affection of the system from the cow-pox virus, was secure from the contagion of the small-pox, he was inoculated the 1st of July following with variolous matter, immediately taken from a pustule. Several slight punctures and incisions were made on both his arms, and the matter was carefully inserted, but no disease followed.
Several months afterwards he was again inoculated with variolous matter, but no sensible effect was produced on the constitution.
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I presume it may be unnecessary to produce further testimony in support of my assertion that the cow-pox protects the human constitution from the infection of the small-pox.
Thus far have I proceeded in an inquiry founded, as it must appear, on the basis of experiment; in which, however, conjecture has been occasionally admitted in order to present to persons well situated for such discussions objects for a more minute investigation. In the mean time I shall myself continue to prosecute this inquiry, encouraged by the hope of its becoming essentially beneficial to mankind.
Edward Jenner · Berkeley, Gloucestershire · 1798