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A comparative sketch of the effects of variolous and vaccine inoculation, being an enumeration of facts not generally known or considered, but which will enable the public to form its own judgment on the probable importance of the Jennerian discovery / [Thomas Pruen].

Pruen, Thomas, approximately 1772-1834.

Date:: 1807

Credit: A comparative sketch of the effects of variolous and vaccine inoculation, being an enumeration of facts not generally known or considered, but which will enable the public to form its own judgment on the probable importance of the Jennerian discovery / [Thomas Pruen]. Source: Wellcome Collection.

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$oné followed:—Instances were not wanting to prove, that when the ¢rue Cow-pox broke out among the cattle, persons who had milked an infected animal, and had, ap. parently, gone thro’ the disease, were still liable to the Small-pox. ‘ This, like the former obstacle,” continues Dr. J. “‘ gave a painful check to my fond and aspiring hopes; but; reflecting that the operations of Nature are generally uniform, and that it was not probable the human constituticn, having undergone the Cow-pox, should, in some instances, be perfectly shielded from the Small-pox, and in many others remain unprotected, I resumed my labours with redoubled ardour. The re- sult was fortunate; for I now discovered that the vi- rus of Cow-pox was liable to undergo progressive changes from the same eauses, precisely as that of Small- pox, and that when it was applied to the human skin in its degenerated state, it would produce the ulcerative effects in as great a degree, as when it was not decom- posed, and sometimes far greater; but, having lost its specific properties, it was incapable of producing \that change upon the human frame which is requisite to render it unsusceptible of the variolous contagion: so that it became evident, a person might milk a cow one day, and, having caught the disease, be for ever se- cure, while another person, milking the same cow the next day, might feel the influence of the virus in such a way as to produce a sore or sores, and, in conse- quence of this, might experience an indisposition to a considerable extent; yet, as has been observed, the spe- cific quality being lost, the constitution would receive no peculiar impression.” In this particular he found a close analogy between the virus of Cow-pox and that of Smal]-pox, which, if taken at an advanced stage of the disease, or, though taken early, if exposed to such agents as cause its decomposition, is equally ineffectual. ‘The pot attending to this circumstance will, he conceives,$