Some years ago the theory was brought forward, under the auspices of the great alchemistical artist, Hufeland, that Vaccination from Tartar Emetic pustules was a perfect substitute for Vaccination with Cowpox, and had the same beneficent effect. With this I fully agree; and I remark further, that if Tartar Emetic pustulation is produced in Cows and Calves, and vaccine matter is then taken from them, such Vaccination is also perfectly harmless. The most convincing proof of the beneficent and identical action of such Vaccination with that of Cowpox, is furnished by the fact that it presents pustules similar in size and form, therefore, necessarily of identical value.[99]
Having identified Horsegrease Cowpox with Smallpox, by reason of similarity of pustules, he went on to assert that such Horsegrease Cowpox was equivalent to Smallpox for inoculation, and was attended with the like prophylaxy, saying--
What renders the Cowpox virus so extremely singular is, that the person affected with it is forever after secure from the infection of the Smallpox; neither exposure to the variolous effluvia, nor the insertion of the matter into the skin producing this distemper. (P. 7.)
It is curious also to observe, that the virus, which, with respect to its effects, is undetermined and uncertain previously to its passing from the Horse through the medium of the Cow, should then not only become more active, but should invariably and completely possess those specific properties which induce in the human constitution symptoms similar to those of the variolous fever, and effect in it that peculiar change _which for ever_ renders it insusceptible of the variolous contagion. (P. 48.)
And so on. The assurance was absolute, and the warrant for the assurance was the Cases adduced, and the similarity of Horsegrease Cowpox pustules and Cowpox pustules! But if the pustules were similar, the effects were not similar. Inoculation with Smallpox produced Smallpox, mild or otherwise, with pustules few or many; but inoculation with Horsegrease Cowpox was attended with no eruption beyond the points of incision--
It is an excess in the number of pustules which we chiefly dread in the Smallpox; but in the Cowpox no pustules appear, nor does it seem possible for the contagious matter to produce the disease from effluvia; so that a single individual in a family might at any time receive it without the risk of infecting the rest, or of spreading a distemper that fills a country with terror. (P. 58.)