About the imagination, there might be little difficulty: the difficulty lay in the production of proof that any disease in man was derived from disease in animals, and that disease so derived was variously manifested. Jenner wished to have it believed that a variety of Cowpox was generated from Horsegrease, which Cowpox was the source of Smallpox. He adduced no evidence, however, to connect outbreaks of Smallpox with Cowpox; nor did he ever suggest that dairymaids caught Smallpox from Cows, or farriers from Horses. His identification of Horsegrease Cowpox with Smallpox was the resemblance of their pustules, and on the ground of this resemblance he affirmed the equivalence of the diseases. Thus in describing his first inoculation of Cowpox, that of Phipps from the hand of Sarah Nelmes on the 14th of May, 1796, he wrote-- The appearance of the incisions in their progress to a state of maturation was much the same as when produced in a similar manner by variolous matter. This appearance was in a great measure new to me, and I ever shall recollect the pleasing sensations it excited; as, from its similarity to the pustule produced by variolous inoculation, it incontestably pointed out the close connection between the two diseases, and almost anticipated the result of my future experiments. (P. 30.) The similarity of the Cowpox and Smallpox pustules _incontestably pointed out_ the close connection between the two diseases! The observation and the conclusion are worth notice, being characteristic of Jenner’s loose and illogical mind. He was familiar with Tartar Emetic, and he might have observed that it produced pustules on the skin exactly like those of Cowpox and Smallpox; wherefore would it have been fair to argue that the pustules being alike, their causes were incontestably identical? Dr. Hamernik of Prague observes-- 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--