This equine virus from Jane King was extensively diffused. It was, we see, sent to London; it was also sent to Edinburgh;[154] and Dr. Baron says he had supplies of it for use in the Gloucester Infirmary. Baron relates that in the following year he was able to return the gift, having obtained virus from the hands of a boy infected directly from the horse. Here is Jenner’s acknowledgment of the present, dated 25th April, 1818-- My Dear Baron,--Yesterday H. Shrapnell brought me the equine virus and your drawing, which conveys so good an idea of the disease, that no one who has seen it can doubt that the vesicles contain the true and genuine life-preserving fluid. I have inserted some of it into a child’s arm; but I shall be vexed if some of your young men at the Infirmary have not done the same with the fluid fresh from the boy’s hand.[155] It is surely unnecessary to adduce further evidence of what was Jenner’s mature faith and deliberate practice. Further, it is manifest that to the end of his career he held that pox in the cow was not only derived from grease in the horse, but that it was exclusively derived from the horse, and, that apart from the horse, Cowpox would cease to exist. Owing to the multiplication of vaccination failures, it began to be conjectured that vaccine might be worn out by transmission from arm-to-arm, and that a reversion to the cow might be expedient; and discussing the question in a letter to Moore, dated 5th March, 1816, Jenner advanced the objection-- If there were a real necessity for a renovation, I know not what we should do; for the precautions of the farmers with respect to their horses have driven the Cowpox from their herds.[156] Why did not Moore rejoin, Where is the difficulty? Suppose pox driven from the herds, what conceivable reason was there for anxiety when the cow had become a demonstrated superfluity?--when, in Jenner’s own words, “the true and genuine life-preserving fluid” might be drawn direct from horses’ heels? Except for the perpetuation of imposture, the cow in the case had ceased to have any value whatever. But, as so often happens with quacks, their minds become so saturated with their own humbug that there is nothing left of common-sense. Having thus proved my assertions concerning Jenner, it may be reasonably asked, How was it that some got Cowpox by means of Horsegrease when others could not? for, it may be argued, that if Cowpox issued straight and invariably from inoculated Horsegrease, not even the most resolute prejudice against Horsegrease could have permanently kept back the truth. The answer is, that Cowpox never came out of what is commonly known as Horsegrease. The statement made by Jenner in his _Inquiry_ of 1798 that-- The limpid fluid which issues from the small cracks or fissures in the inflamed and swollen horse’s heel--