Such are the leading varieties of virus used for vaccination--starting with Jenner’s horsegrease cowpox, then cowpox, then horsepox, then smallpox cowpox, and finishing with cowpox revived; each of them inscrutably modified in transit from child to child and from beast to beast. We are continually hearing of miracles wrought by vaccination in the past and present--especially the past, at home and abroad--especially abroad, the assumption being that vaccination is, and has been, everywhere the same. On the contrary, the condition precedent to serious consideration of any vaccine miracle is a definition of the variety of vaccination practised. It is, we admit, convenient for the administrators of the rite that it should pass for uniform, however multiform; for the practice has become a great and lucrative business--a world-wide poll-tax; and whatever the internal differences of the priesthood, it is their obvious interest to exhibit a decorous unanimity in presence of their customers. Hence the uneasiness recently excited by indiscreet advocates of “pure lymph from the calf” has been judiciously allayed, not by resistance, but by concession and damnation with faint praise; the commercial instinct dictating caution, for if the public did get behind the professional screen, and discovered the mysteries of pox, what might not befall the craft of vaccination! JENNER’S SUCCESSIVE DISCLAIMERS. The story of vaccination is a story of failures, and as each failure has become manifest, it has been more or less artfully apologised for. Much is given to assurance. People like infallible prescriptions. They prefer an unequivocal lie to an equivocal answer. This adventurers understand, and discourse accordingly. Hence when Jenner solicited Parliament for largess, he did so in no doubtful terms. He boldly declared that cowpox was “inoculated on the human frame with the most perfect ease and safety,” and was “attended with the singularly beneficial effect of rendering through life the person so inoculated perfectly secure from the infection of smallpox.” Again he said, “The human frame, when once it has felt the influence of genuine cowpox, is never afterwards, at any period of its existence, assailable by smallpox.”