At the close of last century, variolation had become the custom of the upper and middle classes of England. The trouble and the peril were disliked, but were accepted in the name of duty. The variolation of their children was an anxiety that weighed like lead on the hearts of affectionate parents; and glad and grateful they were when the operation was accomplished without serious mishap. Patients designed for variolation were dieted, purged, and bled; and smallpox from sufferers of sound constitution was diligently inquired for. Mild smallpox was in great demand and was propagated from arm to arm. When Dr. Dimsdale operated on the Empress Catharine he did not venture to convey smallpox direct to the imperial person. He looked out a case of “benign smallpox” with which he inoculated a strong young man, and from the young man the Empress. Unless we realise the inconveniences, the uncertainties, the disasters and the horrors of the practice of variolation, albeit minimised, excused and denied by its professors, we can never understand the enthusiasm with which vaccination was received as its substitute. The promise conveyed in vaccination was a relief inexpressible, bearing with it a show of reason that was well nigh irresistible. The argument ran thus: No one can have smallpox twice, and the mildest attack is as protective from subsequent attack as the severest. Therefore it is that in inoculation with smallpox we find security. But inoculation with smallpox is an uncertain operation with dangerous issues. Here, however, in cowpox is discovered a mild variety of smallpox, which may be inoculated with perfect ease, and with no possibility of harm. And inasmuch as the mildest smallpox is as preventive of future smallpox as the severest, it follows that this gentle cowpox must serve as a full equivalent for smallpox itself. IMMEDIATE TRIUMPH OF VACCINATION.