More than 70,000 children have come under my observation, either in hospital or in private practice; and I need not say that a physician having much consulting practice sees far more than the average of unusual and severe cases. Twice, and only twice, I have seen infants die from vaccination, and in both instances death took place from erysipelas beginning at the puncture. The one case I saw twice in consultation with the family practitioner. The other which I watched throughout was that of a little boy, the fifth child of a nobleman of high rank, both his parents being perfectly healthy. He was vaccinated by the family doctor in the country, direct from the arm of another perfectly healthy infant, from whom ten other infants were vaccinated immediately afterwards. The little boy was seized with convulsions within twenty-four hours, and almost at the same time erysipelas appeared on the punctured arm. The erysipelas extended rapidly, convulsions returned more than once, and on the fourth day from the vaccination the child died. One of the other children vaccinated at the same time died in the country in the same manner; all the others passed through vaccination regularly, and without a single bad symptom. I have no explanation to offer; this case stands by itself just as do those of death from the sting of a bee or death from cutting a corn. That some people die of other diseases since the introduction of vaccination, is undoubtedly true, for many of those who would have died in early infancy of small-pox are cut off later by measles or bronchitis, or die during teething; since it is obvious that vaccination does not protect against any other disease than small-pox. That protection, indeed, is not absolute, nor was the protection afforded by inoculation absolute; but small-pox after vaccination, even when it does occur, is very rarely severe, and still more seldom fatal. There seems good reason for believing that the protecting power of vaccination tends to diminish with the lapse of time; though apparently this is not always the case, nor can any direct statement be made as to the conditions which favour this in one case, or prevent it in another. As a matter of fact, however, we do know that such a tendency does exist, and that this tendency calls for the repetition of vaccination from time to time; such re-vaccination carefully performed being as nearly as possible an absolute guarantee against small-pox. All persons engaged as nurses or attendants at the Small-Pox Hospital during the past thirty-two years, have been vaccinated or re-vaccinated before entering on their duties, and during this period not a single case of the disease has occurred among the whole staff. The experience of other small-pox hospitals for a shorter period is identical. As far as we know, every seventh year is a reasonable interval at which re-vaccination should be performed.