Welsh reports one hundred and ninety-four cases of vaccination performed during the stage of incubation, in which thirty-eight were perfectly protected against smallpox, sixteen almost perfectly protected, thirty-one protected to a well-marked degree, thirty partially protected, and seventy-nine were unprotected. Of these one hundred and ninety-four cases the death-rate was 12.90 among those vaccinated early in the stage of incubation; it was 40.98 among those vaccinated from one to seven days before the eruption of smallpox appeared; while among the unvaccinated cases the death-rate amounted to fifty-eight per cent. As it is well known that a secondary vaccination runs its course more rapidly than a primary one, it is evident that if an exposed patient has been already vaccinated a secondary vaccination is more apt to exert a protective influence. Since vaccination with humanized virus is more speedy in its effect than when bovine lymph is used, it is advisable to employ the former when readily obtainable and to make several insertions in order to increase the probability of success. Even a late vaccination in the stage of incubation may be of value, as it sometimes happens that this period lasts fourteen days or more. Early in the nineteenth century Waterhouse claimed that two days after infection vaccination would save the patient. Good results from the subcutaneous injection of vaccine lymph have also been claimed by Farley and others, but the efficacy of this method of treatment appears to have been assumed rather than proven. The speedy vaccination of all those who have been accidentally exposed to smallpox infection will do no harm, even if it fails to modify the disease when contracted. Indeed, it is always advisable, since the persons exposed, even if not already infected, are liable to contract the disease through possible subsequent exposure; and in the case of a threatening epidemic no precaution should be neglected which might tend to lessen the number of possible cases. Since no drug nor specific remedy exists which administered during the period of incubation will abort or modify the subsequent eruption, the only thing to be done is to prepare the patient by means of a rigid regimen and all possible hygienic measures to withstand the impending attack. When the fact of exposure is certain, forewarned should be forearmed.