One great cause of the failure of the protective power of vaccination is the unintelligent and careless manner in which it is too often performed, especially among the poor. To this same cause it is also due that in some cases of almost infinite rarity one special constitutional disease has been known to be communicated. I have never seen such a case, but I know there are such. They are, however, no more a reason against vaccination than the occasional death from an overdose of opium is a reason against the use of that drug. To avoid any risk of this kind, and also with the idea that the power of the vaccine matter may have become weakened by transmission through many thousands of persons, vaccination direct from the calf has been introduced of late years, especially in America and on the Continent. The time, however, that has as yet elapsed is scarcely sufficient to test the comparative preservative power of this as compared with vaccination from the human subject. Its immediate local effects are somewhat more severe; I do not know any reason why its influence should not be equally abiding. There is absolutely no foundation for the idea that scrofula, consumption, or any similar disease can be transmitted by vaccination. In some infants, whose skin is very delicate, and especially in those, some members of whose family have been liable to eruptions on the skin, vaccination has seemed to act as an irritant, and to give occasion to an eruption, or aggravate an eruption already existing. Such cases, however, are not frequent, and the eruption is not more troublesome than those which often appear in teething children. The occurrence of actual erysipelas around the puncture, while very dangerous, is, as I have already stated, of excessive rarity. A thoroughly dispassionate review of the whole subject appears to me to warrant the following conclusions:-- 1st. That vaccination, though not a perfect guarantee against small-pox, diminishes immensely the risk of its occurrence; and that by periodical revaccination, this guarantee is rendered all but absolute. 2nd. That a very large proportion of the failures of vaccination are due to its careless and imperfect performance. 3rd. That to such careless performance and to the introduction of the blood and not of the vaccine matter alone, from one child to another are due the extremely rare instances in which one special disease has been transmitted by vaccination. 4th. That there is absolutely no evidence of the transmission of scrofula, consumption, or any similar disease by vaccination. 5th. That vaccination direct from the calf appears to present some decided advantages; but it has not yet been practised for a sufficient time to admit of a comparison between its preservative power and that of vaccination from one child to another.