1. The freshest: matter is the most effectual. Whenever therefore it can be done, the insertion should be made immediately with a needle just dipped in the pus of a pustule. The beginning of suppuration is preferable to a more advanced state, as the matter is then more fluid, and comes off easier from the needle into the wound.
2. Instead of barely pricking the skin, the point ought, if possible, to be introduced between the cuticle and the inner skin, to the length of a quarter of an inch, which is easiest done with a flat-pointed needle. The impregnated needle will keep its virtue for several days, provided it is not rubbed against any thing; but it is always safest to use it soon.
3. Instead of the needle thus dipped, a cotton or silken thread may be used, that has lain some time, and been rubbed with pulverized variolous scabs. This thread may be drawn in with a needle, between the scarf and the true skin, to the length of two or three lines, but not left in. This is the method throughout the Indies.
- I have long suspected, that the variolous matter became milder by inoculation; and consequently, that a repetition of the like operations would still render it more harmless, though not less efficacious. This conjecture is now to me become a truth, from the experiments I have tried, and those which were made in England by the most experienced inoculators.