"It is a fact well known to many, that persons who have had the Cow Pox, are for ever after secure from the infection of the Small Pox."

"The cow-pox protects the human constitution from the infection of smallpox."

"It seems to be the determination of some of the jealous members of the ****** (R. *** Soc. y), not to suffer the Institution to sink, but on the / Other hand to master up a force, & support it with al…"

"The cow-pox is a mild disease, and never fatal; the small-pox is a formidable one, and often fatal. The cow-pox is not infectious; the small-pox is highly so."

"I have often reflected, with a degree of wonder, on the slow progress of human knowledge."