Page:The Harveian oration 1866.djvu/52



Among others, John Hunter and Sir George Baker.

Harveii Opera, p. 6. Harvey's Works, by Willis, p. 6.

Harveii Opera, p. 7. Translation, by Willis, p. 7.

In the opinion of Jenner small-pox and cow-pox were the same disease; cow-pox was small-pox in the cow; vaccinia was variola, which had been modified by the constitution of the cow. Later researches seemed to confirm this opinion, which was all the more probable, in that it connected the fact of the protecting power of vaccination with the familiar fact of the protecting power of a first attack of small-pox. But the recent researches of the Lyons Committee furnish evidence which seems conclusive against this opinion. They have proved that small-pox and cow-pox, though closely allied, are yet distinct diseases. So the protective power of vaccination has become an isolated fact.

How little exact knowledge have we of the conditions of the body which increase or lessen the liability to