Note 1 — Chapter XI · WALTER REED IN THE INTEREST OF SCIENCE—AND FOR HUMANITY!

By some unexplained sorceries he got hold of some good poisonous yellow fever blood, and filtered it through a porcelain filter that was so fine no visible microbe could get through it. The stuff that came through that filter Carroll shot under the skin of three non-immunes (history doesn’t tell how he induced them to stand for it)—and presto! two of them got yellow fever. Hurrah! Yellow fever was like foot-and-mouth disease then. Its cause was a germ maybe too little to see, a microbe that could sneak through fine-grained porcelain.⁠[1]