John Snow, Asiatic Cholera and the inductive-deductive method - republished

Lecture 5: Disseminated source outbreaks

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“The duration of cholera in a place is usually in direct proportion to the number of the population.”

We saw in Lecture 3 that Snow deduced by the presence of an incubation period that the morbid poison of cholera needed time to replicate.  Now, he makes a further deduction (page 56).

Snow deduced that it must resemble a cell as it reproduces itself inside the body. This deduction is pure logic as no one had then connected what we now call Vibrio Cholerae Pacini to the onset of cholera. The vibrios were visible with a microscope, but as we shall see in Lecture 17, the connection between micro-organisms and disease had been made in a faraway land. Lacking modern communication, the two had not been reconciled.

When you make a logical deduction from tr…