🚰On the Mode of Communication of Cholera

Cholera is not carried by bad air. It is carried by something swallowed, which passes out of the sick and reaches the next person through water fouled by sewage. He argues it from how the disease behaves in the body, from how it travels along routes of human contact, from one street pump, and most forcefully from the death rates of households supplied by two different water companies in the same streets.

The limits, as I read them.

• He had no mechanism. The organism was not accepted for another generation. He was arguing from pattern alone, which is why the pattern had to be so clean.
• The pump story is weaker than its legend. By the time the handle came off, the outbreak was already falling, because most of the neighbourhood had fled. He says this himself. See 💡 The Broad Street pump handle was removed in September 1854.
• The comparison was a gift, not a design. Nobody assigned houses to companies. He argues that the mixing was as good as random, and it is a strong argument, but it is an argument.
• The counting was done on foot, by him. He went from house to house asking which company supplied the water. Many tenants did not know, and he devised a chemical test on the water to tell. One man's fieldwork, with one man's errors.
• It did not persuade the people it needed to. The official inquiry of the day rejected his conclusion. Being right and being believed were separated by about a decade.

• Adaeze Nwosu's recommendation, made at the break in the last lecture: if you want to see a comparison done properly, read the water companies, not the map. She runs a ward. I did as I was told.
• Read on the 07:42 to Averley on Friday 6 June and finished at Mum's kitchen table on Saturday, in the gaps between visiting hours. A book about a London epidemic, read on the way to a hospital. Not my best planning.
• Public domain, 1855. I could quote it. I have not, because what matters in it is a table.
• Everyone knows the pump and the map. The pump is one chapter. The larger part of the book is a comparison of two water companies, and it is as close to a controlled trial as anyone could get in 1854 without meaning to.
• He is a working doctor writing fast, in the middle of an argument he is losing. It reads that way, in a good sense.