Welch's career as a pathologist was remarkable for his co-discovery in 1882, with George
H.F. Nuttall, of the organism that causes gas gangrene, known as Bacillus welchii, or Bacillus
Photograph of Bacillus aerogenes capsulatus.
Page from Welch's and Nuttall's Gas bacillus notes.
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One of the leading European investigators with whom Welch studied on his
early trips was Robert Koch. In 1885 (three years after Koch announced the discovery of
the tubercle bacillus) he took notes on Koch's demonstrations.
Welch's notes of Koch's demonstrations.
Click on image for full text of Welch's
Welch's notes (in German) from Robert Koch's lecture on "Tuberkel
bacillen" taken by Welch, July 1885.
Koch notes by Welch, "Cholera bacilli," July 1885.
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Welch's drawing of a colony of cholera bacilli, in his notes from Koch's
laboratory, July 25, 1885.
View additional notes by Welch, "Cholera bacilli", page 2.