William H. Welch, MD, and the discovery of Bacillus welchii.

William H. Welch, MD, and his colleagues performed an autopsy at The Johns Hopkins Hospital in October 1891 on a 38-year-old man and discovered a new bacterium, Bacillus aerogenes capsulatus. During the postmortem examination, gas bubbles were noted within many of the patient's blood vessels. Welch's laboratory personnel determined that a previously unknown bacterium was the source of the gas. Through a series of experiments, the organism's characteristics were described and its pathophysiology was detailed, findings that proved accurate in explaining gas gangrene during World War I. Welch never followed up these initial investigations with more experimentation. His subsequent writings regarding the bacterium that came to be known, appropriately, as Bacillus welchii consisted mostly of case reports from other medical institutions and summaries of previous data.