Which journal published Alexander Fleming's original 1929 paper describing penicillin?

Alexander Fleming’s original 1929 paper describing penicillin was published in the British Journal of Experimental Pathology.

The paper’s full title was “On the Antibacterial Action of Cultures of a Penicillium, with Special Reference to their Use in the Isolation of B. influenzæ.” Fleming reported that a mould produced a substance capable of inhibiting bacteria, and he called that substance penicillin. The article appeared in volume 10, issue 3, pages 226–236.

Fleming’s observation followed an accidental contamination of a Staphylococcus culture by mould in 1928 at St Mary’s Hospital, London. His 1929 publication established the antibacterial effect, but it did not immediately lead to a usable drug. The work was initially overlooked because Fleming could not produce penicillin reliably or in sufficient quantity.

A common mix-up is associating the discovery with Nature, The Lancet, or the British Medical Journal. Those journals published other important medical and scientific work, but Fleming’s original report appeared in the British Journal of Experimental Pathology. Howard Florey, Ernst Chain, and their colleagues later developed methods that made penicillin practical as a medicine.