In 1875 T. H. Huxley discovered that a secretion from the mould penicillium glaucum had an ability, unconnected with oxygen deprivation, to inhibit bacterial growth. He recorded his observations in his notebooks and in a single letter to John Tyndall, who at that time was a friend of Lister and a correspondent of Pasteur. Neither Huxley nor Tyndall looked for an explanation of this phenomenon, and neither told anyone else about it.