On the Specificity of Bacterial Mutation, with a Résumé of the Results of an Examination of Bacteria found in Faeces and Urine, which undergo Mutation when grown on Lactose Media

Neisser in 1906 claimed to have discovered an organism which, when grown on lactose-agar, threw off suddenly a new strain capable of fermenting lactose. The identity of the new strain was established by Massini (1907) by many cultural and serological tests, and from that time onwards it has been generally accepted that new bacterial strains of great permanence may arise so suddenly as to justify this type of variation being named “ Mutation.”