At the English Ministry of Health's Pathological Laboratory bacteriologist Frederick Griffith was sent pneumococci samples taken from patients throughout the country. He amassed a large number, and would type—in other words classify—each pneumococci sample to research patterns of pneumonia epidemiology. In 1928 he published "The Significance of Pneumococcal Types," Journal of Hygiene (Cambridge) 27 (1928) 113-59. In this paper he showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. This phenomenon he attributed to an unidentified transforming principle or transforming factor.
Griffith's research was one of the first experiments that suggested that bacteria are capable of transferring genetic information through a process known as transformation. Research by Avery, MacLeod, and McCarty reported in 1944 isolated DNA as the material that communicated this genetic information.
J. Norman (ed) Morton's Medical Bibliography 5th ed (1992) no. 251.2.