Twort, F. W. (1915). "An Investigation on the Nature of Ultra-Microscopic Viruses". The Lancet. 186 (4814): 1241–1243. doi:10.1016/S0140-6736(01)20383-3. Further experiments showed the agent could pass through porcelain filters and it required bacteria for growth. He toyed with the idea that the bacteriolytic agent was vaccinia that invaded the bacteria in search of the "essential substance".
Twort, F. W. (1910). "A Method for Isolating and Growing the Lepra bacillus of Man. (Preliminary Note.)". Proceedings of the Royal Society B: Biological Sciences. 83 (562): 156–158. doi:10.1098/rspb.1910.0074.
Twort, F. W.; Ingram, G. L. Y. (1912). "A Method for Isolating and Cultivating the Mycobacterium enteritidis chronicae pseudotuberculosae bovis, Johne, and some Experiments on the Preparation of a Diagnostic Vaccine for Pseudo-tuberculous Enteritis of Bovines". Proceedings of the Royal Society B: Biological Sciences. 84 (575): 517. doi:10.1098/rspb.1912.0011.
Twort, F. W. (1915). "An Investigation on the Nature of Ultra-Microscopic Viruses". The Lancet. 186 (4814): 1241–1243. doi:10.1016/S0140-6736(01)20383-3. Further experiments showed the agent could pass through porcelain filters and it required bacteria for growth. He toyed with the idea that the bacteriolytic agent was vaccinia that invaded the bacteria in search of the "essential substance".