General Articles And News Medical Statistics Br Med J 1956; 2 doi: https://doi.org/10.1136/bmj.2.4996.823 (Published 06 October 1956) Cite this as: Br Med J 1956;2:823 Article Related content Metrics Responses Peer review Related articles Correction Correction Published: 16 October 1965; Br Med J 2 doi:10.1136/bmj.2.5467.946-e