'Twenty minutes with the brainwave machine'. Photograph shows a brainwave recording in progress at London Hospital. The patient lies on a couch and is required to close her/his eyes in order to relax the brain. The 20 minute session is a humdrum siesta for the patient, during which 50 feet of recording is taken. The passage of each second is marked on the broad graph-tape'.
© Daily Herald Archive / National Science & Media Museum / Science & Society Picture Library