title: [STUDIES ON ELECTROCARDIOGRAPHY IN CHILDREN. I. ON ELECTROCARDIOGRAPHIC CHANGES WITH AGE. 1. ON THE HEART BEAT, P WAVE, PQ INTERVAL AND QRS WAVE].
mesh_terms: D000293:Adolescent; D000375:Aging; D002648:Child; D004562:Electrocardiography; D006321:Heart; D006339:Heart Rate; D006801:Humans; D007223:Infant; D007231:Infant, Newborn
keywords: ADOLESCENCE; AGING; CHILD; ELECTROCARDIOGRAPHY; HEART; INFANT; INFANT, NEWBORN