title: A contribution to the problem of the concept "biological clock". I.
mesh_terms: D001683:Biological Clocks / Q000266:history; D002940:Circadian Rhythm; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D010507:Periodicity; D012621:Seasons; D009626:Terminology as Topic; D013995:Time; D013997:Time Factors