Twenty-four-hour rhythm in the mitotic activity and in the water and dry matter content of regenerating liver

Summary A twenty-four hour rhythm is described in the variations of mitotic activity, dry weight, and water content of the regenerating liver of mice hepatectomized about noon. These variables have their maximal value at the onset of the rest periods in the morning and their minimal values at the initiation of the body activity periods in the evening. The rhythm is well defined on the second day and is repeated on the third day on a higher level.We acknowledge the assistance of Mrs. R. Cavoura in performing the hepatectomies and that of Mrs. M. A. V. Albornoz in making the histologic slides.The present work was carried out with the help of grants from the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and Liga Mendocina de Lucha contra el Cáncer.