at. m i a , MhourlRate of cellular mn&,iplication i s an important factor in normal replacement kf aging tissues, in regeneration and in neoplastic growth. It.is not the same thing as rate of increase in size of any tissue or organ, or of the whole body. Such increase in size is dkmeioned not only by larger numbers of cells but also by inorease in non-living components. Assuming that the rate of cell multiplication i's constant, the number of cells in any grmp will depend 01 the mortality rate. For no cell type in the body are these twa rates known even under mnditions called normal.Epidermal cells of the skin are favorable for, investigation because, except for the questionable dendritic 9r Langerhans cells, they are allof one kind, though they exhibit different properties at different age levels as is to be expected. Moreover the problem is not mmplieated by the presence among these cells of b b d vessels, lymphatics, connective tissue cells and fibers.Evidence has recently been discovered in our laboratory that the epidermal cells of the human foreskin, removed by ckcumcision, do not multiply at a uniform rate throughoct the 24-hour period (Cooper and Schiff, ' 38, and Cooper, '39). The percentage of mitoses is much greater by night than by day.'Aided by a gmat from the W. 6. Public Health Serpiee recommended by the National Advisory Curter (Jouncil.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.