On the location of cellular functions in perfused organs

Rappaport's picture of liver cells performing specialized functions in spatially distinct zones arranged in relation to hepatic blood flow, is arrived at from a new direction. Previously published data from perfused rat livers eliminating labelled acetaminophen, both pre-formed and formed in the liver from phenacetin, are interpreted to imply that the formation takes place wholly upstream of the elimination. This analysis exemplifies a general method of mapping such functional zones in perfused organs.