Before revision: Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.
After revision: citiyjJkhie URL |title=Endogenous | Define Endogenous at Dictionary.com |publisher=Dictionary.reference.com |accessdate=2011-07-11Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.