Insensitivity of a class of nonlinear compartmental systems to the introduction of arbitrary time delays

We examine a class of nonlinear compartmental systems and show that the introduction of arbitrary time delays, including nonconstant ones, in the action of one compartment on another, does not affect system properties such as stability, boundedness, and positivity. The results arise from a combination of techniques introduced separately for the studies of linear time-delay systems and nonlinear systems without delay and are directly testable. Some examples and estimates for the degree of stability are given.