Evelyn Underhill

By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.

The constancy of the blood sugar level is maintained by a complex physiological mechanism, a homeostatic mechanism of the same order as those which maintain the body temperature, the blood pressure or the heart rate at normal levels and control many other functions.