We can continue to live in the very special environment which we carry forward with us only until we begin to decay more quickly than we can reconstitute  ourselves. Then we die. If our bodily temperature rises or sinks one degree from its normal level of 98.6º Fahrenheit, we begin to take notice of it, and if it rises or sinks ten degrees, we are all but sure to die. The oxygen and carbon dioxide and salt in our blood, the hormones flowing from our ductless glands, are all regulated by mechanisms which tend to resist any untoward changes in their levels. These mechanisms constitute what is known as homeostasis, and are negative feedback mechanisms of a type that we may find exemplified in mechanical automata. (Wiener 1989 :95-6)
WIENER, Norbert. 1989 . The human use of human beings: cybernetics and society. London: Free Association Books.