[Systems theory in medicine and biology]

We try to determinate, that systems theory has to be introduced into modern medicine. The biological roots as well as the cybernetic ones are outlined. Among various concepts about systems theory the evaluation by Riedl seems to be the most efficient to explain medical procedures. His basic informations refer to von Bertalanffy, the additional introduction of a 4-cause-principle, Aristoteles, permits the explanation of complex relations. The examples of tumor and inflammation are used to demonstrate the basic idea of the formal cause as well as the final cause. The latter should also become an important fact in the solution of other medical problems.