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194 WALTER R. STAHL

a discussion of simulation of biological systems of all types by Muses

(1962) . A pioneer of biological cybemetics, Warren McCulloch, considers generał philosophical problems of biological cybemetic modeling in a provocative report entitled “The Imitation of One Form of Life by Another—Biomimesis” (McCulloch, 1962).

Since 1960 cybernetics and biological cybemetics have become a major concept of Soviet scientific doctrine. They are held to be important as objective realizations of thought processes and biological control mechanisms, which were once poorly understood and therefore explained away by “vitalism.” A large number of Russian-language reports on cybernetics could be cited. The generał role of cybernetics modeling in modem scientific thought is reviewed by Berg (1963), Sobolev and Lyapunov (1962), and Glushkov (1963a,b). Extensive discussions of the approach and goal of biological simulation are also offered by Frolov (1961) and Novik (1963, 1964). Gaaze-Rapoport (1961) is the author of a book entitled “Automata and Living Organisms.” All of the Soviet works place great emphasis on algorithm and automata theory An algorithm may be defined as a “definite computational procedurę” or “set of rules,” whereas an automaton is commonly said to be a “black box with states” or “switching system” or just “robot.” Soviet cyber-neticists wish to discover and simulate biological algorithms and to represent living organisms as automata.

The similarity invariants appropriate to cybernetics models (see Table I) are considerable morę subtle than those discussed above, but are mathematical in naturę in the sense that they can always be ex-pressed by an algorithm. They include criteria pertaining to controller performance, isomorphisms of automata, algorithm function, and rela-tional invariants of abstract mathematics. The different basie classes of cybemetic models shall be discussed in turn.

VII. Simulation of Physiological Regulation

The present section somewhat overlaps Section VIII, which deals with nerve networks and brain models as such. Extensive work has been done on modeling control mechanisms pertaining to the cardiovascular and respiratory systems, endocrine control, metabolism, and thermal homostasis. Biological control theory is the subject of a book by Grodins

(1963) , that deals almost entirely with electroanalog modeling of physiological regulatory mechanisms. There has been a great deal of recent work in mathematical control theory based on use of fast computers for excution of control algorithms. Some generał aspects of this problem