REGULATION AND CONTROL IN PHYSIOLOGICAL SYSTEMS.

The papers referred to here are grouped in the proceedings of the conference under the heading: Some Aspects of the Heart. The first (commentary) paper outlines the scope of the subject as follows. A multitude of physical and chemical factors influence cardiac performance. The cardiac adaptation to such perturbations may involve either intrinsic or extrinsic mechanisms. The intrinsic mechanisms of adaptation exist in the myocardial cells themselves, and have arbitrarily been divided into those which involve a change in the initial length of the myocardial fibers (so-called heterometric autoregulation) and those which do not depend upon a change in initial length (homeometric autoregulation). The extrinsic mechanisms of adaptation are primarily neural and humoral. The latter involve changes in the blood levels of certain critical electrolytes, blood gases, or hormones. Following is a list of titles and authors: Factors Affecting Cardiac Performance. By Matthew N. Levy. Dynamic Behavior of the Vagus-Heart Rate System. By Gordon F. Chess and Franco R. Calaresu. Atrioventricular Pressure-Flow Dynamics and Valve Motion. By E. L. Yellin, S. Laniado, C. S. Peskin, and R. W. M. Frater. Hypoxic Cardiovascular Dynamics and Control. By Howard H. Erickson and H. Lowell Stone.