N G . 1210 pages. $lCj.OO.The third edition of Guyton's well-knowii text is a wclconie additioii to physiological literature. As with the previous editions, the hook is marked by a clarity of presentation and readability. An np-to-date account is provided of all the standard topics usiially inclnded in books of this sort, inclitding a recent account of protein synthesis. Physiological control mechanisms are discttssed a t length from a qualitative point of view. However, those seeking a more mathematical approach to control now have available a recent text by 3Iilsiim and another by Milhorn. I n the reviewer's opinion this book is one of the best comprehensive introductions to medical physiology now available.

The arterial pressure of the adult human rarely deviates from normal by more than 10 to 15 percent during each day. To achieve such constancy, the body has a network of pressure control systems. Several are based on neural receptors that respond within seconds to help correct any abnormal pressure. The activities of these systems are followed within minutes by activation of hormonal controllers. Within hours or days, a kidney pressure control system is induced that increases body fluid volume when the pressure falls (or decreases the volume when the pressure rises). This kidney-fluid system is the dominant method of establishing long-term pressure control.

Cerebral Arteriovenous Malformation (CAVM) hemodynamic in disease condition results changes in the flow and pressure level in blood vessels. This can cause rupture or decreased blood supply to the tissue through capillary causing infarct. Measuring flow and pressure without intervention along the vessel is big challenge due to occlusion, bending and thinning of the vessel in Arteriovenous Malformation patients. In this paper, we proposed a lumped model for the Bifurcation for symmetrical and asymmetrical networks that will help doctors to find the pressure measurements non-invasively.

Normal and sinoaortic baroreceptor-denervated dogs were monitored continuously (24 hours a day) to quantify the role of the baroreceptors in determining the average level and the variability of arterial blood pressure, heart rate, cardiac output, and total peripheral resistance. The frequency of occurrence over 24-hour periods was obtained for each variable using a fiber optic curve-scanning system to read the variables from continuously recorded charts and a digital computer system to plot curves. The results indicate that the degree of hypertension previously reported for this preparation has been highly exaggerated, presumably due to the methods of study. The average 24-hour mean arterial blood pressure was 101.6 mm Hg in normal dogs and only 112.7 mm Hg in baroreceptor-denervated dogs. The normal dogs exhibited narrowly distributed 24-hour frequency distribution curves for blood pressure; in contrast the denervated dogs exhibited curves with twice the 24-hour standard deviation. Similar analysis indicated that the baroreceptors exerted less influence on the daily stabilization of heart rate than they did on arterial blood pressure and that they had very little if any influence on the daily stabilization of cardiac output and total peripheral resistance. Hemodynamic variables during postural changes were studied along with diurnal rhythms. We concluded that the primary function of the baroreceptor reflex is not to set the chronic level of arterial blood pressure but, instead, to minimize variations in systemic arterial blood pressure, whether these variations are caused by postural changes of the animal, excitement, diurnal rhythm, or even spontaneous fluctuations of unknown origin.

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The normal venous return curve has been determined in 12 open-chest dogs with intact circulatory reflexes and in 14 open-chest areflex dogs. These curves show that venous return reaches a maximum value when the right atrial pressure falls to –2 to –4 mm Hg and remains at this maximum value down to infinitely low negative pressures. As the right atrial pressure rises to positive values venous return falls and reaches zero when the right atrial pressure has risen to equal the mean circulatory pressure. A venous return curve for the normal, intact dog has been tentatively formulated on the basis of these studies and previous studies in which individual points on the venous return curves of intact dogs have been measured.

No abstract

• The use of systems analysis as an experimental tool for solving complex physiological problems is not new. Actually, systems analysis is merely the logical analysis of how systems perform. However, modern usage of the term implies a more formalized type of logic, especially a type of logic that includes quantification at each step in the analysis. Several of the figures in this paper illustrate systems analysis flow diagrams that show interrelationships between the different parts of simple or complex mechanisms for the control of arterial blood pressure. One can readily see that each part of each systems analysis diagram is only a symbolic way in which a composite of individual physiological phenomena fit together in a complete system.The principal advantage of the formalized systems analysis approach to understanding any physiological mechanism is that it often allows greater depth of thought than our minds can perform using simple logical procedures. The mind has the capability of holding and analyzing perhaps five to ten different sequential phenomena, each occurring at different rates and each interrelated with the other phenomena by various cross-linkages. However, beyond this size of system it is almost impossible to think through all the complex relationships simultaneously. On the other hand, the modern computer can handle literally thousands of such crosslinking interrelationships at the same time and can develop answers that the mind alone cannot achieve. Now setting aside this philosophizing about systems analysis per se, we will attempt to show how the systems analysis approach has been useful in the study of long-range arterial blood pressure control and the understanding of hypertensive