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The four auricular arrhythmias, premature systoles, paroxysmal tachycardia, flutter, and fibrillation, have been investigated in over 200 dogs by three methods: (1) high speed cinematography, (2) cathode-ray oscillography, and (3) multiple-channel electrocardiography. The hitherto unexplored body of the left auricle has been surgically exposed and thoroughly studied. Results indicate that all four arrhythmias are of unitary origin and may occur from one ectopic focus. The resulting arrhythmia depends largely upon the rate of discharge from that focus. There is no circus movement. Corroborative observations have been made on the arrhythmias in man. This conception of the auricular arrhythmias simplifies the understanding of their mechanism.S INCE the classic studies of Lewis and his associates' on the nature of the auricular arrhythmias, comparatively little has been published on this phase of the subject. Levi is believed that his experiments established the following concepts concerning the mechanisms of the auricular arrhythmias:1. That auricular flutter is due to a regular circus movement in the auricles which sweeps around the openings of the venae cavae. The main impulse usually travels in a counterclockwise direction up the right auricle, circling the superior vena cava, then down the left auricle, and around the inferior vena cava, thus completing the circus. Regular daughter waves are sent off the main wave to the remainder of the auricles.2. Auricular fibrillation is due to a circus movement of the same general type as that of auricular flutter, but in this instance the impulse pursues a tortuous and redundant path around the venae cavae and sends off irregular daughter waves to the remainder of the auricles.3. Paroxysmal auricular tachycardia is of a different nature. Lewis believed that a rapidly discharging ectopic focus in the auricle is responsible for the arrhythmia; no circus movement is present. Other investigators, however, do favor circus movement as the mechanism of auricular tachycardia. The evidence that Lewis gathered with regard to circus movement appeared so complete that his conclusions have been accepted as fact in most modern textbooks of physiology, cardiology, and medicine.For the past three years we have been taking high-speed, colored cinematographs of the auricles of the intact dog's heart. A Western Electric Fastax 16-mm. camera was used with which films were taken at speeds up to 2,000 frames per second. When films taken at 2,000 frames per second are projected at eight frames per second the motion of the auricles is slowed 250 times. Auricular events that occur in one second take four minutes to view on the screen. A magnifying lens is used which enlarges the auricle 100 or more times on projection. By careful photographic technic, and lighting the field with twelve RSP-2 photospot incandescent lamps, excellent pictures are obtained showing the most minute detail of auricular activity. By means of such pictures, the auricular contraction wave can actually be seen for the first...

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From the physiological point of view elevation of blood pressure may be due to an increase in cardiac output, in the volume or viscosity of the blood or in the resistance of the peripheral vessels. Since cardiac output is not increased in hypertension (1, 2, 3) and the viscosity (4) and volume (5) of the circulating blood have been shown to be normal, there remains only the increased resistance in the peripheral circulation.From an analysis of the literature it appears that investigations on the exact nature of this increase in peripheral resistance are comparatively few in number and have led to conflicting results. It is the purpose of this paper. to deal with the following questions. A. Is the increased peripheral resistance generalized throughout the systemic circulation or confined to the splanchnic area?B. To what extent are the vessels responsible for the increased peripheral resistance capable of dilatation ?C. What part is played by the vasomotor nerves in the maintenance of the increased peripheral resistance; i.e. if arterial hypertonus is present can it be attributed to an increase in sympathetic vasoconstrictor impulses?We have attempted to answer these questions by studies on the blood flow in the arm under various conditions, using the arm plethysmograph as described by Lewis and Grant (6), and to determine whether the nature and distribution of the increased resistance is the same in the different forms of hypertension, which have been designated benign, malignant and secondary (" renal") hypertension. LiteratureIn view of the known physiological importance of the splanchnic circulation it is essential to determine whether the development of hypertension in man is especially due to abnormal behavior of this vascular area. Various forms of evidence have been brought forward to support this possibility. In the first place, pathological studies show that the arterial lesions in hypertension are most intense in the splanchnic region, especially in the kidneys, adrenals, and pancreas. It appears, however, that no constant relationship exists between the severity of arteriosclerosis in the splanchnic area and high blood pressure. Longcope and McClintock (7) obtained transitory elevation of blood pressure by sudden occlusion of the splanchnic vessels in dogs. They attribute this effect to the increase in peripheral resistance, but find no evidence for regarding the splanchnic area as specifically important in the production of hypertension. Jansen, Tams and Achelis (8) found in animals that obstruction of the circulation to a limb caused a greater rise in blood pressure if the splanchnic vessels were first occluded. In subjects with hypertension they state that binding an extremity produced a higher and more sustained elevation of blood pressure than in normal individuals, and conclude from these results that hypertension is due to vasoconstriction in the splanchnic area. Splanchnic section has been performed (9, 10) in patients with hypertension on the basis of the same assumption, and lowering of the...