Summary. 1. The effects of variations in heart rate on ventricular function, myocardial oxygen consumption, and coronary blood flow were studied in anesthetized, open‐chest dogs. The heart rate was held at desired rates by electrical stimulation. 2. The following changes occurred when the rate was increased in steps from 33—80 per min. to 200—280 per min.: cardiac output increased 0 to 73 per cent and reached a maximum at rates varying from 90 to 180 per min.; above these rates there was usually a decrease. Stroke volume decreased progressively. Mean aortic pressure rose slightly, and the pulse pressure was diminished. Myocardial oxygen consumption and left coronary flow increased, even at the high rates when ventricular work was constant or decreasing; there was a marked fall in coronary resistance. 3. Ventricular function curves, i. e. ventricular stroke work plotted against the respective mean atrial pressure, were obtained at the various rates. The curves were always lower at higher than at lower rates. 4. Myocardial oxygen consumption per unit of mechanical work was greater at higher rates, probably because of the larger amount of “isometric work” per min. Coronary blood flow per unit of work increased similarly with rate. Coronary vascular resistance was always much lower at high heart rates than at low, indicating coronary vasodilation. 5. It is concluded that during normal circumstances myocardial oxygen consumption is a major determinant of coronary blood flow. 6. Effects of heart rate during abnormal circulatory conditions were illustrated and discussed.

Many investigators have injected acetylcholine and histamine into man both intra-arterially and intravenously. The effects of intra-arterial injection of acetylcholine on the circulation in the legs were studied by Carmichael & Fraser (1933) who observed skin colour, and by Ellis & Weiss (1932) who measured skin temperature and arterio-venous oxygen differences. We have been unable, however, to find detailed quantitative measurements of their effects on the vessels. Since such observations were required for another purpose we have made them, and this paper describes the results. METHODSObservations have been made on twenty-six men and three women between the ages of 19 and 34. All were in good health, and none suffered from peripheral vascular disease. They arrived at the laboratory at least 1 hr before observations started and were recumbent during, and for half an hour before, the observations. They wore normal indoor clothing, and the trunk and legs and as much as possible of the arms were wrapped in blankets. The laboratory temperature was 20-23' C.Blood flow The blood flow through the hands and forearms was measured every 15 sec, or more frequently, by venous occlusion plethysmography. In most experiments the plethysmographs were filled with stirred water at 32°C for the hand and at 340 C for the forearm. They were fitted with loose gloves for the hands or loose sleeves for the forearms. In some experiments, in which it was desired to measure simultaneously the hand and forearm flow on the same side, a light celluloid air-filled plethysmograph was used on the forearm.The venous occlusion cuffs, at the wrist for the hand, and above the elbow (proximal to the needle in the brachial artery) for the forearm, were, unless otherwise stated, inflated to 70 mm Hg during the periods of collection. A wrist cuff was inflated to 200 mm Hg for 1 min before, and during, observations of forearm blood flow. When, however, the hand and forearm blood flows

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Three cases of persistent Müllerian duct syndrome are reported. All were phenotypically and karyotypically male but with persistent duct remnants. Problems encountered in management and surgery are discussed.