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By means of right and left heart catheterization 70 patients with congenital or acquired heart disease were examined to determine whether or not a gradient in pressure existed between the pulmonary artery and the left ventricle at the end of diastole. In the absence of mitral valvular obstruction in 56 patients there was a statistically significant correlation of pulmonary artery diastolic, left ventricular end-diastolic, and left atrial mean pressures less than 15 mm Hg which was independent of heart rate. Diastolic pressures at identical levels as high as 40 mm Hg were demonstrated in the presence of aortic insufficiency without left ventricular failure, and as high as 47 mm Hg during pulmonary edema in one patient with aortic stenosis and insufficiency. A diastolic gradient in pressure between the pulmonary artery and the left ventricle existed in 14 patients with pulmonary hypertension. These patients all had congenital intracardiac shunts and it may be assumed that they had some obstruction in the pulmonary vascular bed. These findings suggest that within defined limits friction across the pulmonary vascular bed is so small that a state of pressure equilibrium exists at the end of diastole. When the limits are met clinically, the pressures in the pulmonary artery and in the left ventricle at the end of diastole are identical.

An attempt has been made to show that the data available are not altogether adequate for establishing exact criteria for the normal electrocardiogram. Some of the more recent efforts to correct this situation have been reviewed and synthesized so far as possible into a form which it is hoped may be immediately useful. It is emphasized that this report is merely of recent clinical progress in the field. A more comprehensive and statistically complete investigation of the normal electrocardiogram in all age groups remains to be done.

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so far studied. Experiments in which colloidal gold particles were used as a tracer have shown that, in capillaries with a continuous endothelium (muscle capillaries), the particles are transported across it by "pinocytiec' vesicles. At the end of this step they must still transverse the basement membrane.Experiments on glomerular capillaries, which typically have a discontimuon s endothelium, were carried out on normal and nephrotic rats using ferritin as a tracer. By its accumulation on the luminal side of the basement membrane, the ferritin has identified this layer as the main filtration barrier.A similar function of the basement membrane was demonstrated in muscle venules and venous capillaries by experiments in which the endothelium was rendered discontinuous by local treatment with histamine and serotonin.T HERE ARE, I believe, a good number of reasons for a renewed interest in problems of capillary permeability. To begin with, it is clear that we are dealing with a basic process in the physiology of metazoa. In these complex organisms, the life of the multitude of cells in the intimacy of tissue depends, in ultimate analysis, on the ample and continuous exchanges that take place across the wall of capillary vessels between the blood plasma on one side, and the interstitial fluid on the other. To