MICROSCOPIC OBSERVATIONS OF PULMONARY ARTERY REACTIONS

Study of arterial muscle reactions is at present limited to perfusion of surviving organs, and to direct observation of rings or spirals of excised arteries suspended in a balanced solution. Evaluation of results obtained by perfusion is often made difficult by the development of edema and by the presence of capillaries and veins. Suspension of excised arteries fails to approximate the normal intra-arterial tension, and gives no information as to the reactions of the smaller arteries and arteri-oles which play the major role in intact animals. Since fresh sections of lung suspended in Ringer’s solution may be used for the microscopic study of bronchiolar muscle reactions (1), Dr. Torald Sollmann suggested that this method could be used for arterioles, whose muscle is arranged similarly to that of bronchioles. Due to limitations of time, it was necessary to confine the study to a single representative type of artery, the pulmonary artery of the rabbit. Preliminary experiments indicated that only the arteries are available for this method, since the arteriolar elastic tissue closes the lumen on melting the gelatin (similar to guinea pig bronchioles (1)). The limitations of excised arterial spirals and rings are thus present in this method, but to a lesser extent, since it permits the study of preparations a good deal nearer the periphery of the arterial tree, and also of smaller animals