THE NORMAL BEHAVIOR OF THE PULMONARY BLOOD VESSELS WITH OBSERVATIONS ON THE INTERMITTENCE OF THE FLOW OF BLOOD IN THE ARTERIOLES AND CAPILLARIES

Abstract

A method (described) permits direct microscopic observation of the smaller superficial pulmonary blood vessels and air sacs in the unopened chest of the cat. The no. of pulmonary arterioles through which the blood circulates at a given time is not constant. The blood flow within them may change spontaneously in rate and character or after injection of epinephrine, etc.; it may be intermittent. The no. of capillaries through which blood flows at a given time varies greatly and may represent a very small fraction of the total no. of the capillaries in the lung. The velocity of blood flow and the cell content of the blood may vary in capillaries arising from the same arteriole. Intermittent blood flow, often observed in the pulmonary capillaries, sometimes produced by epinephrine, is believed to be normal in them. The changes in the capillary flow are probably governed by changes in the arterioles from which they arise and by slight changes in the pressure in the pulmonary circuit. No proof of contraction of the capillary walls was obtained.