Abstract
Microscopic and photomicrographic measurements were made of the vessel diameter and the width of the axial stream of red cells in blood vessels of the hamster’s cheek pouch, the velocity of blood flow being varied by an annular pneumatic cuff, through which the cheek pouch was passed. From these measurements the width of the plasmatic zone (P.Z.) was found to decrease gradually to zero as the cuff pressure was raised and the velocity of blood flow progressively lowered. From observations on injected graphite particles and blood platelets in plasma-skimmed vessels it was evident that a P.Z. results from the action of axially directed forces on suspended particles. Following injection of pontamine blue into a femoral vein, a narrow unstained zone of plasma was observed next to the vessel wall of arterioles in the cheek pouch when the velocity of blood flow was high; this unstained zone was not apparent when the velocity of flow was low. The significance of this observation is discussed in relation to the concept of there being an immobile layer of plasma in contact with endothelium of living blood vessels and in relation to the phenomenon of wall adherence of blood and plasma in artificial capillaries.
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