The Permeability of the Lymphatic Wall.

Abstract

The permeability of the walls of lymph channels can be studied with the aid of innocuous vital dye solutions isotonic with blood. When such solutions are injected with a micro pipette into the tissue near the edge of the upper surface of the ear of the mouse, the dye rapidly finds its way into the lymphatics draining the region, rendering them clearly visible. When one of the vessels carrying the colored fluid empties this latter into a larger channel draining a normal part of the ear, one sees the color swept away and diluted by a stream that is itself unseen. Lymph formation and flow are thus shown to be active processes in the ear, even in the absence of hyperemia.

Poorly diffusible dyes (Pontamine blue, 1 Chicago blue 6B, vital red, and Congo red), which pass with difficulty out of the blood vessels into the tissues, tend to be retained by the lymphatic wall as well, whereas more highly diffusible ones (trypan red, brom phenol blue) pass out with ease.

According to the accepted view, lymphatics are everywhere separated from tissue spaces by a continuous endothelial wall. Our observations support this view. When lymph carrying the dye that is retained by the lymphatic walls is put under pressure, it passes out into the tissues only when frank ecchymosis of it takes place. No sign is to be found of pre-existing lacunae in the wall.

Lymph flow is stopped by a pressure of 2 to 4 cm. of water exerted by way of a sausage-shaped, collodion bag laid across the lymphatics. The pressure obstacle causes the dye to escape in greater abundance than ordinarily. It does not interfere in the least with the venous channels but so effectively blocks the lymphatics that mild edema develops within the hour.