The interstitial movement of several dyes of widely different chemical constitution and diffusibility, in the connective tissues of the mouse ear, has been observed at high magnification. Dye extension seems to be conditioned by the form and structure of the connective tissue fibers. After escaping from the lymphatics of the ears of living mice, each dye appeared first in the tissues as bristly projections of color. These bent and twisted when pressed upon by a micro probe but sprang back into place when the pressure was removed. The present work and the preceding have shown that the lines of color are formed by dye along or between connective tissue fibers.
Intermittent external pressure applied to the tissue, squeezes and bends the fibers together and greatly increases the spread of dye along them. The connective tissue fibers assume an important role in the spread of substances through tissues subjected to pressure changes.
The experiments have given evidence of the existence of a tissue matrix in the organ but none of the presence of free interstitial fluid. In tissue subjected to irritant stimuli and in frankly edematous tissue, free fluid is readily demonstrated. When it is present the method of extension of dye is completely changed. Dye appears in the tissues as a diffusely colored cloud which can be freely moved by pressure with a micro probe.
The bearing of this evidence upon the condition of interstitial fluid and the nature of the interstitial spaces is discussed.