The smaller blood vessels in areas of inflammation show an increase in permeability as manifested by an increase in the flow of fluid from the capillaries into the tissue spaces. This increase in permeability may also be shown by the localization and concentration of colloidal dyes. Many investigators1 have observed the localization and concentration of blood-borne material in areas of inflammation. Burrows2 has recently stated that "whenever inflammation occurs and from whatever cause, an increased permeability of the capillaries may be expected." Menkin3 has also frequently emphasized the fact that trypan blue and other dyes after intravenous injection promptly accumulate in areas of inflammation.
Recently I reported that trypan blue and india ink do not always concentrate in areas of inflammation produced by local application of xylene to the skin of rabbits.4 These substances concentrate in such areas only when they are injected into the circulation