Observations in vivo on the extravasation of various dye fluids from blood vessels into the connective tissue

Various dye fluids were injected into the blood vessels of frogs and rabbits and observationsin vivo were made of their patterns of extravasation.(1) A relation was noted between the site and mode of extravasation and the diffusibility of dyediffusibility itself being related to the size of dye particles.(2) Following intravenous injection the parts of blood vessels, excepting arterioles, where extravasation can occur were similar with both highly and poorly diffusible dyes. These parts extended from the arterioles to the venules. But the sequence of sites of extravasation and their frequency were in a reverse relationship. With highly diffusible dyes extravasation occurred in the sequence of precapillaries, capillaries, postcapillaries, venules and arterioles, and along the entire course of these vessels, so that the spread of extravasated dyes produced a color band form with the vessels along the long axis of the band. Contrary to this, with poorly diffusible dyes extravasation occurred first from the postcapillaires and venules, especially at the transitional portion of the two, then from the capillaries, and belatedly sometimes from the precapillaries. The mode of extravasation was sporadic and solitary, so that the spread of dye was oval in shape with the vessel running through the axis of the oval.(3) Following intra-arterial injection of highly diffusible dyes leakage of dye occurred in the sequence of arterioles, precapillaries, capillaries and postcapillaries, but not from the venules. With poorly diffusible dyes the sequence was capillaries, pre- and post-capillaries and venules. No leakage occurred from the arterioles. Thus, following intra-arterial injection of any type of dye, extravasation tended to occur in general from the arterial side, when compared with intravenous injection. However, the modes of spread were similar to those following intravenous injection, and highly diffusible dyes escaped from all over the vessels concerned forming a color band, and poorly diffusible dyes sporadically, from here and there, producing oval shaped forms.(4) There was no marked difference in the sites and modes of extravasation between frogs and rabbits.(5) Important factors determing the sites and modes of extravasation were believed to be the size of dye particles and the differences in structure of blood vessel walls according to locality (probably such as the grades in ease of disconnection of the junction between endothelial cells). However, when the local blood flow stops extravasation practically stops, so that the local blood pressure can also be said to promote extravasation. Various physical, chemical, physicochemical and biological factors that influence permeability are also believed to produce changes in size of particles and in structure of blood vessel walls.