VITAL STAINING OF THE CONNECTIVE TISSUES

Trypan blue injected intravenously is bound almost at once by the intercellular connective tissue elements all over the body,—by collagen, reticulin, and elastic fibers. This union of dye and tissue elements is the factor responsible for the early macroscopic blue color and is antecedent to cellular colloidopexic action. Different examples of connective tissue differ among themselves in their ability to hold the dye. Diffuse staining of elastic fibers noted by previous observers is merely a special case of the general affinity of connective tissue for the dye. The evidence suggests that the histiocytes are cells specialized to segregate noxae that become diffusely bound to the intercellular connective tissue matrix.