Under this rather indefinite term, "cells of the blood vessel walls" (Gefasswandzellen), evidently different cell types can be understood: the endothelium proper, certain cells of embryonic character, adjacent to the outer surface of the endothelium, the resting wandering cells or histiocytes, etc.
A part arises through the mobilization of the local resting wandering cells (clasmatocytes, histiocytes) of the connective tissue; another part comes from the blood and represents hematogenous, emigrated lymphocytes and monocytes.
As a result of direct traumatic injury, a varying quantity of fixed cells in the immediate proximity of the foreign body--fibroblasts and histiocytes (resting wandering cells)--are seen undergoing necrosis; they contain disfigured, shrunken and darkly staining nuclei, whereas the protoplasm shows vacuolization and disintegration.
The histiocytes (resting wandering cells) show the first signs of inflammatory reaction--they begin to contract and their protoplasm contains a varying quantity of clear vacuoles, which are especially numerous when egg yolk is injected into the tissue.
HISTIOCYTES OR RESTING WANDERING CELLS (CLASMATOCYTES)
But in the cells, surrounding the capillaries and adjacent to their endothelium--the pericytes, described in the foregoing, and the histiocytes (resting wandering cells), with occasional transitions between the two--the carbon particles are found in larger numbers than in the preceding stage.
Whereas in the preceding stages there was a distinct gap between the local, large, mobilizing histiocytes (resting wandering cells) and the smaller, round (lymphocyte-like and monocyte-like) polyblasts of hematogenous origin, now the local histiocytes seem to have disappeared almost completely and the tissue contains, instead, great quantities of large ameboid, phagocytic cells, among which no distinction can be made as to their local or hematogenous origin.
The two most common results of their differentiation are, on the one hand, the phagocytic and dye-storing histiocytes (resting wandering cells, clasmatocytes) and, on the other hand, common fibroblasts.