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.