[Fibroblast differentiation during collagen formation]

The successive differentiation in the series lymphocyte--(lymphocyte-type cell--precursor)--weakly differentiated cell (polyblast)--profibroblast--fibroblast was shown by means of scanning and transmission electron microscopy. In the focus of aseptic inflammation and in the zones of pneumosclerosis (silicosis), the ultrastructural and cytochemical cell rearrangement took place which was accompanied by the development of protein synthesizing organelles and the formation of folded surface. The collagen fibers run from the surface of the differentiated fibroblasts in the ground substance and preserve the direction of their growth with respect to the spatial position of cells.