The central nucleus-containing regions of the cells have thicknesses of up to 1-5 fim
but the peripheral regions, which contain most of the aligned microtubule portions,
are extremely thin and mainly have thicknesses of about 0-2 fim (Figs 1, 10). As was
the case for osteoblasts, very few microtubule profiles were encountered in thin
sections of the lamelliform portions of fibroblasts.