Cells of P. vulgaris incubated in plain broth (4 hours at 37 C) were treated with TCC in final concentration of 0,1 per cent at 37 C. They presented sites of TTC reduction as granules with volumes proportional to the time of contact with TTC. In microorganisms not fixed with formaldhyde, most of the granules during the electron microscopy ruptured the bacterial membranes leaving remains of these, like "ghosts", in the sites where the granule had been located: in rare cases large granules still were seen deforming the bacilli, whit a crystalline contour. When the cells were fixed with formaldehyde the granules remained in the microorganims. They could be removed from the cells by treatment with acetone leaving empty collapsed membranes.