Figure 5
From: Once upon a time the cell membranes: 175 years of cell boundary research
XIX thcentury doubts about the existence of membranes. A. In this vision, the cell is devoid of any membrane and all the properties of the cell are defined by the activity of the protoplasmic colloid. B. The cell is surrounded by an external layer (membrane) of which the nature is distinct to the rest of the protoplasm. Yet, in this view, the inside of the cell remains a colloid.