Technical methods alteration in membrane permeability (Jacob, Bischel, and Herschler, 1964). Reversible alteration in membrane protein structure and/or the removal of fatty acids from the cell membrane may occur. These findings imply facilitation of movement of some substances by changes in membrane porosity.As with most staining techniques, it is important that solutions be changed after frequent use. It is also helpful to the interpreter to have a control specimen with known P. carinii stained simultaneously with the test specimen. We found that necropsy lung sections from P. carinnii pneumonitis can be maintained in refrigeration several months for this purpose.The procedure has been carried out with excellent results by technicians after brief orientation.