Abstract
The hydrogen ion reversal points of human, dog, and cat serous membranes have been determined with acetic acid-sodium acetate buffer mixtures, and are compared with the reversal points of the same membranes estimated with citrate-phosphate mixtures. The values with acetate buffer are about one-quarter of a pH unit higher (more alkaline) for fat membranes and almost one-half a pH unit higher for lean membranes. The acetate values are believed to correspond more closely to the true hydrogen ion reversal points. The reversal points are again found to be characteristic for membrane and species. No evidence of a postmortem shift in reversal point has been found. The charge of the membranes even in the living animal is capable of ready and repeated reversal.