Volume changes in toad (Bufo marinus) red blood cells, exposed to carbon dioxide, were studied, In vitro blood samples were sequentially equilibrated in (a) air (b) 5% CO₂/air mixture, and (c) air. The haematocrit values of the 5% CO₂/air equilibrated samples, increased rapidly by 6-18% during the one hour equilibration period, When the samples were re-equilibrated, with air, the haematocrit values decreased back to their original levels. The increase in haematocrit values seems to have resulted from the swelling of the erythrocytes during exposure to increased levels of Pco₂ (partial pressure of carbon dioxide; increased from O to 35 mm Hg). The reasons for the swelling phenomenon and the hypothesized underlying mechanism by which it occurs, are discussed.
Beverly Ruth Mitton (Sun,) studied this question.