Haemolymph gases and buffers in Ascaris lumbricoides

1. 1. When worms were collected and exsanguinated in the abattoir the haemolymph gave the following data: pH 6 · 71 (S.D. ± 0 · 13), pCO 2 158 (S.D. ± 47 ·) Torr, and pO 2 26 (S.D. ± 13· 0) Torr. 2. 2. When the parasites were kept in saline there were no significant changes in pO 2 but pH and pCO 2 changed to 6 · 88 units and 55 Torr, and to 6 · 74 units and 88 Torr after 2 and 5 hr respectively. 3. 3. Plots of pH vs. log pCO 2 are given and it is suggested that they represent a bicarbonate : phosphate (3 : 2) buffer. Restoration of pH without full replacement of pCO 2 is explained by a bicarbonate drop from 22 mM, on collection, to 12 mM after 5 hr; this is associated with an increased haemolymph volume in vitro. 4. 4. A trial balance shows good agreement between known constituents and the freezing point depression but there is a discrepancy in the ionic balance.