The mechanism of oxygen concentration in the swim‐bladder of the eel

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Abstract
The P02 [arterial blood O2 tension] of venous blood from the active swim-bladder of the eel decreases with distance from the exit of the rete. This systematic change did not occur in non-secreting bladders, nor during conditions where exchange in the rete was abolished. The observed change in post-rete venous PO2 has the same rate constant as the Root-on shift [sensitivity of the O2-capacity of fish blood to increased pH], These findings modify the accepted model for counter-current multiplication of O2 in the swim-bladder system by introducing rate constants for diffusion and acid action in the rete. The part played by the assumed impermeability to acid of the arteriovenous partition of the rete is replaced by the slow Root-on shift in the modified model. The modified model contradicts the Kuhn model in that extraction of O2 from blood is decreased at low flow, and that at normal flow conditions part of the lactic acid produced can be re-used. Similar modifications are indicated in the model for concentration of inert gases.