Further Observations on the Oxygen Consumption of Nerve. ∗

Abstract

The earlier studies of Fenn 1 and Gerard 2 on the oxygen consumption of frog nerve were not in complete quantitative agreement, even when differences in the experimental temperatures were allowed for. Fenn used American frogs (pipiens?) and a volumetric method, I used European species and a manometric technique, so it was desirable to ascertain whether the divergent results depended on material or methods. It also seemed useful to examine in more detail than previously the influence of various conditions on the rate of oxygen usage of nerve and to compare nerves of several animals. Observations carried on during 2 years by the Warburg technique are here summarized.

The Qo₂ (cmm. O₂ consumed per gm. of moist nerve per hour) of the sciatic of the American green frog, mainly R. pipiens, is lowest in December and January, Qo₂ = 37, and highest in June or a little earlier, Qo₂ = 60+. The Qo₂ shows a temperature coefficient of 2.2, as far as can be judged by experiments run at 18° to 24°C. The various American species do not consume oxygen at the same rate, but no accurate record of specific differences has been kept. The average Qo₂ of 227 experiments, mostly in the winter months, at an average temperature of 21.5 °C. for green frog sciatics in Ringer solution is 42, and the extreme variation is 20 to 80. Fenn's 3 latest value for these same frogs at 20°C., is 45, so our results, with different methods, are in agreement.

Any influence of various substances on nerve respiration is dependent on their ability to penetrate to the respiring regions. The great importanceof the perineurium as a passive barrier to diffusion, as described by Feng and Gerard 4 was not fully realized when most of these experiemtns were erformed; and some of the negative results obtained may have depended on the presence of the sheath.