HYDROGEN-ION CONCENTRATION AND THE RHYTHMIC ACTIVITY OF THE NERVE CELLS IN THE GANGLION OF THE LIMULUS HEART

¹ From the Marine Biological Laboratory, Woods Hole, and the Department of Physiology, University of Chicago

The automatic rhythmic activity of the nerve cells in the ganglion of the Limulus heart is relatively resistant to changes in pH in the external medium as such. Experiments with strong acid and base indicate that no well-marked physiological effect is seen until toxic concentrations are approached. Thus H-ion (N/1,000 HCl) produces a rapid irregular rhythm with decreasing amplitude of contraction followed by cessation of heart-beat, while OH-ion (N/1,000 NaOH) has an inhibitory effect. Weak penetrating acids (e.g., carbonic and acetic acids) inhibit the rhythm with primary increase in intensity of the nervous discharge, while the action of NH₄OH is characterized by a period of temporary inhibition. The contrast is to be related to the characteristic difference in the readiness of penetration of the undissociated molecules and the ions into living cells.