21G 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



taneously at a relatively high frequency (up to about 200 per sec). Be- 

 cause of this spontaneous repetitive firing of impulses, it was difficult to 

 make accurate measurements at high pressures. 



Figure 8 shows the effect of a pressure of 4000 psi upon the propagated 

 action potential. Although the shock-response time was also prolonged by 



Fig. 7. Effect of pressure on 

 the duration of the action cur- 

 rent of the node of Ranvier. 

 Motor nerve fiber of tlie toad. 

 Temperature 24-25°C. 



14 7 1,000 2P00 



8,000 



10,000 



Fig. 8. Effect of pressure 

 upon the action potential of 

 the scjuid. Vertical bar at right 

 subtends 100 mv. Temperature 

 23-24°C. 



pressure (by 5-15% at 5000 psi) the point of maximum membrane po- 

 tential of one record was superposed on that of the other record (in order 

 to facilitate comparison of the configurations of the action potentials). 

 It is seen that the rate of potential fall is reduced by about 40% at 4000 

 psi. 



The impedance of the axon membrane was measured with internal elec- 

 trodes at various pressures. The duration of decreased membrane imped- 

 ance was found to increase with increasing pressures. The maximum 



