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C. EYZAGUIRRE 



Fig. 3. (Upper portion) — a. Slow cell impaled and stretched just above threshold 

 setting up five irregular discharges at a depolarization threshold of 12 mV. At 

 second arrow additional stretch increases discharge rate to from 12 to 14/sec. 

 Firing level marked by broken line remains almost constant while rate of pre- 

 potential rise increases, b. Same cell. Stretch is gradually increased over 4 sec 

 between first arrow and straight line and then held constant. Note rise in firing level 

 as frequency increases while spike declines by several millivolts. The discharge is 

 regular (30/sec) during maintained stretch. Several seconds of rhythmic discharge 

 not shown (dark gap). Relaxation is followed by small transient phase of hyper- 

 polarization. 

 {Lower portion) — A. Adaptation of impaled fast cell, during maintained stretch. 

 Slow stretch for about 2 sec sets up three impulses at a depolarization threshold 

 near 22 mV. At second arrow additional stretch given and maintained for from 

 4 to 5 sec. As depolarization drops below 20 mV discharges stop. b. depolarization 

 fell to 7 mV when at the third arrow additional stretch was given and maintained. 

 Once more the cell discharges at the previous membrane level, c. Fast cell. Extra- 

 cellular recording, small monophasic potentials. Between first and second arrows 

 stretch applied and further extension added and maintained between second and 

 third arrows. Dotted line drawn slightly above the firing levels. Note in both cells 

 the decline of the generator potential below threshold during steady stretch. 

 Time, 1 sec.(From Eyzaguirre and Kuffler, J. Gen. Physiol. 39, 87-1 19, 1955a). 



