180 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



The height of this first electrogram was arbitrarily assigned the value 

 100 and subsequent records were all expressed in terms of this initial 

 height. It is clear (fig. 3) that the action potential increased with time and 

 then suffered a decline. The finding of an increase in spike height as the 

 nerve cooled is not surprising in view of previous reports (13, 22) which 

 demonstrated for single fibers an increase in spike height and a large in- 



320 



1240 



, 160 



< 



80 



T r 



T r 



_L 



20" 



DESHEATHED 



^^HEATHED 



.J L_ 



40 60 



n 



2.2°C 



"80" 



"lies — \h — i4o I5D 1^0 zho 2J0 



-BO 



Fig. 3. Effect of low tempera- 

 ture (2.2°C) on height of A 

 wave. Spike height (in percent- 

 age of initial height) plotted as 

 a function of time (min.) after 

 transfer of nerve to low temper- 

 ature bath. Periods E-F, A-B 

 and C-D represent wash-out pe- 

 riods as described in text. Ordi- 

 nate at right (0-240) applies to 

 curve for desheathed nerve ; or- 

 dinate at left (0-320) to curve 

 for sheathed nerve. 



MINUTES 



s-160 



1140 

 I 



120 



100 



"I 1 1 1 1 r 



/ DESHEATHE&N 



"I r 



T r 



'-' SHEATHED 



I2°C 



J L 1 I I I I I I I 



40 80 120 160 200 



MINUTES 



Fig. 4. An experiment similar 

 to that in fig. 1 but with a tem- 

 perature of 12°C. 



crease in spike area. The interesting feature of these results is that the 

 height, instead of remaining constant after the initial increase, declined 

 progressively and in some experiments even fell below the 100% value. 

 These changes were observed to occur with desheathed as well as with 

 sheathed nerve prejiarations (fig. 3). No extensive study was made of the 

 matter but the B fibers behaved qualitatively in the same fashion in 

 response to low temperature. The C fibers were unable to survive the cold 

 and will not be considered in this discussion. 



The secondary decline in the A spike was associated with the low tem- 



