176 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



addition of the test solution. The test solution, containing all the constit- 

 uents of Ringer's fluid at their usual concentrations except for the KCl, 

 whose concentration was raised 10 fold, i.e. to 18 niM, was then added to 

 a 20-mm nerve segment located between the stimulating and recording 



Fig. 1. Selective respon.ses to potassium and sodium. Dual beam recording with B 

 and C fibers on upper beam and A, B and C fibers on lower beam. Record 1 is control; 

 records 2 to 6 show action of a solution w^ith a concentration of 18 mM KCl. Records 

 were made at 5' (2), 7' (3), 11' (4), 16' (5), and 60' (6) after adding the test solution. 

 Records 7-13 show action of a solution with limiting concentration (11 niM), of NaCl. 

 Records were taken at l'(7), 2'(8), 5'(9), 13'(10), 18'(11), 23'(12) and 31'(13) after 

 the test solution. Records 14-16 picture the recovery in Ringer's solution. Records 

 were made at 30" (14), 1' (15), and 9' (16) after adding the Ringer's .solution. Records 

 17-19 show persistence of many C fibers after adding a solution with 21.6 niM KCl. 

 Record 17 is the control; record 18 was made 20' after adding the test solution and 

 record 19 shows the recovery after Ringer's fluid. 



electrodes. Records 2-6 illustrate the selective aspect of the potassium 

 effect. The A fibers and many of the C fibers were especially sensitive and 

 ceased activity in response to the test solution. In contrast, most of the B 

 fibers and many C fibers were still conducting 60 minutes (record 6) after 

 treatment with the test solution. This section of the experiment (records 

 1-6) reveals the relatively great sensitivity of the A fibers and of many of 

 the C fibers to high potassium and, at the same time, the much lower sen- 



