96 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



period of exposure to these higher temperatures is brief. However, with 

 stimulation by the uniform longitudinal field method of Csapo and Goodall 

 (31), which in effect eliminates the propagated disturbances as a factor 

 in contraction, the tension in the retractor penis of the turtle or the 

 sartorius of the frog is sustained without decrement to 30°C (32), and 

 even higher. 



For any species, the tension-temperature relation is set on the tem- 

 perature scale in relation to the physiological temperature range of the 

 species but for any poikilotherm the position is subject to change by a 



TEMPERATURE 



Fig. 6. A : Tetanus tension in retractor penis of the turtle in relation to temperature, 

 pH. B: Same data as 6^. Broken line indicates curve with a AH of 46,000 for com- 

 parison. 



period of temperature acclimatization (33). In our laboratories this phe- 

 nomenon has been observed in the retractor penis of Chrysemys picta 

 (fig. 6.4) . In the muscle of a turtle acclimatized at 5-10°C for four months, 

 about 80% of the plateau tension is developed at 0°C. However, after 

 a similar period of acclimatization at 20°-25°, the curve is shifted to a 

 higher temperature range with the result that at 0°C only 50% of the 

 plateau tension develops. 



Factors other than acclimatization can modify the position of the curve 

 on the temperature scale. For example, if the intracellular pH is reduced 

 by equilibrating the muscle with 80% COo , the tension-temperature curve 

 is displaced into a higher temperature range with the result that the tension 



