n CHANGE OF FORM IN MUSCLE DURING ACTIVITY 97 



V. EFFECT OF TEMPERATURE ox MUSCULAR CONTRACTION 



The vital manifestations of all protoplasmic tissues are much 

 a fleeted by the temperature of the moment. There is a lower 

 limit of temperature for every organism, at which life is per- 

 manently, or at least temporarily, extinguished, as well as an 

 upper limit at which, principally on account of the coagulation 

 of certain albumens, such a fundamental disintegration of the 

 structure occurs that restoration of the normal functions seems 

 to be impossible. The absolute value of temperature varies 

 enormously in different kinds of protoplasm, and even apart from 

 the " immune " bacteria, many cases are known in which the 

 movements of protoplasmic structures have been observed at 

 a temperature far above 40 C. Within the maximum and 

 minimum range of " obvious contractility," we may assume as 

 a general rule that energy of the movement increases with 

 increase of temperature. This holds for amceboid as well as 

 for flagellated and ciliated movements, and the various kinds 

 of muscle form no exception. But while in the simpler forms 

 of mobile protoplasm it is only possible to determine the upper 

 and lo\ver limits, as well as the " optimum " of temperature at 

 which spontaneous movements of apparently unlimited duration 

 reach their utmost rapidity, in muscle we are able to go a step 

 farther in the analysis of phenomena. 



We have already alluded repeatedly to the great influence 

 exerted upon the manifestations of fatigue and death, by tempera- 

 ture ; an effect denoted by increase of D-products with higher, 

 and a corresponding decrease of these at lower, temperature. 

 Along with these are certain changes in the time-relations, and 

 form and magnitude (height) of contraction, which Gad and 

 Heymans in particular have recently been investigating, and which 

 may be viewed as a specific effect of temperature (60). If a 

 striated, skeletal, curarised frog's muscle is properly cooled, and 

 excited from time to time by an induction shock, it is found in 

 the first place that the (isotonic) curves of contraction are more 

 extended in proportion as the temperature is lower. Comparison 

 of the accompanying curves (Fig. 45) shows that the period of 

 rising energy in particular is much elongated, and the steepness 

 of the ascending portion decreases regularly in ratio with the 



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