330 RESEARCHES ON IRRITABILITY OF PLANTS 



hand, the reverse effect takes place. On account of increase 

 of force of expansion, or diminution of force of contraction, 

 the systolic limit is progressively diminished. When the 



Fig. 174- — Effect of continuous rise from 30° C. to 42° C. and return 

 to 30° C. Note progressive diminution of systolic contraction 

 during warming, and its increase during cooling. 



specimen is allowed to cool, the reverse effect is exhibited 

 by gradual enhancement of systolic contraction. Similar 



Fig. 175. — Effect of continuous rise from 32° C. to 43° C, and 

 return to 33° C. in a different specimen. 



effects are seen to take place in a record (fig. 175) obtained 

 with a different specimen. 



The temperature may sometimes be raised to 45° C. 

 without inducing any arrest of pulsation. A tendency is now 

 observed towards contraction, as shown by the general 



