EFFECT OF TEMPERATURE ON PULSATION 325 



protracted to 96 seconds, the amplitude being enhanced 

 to 35 mm. And finally at 27 C. there was further 

 lengthening of the period to no seconds, the amplitude 

 of pulsation being enhanced to 40 mm. 



In addition to the changes of period and amplitude there 

 is another noticeable effect induced by variation of tempera- 

 ture. We have seen in the case of Mimosa that the lowering 

 of temperature induces a depression of the leaf, and the rise 

 of temperature an erection of the leaf. Effects similar to 



Fig. 167. — Effect of lowering of temperature on the amplitude and 

 frequency of Desmodium pulsation. Note the shifting of base- 

 line upwards, indicating fall of leaflet during cooling ; observe 

 also the enhancement of systolic contraction. 



these are also induced in the leaflet of Desmodium. The 

 result of cooling is thus a slight fall of the leaflet, in conse- 

 quence of which we observe the shifting of the base-line 

 upwards. A still more striking effect is the increase in 

 the extent of contraction, by which the systolic limit is 

 enhanced. This will clearly be noticed in the series of 

 records in fig. 167. 



The rhythmic pulsation of the cardiac tissue is arrested 

 when subjected to a certain low temperature. Similarly the 

 pulsation of Desmodium gyrans is arrested at a sufficiently 



