PULSATIONS OF DESMODIUM GYRANS 299 



detailed consideration of this and of other factors will be 

 given at some length in the following chapters. 



Summary 



The pulsating activity of the detached leaflet of Desmo- 

 dium gyrans can be maintained uniform for a long time by 

 subjecting it to internal hydrostatic pressure. 



The application of a shock to a leaflet in a state of 

 standstill induces a down movement. The phase of 

 down movement is in general quicker. Enforced expansion 

 by increased internal hydrostatic pressure induces move- 

 ment of the leaflet upwards. These facts indicate that the 

 down position of the leaflet represents a * systolic ' contrac- 

 tion, and up position a * diastolic ' relaxation of the motile 

 organ. 



In a typical example of the rhythmic pulsation of 

 Desmodium leaflet the down movement is accomplished 

 in 41 seconds. The maximum rate of down movement is 

 •9 mm. per second, the average rate being -44 mm. per 

 second. The period of up movement is longer, being 

 60 seconds ; maximum rate of up movement is "56 mm. 

 per second, the average rate being -3 mm. per second. 



