MULTIPLE AND AUTONOMOUS ELECTRICAL RESPONSE 215 



then takes place more gradually and at a much slower rate. 

 This movement is due to natural recovery, aided by a 

 moderate excitatory contraction of the upper half of the 

 pulvinus. 1 give herewith a table showing the characteristic 

 rates of movement in the different phases of the entire 

 pulsation. 



TABLE SHOWING RATES OF MOVEMENT AT DIFFERENT STAGES OF 

 PULSATION IN DESMODIUM. 



Down-movement Up-movement 



Total period . . 45 seconds Total period . . 70 seconds 



Average rate . '61 mm. per second 

 Maximum rate . -7 ,, ,, ,, 

 Duration of pause . 40 seconds 



Average rate . '4 mm. per second 

 Maximum rate . -5 ,, ,, ,, 

 Duration of pause . 35 seconds 



Several facts are brought out in this table which are of 

 jpecial importance, and first we observe that the excitatory 

 impulse which causes the down-movement is brief and quickly 

 :xhausted. This is seen by the great distance covered 

 luring the first ten seconds, after which the movement 

 gradually slows down. This indicates a short-lived impulsive 

 tction, the subsequent movement of the leaflet being mainly 

 lue to inertia. There is then a pause in the down-position, after 

 'hich the up-movement commences. It will be noticed here 

 that this movement is more gradual and prolonged than the 

 lown-movement. From the indications given by these 

 laracteristic movements, we may conclude that the excita- 

 >ry reaction by which the down-movement is caused is 

 datively more intense and more quickly exhausted than 

 that which brings about the up-movement. We may gauge 

 le relative intensities of the two impulses approximately, 

 either from the maximum or the average rates of the down 



md up motions. The former gives the ratio of =1-4 ; the 



itter gives =1-52. The intensity of the downward 



'4 



impulse may therefore be taken to be roughly one and a-half 

 times as great as that which occasions the up-movement. 



