54 FUNCTIONAL INERITA 



this " inertia " will not account in its entirety for 

 protoplasmic rhythm. 



Professor Bose gives a physical model * to help 

 us to visualise the process underlying rhythmicity 

 in particular the rhythm that occurs after the 

 application of a constant stimulus. A cistern fed by 

 a constant inflow has an india-rubber outflow pipe 

 constricted near its orifice by a " compressing 

 spring." Water flowing out of the flexible tube 

 encounters resistance at the constriction, and when 

 the internal pressure rises to a certain magnitude 

 it overcomes the spring and makes the w r ater jerk 

 out : this outflow lowers the internal pressure, 

 the spring comes down again on the tube and the 

 outflow is once more diminished. This alternate 

 diminution and increase of the volume of outflow is 

 of course rhythmical. 



Accepting the illustration as sufficient, it is 

 evident that the behaviour of the spring gives us 

 the explanation of the conversion of the steady 

 into the rhythmic flow. By the increasing internal 

 pressure the spring is, after a time, overcome and 

 forced up, and this period, Professor Bose admits, 

 " corresponds to the latent period in plant-response " 

 but the spring returns to the tube, i.e., returns 

 u of itself," i.e., automatically. 



By the possession of what properties of matter does 

 it do so ? by its elasticity and inertia. We have 

 accounted for a rhythmic outflow (under constant 



* " Plant Response as a Means of Physiological Investigation," 

 1905, p. 310. 



