STIMULATION OF SUBTONIC ORGAN 



151 



equal amount of tropic curvature. The maximum positive 

 curvature in the present case was attained in the course of 

 9 minutes. The period of the attainment of this maximum 

 depends on the moto-excitabihty of the tissue and on the 

 intensity of the incident stimulus. The phototropic curve 

 (cf. fig. 86) of growing organs exhibits characteristics similar 

 to those of pulvinated organs. 



Table XVII. — The Variation of Susceptibility at Different 

 Points of the Tropic Curve. 



The organ, of which the phototropic curve is given in 

 fig. 84, was in optimum condition ; the power of transverse 

 conduction was practically absent. I now take up the 

 more complex case of an organ which was in a shghtly 

 subtonic condition at the beginning, and also possessed 

 transverse conductivitv. 



Effect of Stimulation of Subtonic Organ 



It is unfortunate that the terms usually employed in 

 the description of stimulus are so indefinite. A stimulus 

 which is just sufficient to induce excitatory contraction is 

 termed minimal, while an intensity below this minimal 

 [subminimal stimulus) is tacitly assumed to be ineffective. 



