TRA!!JSVERSE TRANSMISSION OF EFFECT OF STIMULUS 28:') 



The diagram whicli I have already given (Fig. W) 

 clearly explains the different tropic effects induced by 

 changing the point of application of stimulus. We may thiis 

 have stimulus applied at the responding region itself (Direct 

 Stimulation) or at some distance from it (Indirect Stimu- 

 lation). The final effect will be modified by the con- 

 ducting power of the tissue. 



DIRECT UNILATERAL STIMULATION. 



Type I. — The tissue has little or no power of trans- 

 verse conduction : stimulus remains localised, the 

 proximal side undergoes contraction, and the distal 

 side expansion. The result is a positive curvature. 



Type 11. — The tissue is transversely conducting. Under 

 strong and long continued stimulation the excita- 

 tory impulse reaches the distal side, neutralising 

 or reversing the first effect. 



INDIRECT UNILATERAL STIMULATION. 



Tifpe I. — The intervening tissue is an indifferent con- 

 ductor : transmitted positive impulse induces ex- 

 pansion and convexity on the same side, thus 

 giving rise to negative curvature {i.e., away from 

 stimulus). 



Type II. — Intervening tissue is a fairly good conductor : 

 tlie effect of positive impulse is over-powered 

 by the predominant excitatory negative impulse, 

 the final result is a concavity and positive curva- 

 ture, with movement towards the stimulus. 



