CHAPTER XXIV 



EFFECT OF ELECTRIC STIMULATION ON THE PULSATION OF 

 DESMODIUM GYRANS 



Effect of electric shock on Desmodium leaflet — Incapability of tetanus 

 — Extra pulsation induced by electric shock — Relative effectiveness 

 of electric stimulus at diastolic phase — Effect of transmitted excita- 

 tion on normal pulsation of heart and on pulsation of Desmodium 

 leaflet — Effects of acceleration and inhibition. 



In the previous chapter we studied the action of electric 

 shock on the leaflet of Desmodium in a state of standstill. 

 We will now inquire into the effect of induction-shock on 

 the pulsating leaflet. 



The cardiac tissue is known to be incapable of tetanus. 



Fig. i6i. — Application of strong tetanising shock at arrow brings 

 about diminished amplitude of pulsation. 



This is also true of the rhythmic tissue of Desmodium. 

 Under tetanising shocks there is no continuous contraction. 

 Under feeble stimulus the ampHtude of pulsation may in 

 certain circumstances be enhanced. Under excessive 

 tetanisation the natural pulsations, generally speaking, 

 become irregular or diminished in amplitude (fig. i6i). 



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