302 RESEARCHES ON IRRITABILITY OF PLANTS 



under j-fogrni. to 8 mm., and finally, under -^V grm. to 4 mm. 

 When the load is increased to 4V grm. the pulsation is 

 arrested. The pulsation is also seen to become slower with 

 increasing load. 



Arrest of Pulsation by Ligature 



A very interesting phenomenon, often observed in a 

 pulsating heart, is the effect of cut or ligature. Thus by the 

 application of what is known as * Stannius' ligature ' above 



Fig. 147. — Effect of increasing load of 3^0, tuo, and -^\ grm. Amplitude 

 of pulsation decreased, and period increased, with increasing load. 



the heart, its beat may be arrested. This arrest takes place 

 in a relaxed condition, that is to say, at diastole. The 

 effect, however, is liable to be modified by the condition of 

 the heart. Sometimes there is a failure of arrest. At other 

 times, on the application of ligature there are a few vigorous 

 pulsations followed by arrest. Effects similar to these are 

 also induced by cut. The various explanations hitherto 

 offered of these peculiar effects have all been pronounced 

 untenable for one reason or another. 



Seeing the remarkable parallelism which obtains be- 

 tween the pulsation of the cardiac tissue and that of the 

 leaflets of Desmodium, I was curious to discover whether in 

 the case of * Stannius' ligature,' also, there was a similar 

 correspondence. It was a great surprise to me, on applying 



