TWO-FOLD CONDUCTION OF STIMULI. 573 



which begins in the venous sinus or auricle passes along to the 

 ventricle through the contractile tissue of the heart, or through 

 its nerves, or through both, that the following experiments were 

 undertaken. 



But the research was not so easy as that upon Medusae, for 

 the bell of the medusa shows by its contraction, or the tentacles 

 on a strip by their motion when the stimulus has reached 

 them, whilst in the heart there is a refractory period during 

 which the application of a stimulus produces no contraction. 



This rendered the research a very long and tedious one, 

 requiring an immense number of experiments, so that although 

 the results of a number of them were communicated to the 

 Eoyal Society in 1881, the full research was not published till 

 1883. 



After the publication of our first notice, an admirable paper 

 by Gaskell appeared on the transmission of stimuli in the frog's 

 heart, but his method of working was different from ours, as he 

 employed compression of the contractile tissue as a means of 

 regulating the passage of stimuli along it. 



The results of our experiments appear to show that stimuli 

 in the heart may pass from one part to another along nervous 

 channels as well as along contractile tissue. 



In regard to this, I may note especially that stimulation of 

 the auricle causes contraction both of the auricle and ventricle, 

 but the ventricular contraction follows the auricular one in a 

 way that seems to indicate that the stimulus has been propa- 

 gated through the muscular substance. On the other hand, 

 stimulation of the venous sinus sometimes produces a simul- 

 taneous contraction of the auricle and ventricle, which appears 

 to indicate that the stimulus has been conveyed along nervous 

 channels to the auricle and ventricle, and not along the 

 muscular substance from the sinus to the auricle and then to 

 the ventricle. 



