1885.] of the Heart in Fishes, especially that of the Eel. 127 



in the rate of the auricular action, which is at times seen as a secondary 

 effect of vagal stimulation, does not depend on the auricle itself, the 

 inherent auricular rhythm being latent ; the acceleration depends on the 

 increased rate of action of the sinus which leads the cardiac beat. 



I shall here mention some results obtained by the application of 

 electricity to the auricular tissue. 



Single induction shocks (as well as mechanical or thermal stimuli) 

 applied to the normal auricle during its diastole cause a single con- 

 traction, accompanied as in the ventricle by a bulging of the auricular 

 wall at the point of stimulation. 



The passage of a weak interrupted current produces some peculiar 

 effects in the auricle. For when an interrupted current of suitable 

 strength is sent through any part of the auricle, that part immediately 

 stands still, becoming distended with blood, while the rest of the 

 auricle goes on beating as before. By gradually increasing the 

 strength of the current a wider and wider area can be inhibited, 

 until at length the whole auricle becomes arrested, while the sinus 

 and ventricle may still go on beating. Any escape of the current to 

 the sinus will, however, cause a stoppage of the whole heart. 



When local inhibition is brought about in the auricle in the way 

 mentioned, there is a marked change in the excitability of the inhi- 

 bited area, as well as a suspension of its rhythmic activity. Its excita- 

 bility to direct stimulation is greatly depressed or temporarily 

 annulled ; the application of a direct stimulus commonly fails to induce 

 any contraction. The inhibited tissue seems to be in a state similar 

 to that into which the whole auricle is thrown by stimulation of the 

 vagus nerve. The action of the inhibited area is not usually resumed 

 for some little time after the discontinuing of the inhibitory current. 



When a projecting corner of the auricle is dealt with, and the 

 electrodes are applied at the points indicated by the letters E and E, 

 only part of the projecting piece of auricle is, as a rule, thrown out 

 of action. The shaded part becomes arrested, while the remainder 

 goes on contracting in unison with the rest of the auricle. 



