The Heart of the Sea-Turtle. 319 



Stimulation of nerve roots from the medulla led to very prolonged 

 inhibition, followed by an accelerated after-rhythm of 7-8. 



IY. Faradisation of the Heart. 



As in the Terrapin, Alligator, and Fish, the result ob- 

 tained depends on the strength .of the current and the con- 

 dition of the heart. 



The sinus being in good condition, and the current suffi- 

 ciently strong, it is arrested, but if the heart be much ex- 

 hausted, no arrest may follow; arrest of the sinus, of course, 

 leads to stoppage of the rest of the heart, unless, as often 

 hajypens, there is escape of current. 



The same arrest of auricles occurs on stimulation, unless 

 the heart be very much exhausted. 



Dilation is less prominent in the ventricle of the sea- 

 turtle than in that of the Terrapin ; but the bluish appear- 

 ance accompanying it, and the light points where the 

 electrodes are applied, are manifest. 



I have never obtained, in the sea-turtle, arrest of the ven- 

 tricle by stimulation of this part of the heart with the 

 interrupted current; on the contrary, stimulation of the 

 ventricle gives rise to a more rapid pulsation ; or, especially 

 if the nutrition be imperfect, a peculiar form of contraction, 

 which, as it does not exactly resemble that denoted by such 

 terms as fibrillar, peristaltic, &c, I have called interver- 

 miform, which seems preferable to peristaltic, inasmuch as 

 the latter has acquired a very definite physiological mean- 

 ing, which it is not well to extend. 



"With a very weak current in all but the freshest hearts, 

 the dilation following the stimulation is much more local, 

 and there may be no marked effects as far as rhythmic 

 variation is concerned. 



But in a heart very much exhausted it is often quite im- 

 possible to arrest the sinus or any part of the heart with 

 the strongest current. 



That the white dots seen at the points of application of 

 the electrodes are due to marked contraction of the heart 

 muscle, the behaviour of the Alligator's heart renders 

 extremely probable ; but that the other effects are due, not 



