190 



A totally different result will be observed when a ventricle, 

 brought to a complete standstill by removing the potassium, is 

 acted upon by the electric disc with quite the same force. Then 

 the isolated heart will pulsate normally and with a rhythm about 

 equal to that which occurred before with Ringer-circulation. On 

 discontinuing the stimulation of the toothed disc the systoles will 

 also cease. 



So there is a marked contrast. Whereas the motionless heart, 

 freed from circulation-potassium, will for some time resume its 

 normal contractility through stimulation with the toothed disc, the 

 normal action of the uranium-heart will cease altogether when 

 acted upon in the same way and with the same force. In both 

 cases this holds good as long as the stimulus lasts or only for 'a 

 slightly longer duration and in both cases the tonus remains unaltered. 



Under similar circumstances the usual Ringerheart is brought into 

 a condition of tonicity and undulation. 



The alternating current just described was obtained through sudden 

 closures and openings of a primary current. We also used instead 

 of it a sinusoidal current of about 1000 complete periods per minute. 

 It goes without saying that a considerably stronger battery had to 

 be inserted in the primary circuit with changes of greater slope. 

 Mostly, however, 8 or 10 volts proved sufficient to achieve similar 

 results. We made use of platinum-electrodes. ^) 



The Ringer-heart did not present anything particular while the 

 alternating current was passing, at the most an increase" of tonicity, 

 which rendered the pulsations somewhat more incomplete. 



The motionless heart freed from circulation-potassium, recommenced 

 its regular beats while the sinusoidal current was passing, its systole- 

 form, rhythm and tonicity being equal to that of the Ringer-heart. 

 A latent period and an after-etfect were often distinctly manifest, 

 mostly, however, they were scarcely visible with a stimulus of 

 about a minute's duration. 



The uranium-heart behaves quite differently. When for instance 

 the same hearts that during a standstill had been experimented upon 

 with sinusoidal stimuli, were restored to action by a uranium-containing 

 circulating fluid, a sudden standstill was seen at making the alter- 

 nating current, which, when the sinusoidal stimulus was discontinued 

 after a minute, would as suddenly make room for the normal 

 rhythm. There is often hardly a latent period or an after-effect. 



1) According to S. Ringer (J. of Phys Vol 4 p. 372) an excessive dosis of 

 potassium or rubidium yields the same effect by faradization as has been described 

 here for tbe uranium-heart. 



