191 



Still, it sometimes occurs that a latent period of in maximo 1 

 minute appears and an after-effect that will occasionally persist for 

 2 or 3 minutes. Then we are in a position to see that, during such 

 an after-standstill, the mechanic excitability has been maintained. 



Whereas the RiNGER-heart and the heart, fed with a potassium- 

 free fluid, generally stand the faint sinusoidal stimuli very well, the 

 uranium-heart does not. In most cases the minute-stimuli can be 

 applied only three times even with intervals of five minutes or 

 more. After that the heart is irrevocably lost (permanent standstill). 



So with the sinusoidal current we also observe: a short recurrence 

 of the pulsations in the motionless heart freed from circulation- 

 potassium, arrest of the pulsations of the heart beating under the 

 influence of uranium. Analogous experiments may be made with 

 the constant current. 



A normally beating RiNGER-heart is only slightly affected by weak 

 currents transmitted with nonpolarizable electrodes. If tiie force of 

 the current be raised to about 3 m.A., the tonus is markedly in- 

 creased while the current passes and a series of rapid undulations 

 reveal themselves in the constantly contracted heart. After breaking 

 the current the heart suddenly relaxes and a pause appears that 

 outwardly bears a resemblance to a compensator}' pause after 

 extrasystole. 



A heart that is arrested through deprivation of circulation-potassium 

 resumes its beats at once under the influence of a constant current 

 of from 1 to 3 m.A., while it as suddenly comes to a standstill 

 when the current is bi'oken. 



If the heart, either fresh or stimulated in the way described, is 

 deprived of potassium and is made to pulsate again perfectly by 

 uranium-containing Ringer's mixture so long that, with fairly strong 

 stimuli no more extrasystoles are produced, a gradual transmission 

 of from Va to 3 m.A. will bring about a complete standstill with 

 relaxation. Again normal systoles will recur after breaking the cur- 

 rent. Only in the case of superexcitation increase of tonicity is noted. 

 In order to observe the very remarkable arrest of the pulsations 

 without further by-effect it is, therefore, necessary : 1 to wait till 

 induction-shocks of moderate force are no longer succeeded by extra- 

 systoles; 2 not to apply stronger currents than are just necessary 

 for the individual heart. 



The direction of the current is of no consequence, the result being 

 the same whether it flows from base to point or conversely. Frequent 

 Stimuli or such as are too strong or last too long destroy the heart. 



