ACTION OX THE HEART'S RHYTHM. 53 



From the nature of the impulse generally remaining much 

 the same till the last, or nearly so, the power of the heart 

 appears to be relatively increased all along ; but as the arterial 

 tension, though it may be increased at first, greatly diminishes 

 afterwards, the absolute force of the heart may be, and prob- 

 ably is, very greatly diminished before death. 



From his observations on the efiect of small doses, such as 

 slow the heart's action, Winogradoff found that no change was 

 produced ; and as I found (Exp. X, 12, 35' 20'') that not only 

 was there no change in the mean pressure, but none in the 

 oscillation, and the breathing quiet, though the pulse had fallen 

 from 140 to 78, though not certain, I am strongly inclined to 

 believe that the force of the heart is neither increased nor de- 

 creased. Later on, and after a farther dose, as at 1.20', I am 

 inclined to think that it may be feebler, though possibly it is 

 only because the pulsations are more frequent. 



The observation of Stannius, that after a strong dose of 

 digitalis a surprising weakness of the cardiac pulsations be- 

 coming finally complete paralysis is observed, may be true in, 

 regard to overwhelmingly large doses ; and in the sheep, which 

 I killed by 2 grains, the condition of the heart was not noted,, 

 but in general the impulse is increased, so generally in fact, 

 that often I have not noted it, looking on it as to be always 

 expected. 



(2) On the Heart's Rhythm. — Dybkowsky and Pelikan* found 

 in frogs wliich were poisoned by digitaline (or other cardiac 

 poisons, producing an identical effect), the rhythm of the 

 heart was at first unchanged, but soon after three, five, or 

 ten minutes (according to the poison), irregularity was notice- 

 able. This was of two kinds — (1.) The ventricular contractions 

 became peristaltic, so that after the contraction of the auricles- 

 the ventricle did not contract as a whole, but first its upper 

 third, whence the^ contractions gradually passed down to the 

 apex ; but before this had contracted the upper third was again 

 dilated. Two or three minutes before complete paralysis the 

 contractions became still more irregular, so that the upper or 



* Mem. de la Soc. de Biologie tome iii ser. ?, p 97. 



