258 ELECTRO-PHYSIOLOGY CHAP. 



diameter. This grows more and more prominent as a congested 

 expansion of the muscular wall of the ventricle, spreading with 

 comparative rapidity on all sides beyond the region of primary 

 relaxation. As Schiff correctly observes, with reference to the 

 analogous effect of local, mechanical excitation, the diastolic 

 relaxation, after attaining a certain amplitude, sometimes appears 

 to stand still for " a brief period," and then spreads slowly over 

 the whole ventricle. 



In other cases, however, we have observed as unmistakably, 

 particularly in much cooled, slowly -beating hearts (which are 

 used by preference in all these experiments), that the diastolic 

 wave spreads with uniform rapidity from the seat of initial 

 relaxation at the anode over the entire ventricle. Exactly the 

 same effects as appear in the contracted ventricle at the anode, on 

 closure of a constant current, occur unmistakably at the kathode 

 immediately after the circuit is opened. 



If with the same experimental conditions the current is 

 reversed without moving the electrodes, it will be seen at break- 

 given adequate intensity and duration of current that at the 

 moment of most pronounced systolic contraction the previously 

 anodic, but now kathodic, part of the ventricle is always the 

 first to relax itself. The diffusion of the originally local diastole 



o / 



increases again with the strength of current, but a second and 

 no less important factor here comes into play, i.e. the duration 

 of closure of the existing current. Up to a certain point a longer 

 period of closure of a weak current can be substituted for the 

 action of stronger currents. Stronger currents, however, are 

 always required a priori to produce the kathodic opening as 

 plainly as the anodic closure relaxation. The polar phenomena 

 of relaxation thus described in the ventricle of the frog's heart 

 contracted in systole may be very elegantly demonstrated, if the 

 two finely-pointed thread, or brush, electrodes are placed at two 

 points on the upper surface of the ventricle as far apart as possible 

 in the longitudinal or transverse direction, with tolerably pro- 

 longed closure of a not too weak current. During the period of 

 closure a local diastole occurs at the anode with each new sys- 

 tolic contraction. At break of the current the relations are 

 inverted, and for two, or even several, successive systoles the 

 kathodic region is the first to relax. 



If it were possible to keep the frog's heart for long in con- 



