400 



ELECTRO-PHYSIOLOGY 



CHAP. 



of the heart-muscle. It is evident that these facts coincide with 

 Hermann's theory, according to which a point of the muscle must 

 remain negative as long as the excitatory (or contraction) 

 process continues. Accordingly, we should expect the surface 

 of the ventricle to be isoelectric during the period of systolic 

 contraction, as actually appears from the experi- 

 ments of Burdon -Sanderson and Page. 



If, in the accompanying Fig. 127, (a, x) is the 

 spot excited, (F) and (m) the two points of the 

 ventricle led off, there will follow on each excita- 

 tion a rapid electrical variation (lasting only a few 

 T ^ sec.), in the direction of a current from the 

 b 



FIG. 127. a, b, Diagrammatic representation of the electrical variation in an artificial cardiac 

 contraction (Burdon-Sanderson and Page). The continuous line corresponds to the process 

 of negativity at the electrode nearest the seat of excitation. The dotted curve, on the 

 contrary, gives the negativity at the more remote contact. The middle line marks the time 

 in h sec. (VN) corresponds with the negative, (VP) with the positive variation on 

 Bernstein's rheotome. 



seat of excitation, succeeded by a longer period (1 2 /r ), during 

 which no current is indicated by the galvanometer; this is followed 

 by an opposite phase of deflection (positive variation) which is 

 much weaker and more prolonged than the initial " negative " 

 variation. The interval separating the two phases corresponds 

 exactly with the duration of the ventricular contraction, so 

 that the one (negative) phase of the action current marks 

 the beginning, the other (positive) the end of the excitation 

 (contraction) of the muscle. The first phase of the action 

 current obviously corresponds with the very short period during 



