82 



PHYSIOLOGY 



CHAP. 



current, but a secretory skin current, as was shown by Hermann 

 and Luch singer. 



is A. D. Waller succeeded in demonstrating the electrical changes 

 that accompany contraction of cardiac muscle in intact animals 

 and man. He used Lippmann's capillary electrometer, by which 

 he was able to record not only the diphasic variation that accom- 

 panies the beats of the human heart, but also the simultaneous 

 distribution of electrical potential in the remainder of the body. 

 In connecting the different points of the cutaneous surface with 

 the capillary electrometer, he obtained the results shown in 

 Fig. 58. If the two electrodes are placed on the two points A 

 and B, or other more remote points ab, situated at eitber side of 

 the oblique equatorial line 00, along which the potential is zero, 

 the mercury of the capillary moves synchronously with the beats 



FIG. 59. Cardiograms of human heart, c c, and simultaneous diphasic variations. (A. D. Waller.) 

 Time tracing, 1 1, in ^ sec. The electrode connected with the sulphuric acid went to the 

 mouth, that with the mercury to the left foot. 



of the heart. This does not occur if the electrodes are applied to 

 two points on the same side of the equatorial plane. If the 

 oscillations of the mercury are closely watched or photographed 

 it can be seen that a diphasic variation corresponds with each 

 systole (Fig. 59). 



We have elsewhere described Gaskell's important discovery on 

 the cardiac muscle of the tortoise when arrested by Stannius' 

 upper ligature (Vol. I. p. 332). He found on leading off a 

 demarcation current excited by injury of the surface to the 

 galvanometer, and then exciting a branch of the vagus, that the 

 variation was not negative, but positive, i.e. the demarcation 

 current was reinforced, not weakened. From this observation he 

 concluded that the vagus has an anabolic action on the heart, as 

 opposed to the katabolic action of the sympathetic. As dis- 

 integrative explosive stimuli produce a negative potential in the 

 active segments of the tissue as compared with the non-active, so 

 integrative processes which spread as a wave of inhibition, after 



