THE CIRCULATION OF THE BLOOD 



291 



ometer. When the base and apex of the frog's heart are thus connected, it 

 will be found that with each contraction, the galvanometer needle will deviate 

 from its position of rest and in a direction that indicates that there is not 

 only a change in their electric potential but also that the base becomes 

 primarily electronegative to the apex which remains electropositive. 

 With the development of the negativity a current passes down the heart 

 to the apex, out through the galvanometer circuit and back to the point 

 of origin. This current has been termed the action current. 



If the heart is connected with a more quickly responsive apparatus, e.g., 

 a capillary electrometer (see appendix) it will be found that the mercury 

 will pulsate twice, but in opposite directions, with each contraction, indi- 

 cating that two action currents are developed, the first indicating that the 



FIG. 129. THE ELECTRONEGATIVE AND ELECTROPOSITIVE AREAS OF THE BODY SURFACE. 

 A and B respectively represents apex and base of the ventricular mass. Then, if at any moment 

 a difference of potential should arise between A and B, a current, c c c, will be established along 

 and around the axis C C; the line O will represent the plane of zero potential or equator; 

 the lines a a a, b b b will represent equipotential curves around A and B. A difference of 

 potential between A and B will be manifested if the two leading-off electrodes are applied on 

 opposite sides of the equator, O; no such difference will be manifested if both electrodes 

 are on the same side of the equator. The equator O will divide the body into two asym- 

 metrical parts, (i) a portion b b b including the head and right upper extremity, (2) a portion 

 a a a including the three other extremities. (Waller, Human Physiology.) 



base is primarily negative to the apex which is electropositive, and the 

 second that the apex is secondarily negative to the base which has become 

 again electropositive: in other words the changes in electric potential are 

 diphasic. With the capillary electrometer Waller demonstrated that the 

 human heart also exhibits similar changes in its electro-potential with each 

 beat giving rise to electric currents which find their way through the sur- 

 rounding tissues to the surface of the body from which they can be led 

 off to the electrometer and then back to the surface of the body and finally 

 to the base of the heart. He was enabled to determine and locate the points 

 which are electronegative and electropositive. The results of his experi- 

 ments are embodied in the accompanying diagram Fig. 129, which, with 

 the legend is self-explanatory. 



