BIOLOGICAL EXPERIMENTS. 239 



seems rather a bold proposition, is really a very simple and easy 

 matter. We need simply dip the two hands into two basins of 

 water, which are in connection with the indicator, when we shall 

 see that the mercury beats up and down with the pulse. These 

 movements of the mercwy are due to the electrical changes ivhich 

 occur with every beat of the heart. Or, we may dip a hand and 

 a foot each into a basin of water with a similar result, 07ily it must 

 be the right hand ; the left ivill not do. This difference, apparently 

 so curious and puzzling at first sight, which seemed unsymmetrical 

 and irrational, is in reality most reasonable, and proved to be the 

 master key which threw open the meaning of every subsequent 

 experiment. The difference depends upon the unsymmetrical 

 position of the human heart, which is tilted somewhat to the left 

 side. 



To return to the physical A B C of the subject. The points 

 are respectively applied to the apex and base of the heart, and if, 

 with the contraction of the organ, these two portions undergo any 

 electrical change, the change will spread over the whole body in 

 accordance with known laws. The form of the change is repre- 

 sented by the oval lines in the diagram (No. 3). If the electrical 



Fig. 3- 

 level falls at A, it falls over the red area (represented by continued 

 lines), which, as we see, includes the left hand and foot and the 

 right foot. If the electrical level falls at B, it falls over the blue 



