240 



TWO IMPORTANT 



area (represented by dotted lines), which includes the right arm 

 and the head. 



Now, it is obvious that the two ends of the indicator must be 

 connected with A and with B before it will indicate any difference 

 between A and B. If both ends are connected with A, or both 

 ends with B, nothing will be seen. This is precisely what happens 

 when the left hand and a foot are connected with the instrument, 

 which begins to pulsate as soon as the right is substituted for the 

 left hand. If, again, the mouth and right hand are connected 

 with the instrument, its index does not move, but it does as soon 

 as the left hand is put in the place of the right one. 



In the case of four-footed animals — dogs, cats, etc, — the heart 

 is more centrally placed than in man — that is, it has not a decided 

 inclination to the left side. In these animals, therefore, the two 

 fore-paws and two hind-paws are opposed to each other, as will 

 be seen in the diagram (Fig, 4). [Perhaps it will be better to 



Fig, 4. 

 explain that the animal is not strung up in spread-eagle fashion 

 to be experimented on, but stands in a natural position with the 

 feet in bowls of water.] We know that no movement can take 

 place in a muscle without a corresponding discharge of electricity ; 

 in fact, that our whole apparatus of muscles and nerves constitutes 

 an elaborate electrical machine, 



Dr, Waller also proves by experiment that the electric shock 

 passes through persons holding each other's hands, when the hands 



