56 STUDIES IN ELECTRO-PHYSIOLOGY: 



loses its electricity by convection. Particles of the air com- 

 ing in contact with the body receive a charge, and pass on, 

 to be succeeded by other particles, each of which carries 

 off its portion, till the whole charge is thus dissipated." 



Dissipation by convection does not fully explain the 

 phenomenon. Hot air, inferentially, is dry air, and dry 

 air is a bad conductor. All the neuro-electricity given off 

 in a room does not, therefore, form a stratum near the 

 ceiling, and a " current of air "may be variously construed. 

 Anyone moving about in the testing-room, draught from 

 the door, window, or floor, or even the breath of the persons 

 present may create such a current. In any case, however, 

 the air is an" earth " of high resistance, and the higher its 

 resistance dimensions being equal the quicker the at- 

 mosphere of the testing-room will become charged with 

 neuro-electricity, because of the increased difficulty placed 

 in its path to a true " earth." 



That being so, it is evident that while the generation of 

 neuro-electricity in the body might be deemed to be 

 constant, the dissipation of it cannot be so by reason of the 

 varying conditions of exterior conductivity. 



Another important point to remember is that the sign 

 of current in individuals is not always the same. The 

 palms of the hands, being free from sebaceous glands, are 

 the most convenient body terminals, but, until determined 

 by test, the body resembles a galvanic cell whose terminals, 

 electromotive force, and internal resistance are unknown. 



The bearing of all this upon error will soon become 

 apparent. Let us imagine ourselves in a laboratory, the 

 floor and walls of which oppose considerable resistance to 

 the escape of electricity, and let there be two people 

 reproducing, say, the experiments of Professor Trowbridge. 

 We, however, will take the precaution of testing 

 them for personal neuro-electricities, and, to quote figures 

 obtained in actual practice, say that A gave a deflection 



