34 GENERAL PROPERTIES OF LIVING TISSUES 



In galvanic cells, in which two metals are 

 immersed in one or more electrolytes, there are 

 three sources of electromotive force: the junc- 

 tion of the metals with the electrolytes, the 

 junction of the two metallic conductors, and the 

 junction of the electrolytes. The junction of 

 the metals with the electrolytes is the principal 

 source ; the electromotive force produced by the 

 junction of the metals is slight, and the ions of 

 different neutral salts move at not far from the 

 same speed, so that the electromotive force at the 

 junction of the electrolytes is also relatively 

 small. 



THE ELECTROMETER, THE KHEOCORD, AND 

 THE CELL 



In order to study differences in electrical 

 potential, 1 a galvanometer or some other elec- 



1 The difference of potential may be compared to the differ- 

 ence of water level between a reservoir and its distributing 

 pipes. It produces an electromotive force, comparable to the 

 force which moves the water from the higher to the lower level. 

 The unit of electrical pressure is the volt. The flow through 

 an hydraulic system is measured by the quantity of water pass- 

 ing any point in a given time ; similarly the quantity of elec- 

 tricity is the amount that flows through a cross-section of the 

 conductor in a given time. The unit of quantity is the ampere. 

 Electricity passing through a conductor meets with a resistance 

 which becomes greater as the cross-section of the conductor 



