72 GENERAL PROPERTIES OF LIVING TISSUES 



whenever the secondary circuit was open (i. e. 

 when the bridge between the ends of the second- 

 ary wire was up) the making and breaking of 

 the primary circuit caused free electricity to 

 gather on the ends of the secondary wire. When 

 the electro-static induction becomes great enough 

 the electromotive force overcomes the resistance 

 in whatever connecting path may be offered, and 

 the, electricity passes from the coil to the earth. 

 If a part of the path is formed by irritable 

 tissues, they will of course be stimulated. 



3. The quantity of electricity passing through 

 the nerve may be increased by approximating 

 the coils or by increasing the electrical capacity 

 of the conductor, as follows : 



Eemove the wire connecting the preparation 

 with the gas pipe. Set the inductorium in action. 

 Touch the muscle with the moistened finger. 



Contraction follows. 



Here the electrical capacity of the preparation 

 is increased by connecting the preparation with 

 the human body, a conductor of large surface 

 (and through it with the earth). A similar 

 result is obtained by unipolar stimulation of 

 nerves and muscles while still in the body of 

 the animal, as in many physiological experi- 

 ments. It is not necessary that the surface of 

 the conductor be enormously large. The follow- 



