ELEMENTS 



OP 



PHYSIOLOGICAL PHYSICS. 



tfart IF. 



ELECTRICITY AND MAGNETISM AND THEIR APPLI- 

 CATIONS IN PHYSIOLOGY AND MEDICINE. 



CHAPTER I. 



FRICTIONAL ELECTRICITY. 



THERE are three principal methods of developing 

 electricity. The first method is by friction, the 

 second by chemical action, and the third by the action 

 of magnets. The electricity obtained by the first of 

 these methods, which is the subject of this chapter, is 

 called therefore Fractional Electricity. 



It was known to the ancients that amber, when 

 rubbed with silk, possessed the property of attracting 

 light bodies ; but it was not till near the close of the 

 sixteenth century that an English physician, Dr. 

 Gilbert, showed that other bodies possessed similar 

 properties. 



Take a small ball of some very light material, 

 like pith, and suspend it, by means of a silk thread, 

 from a glass support (Fig. 1). If now a stick of 

 resin or sealing-wax be rubbed vigorously with cat- 

 skin or flannel, and then brought near to the pith 

 B-7 



