ARE TESTS OF PHYSICAL SCIENCE. 



61 



pulses are called by as many different names as 

 there are different lines of sensorial nerves serv- 

 ing to transmit the action to the brain. This is 

 exemplified in the following table : 



DIFFERENT NAMES GIVEN TO THE SAME ELECTRO-MECHANICAL ACTION 

 TRANSMITTED THROUGH THE FIVE SENSORIAL NERVES. 



From inattention to the functions of the sensorial 

 nerves, an identical electro-mechanical impulse is 

 ascribed to three different causes, Heat, Light, 

 and Electricity. For ages these have been consid- 

 ered " Imponderable Agents of Nature," employed 

 to produce the phenomena appearing on the sur- 

 face of the world around. 



To avoid errors, the student of physical science 

 requires primary instruction in the use of the 

 tools he is destined to employ. Because two 

 different arrangements of nerves those of the eye 

 and of the hand are requisite for holding com- 

 munication harmlessly and painlessly with heated 

 and ignited bodies, this is no apology for calling 

 the cause of these different intensities of excita- 

 tion by the two different names of " Light " and 

 " Heat ; " although it is useful to designate the 

 different effects produced thereby by different 



