SUPERIOR ANIMALS. 163 



.appear in motion, and are of frequent occurrence 

 in some diseases, such as typhus fever, when the 

 invalid sees them upon the bed-cover, and con- 

 stantly endeavours ' to pick them off with his 

 fingers. When a blow is received upon the eye, 

 an intense light is perceived : this must be familiar 

 to pugilists. 



When the optic nerve is cut., no pain is felt ; but 

 an intense flash of light across the eyes is experi- 

 enced. The same flash occurs when an electric 

 current passes through the optic nerve, as some- 

 times happens when a piece of silver and a piece 

 of zinc are made to form a galvanic couple with 

 the tongue or other parts of the mouth. To en 

 sure the success of this experiment, the plates of 

 zinc and silver should be placed upon the inside 

 of each cheek, and connected together, outside 

 the mouth, with a piece of silver wire. 



I have observed very vivid luminous appear- 

 ances, during fever, in my own eyes ; they mani- 

 fested themselves after any violent exertion, such 

 as going upstairs, walking quickly across a room, 

 etc.* The light appeared in the form of myriads 

 of luminous spots, in rapid motion, and of a 

 greenish-yellow tint. 



These phenomena, to which I have given the 



* These actions would not amount to violent in a state of 

 health, but require a great amount of exertion during illness. 



