108 CONSCIOUSNESS AND SENSATION. 



irritations and changes of temperature. It appears 

 then that if we suppose that the consciousness is 

 directly affected by the application of the irritation 

 to the nerve-extremity, we have the simplest pos- 

 sible explanation of differences of colour and of 

 notes, and of the different kinds of sensation, con- 

 veyed by the nerves of general sense. We are in 

 a position to say that as the irritation varies so 

 varies the sensation, without being obliged to 

 assume different kinds or conditions of nerves 

 without evidence. 



The objections may be urged against my theory 

 that irritation of the ulnar nerve produces sensation 

 in the finger ends, that persons after amputation of 

 an arm feel pain in the fingers, and that irritation 

 of one nerve often causes pain in another, as when 

 disease of the hip gives pain in the knee, or tooth- 

 ache pain in the temple ; but it appears to me that 

 all these things are better explained by this theory 

 than by the received one. When one strikes the 

 ulnar nerve at the elbow accidentally with force 

 everybody knows that the acute pain is not felt 

 in the fingers, but at the part struck, and that this 

 is immediately succeeded by pain and a peculiar 

 sense of vibration which travel downwards from 

 the struck part till they reach the fingers. A 

 patient who has had a limb removed, in like 



