CHAP. iv.J FEELING AND TOUCH. 581 



recognise that the object is such as could not under ordinary 

 conditions be touched at the same time by these two portions 

 of our skin, and therefore judge that we are touching not one but 

 two marbles. Upon repetition however we are able to correct our 

 judgment and the illusion disappears. 



Distinct tactile sensations are, as we have seen, produced only 

 when a stimulus is applied to a terminal organ. When sensations or 

 affections of general sensibility other than the distinct tactile sen- 

 sations are developed in the termination of a nerve, we are still able, 

 though with less exactitude, to refer the sensation to a particular 

 part of the body. Thus when we are pricked or burnt, we can feel 

 where the prick or burn is. When a sensory nerve-trunk is 

 stimulated, the sensation is always referred to the peripheral 

 terminations of the nerve. Thus a blow on the ulnar nerve at the 

 elbow is felt as a tingling in the little and ring fingers correspond- 

 ing to the distribution of the nerve, and sensations started in the 

 stump of an amputated limb are referred to the absent member. 

 When cold is applied to the elbow it is felt as cold in the skin 

 of the elbow : but a cooling of the ulnar nerve at this spot, since 

 stimulation of a nerve-trunk gives rise to general sensations only, 

 simply gives rise to pain which is referred to the ulnar side of 

 the hand and arm. 



