FUNCTIONS OF NERVE-FIBRES. 381 



part of a limb has been removed by amputation, the remaining 

 portions of the nerves which ramified in it may give rise to 

 sensations which the mind refers to the lost part. When the 

 stump and the divided nerves are inflamed, or pressed, the 

 patient complains of pain felt as if in the part which has been 

 removed. When the stump is healed, the sensations which we 

 are accustomed to have in a sound limb are still felt; and 

 tingling and pains are referred to the parts that are lost, or to 

 particular portions of them, as to single toes, to the sole of the 

 foot, to the dorsum of the foot, &c. 



But (as Volkmann shows) it must not be assumed, as it 

 often has been, from these examples, that the mind has no 

 power of discriminating the very point in the length of any 

 nerve-fibre to which an irritation is applied. Even in the in- 

 stances referred to, the mind perceives the pressure of a nerve 

 at the point of pressure, as well as in the seeming sensations 

 derived from the extremities of the fibres ; and in stumps, 

 pain is felt in the stump, as well as, seemingly, in the parts 

 removed. It is not quite certain whether those sensations are 

 perceived by the nerve-fibres which are on their way to be 

 distributed elsewhere, or by the sentient extremities of nerves 

 which are themselves distributed to the many trunks of the 

 nerves, the nervi nervorum. The latter is the more probable 

 supposition. 



The habit of the mind to refer impressions received through 

 the sensitive nerves to the parts from which impressions 

 through those nerves are, or were, commonly received, is fur- 

 ther exemplified when the relative position of the peripheral 

 extremities of sensitive nerves is changed artificially, as in the 

 transposition of portions of skin. When in the restoration of a 

 nose, a flap of skin is turned down from the forehead and made 

 to unite with the stump of the nose, the new nose thus formed 

 has, as long as the isthmus of skin by which it maintains its 

 original connections remains undivided, the same sensations as 

 if it were still on the forehead ; in other words, when the nose 

 is touched, the patient feels the impression as if it were made 

 on the forehead. When the communication of the nervous 

 fibres of the new nose with those of the forehead is cut off by 

 division of the isthmus of skin, the sensations are no longer 

 referred to the forehead ; the sensibility of the nose is at first 

 absent, but is gradually developed. 



When, in a part of the body which receives two sensitive 

 nerves, one is paralyzed, the other may or may not be inadequate 

 to maintain the sensibility of the entire part ; the extent to 

 which the sensibility is preserved corresponding probably with 

 the number of the fibres unaffected by the paralysis. Thus 



