MOTOR AND SENSORY NERVES. 593 



anastomoses that take place between sensory nerves, the fibres assume no new relations, 

 except as regards contiguity. 



As motor fibres convey to their peripheral distribution the stimulus engendered by an 

 irritation applied in any portion of their course, so an impression made upon a sensitive 

 nerve is always referred to the periphery. A familiar example of this is afforded by the 

 very common accident of contusion of the ulnar nerve as it passes between the olecranon 

 and the condyle of the humerus. This is attended with painful tingling of the ring and 

 little finger and other parts to which the filaments of this nerve are distributed, without, 

 necessarily, any pain at the point of injury. More striking examples are afforded in neu- 

 ralgic affections dependent upon disease of or pressure upon the trunk of a sensitive nerve. 

 In such cases, excision of the nerve is often practised, but no permanent relief follows 

 unless the section be made between the affected portion of the nerve and the nerve- 

 centres; and the pain produced by the disease is always referred to the termination of 

 the nerve, even after it has been divided between the seat of the disease and the periphery, 

 leaving the parts supplied by the nerve insensible to direct irritation. In cases of disease 

 it is not unusual to note great pain in parts of the skin that are insensible to direct im- 

 pressions. The explanation of this is, that the nerves are paralyzed near their terminal 

 distribution, so that an impression made upon the skin cannot be conveyed to the senso- 

 rium ; but that the trunks of the nerves still retain their conducting power and are the 

 seat of diseased action, producing pain, which is referred by the patient to the periphery. 



In multiplying examples showing the mode of action of the sensory nerves, we may 

 refer to the sensations experienced after certain plastic operations. In the very common 

 operation of restoring the nose by transplanting skin from the forehead, after the opera- 

 tion has been completed, the skin having been entirely separated and cicatrized in its 

 new relations, the patient feels that the forehead is touched when the finger is applied to 

 the artificial nose. After a time, however, the sensorium becomes accustomed to the 

 new arrangement of the parts, and this deceptive feeling disappears. 



There are certain curious nervous phenomena, that are not without physiological 

 interest, presented in persons who have suffered amputations. It has been long observed 

 that after loss of a limb the sensation of the part remains, and pain is frequently experi- 

 enced, which is referred to the amputated member. Thus a patient will feel distinctly 

 the fingers or toes after an arm or a leg has been removed, and irritation of the ends of 

 the nerves at the stump produces sensations referred to the missing member. A few 

 years since, we observed a very striking example of this in a soldier who had suffered 

 amputation of the leg. While this patient was walking about on crutches, before the 

 stump had entirely healed, upon getting up suddenly from his seat, in attempting to 

 walk he put the stump to the ground, producing considerable injury. His explanation 

 was, that he felt the foot perfectly, and it was necessary for him to be constantly on his 

 guard to prevent such an accident. 



A very curious fact has been observed with regard to the imaginary presence of limbs 

 after amputation, which we have had ample opportunities of verifying. After a time the 

 sense of possession of the lost limb becomes blunted, and it may, in some cases, entirely 

 disappear. This 'may take place a few months after the amputation, or the sensations 

 may remain in their full intensity for years. Examples are reported by Mtiller where 

 the sense was undiminished thirteen, and, in one case, twenty years after amputation. 

 In a certain number of cases, however, the sense of the intermediate part is lost, the 

 feeling in the hand or foot, as the case may be, remaining as distinct as ever, the impres- 

 sion being that the limb is gradually becoming shorter. These curious facts, noted by M. 

 Gueniot, show that the sense of the limb becoming shorter is observed in about half of 

 the cases of amputation in which cicatrization goes on regularly ; and, in these cases, 

 the patient finally experiences a feeling as though the hand or foot were in direct contact 

 with the stump. By careful inquiries among a large number of patients in military hos- 

 pitals, we have been enabled to verify these observations in the most satisfactory manner. 

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