THE REPAIR OF A NERVE 425 



one — for a large nerve on division curls up at the end, forming 

 a contorted leash of fibres ; it also retracts, and a considerable 

 amount of scar tissue is formed. This cicatricial tissue, by the 

 time the nerve has begun to regenerate, has become very dense, 

 and so an impediment to the successful growth of the nerve 

 fibres is interposed. Still, in spite of such a barrier, spontaneous 

 restoration frequently takes place. If the cut were made by a 

 dirty piece of sharp machinery, inflammation usually comes in 

 as a complication, and causes still further delay. In animals, 

 where the cut is made with a clean knife, and antiseptic pre- 

 cautions are employed, this danger is reduced to a minimum, 

 the amount of scar tissue is less, and union may be anticipated 

 without suture. But even here suture hastens recovery, and in 

 man thorough cleansing of the wound and the union of the 

 divided nerve by appropriate ligatures should always be carried 

 out. The growing nerve fibres will then not be left to them- 

 selves to find their way into the peripheral end, but will be 

 guided more rapidly to their destination. In a number of cases 

 where the carelessness of the patient has caused him to neglect 

 obtaining this surgical assistance, it may be years before restora- 

 tion of function takes place, but even under these circumstances 

 the surgeon can help him. The old wound is opened up, the 

 swollen lumps at the ends of the two segments of nerve are 

 removed, and the two ends can then be united ; the operation 

 is spoken of as " secondary suture," and recovery is then 

 comparatively rapid. 



In some cases where the gap is a long one, some surgeons 

 have been in the habit of transplanting a piece of nerve obtained 

 in a living condition from a recently killed animal to bridge 

 across the interval. This, however, is not to be recommended, 

 since Marinesco has shown that if a transplanted nerve is 

 obtained from another species of animal it is completely 

 necrosed, just as the blood corpuscles of one animal are 

 destroyed by the body fluids of another. The interposition of 

 a foreign piece of nerve is thus in man rather a hindrance than 

 a help. 



Many surgeons have been steadfast upholders of the auto- 

 genetic theory because they have found in man that sensation 

 may return very rapidly after freshening up and suturing together 

 the ends of a nerve which had been divided a long time 

 previously. They argue that during this time new nerve fibres 



