NERVE INJURIES 135 



completely divided ; they are restored side by side at 

 an equal rate. 



The last point we shall consider is how best to 

 proceed when so much nerve has been lost that the 

 ends cannot be got together. Many methods have 

 been adopted, some of which are of little or no value 

 and should be allowed to drop out of use. Amongst 

 these may be mentioned the introduction of a bridge 

 of nerve derived from a cat, dog, or rabbit (which will 

 undergo dissolution), or of silk or catgut, and the device 

 of splitting the nerve longitudinally and turning down 

 one-half across the gap. It is quite evident why these 

 fail. The silk, catgut, and probably the animal's 

 nerve, cannot provide the necessary chemical attrac- 

 tion for the down-growing nerve fibres. The splitting 

 " en-Y " does not lay down a continuous " scent " 

 along the tract ; it is broken at the stem of the Y. 

 Infinitely better results may be obtained by suturing 

 into the interval a length of human nerve. This 

 may be obtained from an amputated limb, but it is 

 always possible to excise several inches of some 

 unimportant nerve such as the internal cutaneous 

 of the arm, and if this is too slender two or more 

 pieces may be used parallel to one another. It is 

 an advantage to protect the nerve junctions from 

 invasion by fibrous tissue ; this may be done by 

 enclosing them in a ring or tube of superficial vein, 

 or in Cargile membrane. 



There is yet another method, which is sometimes 

 the only one available. Langley made some very 

 interesting experiments on the effects of joining up 

 the cut ends of different nerves, and found that their 



