REGENERATION OF PERIPHERAL NERVES 509 



SUMMARY OF RESULTS 



1. The peroneal nerve of the normal albino rat of 135 grams 

 body weight was found to contain 2288 medullated fibers in its 

 proximal end and 2323 medullated fibers in its distal end. The 

 middle zone is estimated to contain 2306 fibers. The portion 

 of the nerve utilized for these experiments was 10 mm. long. 



2. There is an increase in the number of fibers as we pass 

 from the proximal to the distal end of this 10 mm. of nerve 

 amounting to 1.5 per cent of the proximal number. 



3. The number of fibers is approximately the same for each 

 side. 



4. The number of medullated fibers increases with body weight 

 ( = age) during the first 276 days of life. The increase between 

 the 128-129-day group and the 276-day group (table 4) is about 

 5 per cent. 



5. Crushing the nerve by the method used causes complete 

 degeneration beyond the point of the lesion. 



6. Four days after the -operation no normal fibers are to be 

 found on the distal side of the lesion. The degeneration is 

 assumed to have involved the entire distal portions of the fibers. 



7. Complete degeneration also extends from 2 to 3.2 mm. on 

 the proximal side of the lesion. 



8. Characteristic loss of motor control always follows the oper- 

 ation. In many cases this has seemingly disappeared at the end 

 of ten days, probably as the result of compensatory adjustment. 



9. The general effects of the operation are more pronounced 

 on older animals. 



10. The control nerve of an operated animal contains fewer 

 medullated fibers than the same nerve from a normal animal of the 

 same age. This loss in number is one of the effects of the oper- 

 ation, and in the cases here examined amounted to 16 per cent. 



11. Following the degeneration in the operated nerve, regen- 

 eration, accompanied by branching of axons, takes place and 

 there is an increase of from 64 to 249 per cent in the number 

 of medullated fibers on the proximal side of the lesion. 



