566 ANNALS NEW YORK ACADEMY OF SCIENCES 



nerve compared to the sutured, demonstrates the more rapid recovery 

 of fiber size in the crushed nerves. These experiments were not carried 

 beyond 200 days, and the ultimate amount of recovery of the normal 

 fiber distributions was not determined for crushed nerves. 



The Effects of Delayed Suture on Fiber Diameter Growth 



The method of studying the "maturation" of the fibers by action 

 potential records and diameter measurements was used to determine 

 the influence of delaying the suture after transection. An operative 

 procedure similar to that of Holmes and Young^ was devised, to allow 

 the tibial nerve to degenerate after section and remain free of fibers 

 during a determined delay period. The adjacent peroneal nerve was 

 then transected, and the freshly cut central stump was sutured to the 

 old distal remnant of the tibial. This cross-suture was used to limit 

 the study to effects of delay in the distal segment. 



In the same animal, a reliable control was provided in each experi- 

 ment by suturing the peroneal nerve of the opposite leg to the tibial 

 nerve. This was done in exactly the same manner as on the delayed 

 side, but, in this case, there was no delay between section and suture. 



The procedure may be summarized as follows: The right tibial nerve 

 was exposed, and a long segment removed from the sciatic notch to the 

 popliteal space. To insure the absence of regeneration during the de- 

 lay period, the cut nerve was exposed at 6-month intervals. Then, after 

 a delay of 14 to 476 days, a second operation was performed, in which 

 the right peroneal was sectioned and the central end sutured in the old 

 distal tibial. At this same time, the left peroneal was sectioned and 

 sutured to the distal tibial as a control. 105 to 440 days were then 

 allowed for regeneration before the terminal experiment. 



The shapes of the action potentials and the maximum conduction 

 velocities in the distal segments, after delay periods of 14, 21, 28, 56, 

 84, and 180 days, were similar to those recorded from the nerves of the 

 opposite leg which had been sutured without delay. In each of these 

 experiments, 105 days were allowed for regeneration after suture. The 

 diameter distribution of the fibers was the same on both sides, as illus- 

 trated in FIGURE 6, A and B. The histogram in figure 6 B was from 

 the right tibial, 3 cm. distal to the suture, which was delayed 84 days, 

 and after which the nerve regenerated for 105 days before the fibers 

 were measured. The control from the same animal is shown in figure 

 6 A. Both nerves were analyzed 105 days after suture. The similarity 

 of the two histograms was also found with 14, 21, 28, 56, and 180 days, 

 and indicates that such delay periods had no influence on the diameter 

 growth of fibers, under these experimental conditions. 



