1906.] 



Regeneration of Nerves. 



279 



(5) Experiments on the Influence of Stimulus on Regeneration. 



These experiments were performed on Ehcesus monkeys. A monkey's 

 arm was rendered immobile by the division of a number of the upper 

 posterior roots on one side. In order to be perfectly certain, we usually 

 divided from the second cervical to the second or third thoracic roots 

 inclusive. The anterior cornual cells from which the corresponding motor 

 fibres originate are thus not subjected to stimuli from the periphery and, 

 as Mott and Sherrington were the first to show, the arm is as much paralysed 

 as if the anterior roots had been cut. We have, however, again noticed in 

 some of these animals under the influence of strong emotion (for instance, 

 when the monkey is prevented from reaching with the sound hand a piece 

 of apple) that some efforts were made to move the paralysed limb. These 

 efforts are ineffectual and are limited to associated movements in the upper 

 segment of the limb ; fine movements were never noticed. When the 

 animal is living in its cage under ordinary conditions it makes no effort 

 to move the limb, which in successful experiments (i.e., when a sufficient 

 number of roots have been entirely cut through) hangs helpless like a flail. 



In the case of one or two of the wilder animals we first operated on, the 

 hanging limb was apt to get injured by their jumping about the cage. 

 Wounds so produced heal with difficulty, and the presence of such wounds 

 necessitated the sacrifice of the animals. Later we obviated such accidents 

 by providing the animals with jackets, the sleeve containing the paralysed 

 limb being well packed with cotton wool. 



After the healing of the neck wound produced by the cutting of the 

 posterior nerve roots was accomplished, a matter usually of one or two 

 weeks, a large nerve in the arm (median or ulnar)* was then divided and 

 the ends sutured together. The corresponding nerve was cut and sutured 

 on the non-paralysed side as a control experiment. The animal was finally 

 killed ; the interval between the operation and death varied in different 

 experiments, but the best time for making the observation we finally 

 determined to be between 60 and 70 days after the nerves had been cut. 

 This is a date when regeneration is perfectly evident, but not too far 

 advanced ; it, therefore, permits of comparative observations on the amount 

 of regeneration. 



* We found a considerable anastomosing branch passing from the median to the ulnar 

 nerve in the lower part of the fore-arm ; some branches which, still lower down, 

 apparently come off from the ulnar, are really median in origin. A non-recognition of 

 this fact is apt to cause confusion (as it did in some of our early experiments), for after 

 section of the ulnar some of the branches to the last two fingers show no sign of 

 degeneration. 



