TRANSACTIONS OF SECTION I. 783 



stump of the divided nerve, and those who consider that the nevsr fibres have a 

 peripheral origin. Those who hold the latter view rely almost exclusively on 

 histological evidence ; a strand that looks like a nerve-fibre to the microscope 

 cannot be a nerve-fibre unless it is shown experimentally by stimulation to be both 

 excitable and capable of conducting nerve-impulses. Among recent writers, 

 Howell and Huber, who have used both histological and experimental methods, 

 have arrived at the conclusion that although the peripheral structures are active 

 in preparing the scaflblding, the axis cylinder, the essential portion of a nerve- 

 fibre, has an exclusively central origin. Our experiments, which have been mad« 

 on monkeys, are at present incomplete, and this communication must therefore be 

 regarded as only of a preliminary nature. But so far as we have gone at present 

 our conclusions tend to confirm those of Howell and Huber. 



One experiment which we have done was suggested to us by Professor Gotcb, 

 and the result was very striking. A large nerve was divided and the ends sutured 

 together. After a sufficient length of time had passed, restoration of function led 

 us to suppose that regeneration had occurred. The nerve was exposed ; the union 

 of the two ends was found to have been accomplished, and the nerve was excitable 

 below and above the junction. A piece of the nerve was then excised a little 

 distance below the junction, and on histological examination of this, new nerve- 

 fibres were discovered in it. After this second operation the wound was closed 

 up and the animal allowed to live for ten days longer. It was then killed, 

 and the nerve both above and below the second cut examined; no degenera- 

 tion was found in the nerve-fibres above the lesion, but there was distinct evidence 

 of the degenerative process in the fibres of the peripheral end, which was quite 

 inexcitable. This showed us that the degeneration process which followed the- 

 direction of growth had occurred in a peripheral direction only, and is a strong- 

 piece of evidence that growth had not started from the periphery centralwards, or 

 at any rate that the direction of nutritive control is from the centre towards the 

 periphery. 



Other experiments which we have done illustrate the important influence of 

 stimulus in the regenerative process. A monkey's arm was rendered immobile by 

 the division of a number of the upper posterior roots. The anterior comual cells- 

 from which the motor-fibres originate are thus not subjected to stimuli from the 

 periphery, and the arm is as much paralysed as if the anterior roots had been cut. 

 Warrington has already shown that under these circumstances the anterior horra 

 cells undergo the chromatolytic change which is associated with inactivity. A 

 large nerve in the arm (ulnar or median) was then divided, and the same nerve 

 was divided 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. We have already found that if sufficient time had elapsed, union of 

 the divided ends occurred on both sides' of the body, but on the side corre- 

 sponding to that on which the posterior roots had been divided the nerve was either 

 inexcitable or required very strong Faradic stimulation to make it respond ;; 

 histologically the nerve showed a much looser texture, and new nerve-fibres 

 though present were less numerous than on the control side, where the microscope 

 revealed that regeneration had occurred in the usual way, and the new nerve- 

 fibres responded to stimuli readily. This tends to show the importance of stimulus, 

 to the reparative process. 



SATURDAY, SEPTEMBER 13. 

 The Section did not meet. 



