Nerve-suturing (neurorrhaphy) : degeneration and regeneration following section : microscopical appearances : one of the Mütter course of lectures delivered before the Philadelphia College of Physicians / by De Forest Willard.

  • Willard, De Forest, 1846-1910.
Date:
1894
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Licence: Public Domain Mark

Credit: Nerve-suturing (neurorrhaphy) : degeneration and regeneration following section : microscopical appearances : one of the Mütter course of lectures delivered before the Philadelphia College of Physicians / by De Forest Willard. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    medullary sheath was developed ; they regarded regeneration as independent of reunion. Other experiments have been undertaken to show that after regeneration of nerves the different trunks which were united in the animals were still able to perform their original co-ordinate movements. Reichert had the hypoglossus cut close to its exit from the cranium and the vagus at the thyroid. The peripheral end of the hypoglossus was sutured with silk to the central end of the vagus. Microscopical examina- tion later of the hypoglossus trunk showed that it contained degenerated fibres and a large number of small fibres in the medullary sheath, proving that the motor fibres of the vagus had actually become united to similar filaments of the hypoglossus, and that the hypoglossus fibre conveyed im- pulses which were peculiar to the vagus. In one case he found that sensory- fibre irritation of the hypoglossus trunk produced effects like those induced by excitation, thus showing that motor and sensory nerves can convey im- pulses peculiar to another motor or sensory nerve of entirely different func- tion. He calls attention also to the fact, as shown by Bert’s experiments, that sensory fibres can convey impressions in both directions. This Bert proved by grafting the tail of a rat upon the animal’s back, and, after union had occurred, severing the tail from its normal connection and then trans- mitting sensation in the reverse direction. With regard to the process of regeneration which takes place in favor- able cases after division and regeneration of a nerve, there has been a differ- ence of opinion among investigators. Korybutt-Daskiewicz1 has described it thus : “ After liquefaction of the old medulla in the central end there occurs the formation of new myeline with the peculiar appearance that be- tween the two former constrictions one or two new ones are formed. The nuclei of the sheath of Schwann also undergo changes in the central end near the division of a nerve; they swell up, become surrounded by gran- ular protoplasm, and, after becoming separated from the fibres, assume an elongated form, whether finally developing into nerve-fibres cannot be defi- nitely ascertained. The axis-cylinders in the peripheral part break up into more or less numerous fragments during segmentation of the medulla, and of these some apparently liquefy and participate in the same changes as the myeline, while others persist and clothe themselves with a new medullary sheath. Before the degeneration of the myeline begins to lessen, the frag- ments of the axis-cylinder commence to lengthen in each direction, and the nuclei existing within the sheath begin to elongate and lie at certain dis- tances from each other. Simultaneously with this process the new medullary sheath makes its appearance as a varicose or uniform deposit upon the axis- cylinder. Thus the fragments of the axis-cylinder remaining serve as a starting-point for a new endogenous formation of nerve-fibres. They pre- sent no tendency to blend with one another, but remain in contiguity, grow- 1 Gaz. des Hopitaux, 1861.