Physiology of the nervous system / J.P. Morat.

  • Jean-Pierre Morat
Date:
1914
Catalogue details

Licence: In copyright

Credit: Physiology of the nervous system / J.P. Morat. Source: Wellcome Collection.

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    some neurons in thenoiddle of others), may be an artificial result which is due to the action of the re-agent employed ; thus has arisen once more the discussion on the continuity or tlie contiguity of the articulated prolongations of these neurons. It does not enter into the object of this work to take jDart in these technical discussions : the question wliich has thus arisen, whatever may be its impor- tance, must be fought out by anatomists. But it seems that, in pursuing this detail, the essential point which this large and admirable collection of observa- tions has so vividly brought out, the essential point of view has been lost sight of. This point is the individuality of the nerve element, of the neuron. For a long time this was unknown to us. It was generally admitted that the nervous sj^^stem is formed of two species of elements, fibres and cells, and the point of departure between them was placed in a locality where it is clear that there neither was, or had been at any period of develojDment, anj^ discontinuitJ^ We now Imow that in the nervous system there is no fibre which is not the prolonga- tion of a nerve cell, and when tliis fibre passes from one cell to another, we can affirm to which of the two it belongs. Thanks to the new methods introduced by Golgi, the nerve element can now be demonstrated as regards its general structure, its exact boundaries and its principal details. 3. Individuality of the Neuron.—Its proofs.—The two following facts established, one by embryology, the other by the method of degenera- tion, are convincing on this most important point. (1) The nervous elements, the neurons, arise from independent cells ; these cells, as His has observed, give out prolongations in different directions, in order to be mutually connected and to associate them- selves with the fixed elements of the organism. (2) When the prolongations are separated from the cell by section they become the seat of a degeneration ivhich terminates precisely at their extremity. In leaving undetermined the question whether these prolongations have contracted connexions which establish their continuity by means of welding, or whether they remain in simple contact, these two facts I- prove to demonstration that each nerve cell, each neuron, has a definite territory, instead of the indeterminate distribution which the hypo- thesis of a vague network connecting the cells formerly held to be the case. Further, we can recognize the limits of this territory. Hence it follows that the individuality of the nerve elements is no longer a contestable matter. His has remarked that the nerve elements pro- ceed from cells definitely separated the one from the other, and that ^ these latter give rise to polar prolongations with free extremities, of which one especially is of long extension, in order to form the different connexions of the nervous system. Ranvier had also seen that the regeneration of nerves, after section, was effected, just as is their origin, by a progressive budding of the axis cylinder towards the localities to be innervated. These facts, however, had not attracted attention, and all the conclusions to which
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