Licence: Public Domain Mark
Credit: On the peripheral nervous system / by Samuel Rhind. 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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![80 come in contact with the axis cylhider, and 60 the shai-p pain is produced; for, as I have stated, the conducting part of a fibre and its periphery ai-e continuous, and that it is the sheath which deter- mines which portion of a fibre shall be its peri])hery, and which its course. A word iu passing witli regard to the Pacinian corpuscules. It has been held by some that tliese organs are the result of disease. The nerve fibre, as it passes into one of these bodies, becomes plain; and we have every reason to believe it does so from either partially or entirely losing its sheath. If such is the case, I thiuk, when the views expressed in tliis paper ai’e considered, we must discai'd the idea above mentioned with regard to these bodies. If, indeed, there is this connection of nervous peiiphery with special structure, we must certainly conclude that they perform some office in the animal economy. One or two cir cumstances support this view. If a Pa cinian corpuscule bends on it itself, then, at the angle of flexion, the double con- tour is seen, as if at this distorted part the functional relation of this organ and tlie nerve-fibre was desti’oyed. Again, a fibre, if it passes from one corpuscule into another, in the interval resumes its double contour. We Avill now pass on to the last por- tion of my communication—namely, a consideration as to how far any of the views advanced in the previous portion of the paper elucidate or explain some of the phenomena observed in tlie sym- pathetic system: and let us also see how far they may aid us iu investigating the functions, relatively considered, of the two great divisions of the nervous system—the cei-ebro spinal and symi)a- thetic, or ganglionic. It has been sup- posed that the great cause of the difl'er- ence of tlie phenomena observed in the latter system to those in tlie former depends on the number of ganglia that any one fibre has to pass through, and so that by ganglionic influence the conducted impression is diffused. Doubtless tills is a inincipal cause of the difference; but it does not explain all; for it seems to me that physiologists by such reasoning seem to lose sight of the fact, that an impression made in the periphery of a spinal nerve-fibre, ere it reaches the sensoriuin, and is ]ierceived there as a sensation, passes through the mass of ganglia that make up the s])iual cord. Yet, iu this case for the most part the imjirossion is con- veyed in all its integrity. Since, there- fore, both impressions are subject to continued ganglionic influence ; and since, also, those conveyed along sympa- thetic fibres seem always diftlised, whilst those in the cerebro-spiual are only occasionally so, I think we must look for some additional cause to account for the difference of the phenomena observed. Now this difference, that probably cannot be alone explained by refemng it to ganglionic inffuence, receives, I think, some elucidation from a consi- deration of the previous communication. The white sheath has before been spoken of as the economizer or allowancer out of the true functional periphery of the cerebro-spinal fibres. Now since there is no such sheath in the sympa- thetic, there is, anatomically considered, an unlimited periphery ; whilst, func tionally regarded, we must limit this to that portion of those fibres in relation with a sentient surface or contractile tissue. Thus a centripetal sympathetic fibre may be capable of detecting im- pressions for a great length of its course; and thus, I thiuk, might we explain with much probability some of the phenomena hitherto referred to the diffusion of impressions by ganglia. A consideration of this view may also help us much, I conceive, in under- standing the reasons of the differences of contraction observed in the striated, muscular fibres, and those of organic life. For whilst in the former a nerve- fibre may be in anatomical relation with tlie contractile tissue for a great part of its course, yet, from having its non- conducting sheath in considerable thick- ness, the imjirossion cannot escape; but near its end the fibre either loses entirely, or iu gi*eat part, its sheath, and there the impression escapes from its vital relation- ship with the muscular tissue, and in all its sti'ength communicates to the few surrounding fibres the motor impulse, and so we have the shai’p quick contrac- tion. I have said that the sheath may not entirely cease; but we can easily understand how that though the fibre be iu anatomical relatioushi]) with the muscuhu- tissue, yet from the central axis being coated by a considerable quantity of its non-conducting sheath, the impression cannot at first escape, but when the sheath is reduced to its minimum, then, from the superior vital](https://iiif.wellcomecollection.org/image/b22424635_0006.jp2/full/800%2C/0/default.jpg)
