On the peripheral nervous system / by Samuel Rhind.

  • Rhind, Samuel.
Date:
[1850]
Catalogue details

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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    ON THE PERIPHEfiAL NERVOUS SYSTEM. By SAMUEL RHIND. Bead on Thursday, October 17, 1850. The microscope reveals to us that the nerve fibres of the cerehro-spinal sys- tem are composed of two parts—a cen- tral gi-ey portion, termed the axis cylin- der, or gi'ey band of Remai'k, and an outer sheatb, called the white matter of Sell wan, after its discoverer: these ner- vous elemeuts are inclosed in a thin membranous investment, termed the neurilemma. There can he no doubt but that these two elements perform ditferent functions. The central axis seems to he the time conducting portion; for, fi’om Schwan’s observations on the nerve fibres of the tail of the tadpole, plain fibres at first are only seen: these must perform tlieir proper function of conduction : it is only at a subsequent period in tlieu- development that they seem to have added to them their in- vesting white sheaths. Again, whilst the sheatb appears to cease near a gan- glionic cell, the grey axis is continued into it; this, also, is veiy significant: and, lastly, the sympathetic fibres seem exclusively formed of the central axis. I shall speak of the function of the sheath presently. As these cerehro-spinal fibres ap- proach their peiipheral termination, they lose the double contour, and assume, for the most part, a perfectly plain ap- pearance; either from losing entirely Sebwan’s matter, or from this becoming so extremely diminished as to he no longer visible. This peripheral con- dition is shown very well in the fibres of the retina; and here, according to Messrs. Todd and Bowman, the invest- ing sheath is qnite absent. It is also shewn well in the olfactory region, and in the fibres of the anditory nerve, dis- tribnted in the vestibule. Simple fibres have also been observed in the papillae of the tongue. From Dr. Wallers very interesting observations, some of the fibres in certain of the papillae of this organ end, as it were, with open mouths, as if the extremity of the central axis was only exposed. Wagner states that the fibres in the electric apparatus of the torpedo ultimately assume the plain condition. M. Quatrefages has shewn that the cutaneous fibres of the am- phioxus divide into delicate homoge- neous filaments. In muscular tissue the ultimate fibres indicate much the same condition, and the fibres of the tooth-pulp have pre- sented similar appearances. The very interesting observations of Professor Kblliker show that the fibres that j)ass into the cutaneous papillae are plain, and without apparent structure. Now it is this plain, aud, apparently, homo- geneous portion of the cerelro spinal nerve-fibre, that I would regard as its true periphery—namely, that portion of centripetal fibres which, being in func- tional relation with a sentient surface, is capable of detecting the various sti- muli, or that portion of centrifugal fibres which, being in functional relation with contractile tissue, communicates to it the motor impulse. I would therefore, for the sake of distinction, call the plain portion of the centripetal fibre the ex- citable portion ; that in the centrifugal