On the course of the taste fibres / by A. Francis Dixon.

  • Dixon, A. Francis (Andrew Francis), 1868-1936.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: On the course of the taste fibres / by A. Francis Dixon. 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.

    6/15 (page 396)
    tions in some cases. A very strong plea that the fifth nerve is the nerve of taste is made out by Dr. Gowers in Ins “ Diseases of the Nervous System,” vol. ii. p. 225, where, after examining the evidence, he concludes that, although cases occur in which there are symptoms of disease of tlie fifth nerve, without loss of taste, yet there is no recorded case of any loss of taste where disease has been limited to the nerve roots of the medulla. The course which the taste impulses are supposed to take by such investigators, in travelling towards the brain, is a very com- plicated one, and we may be forgiven if we are sceptical regarding it, unless the fact is demonstrated in a very complete and con- clusive manner. It is maintained tliat the nerve fibres wliich convey taste impulses from the anterior part of the tongue, and which run in the lingual nerve, leaving it by the chorda tympani to join the facial nerve, are to be found later on continued from the facial into the great superficial petrosal and Vidian nerves, by which means they reach Meckel’s ganglion, and thence the brain by the second division of the trigeminal nerve. From the posterior part of the tongue taste sensations are believed by the supporters of the fiftli nerve theory to travel first in the fibres of the glosso-pharyngeal nerve. Leaving this, however, by the tympanic branch or nerve of Jacol)Son, they reach the tympanic plexus, and are conveyed finally either into tlie third division of the fifth nerve, tlirough the small superficial petrosal nerve and the otic ganglion, or possibly, as lias been suggested by others, into the second division of the fifth, by the communication which exists between tlie tympanic plexus and the great superficial petrosal nerve. Several other complicated courses for the taste fibres, both for the anterior and posterior parts of the tongue, have been suggested.^ The accompanying diagram (Fig. 1) illustrates in its simplest form the course assumed for the taste fibres, by those authorities who believe the fifth nerve to be the nerve of taste. We are asked to believe in this complicated course for these impulses, from observations made on cases in which the lesion was supposed to affect only the roots of the fifth nerve, yet in very many of them an opportunity did not present itself of verifying the diagnosis by a post-mortem examination. It must necessarily be extremely difficult to be certain that, in a case where the whole of the fifth nerve root is paralysed, we are justified in attributing all the symptoms present to disease of this nerve alone. Seeing that the distance between the fifth and seventh nerves at their attach- ments to the brain is only 10 mm., and the points where they pierce the dura mater are only the same distance apart, a lesion to affect all the fibres of one and permit all those of the other to escape must indeed be very sharply circumscribed. ^ See, for instance, Schwalbe’s “Lehrbuch der Neurologie,” p. 856.