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.

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    grew out, and from this ganglion by the sensory root to the brain or spinal cord. This appears to be the universal experience. A few years ago, while studying the development of the fifth nerve branches in man, I had an opportunity of paying special attention to the mode of development of those nerves which in the adult connect the fifth with other cranial nerves. Applying the developmental test to the chorda tympani, there is no doubt we have here to do with a true branch of the facial nerve. Indeed, it has been figured and described as such in 1888 by Professor His.^ During my observations I had ample opportunity of verifying this, both in the human and rat embryos.^ The nerve is found uncon- nected with the lingual at first, and lies in the region of the developing tongue, before the lingual is of any considerable size. Since the nerve is a sensory one, it seems fair to assume that it conveys impulses towards the ganglion of the facial, of which it is a branch. Similarly, the great superficial petrosal nerve is formed very early, and is developed as an outgrowth of the cells of the geniculate ganglion. It is connected at first with the seventh nerve, and only in a later stage acquires connections with the fifth nerve. We may assume, then, that the impulses which pass in the great super- ficial petrosal, of whatever kind they may be, reach the central nervous system by the roots of the seventh nerve. If this is not so, we have in the chorda tympani and great superficial petrosal nerves exceptions to what is found to be the case in all other nerves developed from ganglia of the spinal ganglion type. The same series of investiga- tions proved that the nerve of Jacobson is an outgrowth of the ganglion of the glosso-pharyn- geal nerve, and hence almost certainly carries impulses into tion.s of the chorda-tympaiii, great the course of that nerve, and superficial petrosal, and tympanic j-pg trigeminal. ( aco son s) neives. Figure 2 illustrates the direc- tions in which the nerves are developed, and the arrows the course of the impulses which they carry, as inferred from their mode of development. This being so, can we resist the conclusion that ^ Abhnndl. d. math.-phys. Cl. d. k. sdchs. Oesellsch. d. Wissevsch., Bd. iv. - “On the Development of the Branches of tlie Fifth Cranial Nerve in Man, Trans. Roy. Bub. Soc., Ser. 2, vol. iv. Fig. 2.—To illustrate the earliest connec-