GUSTATION. 763 



distributed, one to the carotid canal, where it anastomoses with a hranch from the supe- 

 rior cervical ganglion, and the other to the mucous membrane of the Eustachian tube ; 

 two superior branches are distributed to the otic ganglion and, as is stated by some anat- 

 omists, to the spheno-palatine ganglion. 



A little below the posterior foramen lacerum, the glosso-pharyngeal sends branches 

 to the posterior belly of the digastric and to the stylo-hyoid muscle. There is also a 

 branch which joins a filament from the facial to the stylo-glossus. 



Opposite the middle constrictor of the pharynx, three or four branches join branches 

 from the pneumogastric and the sympathetic to form together the pharyngeal plexus. 

 This plexus contains numerous ganglionic points, and filaments of distribution from the 

 three nerves go to the mucous membrane and to the constrictors of the pharynx. Prob- 

 ably, the mucous membrane is supplied by the glosso-pharyngeal. As we have stated in 

 another chapter, it is probable that the muscles of the pharynx are supplied by filaments 

 from the pneumogastric, which are originally derived from the spinal accessory. 



Near the base of the tongue, branches are sent to the mucous membrane covering the 

 tonsils and the soft palate. 



The lingual branches penetrate the tongue about midway between its border and 

 centre and are distributed to the mucous membrane at its base, being probably connected 

 with the papillsB. 



General Properties of the Glosso- Pharyngeal. As in the case of other sensory nerves 

 emerging from the cranial cavity, it is important, in studying the general properties of 

 the glosso-pharyngeal, to make our observations under certain conditions. First, it must 

 be remembered that this nerve contracts anastomoses a short distance from its origin. 

 As we desire to know the properties of the original filaments of the nerve, we must 

 operate upon it before it has received communicating fibres. Next, in irritating sensory 

 nerves, we are liable to produce reflex contractions. To avoid this, the nerve must be 

 divided, when the reflex contractions will only follow stimulation of the central end. It 

 is probably from a neglect of these essential experimental conditions, that the results of 

 direct observation have been so discordant in the hands of different physiologists. 



To begin with, we shall assume that the glosso-pharyngeal nerve must be irritated be- 

 tween its origin and the ganglion of Andersch, in order to avoid anastomosing filaments 

 from motor nerves, and that the nerve must be divided and irritation be applied to its 

 peripheral end, to avoid reflex movements. Assuming these conditions as essential, we 

 can discard most of the earlier experiments, as open to the objections we have mentioned. 

 Longet, operating upon horses and dogs, after removal of the cerebral lobes and division of 

 the glosso-pharyngeal, found that galvanization of the peripheral extremity of the nerve 

 did not produce movements of the palate or pharynx ; and, from these experiments, he 

 concludes that the nerves are exclusively sensory at their roots, or, at least, that they do 

 not contain motor filaments. In another chapter, under the head of movements of the 

 palate and uvula, we have cited in detail a series of experiments which illustrate the 

 reflex movements of the velum palati through the facial, produced by galvanization of 

 the glosso-pharyngeal. As a complement to the first experiments of Longet, just cited, 

 the same observer noted contractions of the pharyngeal muscles following galvanization 

 of the peripheral end of the divided nerve in the neck, which could only be produced by 

 the action of motor anastomosing filaments. 



As regards general sensibility, there can be no doubt of the fact that the glosso- 

 pharyngeal is sensory, although its sensibility is somewhat obtuse. In the experiments in 

 which the nerve has seemed to be insensible to ordinary impressions, it is probable that 

 the animals operated upon had been exhausted more or less by pain and loss of blood in 

 the operation of exposing the nerve, which, it is well known, abolish the sensibility of 

 some of the nerves. Longet states distinctly that, unless the animals (dogs) be already 

 exhausted by resistance during the operation, they have always appeared to suffer pain 

 on pinching or dividing the glosso-pharyngeal. 



