34 ON THE NERVOUS SYSTEM 



IV. 



numerous zigzag folds, which adapt it to the peculiar extensibility of that organ. 

 This nerve was not traced to any of the muscles among which it passed, nor were 

 any contractions of the hyoid and glossal muscles produced when the nerve was 

 excited by galvanism, proper care being taken to secure its complete insulation. 



The distribution of this nerve to the mucous membrane of the tongue pharynx 

 indicates that it is a nerve of sensation, and its connection with the vagus shows 

 that it can be no other than the glosso-pharyngeal, which in the higher animals 

 becomes disjoined and forms an independent pair. 



Muller says : " The glosso-pharyngeal of the vagus (in Frogs) is the only branch 

 analogous to the glosso-pharyngeal in the human body, and this he regards as sup- 

 plying the place of the gustatory branch of the fifth." This distribution has an an- 

 alogical interest, since if it be the seat of the sense of taste (and it is the only sensi- 

 tive nerve going to the tongue) in these animals, it tends to show that the glosso- 

 pharyngeus in Man, about the function of which so much controversy has existed, 

 may be a gustatory nerve. " The glosso-pharyngeus and vagus are separate at their 

 roots, but unite immediately in the skull into one nerve which swells into a large 

 ganglion outside of the skull. Before the glosso-pharyngeus enters the vagus, it 

 sends off a minute branch, which runs forwards in the pia mater under the acousti- 

 cus over the cerebral portion of the sympatheticus, and penetrates the ganglion 

 Gasseri. According to Volkman's description it does not exist in Rana, neither 

 could I convince myself with certainty of its existence in Bufo cinereus, for the 

 large collection in the membranes of the brain of masses consisting of micro- 

 scopical crystals, prevents to a great extent the preparation of so fine a filament. 

 In Bufo pantherinus, however, I have it before me so completely prepared, that no 

 doubt can remain of its existence and its course as described above. The glosso- 

 pharyngeus leaves the ganglion of the vagus nearly as large a nerve as the vagus 

 itself, gives the uniting branch to the facial is (which Volkman calls the laryngeal 

 branch of the vagus), then runs downwards, sends a branch to the region of the 

 glottis, and branches in the tongue as far as the tip. The real vagus runs exactly 

 the course described by Volkman, along the oesophagus, with branches to the im- 

 mediate muscles, and gives off the recurrent and the branches to the skin." * 



C. This is the largest of the vagal branches, and corresponds with the vagus of 

 the higher animals (Plate II. Fig. 2, /), in them the glosso-pharyngeal being a 

 separate nerve ; it descends along the sides of the neck, having the glosso-pharyn- 

 geal in front and the hypoglossal behind, the latter crossing its course over the 

 stylo-hyoid muscle. The first branch which is given off by it is a minute twig 

 to the stylo-hyoid muscle at its upper part, and may be distinctly traced by 

 the naked eye among its fibres as far as the middle. A little below this a much 

 larger brapch leaves, but runs parallel to its course for a short distance, but soon 

 passes in front of the pulmonary artery, then beneath, and ascends a short dis- 

 tance behind it, and is distributed to the muscles of the larynx, f This, therefore, 



* Vogt, op, cit. 



t Weber has shown that even in the Frog a branch of the vagus gives off a filament which takes a 

 retrograde course to the larynx. Muller's Physiol., Baly's Trans., 2d edit., Vol. I. p. 838. 



