No. I.] THE VERTEBRATE EAR. 133 



the posterior ampulla, which, by its division, has caused a divis- 

 ion in the nerve, one twig of which supplies the crista acustica 

 ampullas posterioris, and another of which passes to the crista 

 acustica abortiva division. The saccular ramulus, by a second 

 division, has given rise to a ramulus lagense, which supplies the 

 papilla acustica lagense, the parent of the cochlear organ. 



As regards the relation of the auditory nerve to the facial 

 and glossopharyngeal, we know the following facts. According 

 to Stannius (268, 1849), the auditory nerve in Raja batis and 

 clavata, in Myliobatis aqiiila, and in some few other forms, but 

 by no means regularly among the Elasmobranchs, gives off a 

 branch to the IX, which in turn sends a branch to the ampulla 

 of the posterior canal. 



In Spinax acanthias and Carcharias glauciis the ramus dorsalis 

 of the glossopharyngeal nerve proves to be a very interesting 

 branch, which arises from the nerve during its transit through 

 the cartilaginous wall of the ear capsule. After leaving the IX, 

 the ramus dorsalis curves dorsad behind the posterior canal, 

 runs along on the top of the skull, underneath the muscles, 

 until it reaches the region of the porus acusticus, where it breaks 

 up into cutaneous branches to the sense organs of the canal 

 communicating with the porus acusticus. This branch is not 

 present in Batoid forms. 



Scarpa (250, 1800) found the auditory nerve to be composed 

 of two parts, a portio mollis, which he thought was a branch of 

 the V, the VIII of later investigators, and a portio dura, the IX 

 of more recent workers. The first of these supplied the ante- 

 rior and external ampullae and the anterior portion of the ear 

 sac ; the second part supplied the posterior ampullas and occa- 

 sionally the small otolithic sac, or what is now designated the 

 sacculus. But this nerve always anastomosed with the anterior 

 one before sending branches to the ear sense organs. 



Weber (285, 1820) describes this anastomosis as made up of a 

 branch of the nervus auditorius accessorius, which receives 

 a small branch from the auditory proper and sends a relatively 

 large one to the posterior ampulla. 



Max Schultze (1858, 256) studied the anastomosis between the 

 VIII and IX nerves, and concluded that there was certainly an 

 interchange of fibres between the two nerves and not merely a 

 contact of the two trunks. 



