552 MR. T. GOODEY ON THE SKELETAL [Mar. 15, 



Arising from the dorsal end of the anterior utricle, and pro- 

 ceeding in a posterior and outward direction, is the external 

 canal, which bends downward and comes to lie in an almost 

 horizontal position. At its anterior end it is slight]}' elevated 

 a,nd expands into the ampulla externus, which communicates with 

 the anterior utricle again by means of a short canal which rests 

 on the upper side of the recessus utriculi, but does not open 

 directly into it. 



The posterior utricle, which is situated more internally than the 

 rest of the labyrinth, is somewhat cylindrical in shape and is 

 slightly curved upon itself. It communicates directly with the 

 sacculus by means of a short, almost vertical canal, the ductus 

 utriculo saccularis posterior. Arising from its dorsal end is the 

 posterior canal, which curves outward and downward, and then 

 expands into the posterior ampulla, which opens into the lower 

 end of the utricle again. 



All three canals, anterior and posterior vertical and external 

 horizontal, are not rounded in section, but are markedly flattened, 

 so that their height is equal to about twice their width. The 

 external canal in its almost horizontal position lies with its 

 compressed sides in the horizontal plane. 



Nerve-Supply. 



The sensory areas of the membranous labyrinth are supplied 

 by branches of the eighth cranial nerve. 



After passing from the brain through its foramen, the nerve 

 breaks up into a number of ramuli which supply their particular 

 regions. 



The ramulus ampulla anterior is a rather fine branch which 

 extends from the main nerve-trunk to the anterior ampulla, lying 

 chiefly on the outer side of the lower portion of the anterior 

 utricle. 



Arising next from the main trunk are two ramuli, which 

 appear to have a common origin. These are the ramulus recessus 

 utriculi and the ramulus ampulla externus. Both curve under 

 the recessus utriculi and come to lie on its outer surface, the 

 ramulus ampulla externus proceeding upward on to the external 

 ampulla, where it supplies the two rounded crista?. The main 

 portion of the nerve now goes on to form the ramuli sacculi. It 

 first gives rise to a flattened branch which extends upward and 

 follows the inner anterior border of the sacculus, thus forming 

 one ramulus sacculus. The rest of the nerve proceeds in an 

 almost horizontal direction and lies on the inner surface of the 

 sacculus, forming the main ramulus sacculus. This gives off fine 

 branches on its lower side which supply the macula? of the 

 sacculus. Arising from its posterior end are three fine branches : 

 a lower one, the ramulus lagencc. supplying the macula? of the 

 lagena ; a median one, the ramulus ampulla posterior, lying chiefly 

 on the inner surface of the posterior utricle and supplying the 



