THE EAR. 395 



and rapidlv widen* to form a short, flattened, blind sac (saccu* 

 { rae oralis], which is lodged in the' fossa (sfo). Its walls are 

 thin and pigmented. 



: ) The ductus perilym- 

 phaticus (Hasse), (Fig. 245 

 tip] passes above and behind 

 the (h'ctiis fenestrae oratig, be- 

 hind the auditory nerve, and 

 near the cochlea, then behind 

 and above the lagena to the ^ 

 atpuuductu* cochleae (Fig. 244 

 ac], where it forms a short, 

 wide tube, which passes back- 

 wards and inwards through Pa ? of ' he uter v 



after Retzius. V6nck s brst., Obj. Ill, Oc. 3. 



this canal to the canalh jvyv- pr. Periosteum. 



hiris ; here it lies close to the ^ J^gf* network ' 



nerves and forms a short oval 



sac (taccv* perifymp&atictHi) (dp'}, which communicates with the sub- 

 arachnoid space of the cranial cavity by means of a tube from the 

 neck of the sac. The walls of this structure are thin and formed of 

 connective-tissue with very few pigment-cells. The other extremity 

 of the tube passes to foefarshuiforusaaA under the sinus post, utri., 

 between it and the pars neglecta it then courses to the outer side 

 of the hinder end of the external semicircular canal : the tube 

 then bends downwards to the outer side of the utricle and saccule t<> 

 open into the general perilymphatic space. 



d. The membranous labyrinth. (Figs. 247, 248) has the fol- 

 lowing parts : the utricle and $inii$ superior, the recessus //////////'. 

 the anterior semicircular canal and anterior ampulla, the external 

 semicircular canal and external ampulla, the posterior semicircular 

 canal and the posterior ampulla, the saccule, (htctit* aublpmptaticiU, 

 and saccus en(lol>/mp/iaticu$, the pars ttegfecta, the lagena cochleae, the 

 parg bofilaru cochleae, and the so-called tegmenfnm raxculogum. 



In addition the following nerve-terminations can be distinguished : 

 (i) The macula ac. rece**>i* ntriculi, (2) the three crisfae acv.sticae am- 

 pnUorurn, (3) the macula ac. saccvli, (4) the macula ac. neglecta, (5) the 

 papilla ac. lagenae cochleae, and (6) thepapilfa ac. hazilaris cochleae. 



The auditory nerve divides immediatelv bevond its origin from 

 the medulla oblongala to form a ramus {interior and a ranni* posterior, 

 which course alongside each other for a short distance, the latter 

 lying behind and above the former. The E. anterior runs forwards 



