DISSECTION OF THE HEAD AND NECK 393 



(d) Modiolus. 



(da) Base of modiolus (basis modioli). 



(db) Shelf of modiolus (lamina modioli). 



(e) Osseous spiral shelf (lamina spiralis ossea). 



(ea) Hooklet of spiral shelf (hamulus laminae spiralis). 



(f) "Staircase" of vestibule (scala vestibuli). 



(g) "Staircase" of tympanum (scali tympani). 



(h) Helicotrema (helicotrema) (" pore of the helix"). 



(i) Secondary spiral shelf (lamina spiralis secundaria). 



(j) Spiral canal of modiolus (canalis spiralis modioli). 



(k) Longitudinal canals of modiolus (canales longitudinales modioli). 



FIG. 195. 



194 



The labyrinthus membranaceus of the right internal ear of a human embryo at the fifth month, 



seen from the medial side. 



1-5, utriculus ; 2, recessus utriculi ; 3, macula acustica utriculi ; A, sinus posterior ; 5, sinus superior ; 

 6, ampulla membranacea superior ; 7, ampulla membranacea lateralis ; 8, ampulla membranacea pos- 

 terior ; 9, ductus semicircularis superior ; 10, ductus semicircularis posterior ; 11, ductus semicircularis 

 lateralis; 12, widened mouth of crus simplex of the lateral semicircular canal opening into the 

 utriculus ; 13, sacculus ; Ik, macula acustica sacculi ; 15, ductus endolymphaticus ; 16, ductus utriculo- 

 saccularis ; 17, ductus reunions ; 18, caecum vestibulare of ductus cochlearis ; 19, ductus cochlearis ; 20, 

 N. facialis; 21-2!,, N. acusticus; 21, N. vestibuli; M, N. saccularis; 23, N. ampullaris inferior: .",. X. 

 cochleae ; 25, distribution of N. cochleae within the lamina spiralis ossea. (After G. Retzius, as slightly 

 modified by A. Rauber. ) 



In the meatus acusticus internus study 



(a) Internal acoustic opening (poms acusticus internus). 



(b) Bottom of internal acoustic meatus (fundus meatus acustici interni). 



(ba) Transverse crest (crista transversa). 



(bb) Area of facial nerve (area N. facialis). 

 (be) Area of cochlea (area cochleae). 



(bca) Foraminous spiral tract (tractus spiralis forami- 



nosus). 

 (bd) Superior vestibular area (area vestibularis superior). 



