852 



THE OKGANS OF SENSE. 



presents a firm, homogeneous border, and opposite the inner row of hair cells contains a 

 clear, spirally arranged band, named Hensen's stripe. 



Nervus Acusticus (Fig. 726). The acoustic nerve divides within the internal 

 acoustic meatus into an anterior or cochlear and a posterior or vestibular nerve. 



Sinus superior 

 Ampulla of lateral duet 

 Ampulla of superior duct 

 Macula acustica utriculi 



Macula acustica sacculi 



Vestibular nerve 

 Nervus facialis 

 Cochlear nerve - . 



Superior semicircular duct 



Lateral semicircular duct 

 Posterior semicircular duct 



Ligamentum 

 spirale 

 Membrana basilaris 



Brandies of cochlear 

 nerve to organon spirale 



Branch of cochlear 

 nerve to ampulla of posterior duct 



Ampulla of posterior duct 

 Sinus inferior 

 Ductus endolymphaticus 



Spiral fibres 

 Ganglion spirale 



Nerve-fibres which pass out 

 between the two layers of the 

 lamina spiralis ossea 



Ductus reunions 



FIG. 726. MEMBRANOUS LABYRINTH OF A FIVE MONTHS' FCETUS, 

 viewed from its postero- medial aspect (Retzius). 



N. Cochleae. The cochlear nerve is distributed to the hair cells of the organoc 

 spirale, the branches for the basal and middle coils entering the foramina in the 

 tractus spiralis foraminosus, those for the apical coil running in the canalis cen trails 

 of the modiolus. Extending through the bony canals of the modiolus, the nerve- 

 fibres radiate outwards between the lamellae of the lamina spiralis ossea. Contained 



in the spiral canal of the modiolus, neaj 

 the attached margin of the lamina, is e 

 ganglion of bipolar nerve-cells whicl 

 winds spirally round the modiolus, anc 

 is named the ganglion spirale (O.T 

 ganglion of Corti) (Fig. 727) ; the fibre: 

 of the nerve arise from the cells of thii 

 ganglion. Beyond the ganglion spiral* 

 the nerve-fibres extend outwards, at firs 

 in bundles, and then in a more or les 

 continuous sheet, from the outer edg' 

 of which they are again collected int< 

 bundles, which pass through th 

 foramina nervosa of the labium tym 

 panicum. Beyond this they appea 

 as naked axis -cylinders, and, turning in a spiral manner (inner or first spira 

 fasciculus), send fibrillae towards the inner row of hair cells. Other fibrils ru: 

 between the inner rods and form a second spiral fasciculus in Corti's tunne 

 from which fibrils extend outwards across the tunnel, and, passing betwee 

 the outer rods, enter Nuel's space. They form a spiral fasciculus on the inne 

 aspect of each row of Deiters' cells, and fibrillse pass from these fasciculi toward 

 the bases of the outer hair cells. 



The cochlear nerve gives off a vestibular branch, the terminal filaments < 



FIG. 727. PART OF COCHLEAR NERVE, highly 

 magnified (Henle). 



