THE INTERNAL EAR 



713 



panic lip of the sulcus. Here the nerve fibers lose their medullary 

 sheath and come almost at once into relation with the inner hair 

 cells. From this point the path of the non-medullated fibers varies, most 

 of them passing for some distance along a spiral course through the 

 organ of Corti. One such spiral bundle is found on the inner, and 

 another on the outer side of the inner pillars, the latter lying within 

 the canal of Corti. Still other fibers, the tunnel fibers, cross the canal 

 of Corti to form a spiral plexus beneath the outer hair cells and the cells 



/ i'.p. v.8. o.p Z)i Z> Z> B. 



FIG. 589. AXIAL SECTION THROUGH CORTI'S ORGAN OF THE GUINEA-PIG, SHOWING 

 THE TERMINAL NERVE FIBRILS. 



B, cells of Bottcher; D l , D 2 , D 3 , three rows of Deiters' cells; H, cells of Hensen; 

 i.b., inner border cell; i.h., inner hair cell; i.p., inner pillar cell; n, terminal branch of 

 the cochlear nerve; o.h.-l, 2, 3, three rows of outer hair cells; o.p., outer pillar cell; 

 p., phalangeal process of the outer sustentacular process. Very highly magnified. 

 (After Held.) 



of Deiters. Terminal fibrils from these spiral plexuses end in relation 

 with both the inner and the outer hair cells. 



The relation of the nerve cells of the spiral ganglion and the vestibu- 

 lar ganglion to the termination of the nerve fibrils about the hair cells 

 of the organ of Corti, the macula?, and the crista?, is essentially the same. 

 The ganglia contain the cell bodies of the peripheral sensory neurons 

 of the eighth cerebral or acoustic nerve. These are bipolar cells, of 

 which the central process or axon enters a medullated nerve fiber of the 

 acoustic nerve, while the peripheral process is distributed to the hair 

 cells of the several areas of specialized neuro-epithelium, as above de- 

 scribed. 



45 



