

1056 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT 



Basilar Membrane. The basilar membrane stretches from the tympanic lip of 

 the osseous spiral lamina to the basilar crest and consists of two parts, an inner 

 and an outer. The inner is thin, and is named the zona arcuata : it supports the spiral 

 organ of Corti. The outer is thicker and striated, and is termed the zona pectinata. 

 The under surface of the membrane is covered by a layer of vascular connective 

 tissue; one of the vessels in this tissue is somewhat larger than the rest, and is 

 named the vas spirale; it lies below Corti's tunnel. 



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Fia. 930. Limbus laminse spiralis and membrana basilaris. (Schematic.) 1, 1'. Upper and lower lamella 

 of the lamina spiralis ossea. 2. Limbus laminae spiralis, with a, the teeth of the first row; b, b', the auditory teeth 

 of the other rows; c, c', the interdental grooves and the cells which are lodged in them. 3. Sulcus spiralis internus, 

 with 3', its labium vestibulare, and 3", its labium tympanicum. 4. Foramina nervosa, giving passage to the nerves 

 from the ganglion spirale or ganglion of Corti. 5. Vas spirale. 6. Zona arcuata, and 6', zona pectinata of the basilar 

 membrane, with a, its hyaline layer, B, its connective-tissue layer. 7. Arch of spiral organ, with 7', its inner rod, and 

 7", its outer rod. 8. Feet of the internal rods, from which the cells are removed. 9. Feet of the external rods. 10. 

 Vestibular membrane, at its origin. (Testut.) 



Membrana tectoria 



Outer hair cells 



Limbus 



Outer rod 

 Basilar membrane 

 FIG. 931. Section through the spiral organ of Corti. Magnified. (G. Retzius.) 



I 



Nerve fibers 



The spiral organ of Corti (organon spirale [Corti}; organ of Corti} (Figs. 931, 932) 

 is composed of a series of epithelial structures placed upon the inner part of the 

 basilar membrane. The more central of these structures are two row r s of rod-like 

 bodies, the inner and outer rods or pillars of Corti. The bases of the rods are supported 

 on the basilar membrane, those of the inner row at some distance from those of the 



