BLOOD-VESSELS OF THE LABYKIXTH. 767 



cilia projecting from their upper extremities. The inner ciliated cells form 

 a single row resting on the articulating ends of the inner rods : the outer 

 ciliated cells (pedunculated cells of Corti) are placed in three rows external 

 to the outer rods, aud are described as attached by pointed extremities to 

 the membrana basilaris, and with their ciliated ends opposite the three rows 

 of openings in the lamina reticularis ; so that sometimes when the lamina 

 is detached the ends of the cells are detached with it. Alternating with 

 the outer ciliated cells are the cells of Deiters, which are fusiform and 

 prolonged into a thread at each extremity, one passing up to the 

 lamina reticularis, and the other down to the outer zone of the membrana 

 hasilaris. The upper surface of the remaining part of the basilar membrane 

 is covered with hexagonal epithelium-cells. The sulcus spiralis is likewise 

 filled with large epithelial cells, which, according to Kolliker, project in a 

 swelling distinct from the proper organ of Corti. 



The mode of termination of the nerves, as has been already said, is uncer- 

 tain, but minute fibres, consisting of axis-cylinders only, have been traced 

 by Deiters into the organ of Corti, and his statements receive some support 

 from Kolliker and Henle. These fibres are said to divide into a radiating set 

 distributed both above and beneath the rods, and into a spiral set which are 

 continued in the longitudinal direction of the canal. 



The membrana tectoria is described by Henle as presenting three zones. 

 The inner of these is delicate and presents large openings corresponding to 

 elevations of the limbus ; the middle or generally recognised part is formed 

 of layers of fibres directed outwards, but yet crossing each other ; and the 

 outer part, unrecognised by most observers, is extremely delicate, forming a 

 network, the openings in which are elongated in the direction of the canal. 



The membrane of Heissner is an extremely easily torn membrane, on both 

 sides of which epithelium has been described. 



On the microscopic anatomy of the cochlea may be consulted Henle's Systematische 

 Anatomic ; Kolliker's Gewebelehre, 4th edition ; also the papers of Corti, Claudius, 

 Deiters, and Hensen, in Vols., III. VII., X., and XIII. of Siebold and Kolliker's 

 Zeitsch. f. Wissensch. Zoologie; and Deiters Untersuchungen liber die Lamina Spiralis 

 Membranacea. 



BLOOD-VESSELS OF THE LABYRINTH. 



Arteries. The internal auditory artery, a branch from the basilar, enters 

 the internal meatus of the ear with the auditory and facial nerves, and 

 at the bottom of that shallow canal divides into vestibular and cochlear 

 branches. 



The vestibular branches are distributed to the common sinus, sacculus, 

 and semicircular canals, with the branches of nerve which they accompany 

 through the bony foramina. At first they ramify on the exterior of the 

 membranous labyrinth, and end in capillaries both on the outer surface and 

 in the substance of the special glassy layer. The plexus is best marked 

 internally near the ending of the nerves. 



The cochlear branches, twelve or fourteen in number, traverse the many 

 small canals in the modiolus and bony lamina spiralis, and form in the 

 latter a capillary plexus that joins at intervals the vas spirale, to be pre- 

 sently described. From this plexus offsets are distributed in the form of a 

 fine network on the periosteum, but the vessels do not anastomose across 

 the membrana basilaris. The vas spirale is a single, sometimes branched 

 vessel which runs along the under surface of the membranous zone, near 

 the bone : it is like a capillary in texture,, but larger in size, and is pro- 



