THE EAK. 775 



The vessels of the cocldea, though fine, are yet very numerous ; they 

 are distributer!, in the first place, to the parietal periosteum of the 

 cochlear canal, and secondly, to the lamina spiralis. In the former 

 situation, besides the capillary plexus, wnich is found throughout, they 



the cochlear nervos do not terminate in the scala tympani, but tliat the fibres penetrate 

 through ojienings in the membranous himina spiralis into the scala vestibuli, where they 

 become attached to the " teeth of the second series." These latter as well as the peduncu- 

 lated cells they support, he now regards as a nervous apparatus constituting the true termi- 

 nations of the cochlear nerves, and, he adduces in proof of the correctness of this opinion 

 the following histological observations. 



The membranous lamina spiralis, is not merely a continuation of the periosteum of the 

 vestibular surface of the osseous zone, but also of that of its tympanal surface. The first- 

 mentioned periosteal lamella forms the habcnula sulcata with its teeth and the commence- 

 ment of the habenula denticulata, and then unites externally to the " apparent teeth," and 

 the " teeth of the second series" with the other periosteal layer. This besides lining the 

 bone, extends bej'ond the edge of the osseous zone as a covering to the nerve-fibres, which 

 are thus, even after leaving the bone, enclosed between two layers of periosteum, and hence 

 do not, as stated by Corti, lie free in the scala tympani. Now in vertical sections of the 

 lamina spiralis, treated with chromic acid, the pale nerve-fibres may be traced running 

 towards the scala vestibuli, and perforating the habenula denticulata near the external 

 extremities of the " apparent teeth.' Exactly over the perforated portion of the habenula 

 denticulata (habcmda perforata) are seated the teeth of the second series, which may be 

 seen to be connected with the dark-bordered nerve-fibres, by means of delicate pale pro- 

 cesses. 



The nervous nature of the " teeth of the second series" Kolliker states, becomes further 

 apparent by a micro-chemical analysis. Corti affirms them to be chemically similar to the 

 membranous lamina spiralis, but this Kolliker proves to be incorrect. He found them on 

 the contrary to correspond most closely to the dark-bordered nerve-fibres, and the processes 

 of the ganglion-cells. Caustic soda and potassa destroyed them almost immediately. The 

 addition of water produced in them two or three varicose enlargements, containing a fila- 

 ment precisely similar to an axis-cylinder. The nucleated swelling at their commencement 

 described by Corti, he regards as a bipolar ganglion globule, one process of which is con- 

 nected with the dark-bordered nerve-fibres, whilst the other supports three unipolar nerve- 

 cells (" three epithelial cells" of Corti). 



Based upon these histological data, KOUiker advances some interesting and novel views 

 with regard to the physiology of the cochlea. The existence of tVie peculiar nervous appa- 

 ratus at the extremity of the cochlear nerves, renders it, he thinks, highly probable that this 

 is the only portion of the nerve which possesses the power of receiving sonorous undulations. 

 These undulations reach the cochlea through the fenestra ovalis, and are not communi- 

 cated, as most physiologists suppose, by the osseous lamina to the cochlear nerve, since the 

 latter lies free in the labyrinth and is unconnected with the osseous zone. The isolated po- 

 sition of the cochlear nerve, its movability and great softness, renders it, Kolliker further sur- 

 mises, specially applicable to receive the undulations transmitted by the lluitlof the labyrinth. 

 Regarding the special function of the cochlea, he is inclined to attribute to it a greater phy- 

 siological importance, than to any of the other parts of the labyrinth. The free position of 

 the expanded portion of the nerve, and the extent of surface over which its numerous 

 terminal fibres are spread, constitute it, he thinks, an organ of great delicacy of hearing, 

 enabling us to distinguish several sounds at once, and also to estimate accurately their 

 exact pitch. The ganglionic termination of the cochlear nerves, Kolliker concludes, esta- 

 blishes a surprising analogy between the auditory, and visual apparatus, since the sensory 

 nerves of both are possessed at their peripheral expansion of a ganglion, which receives the 

 impressions, the nerve-fibres merely serving to conduct them to the brain. [Vid. Kolliker, 

 "Ueber die Endigimgen des Nervus Cochlete und die Functions der Schnecke," Wurzburg, 

 1854.)— DaC] 



