59^ STRUCTURE OF BASILAR MEMBRANE. [sect. 234. 



size, which are shown to be nuclei by the addition of acetic acid ; 

 by means of this re- agent, small nucleated cells also occasionally 

 become distinct in the pale and swollen teeth aud ribs ; these 

 parts, as well as those to be immediately described, are to be 

 regarded as belonging to the group of connective tissues. 



The habenula externa s. denticulata (fig. 242, h-t) arises imme- 

 diately from the habenula sulcata above described, beneath the 

 base of the teeth of the first series ; it forms, at first, the floor of 

 the above-mentioned spiral furrow. Its thickness amounts, in 

 most places, to only o'ooi'" (about the same as that of the other 

 membranous lamellae, especially the zona pectinata), and its 

 breadth increases towards the cupola of the cochlea in proportion 

 as that of the habenula sulcata diminishes ; thus it measures at 

 first only 0'05"', but at the apex of the cochlea o'l'" in breadth. 

 With regard to its structure, it continues to present, upon the 

 side next the scala vestibuli, a certain number of prominences, 

 while towards the scala tympani it is perfectly smooth and even. 

 The prominences when traced from Avithin outwards, present the 

 following arrangement. First of all come the so-called ' apparent 

 teeth' (dents apparents, Corti), forming a close series of elongated 

 projections, o'oi'" long, o - 02"' broad, which are separated from 

 each other by shallow grooves ; they become slightly raised to- 

 wards their outer extremity, and then suddenly slope down again. 

 Taken together, these apparent teeth produce a structure which I 

 have designated the habenula perforata j in the first turn of the 

 cochlea, they lie beneath the teeth of the first series, still upon 

 the zona ossea, while in the second and third turns, on the other 

 hand, they lie external to them, and with their under surface 

 in immediate contact with the nerves; they exhibit fissures or 

 canal-like spaces between their outer extremities, and these are 

 found not only in the first half-turn of the cochlea, as Corti 

 assumed, but throughout the whole extent of the spire. External 

 to these ' apparent teeth/ there follow in equal numbers the teeth 

 of the second series (figs. 242, 243, n-t), very curious structures, 

 discovered and named by Corti, and regarded by him as direct 

 out-growths of the basilar membrane. I have shown, however, 

 that they are in connection with the cochlear nerves, and I have 

 designated them in their totality, the ' organ of Corti/ and their 

 separate elements, the ' Cortian fibres/ 



According to my most recent observations, compared with those 

 of Corti, Claudius, Bottcher, and M. Schultze, the organ of Corti, 

 as far as we arc warranted in making any positive statement about 



