ORGAN OF CORTI. 163 



The membrana tectoria of Claudius (Cortis membrane, 

 Kolliker) (figs. 321 and 322, M f) commences at the line of 

 attachment of the membrane of Reissner to the crista spiralis 

 as an immeasurably fine lamina. It covers the crista, adhering 

 very intimately to it, and, gradually increasing in thickness, 

 attains its maximum at the sulcus spiralis internus, and termi- 

 nates (as I agree with Henle and Grottstein in finding), after 

 gradually becoming extremely attenuated, as a thin edge in 

 the neighbourhood of the hair cells. It here closely overlies the 

 whole surface of the organ of Corti, that is to say, of the lamina 

 reticularis. (See below.) 



The principal portion of the membrana tectoria appears to 

 be finely striated in a radial direction; but where the membrane 

 rests upon the crista, its under-surface presents an irregularly 

 plexiform perforated appearance (relief of the crista), whilst its 

 outer terminal portion, according to the descriptions of Lb'wen- 

 berg (39) and Henle (26), runs out with a fine plexiform 

 marking, which is, in all probability, occasioned by the pro- 

 jecting brushes of cilia belonging to the external hair cells. 

 The application of additional names to indicate the several 

 zones of the membrane would indeed be superfluous for an 

 organ so overloaded with terms as this of Corti. On the other 

 hand, -the consistence of the membrane of Corti is a matter of 

 special interest. I do not know what claim it has to be called 

 an elastic membrane. Fragments of it, when fresh, are per- 

 fectly soft ; and whatever may be the manipulation to which 

 they are subjected, the edges never exhibit any tendency to 

 curl inwards. After being hardened in alcohol, the membrane 

 undergoes considerable contraction, but preserves on its surface 

 the impressions of structures accidentally adhering to it. Thus 

 I have occasionally found the brushes of hair of the outer hair 

 cells almost imbedded in the substance of the membrane. 

 These have consequently undergone some displacement, and 

 the lamina reticularis, together with the hair cells, have been 

 carried away in addition to the hairs of the latter. These 

 points are not unimportant, and I shall again have occasion to 

 refer to them. It is demonstrable, however, that the mem- 

 brane of Corti, as Henle (27) alone, so far as I know, has 

 stated, is of rather soft and almost gelatinous consistence. 



M 2 



