of the Cochlea in Man and other Mammals. 151 



The other, the lamina spiralis nienibranacea, proceeds directly 

 outwards from the linibus to the ligament of the cochlea. 



This membranous lamina is composed of two horizontal mem- 

 branes, having between them certain delicate structures. The 

 upper of these (the membrane tectoria) arises from the limbus just 

 external to the membrane of Eeissner, and passes directly outwards, 

 covering and overlapping the end of the limbus, but not actually 

 reaching the ligament of the cochlea (Fig. II.). It may be well to 

 state, by the way, that on this point I differ from most of the 

 previous writers, with the exception of Bottcher. The portion 

 which covers the limbus is moderately thin, but the outer portion 

 which overlaps it is exceedingly thick, and the whole is marked 

 with radiating wavy lines. 



The lower, or membrana basilaris, arises from the lower lip of 

 the limbus, while its other end is firmly attached to a well-marked 

 ridge on the ligament of the cochlea. 



Between the membrana tectoria above, and the membrana basilaris 

 below, are situated the so-called rods of Corti. 



The Bods of the Cochlea. 



These interesting little bodies were first discovered and de- 

 scribed by the Marquis of Corti, whose name they now bear, and 

 although since then many observers have studied and written on 

 the subject, yet scarcely two are agreed as to their exact form, while 

 many of the later authors have gone so far as to state that their 

 shape is of a most varied character. The greatest difference of 

 opinion exists as to the shape of the rods at their articulation. 

 Deiters described them very minutely in his first paper, but in a 

 second communication he completely altered his description of them. 



The following is a free translation of an extract from Deiters' 

 first paper in Siebold and Kolliker's ' Zeitzchrift von Wissenschaft 

 Zoologie,' vol. 10. 



" The outer rods do not directly join the inner, but are con- 

 nected by a curious body, which partly belongs to the true rods of 

 Corti and partly to the lamina reticularis, and which we will call 

 the middle union joint. These middle joints vary much in form, 

 owing to their easy compressibility, and have not on that account 

 been as yet properly distinguished." " This (middle joint) will best 

 be likened to a boat which terminates at one end in a pointed 

 keel, and at the other in a straight back or plate." 



" In the natural position this back plate is turned upwards and 

 lies parallel to the membrana basilaris ; the keel, on the contrary, 



looks downwards and somewhat forwards The back plate 



is nearly rectangular in form, but only the anterior corners are 

 perfect, the posterior being rounded, and perhaps only appear 

 angular on account of the plates lying side by side." 



