TRANSACTIONS OF THE SECTIONS. 157 



Odeiiiiis and KoUikev's researches confirmpd these observations, but Ilasse gives 

 a totally dllierent account of the structure. He describes it as consisting: of alter- 

 nating elongated cells, the one bearing the ciliuni, the other isolating the ciliated 

 cells, and resting with a broad base on the menibrana propria. 



liudinger sominvhat reverses the description of Hasse, and states that the 

 isolating cells are triangular, with their bases turned upwards so as to form the 

 free border of the epithelial mas.^, and doubts the existence of the deep layer of 

 nuclei. 



Ebner believes the essential elements to consist of two forms — a superficial layer 

 of cylindrical ciliated cells rounded oft' below, and a deep multiple layer of filiform 

 cells with their filaments passing up between the cjdindrical cells. 



Ijastly, Paul Meyer describes it as made of two parts — a deep layer of nuclei, and 

 a superficial one of cylindrical ciliated cells tapering off below. 



The author's observations have led him to conclusions which, although they arc 

 essentially difierent from those of the authors just alluded to, yet appear to him to 

 reconcile to a great degree their various conflicting descriptions. 



The appearance of this structure differs according to the position in the macula 

 of the portion examined. 



A typical portion, such as may be seen midway between the centre and circum- 

 ference of the spot, consists of a layer of alternating elongated cells, l)ordered above 

 l)j' a distinct cuticular membrane, and connected below with those nuclei which 

 form the deep layer described by most authors. So that the cellular elements may 

 be said to consist of two alternating forms of elongated cells, each having an upper 

 and a lower nucleus. The author calls the first the thorn-cells, on account of the 

 shape of their cilium, and the second the bristle-cells for a similar reason. 



The thorn-cells have a fusiform body containing an oval nucleus; from this body 

 passes upwards through the cuticular membrane a tapering cilium or thorn ; the 

 lower extremity is prolonged downwards, and again expands to enclose its second 

 nucleus. 



The bristle-cells have a triangular body containing an oval nucleus ; the base of 

 this is intimately connected with the cuticular membrane, and from this base 

 passes upwards a narrow bristle-like ciliuni ; the apex of this triangular ))ody is 

 prolonged downwards and has a second nucleus like its fellow thorn-cell. 



The cuticular membrane is a very thick, well-marked membrane, holding the 

 cellular elements in their place, and perforated for the passage of the cilia. This 

 membrane is analogous to the membrana reticularis of the organ of C'orti, and 

 the author therefore proposes to call it by the same name. 



Modifications of the nerve epithelium. — As there is a general increase in thickness 

 of the macula from circumference to centre, so the cells and their various parts 

 elongate ; the cilia, which are short and stumpy at the edge, become very much 

 longer and comparatively finer at the centre of the acoustic spot. At Ihe circum- 

 ference the cells pass by insensible gradations into the columnar epithelial celks, 

 which surround the whole macula. Towards the centre the upper nucleus and 

 surrounding protoplasm of the bristle-cells gradually diminisli and then are lost 

 altogether, this part of the cell being represented by a trabecula from the mem- 

 brana reticularis. The bristle-like cilium remains after the upper protoplasmic 

 mass has disaj^peared ; but eventually this also is lost. 



The termination of the nerves in the macula. — The uerve-fibres arriving at the 

 membrana propria lose their white substance, and enter the nerve epithelium 

 without it. After passing this point there is considerable difficulty in tracing the 

 nerve-filaments ; but there is no doubt that they form a plexus around the deeper 

 layer of nuclear bodies, and that some of the filaments may be traced directly or 

 indirectly into the ciliated cells. 



The otolith mass. — Covering the acoustic spot is a soft mass into which the cilia 

 pi-ojoct to a certain distance ; this is evidently of a cuticular nature, and is analogous 

 to tiie menibrana tectoria of the cochlea. The otoliths are fixed by this mass, 

 being chiefly contained in its outer portion. 



1876. 15 



^^ 



