TERMINATION OF NERVES IN VESTIBULE. 401 



authors just alluded to, yet appear to me to reconcile, to a 

 great degree, their various conflicting descriptions. 



As this structure is admitted by all observers to be vir- 

 tually the same in the vestibule and ampullae, a description 

 of the macula acustica of the saccule will suffice for all. 



Figs, A, B, and C (Plate XXVIII) represent a transverse 

 section of the macula at different points, and is drawn from 

 a preparation of the labyrinth of a cat ten months old. 



A glance at the drawing will suffice to show that this 

 nerve epithelium does not present the same appearances 

 throughout the whole macula, I therefore propose, first, to 

 describe the type of this structure, and then its modifications. 



A typical portion, such as may be seen midway between 

 the centre and circumference of the spot, consists of a row 

 of alternating elongated cells, bordered by a distinct cuticular 

 membrane. Below these is a nuclear layer, such as has been 

 described by all recent observers with the exception of 

 Riidinger ; however, connections may be clearly traced 

 between the upper elongated cells and this deep layer of 

 nuclei ; so that the cellular elements of this tissue may be 

 described as consisting of two alternating forms of elongated 

 cells, each having an upper and a lower nucleus. 



The first I call 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 a single cilium, 

 which gradually tapers to a point; this cilium or thorn 

 passes through an opening in the cuticular membrane, but 

 appears to be totally unconnected with it. The lower taper- 

 ing extremity of the body passing downwards again expands 

 and encloses a second oval 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 single narrow cilium or bristle, having parallel and not 

 tapering borders, thus resembling in shape, though much 

 larger, those found oTi the ciliated cells of Corti in the mam- 

 malian cochlea. The apex of this triangular body is pro- 

 longed downw^ards, and has a second enlargement containing 

 a second oval nucleus ; this is usually situated at a diflferent 

 level to that of the corresponding enlargement of the thorn 

 cell, and thus the alternating cells appear to dovetail, as it 

 were. 



The cuticular membrane is a very thick, well-marked 

 membrane, keeping the cellular elements in their place, and 



