MULLENIX: EIGHTH CRANIAL NERVE. 231 



largely occupied by the terminal expansions of axis cylinders, desig- 

 nated by Retzius and other investigators as "Kelchbildungen." Such 

 groups of terminal structures are shown in Figures 12, 14, 16 (Plate 3). 

 There are other places, however, in which there is no evidence of such 

 expansions, and the sense cells appear to rest directly upon the surfaces 

 of the fibres which constitute the so-called plexus beneath the sensory 

 epithelium. Such a condition is represented in Figure 13 (Plate 3). 



In the cristae there are abundant terminal expansions, which are 

 appropriately compared to the calyces of flowers, since they do not 

 extend simply in the direction of the plane of the section, but, rather, 

 more or less radially from the end of the axis cylinder. Consequently 

 they are related to very many more sense cells than are visible in a 

 single optical plane. Figure 11 (Plate 3) represents such a structure, 

 to which eight sense cells are visibly related. The real number of 

 sense cells supplied by this terminal expansion is obviously many times 

 as great as the number lying in any one optical plane. I have observed 

 no cases of single cells being related to more than one such terminal 

 organ. 



The boundary between the sense cells and the nervous material 

 of which the terminal expansions is composed is always distinct and 

 sharp. There is no evidence, in my preparations, for any gradual 

 transition from one to the other, but the dark color of the calyx ends 

 abruptly where the yellow of the sensory cells begins. In no case have 

 I been able to find structures corresponding in any way to the intra- 

 cellular network described by Kolmer (:05^, :07). 



In those preparations in which the cell boundaries are best preserved 

 it has not been possible to distinguish the cell wall in places where the 

 cell was in contact with nervous material. Figure 24 (Plate 4), how- 

 ever, represents two cells in the crista, one of which appears not to 

 have been in contact with nervous material at its base, the cell wall 

 being traceable with clearness to the basal part of the cell. The ad- 

 jacent cell has a nerve fiber running to its base, where it bifurcates, 

 one branch passing between the two cells, the other passing between 

 the observer and the cell. I believe it is safe to assume that these two 

 cells are alike in possessing a cell wall at the base, as well as at the sides, 

 ahhough the method employed does not enable us to distinguish that 

 portion of the cell wall which is in contact with the nervous material, 

 which is stained black. 



Likewise, it seems probable that those sense cells which rest upon 

 the terminal nervous expansions are separated from the expansion 

 by cell membranes. 



