656 



MANUAL OF HISTOLOGY. 



mushroom. Under the microscope we may easily recognise the fact, that 

 the ordinary simple pavement epithelium of the internal ear has given 

 way to another species, namely, to a deeply laminated, whose uppermost 

 elements (a), which are cylindrical in shape, and dotted with yellowish 

 granules, have a strong resemblance to the cells met with in the regie 

 olfactoria ( 307). 



It is between these cylinders on the septum nerveum that the fibres of 

 the auditory nerve terminate, in a manner similar to that of the olfactory 

 and gustatory nerves. 



The structure of this portion of the organ of hearing is, however, very 

 complicated, and by no means as yet fully understood. 



The first thing remarked in fishes, such as young tritons (Schulze) 

 over the free surface of the whole yellow layer, is a multitude of extremely 

 long (O0902 mm.) stiff filaments, projecting beyond the surface (the 

 " auditory filaments"), whose relation, however, to the cells below requires 

 farther investigation. Deeper down, seated on the fibrous substratum, 

 there appears another kind of cell (b), supported upon an expanded base 

 (basal cell of Schuttze). Finally, we meet with small colourless cells in 



great number, which give off a process at 

 either pole of their rounded or fusiform 

 bodies (c) ; these are the fibre cells of 

 Schultze. The superior process (d) is the 

 thickest, and of rod-like form, ending on 

 the surface of the complex epithelial 

 stratum, with truncated extremity. The 

 inferior (e) is thinner, and dips down to- 

 wards the connective-tissue substratum. 

 The nerve fibres (/) appear at first sight 

 to terminate at the border of the fibrous 

 layer, under the epithelial covering, but 

 only merge here into pale axis cylinders, 

 which enter the latter (g), and after split- 

 ting up into a large number of branches, 

 disappear eventually from view. It is not 

 improbable, although not yet proven, that 

 these terminal fibres are continuouswith the 

 inferior processes of the fibre cells (Schultze). 

 /Schultze maintains, and possibly with per- 

 fect right, that the divided non-medullated 

 axis cylinder is prolonged directly into the 

 long hairs already mentioned. 

 The same structural relations, with shorter hairs, however, have been 

 observed in the otolith sac of fishes. 



Statements have also been made to the same effect as regards other 

 vertebrates ; but the opinions of investigators still differ widely. 



The two nervous projections of the human vestibular saccules, or 

 maculce acusticcB, as Henl.e calls them, are less marked than the septa 

 nervea of the ampullae, but are wider, and present a larger surface on the 

 other hand. 



These maculae acusticae were very accurately described some years ago 

 by Odenius. In the utriculus a complicated plexus of nerves spreads out 

 towards the surface through the connective-tissue substratum, terminating 

 finally in delicate axis cylinders, which penetrate into the epithelial layer. 



Fig. 605. From the critta acustica of 

 the ampulla of raja clavatu (after 

 Schultze). a, cylinder cells; 6, basal 

 cells ; c, fibre cells, with an upper rod- 

 like process d, and lower filiform e ; 

 /, nerve fibres, passing into pale axis 

 cylinders at g. 



