RETINA. 285 



hitherto employed, cannot be regarded as being of a ner- 

 vous nature, but are peculiar appendages of the nerves, 

 though they are certainly stated by other observers to 

 be directly connected with nerve-fibres, as for example 

 in the nasal mucous membrane. This namely is regu- 

 larly clothed with cylindrical epithelium, which is plen- 

 tifully provided with cilia and forms several layers, lying 

 one above the other, so that there are several rows of 

 cells covering one another. In these, according to seve- 

 ral recent observers, cells are met with, which terminate 

 in a somewhat long filament, and do not, like other epi- 

 thelial cells, end upon the surface, but run in an inward 

 direction, so as to become directly continuous with the 

 ends of the nerves. According to others, particularly 

 Max. Schultze, on the contrary, and this view seems to 

 be the more correct one, peculiar filiform ends of nerves 

 force their way out between the epithelium. The objects 

 of smell would therefore according to both views really 

 come directly in contact with the structures forming the 

 terminations of the nerves. Similar epithelium-like struc- 

 tures have recently been described as occurring also in 

 the mucous membrane of the tongue, seated upon pecu- 

 liar papillae, which appear to possess a pre-eminently 

 nervous character. 



These structures moreover might lay claim to a certain 

 resemblance with the ultimate terminations which we find 

 in the case of the optic nerve in the retina, and in that 

 of the auditory nerve especially in the cochlea termina- 

 tions, which may in the latter case, as far as their exter- 

 nal shape is concerned, be compared to long-tailed epi- 

 thelial cells, whilst those in the retina constitute struc- 

 tures of peculiar delicacy. In the retina namely the 

 optic nerve, after its entrance into the interior of the 

 globe of the eye, spreads out in such a way, that its fibrous 

 elements run alonp- on the anterior side of the retina, that 



