166 STRUCTURE OF THE NERVOUS SYSTEM, BY MAX SCHULTZE. 



cells. Similar conditions are found in the auditory organs, 

 since in those parts where the nerve terminations are simple, 

 the terminal branches of the medullated acoustic fibres, after 

 losing their medullary sheath, penetrate between the epithelial 

 cells, especially between those of the otolith sacs and of the 

 ampullae of the semi-circular canals, and after breaking up 

 into primitive fibrils become continuous with peculiar ciliated 

 auditory cells.* The mode of termination of the nerves in the 

 cochlea is of greater complexity, especially because a portion 

 of the non-nervous cells of the epithelial investment of the 

 cochlear canal develops into the several structures forming 

 the organ of Corti. But even here the terminal nerve struc- 

 tures appear to consist of cells supporting hairs, which are 

 continuous with extraordinarily delicate non-medullated nerve 

 filaments (primitive fibrils). The terminal nerve apparatus of 

 the optic nerve in the retina presents quite peculiar features. 

 Here are found the layer of rods and cones, and the nucleated 

 external granules, which last, like the terminal apparatus of the 

 olfactory nerve, appear as fusiform cells, with a centric and 

 a peripheric process. The centric process of the rods is a 

 single primitive fibril, but that of the cones is a fasciculus 

 of primitive fibrils.*!* The peripheric process terminates 

 in the case of the so-called rods and cones in an essentially 

 similar manner, the extremity in each consisting of a pale 

 inner segment resembling ganglionic cell substance, and a 

 bright highly refractile external segment, which is separated 

 from the former by a sharply defined line, and which in the 



* See Max Schultze's Ueber die Endigungsweise des Hornerven im 

 Labyrinth, Miiller's Archiv, 1858, p. 343 ; Franz Eilh. Schulze in idem, 

 1862, p. 381 ; Odenius, Archiv filr Mikroskopische Anatomic, Band iii., p. 

 115. Hasse so far gives a different account, in that he has not been able 

 to observe the division of the axis cylinder into finer filaments (primitive 

 fibrils). See others in Zeits.fur wissens. ZooL, Bd. xvii., p. 638 ; Bd. xviii., 

 p. 89. I must, however, maintain the correctness of my assertions respecting 

 and illustrations of the above-described objects. The consideration of the 

 auditory organ of invertebrate animals is of great importance in regard to 

 the relations in question. See Hensen, Zeitschrift filr wissenschaftliche 

 Zoologie, Band xiii., p. 319, " On the Auditory Organs of the Crab." 



f Max Schultze, Archiv fur Mikroskopische Anatomic, Band ii., Taf. 10. 



