PERIPHERIC TERMINAL ORGANS OF THE NERVES. 167 



rods is of cylindrical, and in the cones of conical form. The 

 structure of the outer segments, which, in all probability, con- 

 stitute the proper terminal structures, upon the excitation of 

 which perception depends, differs from that of any other 

 nervous organ, especially in its consisting of a series of thin 

 plates superimposed on one another in the direction of its long 

 axis * The tactile nerves of the skin, lastly, terminate in the 

 so-called tactile corpuscles, which are oval or spherical, very 

 soft, and easily alterable bodies, occupying the interior of many 

 tactile papillae of the skin,~f* each of which is continuous with 

 one or more medullated nerve fibres that divide in their 

 interior, though up to the present time the precise mode of 

 termination of the primitive fibrils in them has not been 

 completely elucidated. 



In immediate relation to the sense of touch stand also in all pro- 

 bability the nerve hairs found on the surface of young fish and 

 naked amphibia, which have been ascribed by F. E. Schulze,| and 

 the arrangement of which in the form of pencils or brushes calls to 

 mind the nerve hairs in the ampullae of the auditory organ. These 

 appear to be well adapted for the perception of movements of the 

 water in which the animals live. In fishes also is found the lateral 

 canal system, with the nerve bulbs described by Leydig. I have 

 also observed a very similar disposition of the nerves in regard to 

 hair-bearing epithelial cells in the vesicles of Savi present in the 

 torpedo. According to recent investigations by Franz Boll, the 

 highly nervous ampullae of the so-called mucous canals of the head 

 of rays and sharks are covered with cell-supporting hairs. 



We may also regard the corpuscles of Vater or Pacini as 



* Max Schultze, Archivfur Mikroskopische Anatomie, Band iii., p. 215. 

 A reference may also be made to the differentiation of one or several axial 

 fibres in the outer segment, first observed by Hitter. See especially Hensen, 

 Virchow's Archiv, Band xxxix., p. 475, Taf. 12. 



f We owe the discovery of these structures to Meissner and Hud. 

 Wagner. See Gottinger, Nachrichten, 1852, No. 2 ; or in more detail 

 Meissner, Beitrdge zur Anatomie und Physiologic derHaut. Leipzig, 1853. 



J Muller's Archiv, 1861, p. 759. 



Untersuchungen uber den Bau der Nasenschleimhaut, 1862, p. 11. In 

 this essay will be found a more detailed account of the refetions at present 

 known to exist between nerves and epithelial investments. 



