residing in the Tubular Organs of Sharks and Rays. 15 



inhabiting chiefly the great seas ; and it is difficult to ima- 

 gine on what occasions these organs could be so exercised so 

 as to ascertain the presence of other bodies by touch. 



G. R. Treviranus, to whom the minute anatomy of insects 

 owes so much, has advanced the opinion, that the tubular or- 

 gans of sharks and rays exercise a sense perfectly peculiar and 

 distinct from those which man and other animals possess ; 

 that the number of the senses which may exist in animals 

 ought not to be limited to five (the number usually assign- 

 ed to man) ; but he at the same time admits, that the precise 

 nature of the functions exercised by these organs remains 

 still a profound mystery. 



We need not here stop to discuss these hypotheses, which 

 are really without any foundation ; they may be classed with 

 the sixth sense invented by Bufibn, with the theories of Spal- 

 lanzani relative to the accurate flight of bats through darken- 

 ed chambers, after he had destroyed the organs of sight and 

 hearing, leaving to them that organ of sense, by which the flight 

 was really directed ; or with the sense of resistance, which a 

 skilful metaphysical writer invented and defended so plausibly. 



We cannot, I imagine, greatly err in considering these or- 

 gans as organs of touch, so modified, however, as to hold an 

 intermediate place between the sensations of touch and hear- 

 ing. They may perceive the undulations of the waters, and 

 seem admirably adapted for this purpose by the quantity of 

 nerves distributed to them ; by the interposition of a tremu- 

 lous gelatinous body interposed between the sentient extremi- 

 ties of these nerves and the impressing medium, and by the 

 intimate connection of the sixth and auditory pairs of nerves 

 of fishes. * 



The boldness and rapacity of the shark, and perhaps also 

 of the ray, imply the presence of active organs of sense. 

 The eye-ball is large, and the sight apparently tolerably 

 good, but quite inadequate to explain the facility with which 

 the shark discovers and follows a vessel through the trackless 

 ocean ; it is not improbable, therefore, that he owes this fa- 

 culty to the organs we have just endeavoured to describe. 

 The undulation of the water caused by a tolerably large ves- 

 sel must be sufficiently strong to impress a sensation on or- 



• The similarity of the peripheral terminations of these nerves with the auditory 

 in most animals is forcible and very striking. 



