64 SMELL, TASTE, ALLIED SENSES 



fish's snout and did not stimulate the olfactory apparatus 

 at all. Nor was the discovery made by Steiner (1888), 

 that the spontaneous appropriation of food by the shark, 

 Scyllium, ceases on the removal of the cerebral lobes or 

 simply on cutting the connection between these lobes and 

 the olfactory bulbs, satisfactory evidence that the olfac- 

 tory apparatus in these fishes is an organ of smell rather 

 than a receptor for taste or some closely allied sense. 

 Nagel (1894) noted that the front of the head of the fish, 

 Barbus, was as sensitive to sapid substances after the 

 olfactory tracts had been cut as before that operation, and 

 Sheldon (1909), who studied the dogfish with great ful- 

 ness, demonstrated that the decided sensitiveness of the 

 nostrils of this fish to weak solutions of oil of cloves, 

 pennyroyal, thyme, and the like, was not influenced by 

 severing the olfactory crura, but disappeared on cutting 

 the combined maxillary and mandibular branches of the 

 trigeminal nerve. Evidently the nasal surfaces of fishes 

 like those of the higher vertebrates, are innervated by 

 fibers from the trigeminal nerve, and it is this nervous 

 mechanism rather than the true olfactory apparatus, that 

 is stimulated by the substances that have ordinarily been 

 applied by experimenters. In 1909, Baglioni showed that 

 blinded fishes were excited by the presence of food. None 

 of these experiments, however, demonstrated conclu- 

 sively that smell rather than taste or some other allied 

 sense, was concerned as the receptor. 



As early as 1895 von Uexkiill observed that dogfishes 

 from which the olfactory membranes had been removed 

 did not respond to the presence of food whereas normal 

 dogfishes three to five minutes after food had been in- 

 troduced into their tank, sought it with great eagerness. 



