THE SENSE OF SMELL IN FISHES. 
By G. H. PARKER and R. E. SHELDON. 
INTRODUCTION. 
That fishes scent their food in the water much as many land animals do in the air 
is a belief that is held by many fishermen. This opinion has led to the practice of 
chum mi ng or baiting up; i. e., of spreading bait in a region preparatory to fishing it, 
a practice that, in the case of sharks, mackerel, and bluefish, seems to be justified by 
the results. Such practice is based on the assumption that fishes have a sense of smell, 
but this opinion has been unsupported by physiological evidence, for up to the present 
time investigators of the subject have not been able to demonstrate any form of stimu- 
lation or reaction characteristic of the olfactory apparatus in water-inhabiting verte- 
brates. The observations of Aronsohn (1884, p. 164) that a goldfish which ordinarily 
will eat ant pupae with avidity will not take these pupae after they have been smeared 
with a little oil of cloves, are not conclusive evidence that the fish scents the oil, for it 
is entirely possible that this oil merely irritates the skin of the fish’s snout and does not 
stimulate the olfactory apparatus at all. Nor is the discovery made by Steiner (1888, 
p. 47), that the spontaneous appropriation of food by the shark Scyllium ceases on the 
removal of the cerebral lobes or simply on cutting the connections between these lobes 
and the olfactory bulbs, satisfactory evidence that the olfactory apparatus in these fishes 
is an organ of smell rather than a receptor for taste or some closely allied sense. 
Nagel (1894, p. 184) noted that the rostral portion of the head of Barbus was as 
sensitive to sapid substances after the olfactory tracts had been cut as before that 
operation, and Sheldon (1909, p. 291), studying the dogfish, demonstrated that the 
decided sensitiveness of the nostrils of this fish to weak solutions of oil of cloves, penny- 
royal, thyme, etc., was not influenced by severing the olfactory crura, but disappeared 
on cutting the combined maxillary and mandibular branches of the trigeminal nerve. 
Evidently the nostrils 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 
olfactory apparatus that is stimulated by the substances that have ordinarily been 
applied by experimenters. In fact, so far as the olfactory apparatus of the fishes and 
amphibians is concerned, we must agree with Nagel (1894, P- di) that no one thus far 
has diseovered anything positive concerning its function. It is, therefore, a matter of 
interest to record what seem to be unquestionable reactions dependent upon the olfactory 
apparatus of three of our common fishes: The fresh- water catfish (Ameiurtis nebulosus) , 
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