THE SENSES OF FISHES 



C. JUDSON HERRICK 



Professor of Neurology in the University of Chicago 



Our human world is a very limited 

 part of nature. The unaided senses of 

 primitive man open a few doors of com- 

 munication between the individual and 

 his surroundings, through which the sum 

 total of his knowledge of things as they 

 are must be derived. Science has great- 

 ly enlarged the efficiency of the natural 

 sense organs — the microscope and the 

 telescope have extended the range of 

 vision, the periscope enables us to see 

 around a corner, the spectroscope, photo- 

 graphic plate, X-ray machine, and innu- 

 merable other aids have enabled us to 

 see deeper into nature. But no new 

 senses have been developd and our 

 furthest scientific advances and most 

 recondite philosophical theories must be 

 based in last analysis on such frag- 

 mentary knowledge of the cosmos as is 

 revealed to us by our senses. Great 

 realms of nature remain wholly unex- 

 plored, although new artificial aids per- 

 mit constant advances into the hitherto 

 unknown — Hertzian waves and wireless 

 telegraphy, ions and the new chemistry, 

 electrons and the new physics. 



Fortunately the traditional five senses 

 do not represent our whole physiological 

 equipment for this task. In fact, the 

 human animal is endowed with about 

 twenty distinct senses, including two in 

 the ear, at least four in the skin, and 

 numerous Dthers in the deep tissues, 

 such as muscle sense, hunger, thirst and 

 other visceral senses. 



It is well known that fishes and other 

 lower vertebrates possess numerous 

 types of sense organs quite unlike any- 



thing in our own bodies, and it is quite 

 impossible for us to form any conception 

 of what the world appears like to these 

 animals except in so far as their sensory 

 equipment is similar to our own. Even 

 the companionable dog, who responds so 

 sympathetically and intelligently to our 

 moods, lives in a very different world. 

 Recent experiments have shown that his 

 sense of vision is very imperfect, espe- 

 cially for details of form, and everybody 

 knows the inconceivable delicacy of the 

 hound's sense of smell. With us vision 

 is the dominant sense and our mental 

 imagery is largely in terms of things 

 seen. Even a blind man will say, "I see 

 how it is," when he comprehends a dem- 

 onstration. 



What sort of a world is it to a dog, 

 whose finest experiences and chief in- 

 terests are in terms of odors ? And how 

 does it feel to be a catfish, provided not 

 only with large olfactory organs whose 

 central nervous centers make up almost 

 all of the cerebral hemispheres of the 

 brain, but also with innumerable taste 

 buds all over the mucous lining of the 

 mouth and gills and freely distributed 

 over the entire outer skin from the bar- 

 blets ("feelers") around the mouth to 

 the tail fin ? We cannot conceive the epi- 

 curean delights which such an animal 

 may feel when he swims into the water 

 surrounding a juicy piece of fresh meat, 

 by whose odorous and savory juices he is 

 bathed. One wonders, parenthetically, 

 how far the fish himself is able to con- 

 ceive or even enjoy the pleasures of life. 

 With how much mind of any sort the 



