Ii6 The Life Story of the Fish 



to have none at all, and many others use sight much more 

 than smell in feeding. Certainly the trout rising for surface 

 food depends solely on its eyes. But trout and salmon, and 

 the other game fish so far as is known, do smell, and in some 

 this sense is very acute. 



OTHER SENSES 



The existence of the kinesthetic sense in fish is one thing 

 which it might be expected that we should never be able 

 to demonstrate. If you close your eyes, and I take hold of 

 your arm and lift it until it sticks straight out in front, and 

 ask you where your arm is, and you answer correctly, and if 

 I then move it so that it sticks out at the side, and you again 

 give the correct answer, I know that you have the kinesthetic 

 sense. From this it would be only natural to assume that 

 until fish learned to talk there would be no way of testing 

 them for this sensibility. However, scientists are impatient, 

 inquisitive, and inventive. By delicate measurements they 

 have recently shown that the electrical discharge from the 

 lateral-line nerve varies with the amount of tension in the 

 body muscles. No one has yet followed this lead far enough 

 for certain proof, but the indication is that the lateral line, 

 in addition to its other functions, keeps the fish advised of 

 the disposition of its body, and that the kinesthetic sense 

 does exist. 



Of the sense of pain we can speak with more definiteness, 

 but as we shall be in a better position to do so after we have 

 considered the fish's brain, we shall leave it until then. 



THE BRAIN 



It is the intention of this book to give the reader not a 

 detailed knowledge of the physiology of fish, but a general 

 understanding of why fish behave as they do. It would be 

 out of place, therefore, to go into a particularized description 



