SOUND SENSATIONS 



239 



without any special hearing organ, cannot perceive sounds. Yet the 

 whole skin will receive vibrations of certain frequency, and transmit 

 them along nerve fibers, as cart be seen when an earthworm is placed 

 on a piano and the instrument is played. Fishes are deaf in the usual 

 sense of the word, but they are capable of detecting vibrations in the 

 water, of a kind that we should not notice at all. The fishes probably 



Fig. 100. Sound-perceiving organs in insects 



In the locust, .4, there is a nearly circular membrane, connected with nerve endings, 

 on the first segment of the abdomen. In the cricket, B, a similar hearing organ is found 



on one of the joints of the front leg 



receive these vibration impressions through a row of little spots ex- 

 tending along each side of the body, under the skin. This " lateral 

 line " is very prominent in some fishes (see Fig. 99). 



283. Hearing in fishes. It is commonly believed that fishes hear 

 sounds through the water, and that they will even recognize the voice 

 of the person who feeds them. Experiments, however, show that 

 some species are much more sensitive than others to different kinds 

 of sounds and other vibrations. Nearly all fish can probably distin- 

 guish vibrations through the water, especially those of low pitch. It 

 is doubtful whether any fish can perceive sounds made in the air, since 

 such sounds are very largely reflected from the surface of the water. 



