VENOM, ELECTRICITY, LIGHT, AND SOUND 157 



vocal efforts, the sounds are produced by the rapid vibration 

 of a special muscle, which is not always attached directly to 

 the bladder, but may run from the abdomen on either side to 

 a central tendon situated above the bladder (Fig. 64B). The 

 rapid contraction and expansion of the muscle (at the rate of 

 about twenty-four contractions per second) causes the walls 

 of the bladder to vibrate, and since this has a complicated 

 structure, it acts as a sort of resonator and intensifies the sound. 

 Mr. Tower, an American investigator, has performed a number 

 of experiments on living fish which are of some interest. He 

 found that if the bladder was deflated or removed altogether 

 the drumming entirely ceased, but if he introduced an artificial 

 india-rubber bladder it again commenced. In the Gurnards 

 or Sea Robins {Triglidae), and in the Toad-fishes [Batrachoididae) 

 the grunting noises are produced by special muscles lying in 

 the walls of the bladder itself, which, when they contract, throw 

 the walls into rapid vibrations. By experiments it has been 

 shown that if either the muscle or the nerve supplying the 

 bladder is artificially stimulated, a perfectly normal sound is 

 produced, even when the bladder has been removed from the 

 fish and placed on the operating table. No sound is produced 

 if the bladder is punctured, but the introduction of a rubber 

 balloon inside the bladder leads to a sound when the muscle 

 is stimulated by electricity. 



The actual noises produced by the different fishes present 

 great diversity, ranging from a more or less melodious vocal 

 effort to a mere grunt. A South American Cat-fish (i)orai) is 

 said to produce a sound described as a "deep, growling tone," 

 distinctly audible at a distance of one hundred feet when the 

 fish is out of the water. There can be little doubt that when 

 in their native element the sounds made by fishes must travel 

 for considerable distances, as water is a much more efficient 

 conductor of sound waves than air. The elastic spring 

 apparatus of the Electric Cat-fish {Malopterurus) causes a hissing 

 sound, the Trunk-fishes {Ostraciontidae) and Globe-fishes {Tetro- 

 dontidae) are credited with "growhng Hke dogs," and the httle 

 Sea Horses {Hippocampus) are said to utter a " monotonous sound 

 analogous to that of a tambour, which is characteristic of both 

 sexes, but is more intense and frequent in the breeding season." 

 An Indian species of Horse Mackerel [Caranx hippos) has been 

 described as grunting like a young pig, and a related species 

 from Egypt (C. rhonchus) is known to the Arabs as "Chakoura" 

 The sounds made by the Drums [Sciaenidae) 



