AIR-BREATHING IN FISHES 



37 



Table 5 

 Size of the swimbladder of teleost fishes 



Manometer 



To pump 



(a) 



(b) 



(c) 



Fig. 11, 



Diagrams of an experiment in which the pressure above a physo- 

 stomatous fish is reduced and leads to the release of gas from the 

 swimbladder, (a). Two such 'deflated' fish (Crucian carp) are placed 

 in a tank and one only (b) is allowed to reach the surface and gulp air. 

 This fish becomes neutrally buoyant again, but the other (c) sinks to 

 the bottom when at rest. 



