FUNCTIONS OF SWIMBLADDER OF FISHES. 



95 



which the fish was accustomed to live. This water contained 

 a normal amount of oxygen. The apparatus was tested several 

 times to make sure that no leak occurred and that no change in 

 volume took place when fishes and normal water were in the 

 bottle or when water containing large amounts of carbon dioxide 

 and no fish was used. There was no indication of any volume 



I JL 



FIG. 2. Apparatus for determining the volume change in fishes. C, large 

 mouth bottle; R, rubber stopper; 5, three way stopcock; T, tambour; D, drum; 

 B, constant temperature water bath. 



change in any of these tests. Individual perch were placed 

 in the bottle, the water having previously been charged with a 

 small amount of carbon dioxide, the rubber stopper pushed 

 tightly into the aperture ; the water rose and passed out through 

 the tube 0, the stopcock was turned so as to connect the bottle 

 with the tambour. The drum was started and a record of the 

 volume change made. 



A typical graph is shown in Fig. 4. It will be observed that 

 the most rapid changes took place within the first few minutes. 

 Is this response of the fish to carbon dioxide due to the acid 

 nature of the dissolved gas or to some other property? It is 

 evidently not due to the acid property, for when lactic acid is 



