FUNCTIONS OF SWIMBLADDER OF FISHES. 



103 



stopcock 2 was then turned to connect the equilibration chamber 

 with the test tube. The levelling bulb was then lowered and 

 the blood in the test tube drawn up into the equilibration chamber 

 C. The stopcocks were then closed and the chamber shaken 

 for several minutes until the gases in the blood and the swim- 

 bladder gases came into equilibrium with each other. The blood 

 was then allowed to run back into the test tube. Another 

 series of Van Slyke determinations were made. Constant 

 temperatures were maintained throughout the experiments. By 

 this method differences of tensions could be determined. For 

 if the analyses showed an increase or decrease in the determina- 

 tions before and after equilibration of the blood with the swim- 

 bladder they would denote a greater or lesser tension of the gases. 

 The results of the determinations are shown in Table VIII. 



TABLE VIII. 



RESULTS OF EQUILIBRATION OF FISHES' BLOOD WITH SWIMBLADDER GAS. 



Air was previously removed from the swimbladder in order to stimulate secre- 

 tion. The gas composition recorded represents the percentages at the time the 

 blood was removed from the fishes. 



It will be observed that in experiments with the bass a greater 

 tension of oxygen existed in the swimbladder than in the blood, 

 indicating that an active secretion of oxygen takes place. 



