FUNCTIONS OF SWIMBLADDER OF FISHES. 



Ill 



Autopsies were made to ascertain the extent of the injury due to 

 the puncturing and in no case was there any apparent evidence 

 of injury to the gland. 



As a control in some cases the swimbladders of normal fish 

 were punctured with a sewing needle approximately the size of 

 the hypodermic needle. No gas was removed. The results are 

 shown in Tables IX. and X. 



In the second series of experiments fishes were subjected to 

 high pressures for several hours. The apparatus as described 

 previously for pressure experiments, page 91, was used. The 

 pressure in the apparatus registered from thirty-eight to forty- 

 five pounds per square inch. The pressure was applied gradually 

 and removed gradually. The results of these experiments are 

 shown in Tables XI and XII. 



TABLE XI. 



DETERMINATIONS OF THE pH OF THE SWIMBLADDER GLAND OF NORMAL PERCH. 



The gland was allowed to dialyze as in the preceding experiments; the same 

 amounts of the carbon dioxide free water were used. 



These determinations show that the hydrogen ion concentration 

 of the swimbladder gland increases when the fish are placed 

 under pressure or when the pressure within the swimbladder is 

 diminished. When five cubic centimeters of the gas was removed 

 from the swimbladder the hydrogen ion concentration of the 

 glands averaged 6.38 as compared with 7.05 of the controls. 

 When fish were subjected to an increased pressure the hydrogen 

 ion concentration of the glands averaged pH 6.64 as compared 

 with pH 6.96 of the controls. 



The swimbladder gland consists of connective tissue, a bed 

 of capillaries, and a thick layer of epithelium (Plate I). Increase 



