THE PHYSIOLOGY OF THE RESPIRATION OF FISHES IN 

 RELATION TO THE HYDROGEN ION CONCEN- 

 TRATION OF THE MEDIUM.* 



By EDWIN B. POWERS. 

 {From the University of Nebraska, Lincoln.) 



(Received for publication, October 31, 1921.) 

 INTRODUCTION. 



Within recent years much has been added to the knowledge con- 

 cerning the mechanism of the respiratory function of the blood. 

 Haldane and Priestley (1905) have shown that, at least in the higher 

 animals, the respiratory movements are affected by the carbon 

 dioxide tension of the arterial blood. It has been shown definitely 

 (Hasselbalch, 1912 and citations) that the exciting agent is the 

 hydrogen ion concentration of the blood bathing the respiratory 

 center. 



Krogh and Leitch (1919) undertook to study the respiratory function 

 of th6 blood of fishes in view of the knowledge of the influence of 

 temperature upon the dissociation curve of oxyhemoglobin as investi- 

 gated by Barcroft and Hill (1909) and Barcroft (1914). These 

 workers found that the blood of the fish was especially adapted to 

 its needs. 



Certain marine fishes are known to react to a gradient of acidity 

 and alkalinity (Shelford and Powers, 1915). It has been found that 

 certain species react positively to a definite range of hydrogen ion 

 concentration of the sea water, others are less definite in their reaction, 

 and still others seemingly do not respond to differences in alkalinity 

 and acidity (Powers, 1921). 



In view of these facts experiments were undertaken to determine 

 the ability of marine fishes to extract oxygen from the sea water at 

 different hydrogen ion concentrations. Interest in this question was 



* Studies from The University of Nebraska, No 131. 



305 



