ON THE ACTION OF CERTAIN SUBSTANCES ON 

 OXYGEN CONSUMPTION. 



VI. THE ACTION OF ACIDS. 



L. H. HYMAN, 

 DEPARTMENT OF ZOOLOGY, UNIVERSITY OF CHICAGO. 



In recent years the role of acidity and alkalinity in biological 

 processes has been the subject of numerous investigations. The 

 impetus to this field of research was given by the invention of 

 methods for determining the true hydrogen ion concentration of 

 biological fluids and materials. As a result of the great mass of 

 work accumulating along this line of research, there prevails 

 among biologists the impression or opinion that hydrogen ion 

 concentration is of tremendous importance in the life of or- 

 ganisms. Yet, looking back upon the history of science, one 

 may be pardoned for a certain degree of skepticism. Biologists 

 appear prone to attach undue significance to whatever field of 

 investigation happens to be the fashion of the decade and time 

 alone can assign a mass of research on one particular topic to its 

 proper place. 



The present series of experiments was undertaken in part as a 

 test of the proposition that hydrogen ion concentration is of 

 fundamental importance in physiological processes. The con- 

 sumption of oxygen in respiration was chosen as a physiological 

 process essential to the organism in the highest degree and 

 readily susceptible to quantitative measurement. An attempt 

 was made to determine: (a) whether increasing the acidity of 

 the environment of an organism has any effect upon the rate of 

 oxygen consumption ; (b) whether this effect is assignable to the 

 free hydrogen ions or to some other factor. The experiments 

 prove that alterations in external acidity markedly affect the 

 rate of respiratory metabolism of animals; but they also show 

 that the free hydrogen ions are little, if at all, responsible for the 

 observed effect. 



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