THE CONTROL OF THE RESPIRATION 



361 



dependent upon an increase in the nonvolatile acid content of the blood 

 That such is really the case has been conclusively shown both by titra- 

 tion methods and by observing the dissociation curve of hemoglobin, 

 which, as will be explained later (see page 386), may be made to serve 



Fig. 130. The horizontal interrupted lines represent the mean normal alveolar CO 2 and O^ 

 pressures at sea level (i.e., Oxford and New Haven); the thick line, alveolar CO 2 pressure; and 

 the thin line, alveolar O* pressure. (From Douglas, Haldane, Henderson, and Schneider.) 



as an index of the H-ion concentration of the blood. The exact chemical 

 nature of the nonvolatile acids that accumulate in the blood is not as yet 

 known. Two types of acid can be thought of, either unoxidized organic 



