THE CONTROL OF THE RESPIRATION 355 



work in our judgment fails to pay sufficient regard to the extraordinarily 

 complicated conditions existing in the animal body, and more particu- 

 larly, to correlate the purely physicochemical data with the numerous 

 observations that have from time to time been recorded by physiologists 

 regarding the behavior of the respiratory center. Physical chemists have 

 recently, for example, gone so far as to define acidosis as a condition in 

 which there is a diminution in the bicarbonate content of the blood in- 

 duced by the discharge into it of fixed acids. This is going too far, for 



it fails to recognize acidosis due to an increase in the C0 2 of the blood. 



r TT CO ~\ 

 It is the molecular ratio , T *^A which determines the tension of C0 2 . 



[NaHCOg J 



When C0 2 is added to the blood, either experimentally by respiring the 

 gas, or naturally OAving to muscular exercise or to pathologic conditions in 

 which there is a deficient excretion of C0 2 , as in heart disease, the ten- 

 dency of the equation to change, by increase of the numerator, is pre- 

 vented partly by stimulation of the respiratory center, which gets rid of 

 C0 2 , and partly by an increase in the denominator. The respiratory 

 center is so sensitive to slight increases in CH that it becomes excited 

 before a sufficient increase in H 2 C0 3 has occurred to disturb the normal 



r H CO ~\ 



ratio HT t T ^A When fixed acids are added to the blood the denom- 



L NaHCOg.J 



inator of the equation, NaHC0 3 , is lowered and consequently C H rises, 

 and increased respiration occurs, lowering H 2 C0 3 and thus reestablishing 

 the ratio. 



