Rapid Changes in Reaction of Blood. 119 



In no normal person have we found a disagreement of over 

 10 per cent, in the ratio of alveolar/plasma C0 2 . Discrepancies 

 observed seem to fall into two large classes: (1) Those due to a 

 mechanical interference with the gaseous exchange, and (2) those 

 due to changes in the control of the respiratory mechanism. 



The first class is best illustrated by patients with cardiac 

 dyspnea or very great dimunition of the pulmonary capacity. 

 In these the alveolar is invariably lower than the plasma reading. 

 If compensation is established the two again come into agreement. 

 This, we believe, is due to an impairment of the lungs that renders 

 the excretion of C0 2 more difficult. The body overcomes this, 

 in response to stimulation of the respiratory center by the retained 

 C0 2 , with a greater pulmonary ventilation. In this way a pres- 

 sure difference is established between the carbon dioxide ten- 

 sion in the blood and in the alveoli, sufficient to compensate 

 for the impairment in the lungs. The increased minute volume> 

 the intolerance to carbon dioxide in the inspired air, the dyspnea 

 and the disproportionate response to exercise are all expressions 

 of the same thing. 



The second class is best illustrated by the discrepancies ob- 

 served after rapid changes in the reaction of the blood. The 

 alveolar air tends to lag behind the plasma in its response. 

 This is susceptible of an easy explanation during a sudden increase 

 of the H-ion concentration of the blood, when the demand on the 

 respiratory mechanism is overwhelming and the lungs are flooded 

 with C0 2 . We have been unable to study any patients who 

 have developed spontaneously a persistent acidosis, to determine 

 the time relations of the change. We have found that adrenaline 

 given intramuscularly to normal and diabetic persons produces 

 an acidosis, the curve of which is somewhat more rapid than that 

 of the hyperglycemia. After adrenaline and after exercise the 

 return to normal is very rapid. In none of our cases did the 

 alveolar C0 2 fall as far as the plasma C0 2 . 



A similar retardation of the alveolar response is found after 

 rapid alkalinization of the blood. This was first noted after the 

 administration of carbonates for therapeutic purposes, but has 

 since been determined in several cases of diabetic acidosis of 

 various degrees that have recovered without bicarbonate. In no 



