334 CO, Capacity of Blood. I 
cal conceptions in this field, and will, we believe, find wide reach- 
ing practical applications. 
In brief, the experiments to be described in this series of papers 
seem to indicate that when in an otherwige normal organism 
respiration is stimulated to excessive vigor by pain, by a drug, 
e.g., ether (or probably by any condition which lowers the thresh- 
old and increases the sensitivity of the respiratory center), the 
blowing off of carbon dioxide produces a reduction in the CO, 
content of the blood. ‘This condition very soon leads to (and in 
respect to C, is probably in part compensated by) a reduction 
also in the CO: capacity (alkaline reserve) of the blood. Appar- 
ently alkali passes out of the blood into the tissues. Thus the 
acid-base equilibrium or COs: alkali balance of the blood is re- - 
stored at a level much below normal, and a condition simulating, 
but in certain respects markedly distinct from true acidosis re- 
sults. Infact, until thus compensated, the condition is a sort of 
low CO: alkalosis. It may be conveniently designated acapnia,?® 
although the term thus applied has a significance much broader 
than heretofore. It indicates a blood low not only in CO2 (H2CQs), 
but also in sodium bicarbonate. Unlike a true acidosis the total. 
alkali in the body remains, so far as we can judge, unaltered; it 
is merely abnormally distributed. 
On the. other hand when the respiratory center is depressed 
e.g., by morphine, or when by the administration of high concen- 
trations of CO, in the air breathed, the alveolar CQ, is raised, 
the CO, content of the blood is also raised. This causes (and in 
respect to the C, of the blood is probably compensated by) an 
increase in the CO, capacity or “alkaline reserve” of the blood, due 
apparently to the passage of alkali from the tissues into the 
blood. Thus a pseudoalkalosis or, if one thinks only in terms of 
C,, a CO, acidosis, is produced. It may conveniently be termed 
hypercapnia: both the CO, and the sodium bicarbonate in the 
blood are above normal. Probably the total alkali in the body is 
unaltered. It is merely redistributed. 
Either of these conditions, when once induced, shows a distinct 
tendency to be maintained. Any rapid variation from the new 
’ Henderson, Y., Am. J. Physiol., 1908, xxi, 126; 1908-09, xxiii, 345; 
1909, xxiv, 66; 1909-10, xxv, 310, 385. Henderson, Y., and Scarbrough, 
M. McR., zbid., 1910, xxvi, 260. Henderson, tbid., 1910-11, xxvii, 152. 
