346 CO, Capacity of Blood. | II 
of the blood is abnormally increased by the blowing off of COs, 
alkali passes out of the blood into the tissues. | As a result of these 
two processes both the CO, and the alkali in the blood are de- 
creased, and the proportion of H,COs:INaHCO; and conse- 
quently the C,, of the blood are much less decreased than would 
be the case if only the CO: were altered. — 
If the “level of CO, and alkali” (as defined in the previous 
paper) is reduced below the critical value lying between 33 and 
36 volumes per cent of COs, a condition of general depres- 
sion of all vital functions results. Above the critical level the 
process appears to be reversible, for if CO, is administered in the 
air breathed and the CO, content of the blood is thus raised the 
CO, capacity follows it upward, probably because of the passage 
of the alkali from the tissues back into the blood. On the other 
hand if the marked resistance to further depletion of CQ, ca- 
pacity which occurs at the critical level is broken down and the 
CO, capacity further reduced, the result is a condition of vital 
depression from which the subject does not spontaneously re- 
cover. This condition may be termed acapnial shock. 
In the experiments to be reported here the methods were iden- 
tical with those in the first paper of this series, and the controls 
reported there apply equally here. 
EXPERIMENTAL. 
In the first experiment are shown the effects (in the dog) of 
careful and skilful etherization by the open method. The initi- 
ation of anesthesia was rapid, the administration as nearly uni- 
form as practicable by this method, and both excitement of respi- 
ration from too little ether and depression from too much were 
avoided. The CO, content was reduced in the course of the Ist 
hour from the normal of 50 down to 45. It underwent no con- 
siderable change during the succeeding 5 hours. 
