Y. Henderson and H. W. Haggard 363 
from circulatory failure may follow’. If the artificial respiration, 
instead of being made with fresh air, is carried on by continual 
reinjection mainly of expired air, so that the CO, content of the 
blood is not reduced, the CO, capacity and arterial pressure do 
not fall and the other ill effects also fail to appear. 
2Ewald, A., Arch. ges. Physiol., 1873, vii, 580. Henderson, Am. J. 
Physiol., 1908, xxi, 126. 
