Ne Henderson and H. W. Haggard 309 
45 minutes the CO, content of the blood was reduced to 28 vol- 
umes per cent, the CO» capacity to 34, and the arterial pressure 
to 70 mm. After termination of the mechanical artificial respi- 
ration it was found necessary for a time to squeeze the chest 
occasionally to prevent death in apnea. 
In the course of half an hour spontaneous respiration of a shal- 
low rapid type returned, but the animal continued to sink and 
died an hour and 40 minutes after the cessation of the period of 
excessive ventilation. | 
In this and in the preceding experiment it was observed that 
at first the reflexes, particularly the knee-jerk, seemed to be actu- 
ally increased in responsiveness, but that after the excessive arti- 
ficial respiration was stopped the reflexes decreased in responsive- 
ness until they had practically disappeared. 
Experiment 3.—Dog, male, 7 kilos. Passive overventilation, similar 
to Experiment 2, but not so active. Equilibrating air 5.6 per cent CO. 
Blood COs. 
‘ rig: Arterial 
Time. Condition. pressure. 
Content. | Capacity. 
p.m. vol. per cent} vol. per cent mm, 
3.00 Normal. 55 56 
3.20 Chloratone, 1.4 gm. 
4.50 54 55 130 
515 Ventilation started. 
5.30 37 4] 130 
6.00 31 37 120 
6.15 Reflexes hyperactive. 
6.30 31 35 95 
7.00 28 34 70 
7.05 Ventilation stopped. Artificial 
respirations 3 min. (manual). 
7.30 Reflexes partially abolished. 
7.30 28 38 50 
8.00 Respirations shallow and rapid, 
44 per minute. 
8.00 50 
8.30 Respirations, 55 per min. 50 
8.35 26 35 48 
8.47 Dog dead. 
Autopsy.—No pulmonary lesions. No air emboli in coronary vessels. 
