416 STUDIES IN GENERAL PHYSIOLOGY 



Finally, it was of interest to compare the resuscitating 

 effect of air with the resuscitating effect of hydrogen. Fun- 

 dulus embryos were introduced into two gas-chambers. At 

 the beginning of the experiment the heart under observation 

 in one of the chambers beat 90 times a minute; that in the 

 other, 96 times a minute. Hydrogen was passed through 

 the chambers, and after an hour and fifty minutes the 

 frequency of the heart-beats had fallen in both cases to 18 

 per minute. In place of the hydrogen, carbon dioxide 

 was then passed through the chambers. In fifteen minutes 

 the ventricles stopped beating, and the pulsations of the 

 auricles became much weaker. After 45 minutes one of the 

 hearts was apparently dead, while the auricle of the other 

 still beat 18 times a minute, though the beats were scarcely 

 perceptible. One of the .gas-chambers was then opened 

 and the embryo exposed to the air, while in the second cham- 

 ber the CO 2 was replaced by hydrogen. After fifteen 

 minutes the heart which had been apparently dead and 

 which was exposed to the hydrogen beat 24 times a minute, 

 but only the auricles contracted. Both the auricle and the 

 ventricle of the heart which was exposed to the air beat 

 60 times. Two hours later the heart beat 30 times per 

 minute in the hydrogen, but the contractions were still 

 limited to the auricle, while the heart exposed to the air 

 beat 72 times. When a little later I exposed the em- 

 bryo kept in the hydrogen to air, the ventricle did not 

 recover. The number of auricular contractions did rise 

 within fifteen minutes from 18 to 54, but shortly there- 

 after the entire heart ceased to beat. In resuscitating a 

 heart poisoned by CO 2 , oxygen is therefore more effect- 

 ive than the simple removal of the CO 2 by hydrogen. 

 We are not able to explain why the ventricle ceases to 

 beat when exposed to carbon dioxide sooner than the auricle. 



We meet with an entirely different relation between car- 



