PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 411 



I have repeated this experiment eight times, always with 

 the same result. It was of importance now to determine 

 whether the number of heart-beats increases, and how much 

 it increases, when a heart which has attained its minimum 

 rate in hydrogen is again exposed to the oxygen of the air. 

 T In one such experiment the current of 



hydrogen was turned on at 9:10 A. M. 

 The number of heart-beats was 120 per 

 minute. At 11 the number of heart-beats 

 had fallen to 42, and soon thereafter the 

 minimum of 24 heart-beats was reached. 

 At 2 : 40 the number of heart-beats was 

 still 24. At 2 : 44 the embryo was taken 

 out of the gas-chamber and brought 

 into fresh water, and at 2:48 the num- 

 ber of heart-beats was counted; it was 

 then 30. The further 

 course of the experi- 

 ment is shown in the 

 following table: 



FIG. 125 



2:48 

 2:49 

 2:50 

 2:55 

 3:00 

 3:03 



- 40 beats per minute 

 51 " 



fiO " " " 

 66 " " " 



- 66 " " 

 69 " " 



