PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 409 



When the number of the heart-beats has decreased to the 

 minimum of about 20 per minute, the heart continues to 

 beat at this rate for about eight to ten hours in an uninter- 

 rupted and regular manner, until at the end of this time it 

 comes to a standstill. Since our earlier experiments rendered 

 it possible that after two hours all the exhaust- 

 ible oxygen has certainly been driven out by 

 the current of hydrogen, we are perhaps justified 

 in assuming that the energy for this long- 

 continued and regular, but slow, activity of the 

 heart is derived from processes of hydrolysis. 

 It seems as if we are able in the Fundulus 

 heart to separate numerically the energy derived 

 from hydrolytic processes from that derived 

 from processes of oxidation, in that the former 

 source of energy yields about 20, the latter the 

 remaining, about 80 to 100, heart- 

 beats per minute. I would especially 

 emphasize the fact that during the 

 entire time of the experiment the 



lo 



FIG. 124 



current of hydrogen was passed through the gas-chamber 

 uninterruptedly, and that in consequence every action of the 

 carbon dioxide had been shut out in these experiments, as 

 in those upon the Ctenolabrus embryo. 



We shall now describe a few of the individual experi- 

 ments. In one case the hydrogen current was turned on at 

 8:42 A. M. The number of heart-beats was 108 to 114 per 



