PHyYsioLocicaL Erreots or Lack or Oxyarn 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 astandstill. Since our earlier experiments rendered 
it possible that after two hours all the exhaust- 
> pal ible oxygen has certainly been driven out by 
ie the current of hydrogen, we are perhaps justified 
» too 4 in assuming that the energy for this long- 
& continued and regular, but slow, activity of the 
[ee heart is derived from processes of hydrolysis. 
go -| It seems as if we are able in the Fundulus 
heart to separate numerically the energy derived 
oe from hydrolytic processes from that derived 
bo from processes of oxidation, in that the former 
source of energy yields about 20, the latter the 
50 J remaining, about 80 to 100, heart- 
ae beats per minute. I would especially 
emphasize the fact that during the 
ae entire time of the experiment the 
Zo 4 
fo 4 
T T T T qv qT ' T 1 qv Ls 
° 1 2 3 ¥ $F 6 7 8 7 «&@ 4 & 
— Hours 
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 
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