PHYSIOLOGICAL EFFECTS oF Lack or Oxyaen 418 
in the number of beats. I had expected that the number of 
heart-beats would be only the minimal one after removing 
the gas-chamber from the ice. Possibly all the oxygen had 
not been driven out. I therefore repeated the same experi- 
ment, but allowed the gas-chamber to remain for three hours 
on the ice. This time I expected that at room temperature 
the number of heart-beats would only reach the minimum 
which corresponded to the temperature. But this time also 
the number of heart-beats rose in six minutes to 66, after 
which the rate decreased steadily. One hour later the heart 
beat 42 times, and after thirty-five minutes the minimum of 
24 was reached. I do not doubt that after passing a vigor- 
ous current of hydrogen through the gas-chamber for three 
hours all the oxygen is exhausted from the egg. If this 
assumption is correct, these experiments can be made to har- 
monize theoretically with the results obtained earlier only 
by assuming that the processes of hydrolysis do not occur 
with uniform intensity, but that they occur much more rap- 
idly at first when the oxygen is first withdrawn (or perhaps 
also under the ordinary conditions of oxygen supply) than in 
the continued lack of oxygen.’ 
It is, moreover, to be noted that the data necessary for 
calculating the work of the heart are lacking in these ex- 
periments. Only by assuming that these data are the same 
in the presence of oxygen as in its absence can conclusions 
be drawn as to the behavior of the two sources of energy. 
If we make this assumption, we come to the conclusion that 
of all the energy which is used up by the Fundulus embryo 
in normal heart-activity, that much at least which cor- 
responds to the minimal number of heart-beats in the lack 
of oxygen is dependent upon processes of hydrolysis. This 
number is about one-sixth or one-fourth of the total number 
of heart-beats which occur under normal conditions of 
1 Perhaps in this case the effects of poisonous substances are to be considered, 
[1903] 
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