PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 413 



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 idly at first when the oxygen is first withdrawn (or perhaps 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. 1 



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 



i Perhaps in this case the effects of poisonous substances are to be considered. 

 [1903] 



