PHYSIOLOGICAL Errreots or Lack oF Oxycen 407 
opaque and sank to the bottom. Twenty-five minutes after 
turning on the hydrogen the changes which we have described 
in detail above—namely, the appearance of the strongly 
refractive droplets—were often clearly visible. 
If now we ask for the cause of the rapid and sudden 
standstill of the heart of Ctenolabrus embryos when deprived 
of oxygen, we must admit, first of all, that a failure of the 
energy which is supplied perhaps by processes of oxidation 
cannot be the cause. For, since the oxygen is replaced by 
hydrogen only gradually, the number of heart-beats should 
under these circumstances also decrease only gradually until 
a minimum is reached. The behavior of the heart was, how- 
ever, entirely different. The heart usually came to a stand- 
still without a noteworthy decrease in the number of heart- 
beats; sometimes a decrease was noted. For the same 
reasons the view that in three to ten minutes after turning 
on the current of hydrogen all the potential energy present 
in the heart has been used up is also to be set aside. After 
the heart had ceased to beat, the entire animal still executed 
spontaneous movements, and the heart remained generally 
active in case of lack of oxygen longer than the rest of the 
body of an animal.’ The rapid and sudden standstill of the 
heart of Ctenolabrus is the consequence either of a sudden 
poisoning, or of a structural change in the heart brought 
about by the removal of oxygen. It might also be that the 
poisonous effect consists only in bringing about molecular 
changes. The experiments on the cleavage of the Ctenola- 
brus egg showed that a change occurs in the cell-walls in 
consequence of which they break up into droplets. We 
must assume that these changes are brought about by the 
beginning lack of oxygen, or the metabolic products formed 
in consequence of this lack of oxygen. Might it not be pos- 
sible that a liquefaction of solid elements and the formation 
1 Miss Moore has since found that in young fish whose respiratory and sponta- 
neous motions have ceased the heart still continues to beat for hours. [1903] 
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