PHYSIOLOGICAL EFFECTS OF LACK OF OXYGEN 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 iurning 

 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. 1 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 arid the formation 



i 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] 



