GENERAL CHEMISTRY OF LIFE PHENOMENA 19 



muscle works in lack of oxygen, while these substances are not found 

 in the presence of abundant oxygen. They are probably formed in 

 the latter case also ; but if atmospheric oxygen is present, are immediately 

 oxidized, while in the case of lack of oxygen they remain in the muscle. 

 This may serve as an example of the fact that metabolism in the presence 

 of abundant oxygen is different from that in lack of oxygen. Richet 

 and Broca have shown that if an excised muscle is stimulated in the 

 presence of oxygen until fatigue sets in, it will recover, but not if stimu- 

 lated in the absence of oxygen. It stands to reason that in the latter 

 case the recovery is prevented by noxious substances which would 

 have been oxidized and rendered harmless in the presence of oxygen. 



Bacteriology furnishes examples of the fact that in the case of lack 

 of oxygen more virulent substances may be formed, or exist, than in 

 the presence of atmospheric oxygen. Kastle quotes the statement that 

 the toxin of the diphtheria bacillus is weakened under the influence of 

 light in the presence of free oxygen, while the light has no such effect 

 in the absence of oxygen. Pasteur observed that cultures of the anthrax 

 bacillus and of chicken cholera become less poisonous when exposed 

 to the air. Recent experiments by Kastle and Elvove* have shown 

 that substances which have a high reducing power are especially toxic, 

 and these authors are inclined to assume that many toxins belong to 

 the group of reducing poisons. 



The fact that lack of oxygen is capable of producing irreversible 

 changes, and thus death, is rendered more easily comprehensible through 

 the direct observation of physical changes of living matter under such 

 conditions. I have made such observations in the segmenting egg of 

 a teleost fish, Ctenolabrus.f When these eggs are deprived of oxygen 

 at the time they reach the 8 or 16 cell stage, it can be noticed that the 

 membranes of the blastomeres are transformed into small droplets 

 within half an hour or more, according to the temperature. These 

 droplets begin to flow together, forming larger drops. Figures i to 5 

 show the successive stages of this process. When the eggs are exposed 

 to the air in time, segmentation can begin again ; but if a slightly longer 

 time is allowed to elapse, the process becomes irreversible and life becomes 

 extinct. Such clear structural changes cannot be observed in the eggs 

 of other animals under the same conditions. Are these changes of 

 structure (apparently liquefactions of solid elements) responsible for 

 death under such conditions? In order to obtain an answer to this 

 question, I investigated the effect of the lack of oxygen upon the heart- 

 beat of the embryo of Ctenolabrus. The egg of this fish is perfectly trans- 



* Kastle and Elvove, Am. Chetn. Journal, Vol. 31, p. 195, 1904. 

 t Loeb, Pfluger's Archiv, Vol. 62, p. 249, 1895. 



