l8 DYNAMICS OF LIVING MATTER 



It is quite possible that the idea of Schmiedeberg will prove ex- 

 tremely fertile in further work in this direction.* 



But even this addition does not exhaust the r61e of oxygen in life 

 phenomena; there are indications which make it appear as though 

 the oxygen acted as a protective substance. When respiration is 

 interrupted for but a short time in mammals or birds, loss of conscious- 

 ness, and very soon death, follow. Lack of oxygen therefore affects 

 first the cerebral hemispheres, and especially the ganglion cells. The 

 blood supply to the nerves is either lacking, or is so meager that we 

 must conclude that the functions of the nerves require very little oxygen. 

 The experience in drowning shows that lack of oxygen leads in a limited 

 number of minutes to death. In the case of death through lack of 

 oxygen, the respiratory ganglia evidently undergo irreversible changes, 

 which make attempts at revival futile. The heart retains its irritabihty 

 much longer than the respiratory ganglia. Kuliabko has recently 

 shown that the heart of a child can be caused to beat, or to show fibrillary 

 contractions, eighteen hours after death.f This shows that death was 

 not due to the inability of the heart to resume its beat, but to the inability 

 of the respiratory ganglia to work properly. It has often been observed 

 in my laboratory that in dying larvae of fish or frogs the respiration 

 stopped sooner than the heartbeat. The irreversible changes which 

 mark death occur with unequal rapidity in the various tissues of an 

 animal. 



When the egg of- a Fundulus is kept in an atmosphere of pure hydro- 

 gen, segmentation comes to a standstill in about twelve hours, but 

 permanent death occurs much later. The time required for permanent 

 death to occur in the absence of oxygen is the longer the younger the 

 egg. When eggs were deprived of oxygen immediately after fertiUza- 

 tion, they remained alive in the absence of oxygen for three or four 

 days (at a temperature of about 22°). When embryos of three days 

 were exposed to the same condition, death occurred in about thirty- 

 four hours. 



The higher the temperature the sooner lack of oxygen seems to cause 

 death. I make this statement on the basis of casual observations, and 

 I do not know whether or not any definite experiments exist on this 

 point; should further investigation confirm this idea, it would seem to 

 indicate that the changes in the tissues which cause death are produced 

 by noxious substances formed in the absence of oxygen. Araki % found 

 that in the active muscle dextrose and lactic acid are found when the 



* O. Schmiedeberg, Archiv fur experiment. Pathologie und PJmrmakologie, Vol. \\, 

 pp. 288 and 379, 1881. 



t Kuliabko, Pfiitger's Archiv, Vol. 97, p. 539, 1903. 



% Araki, Zeitsch. fur physiol. Chemie, Vol. 15, p. 335, 1891. 



