FURTHER EXPERIMENTS ON NATURAL DEATH AND 

 PROLONGATION OF LIFE IN THE EGG^ 



JACQUES LOEB 



The Rockefeller Institute for Medical Research, New York 



1. The unfertilized egg dies in a comparati^-ely short time, 

 while the act of fertiUzation gives rise to a theoretically at least 

 unlimited number of generations. The death of the unfertilized 

 egg may be called a case of ''natural" death of a cell; it is per- 

 haps the only case in which we can feel sure that death is caused 

 by internal ''natural" causes and not by avoidable injuries. The 

 act of fertiUzation is the only one known to prevent natural 

 death. 



The velocity with which the unfertilized eggs die differs for 

 the eggs of various species; the mature egg of the starfish dies 

 much more rapidly than the egg of the sea urchin. The writer 

 pointed out that this difference might be connected with a differ- 

 ence in the rate of oxidations in the two kinds of eggs, since he 

 had been able to show that the suppression of oxidations by the 

 withdrawal of oxygen from the sea water or by the addition of a 

 trace of KCN prolongs the life of these eggs. Last year, Loeb 

 and Wasteneys were indeed able to prove a difference in the rel- 

 ative rate of oxidations between the eggs of these two kinds of 

 animals in the sense which is demanded by our hypothesis. The 

 mature unfertilized egg of the starfish has a rate of oxidations 

 which equals that of the fertilized egg;^ while the rate of oxida- 

 tions in the unfertilized mature egg of the sea urchin is only 

 about one-fourth or one-sixth of that of the fertilized egg of the 

 same species. 



1 Loeb, Maturation, natural death and the prolongation of life, etc. Biol. 

 Bull., vol. 3, p. 295, 1902. The mechanistic conception of life, 1912. 



2 Loeb and Wasteneys, Arch. f. Entwicklungsmechanik, vol. 35, p. 555, 1912. 



201 



