No. 581] 



GERM CELLS AND SOMATIC CELLS 



297 



to prevent those changes which lead to differentiation 

 and death ; thus in the case of tumor cells through con- 

 stant transfer into a new host we can enormously in- 

 crease the number of as yet less differentiated cells 

 on which the propagation depends by causing an in- 

 tense multiplication of these tumor cells, many of which, 

 if left in the same organism, would have undergone sec- 

 ondary degenerative changes. Through experimental 

 means, viz., through the transplantation into different 

 kinds of hosts tlie relative preponderance of propagation 

 and differentiation of tumor cells can be varied. We fur- 

 thermore know that through "chemical" sensitization 

 combined with mechanical stimulation, the same effect can 

 be produced, at least temporarily, in the connective tissue 

 cells of the uterine mucosa. Under those conditions a 

 large number of cells are induced to propagate and re- 

 main young while their offspring gradually change into 

 fully differentiated cells. If we grant the possibility that 

 differentiation of such cells as ganglia cells, while it en- 

 tails loss of the power to propagate and greater sensitive- 

 ness to insults, does not necessarily mean the necessity to 

 die, then the problem of prolongation of life would to a 

 great extent depend upon the possibility of preventing 

 injurious influences which at present disturb the function 

 of ganglia cells from attacking these cells and causing 

 their death. 



II. The germ cells are potentially immortal, but this 

 potential immortality can only be realized, if at certain 

 periods certain changes take place within the cells, which 

 concern especially the nucleus, phenomena consisting in 

 maturation, followed by fertilization or parthenogenetic 

 development. In a similar manner the observations of 

 Woodruff and Erdmann suggest that at the time of de- 

 pressions in the life of the protozoa, possibly similar nu- 

 clear phenomena take place at least in certain cases. We 

 nave seen that in the case of somatic cells there are also 

 indications of the existence of potential immortality. The 

 question may therefore be raised, whether similar periodic 

 rearrangements of the nucleus, as in the case of the germ 



