No. 581] 



GERM CELLS AND SOMATIC CELLS 



291 



possibility of nuclear reorganization of the cell necessary 

 for continued life. In a somewhat related way, Minot 

 considers, as mentioned above, the death of somatic cells 

 as inevitable and as the result of cytomorphosis, which 

 means the relative increase in size and differentiation of 

 somatic cells during life. In this connection it is inter- 

 esting to note that while K. Hertwig considers (in pro- 

 tozoa primarily, but secondarily also in other cells) an in- 

 crease in the size of the nucleus — the result of the activity 

 of the cells — as the cause of functional disturbances lead- 

 ing to senility, Minot on the other hand connects senility 

 with a relative decrease in the size of the nucleus and an 

 increase in the mass of the cytoplasm. Now as far as the 

 protozoa are concerned, the controversy does not seem to 

 concern so much the potential immortality of these organ- 

 isms as the problem as to whether the individual pro- 

 tozoon corresponds to a germ cell or to a somatic cell of a 

 metazoon, or whether it partakes of the character of both. 

 There can be little doubt that individual protozoa possess 

 potential immortality, a conclusion which would not be 

 invalidated through a loss of certain parts of the pro- 

 tozoon body at certain periods of its life cycle. 



We may there fore conclude that all three kinds of cells, 

 protozoa, germ cells, as well as certain somatic cells of 

 metazna, possess a potential immortality. 



Tumor cells are somatic cells in which such secondary 

 changes leading to a cessation of proliferation as take 

 place under certain conditions in all the individual cells in 

 some kinds of somatic tissues, are affecting only a certain 

 number of cells. In the case of some somatic cells, as, for 

 instance, those of the epidermis, it is evident that the 

 secondary changes in structure and metabolism, which 

 lead to a cessation of proliferative power, arc due to un- 

 favorable conditions of blood-supply. What Minot calls 

 cytomorphosis can therefore in this case be referred not 

 to necessary transformations inherent in the cells, but to 

 unfavorable environmental conditions into which the 

 cells are placed as a result of their multiplication. Such 

 secondary degenerative changes take place also in tumor 



