30 Living and Dead Matter and 



as otherwise the synthesis of specific proteins would 

 have to come to a standstill. 



This problem of synthesis leads to the assumption 

 of immortality of the living cell, since there is no a priori 

 reason why this synthesis should ever come to a stand- 

 still of its own accord as long as enough food is avail- 

 able and the proper outside physical conditions are 

 guaranteed. It . is well known that Weismann has 

 claimed immortality for all unicellular organisms and 

 for the sex cells of metazoa, while he claimed the neces- 

 sity of death for the body cells of the latter. Leo Loeb 

 was led by his investigations on the transplanta- 

 tion of cancer to assume immortality not only for 

 the cancer cell but also for the body cell of the 

 organism. He had found in transplanting a malignant 

 tumor from one individual to another that the tumor 

 grew; that it was not the cells of the host but the 

 transplanted tumor cells of the graft which grew and 

 multiplied, and that this process could be repeated appar- 

 ently indefinitely so that it was obvious that the trans- 

 planted tumor cells outlived the original animal. Such 

 experiments have since been carried on so long that 

 we may now say that an individual cancer cell taken 

 from an animal and transplanted from time to time 

 on a new host lives apparently indefinitely. Leo Loeb 

 had found that these tumor cells are simply modified 

 somatic cells. He therefore suggested that the somatic 

 cells might be considered immortal with the same right 



