CONDITIONS OF CELLULAR IMMORTALITY 63 



strain of connective tissue obtained from a piece of chick 

 heart is still alive, and will be nine years old the seven- 

 teenth of January, 1921." Figure 17 is a photograph 

 showing the present condition of this culture. It should 

 be understood that this long continued culture has gone 

 on at body temperature in an incubator, and not by keep- 

 ing the culture at a low temperature and merely slowing 

 down, the vital processes. 



This is indeed a remarkable result. It completes the 

 demonstration of the potential immortality of somatic 

 cells, when removed from the body to conditions which 

 permit of their continued existence. Somatic cells have 

 lived and are still living outside the body for a far longer 

 time than the normal duration of life of the species from 

 which they came. I thinJt the present extent of Carrel's 

 cultures in time fully disposes of Harrison's criticism 

 to the effect that we are "not justified in referring to 

 the cells as potentially immortal or even in speaking 

 of the prolongation of life by artificial means, at least 

 not until we are able to keep the cellular elements alive 

 in cultures for a period exceeding the duration of life 

 of the organism from which they are taken. There is 

 at present no reason to suppose this cannot be* done, but 

 it simply has not been dope as yet." I have had many 

 years ' experience with the domestic fowl, and have par- 

 ticularly studied its normal duration of life, and discus- 

 sed the matter with competent observers of poultry. I 

 am quite sure that for most breeds of domestic poultry 

 the normal average expectation of life at hirth is not 

 substantially more than two years. For the longest 

 lived races we know this normal average expectation 

 of life cannot be over four years. I have never been able 

 to keep a Barred Plymouth Rock alive more than seven 



