1 IS 



scrvt'd This rcsiilk'd from llu- sii|)|)rc'.ssi()n in the medium 

 ol" the iiclivc subslancc-s contaiiU'd in cinhryonic juice. If 

 the growlli was compared of Iwo such fra<^menls in i)hismn 

 ah)ne. the one cultivated in jjlasma from a young cliicken 

 and the oliui' in phisma from an old chicken, it was ob- 

 served thai llu- gi'owlli and pi'oliferation slopped entirely 

 and Ihe death occuri-ed much sooner of the fragnuiil eul- 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 n 18 19 



Passage 



Fig. 31. 

 Comparison of the rate of growtti of fibroblasts in the plasma of a 6 week 

 old chicken and a 3 year old hen. The sudden drop in the rate of growth 

 of the culture in the 6 week plasma was accidental. The small amount of 

 growth obtained at the 5th passage was due to the transfer of the tissues 



to a fresh medium after 24 hours instead of 48 hours. 



From Carrel and Ebeling: Age and multiplication of fibroblasts. Journ. 



of Exp. Med., 1921, XXXIV, 602. 



tivatcd in the jjlasma of Ihe old chicken, Ihan of the 

 fragment in the plasma of the young annual (Fig. 31:. In 

 many cases the fragment cultivated in plasma from a 3 

 months old chicken died after 11 i)assages, while the frag- 

 ment cultivated in plasma of a 3 years old chicken died 

 after 7 passages. — In another experiment a fragment cul- 

 tivated in ])lasma of a 3 months old chicken died after 16 

 |)assages. while a fragment cultivated in plasma from a 9 

 years old chicken died after 3 passages. The duralion of 

 life of the cultures in the plasma of the old animal was 



