A Ten-Year-Old Strain of Fibroblasts. 315 



Salt Concentrations which Limit Bacterial Growth 

 (Incubation Period — Three Days). 



Salt. 



Molar Cone 

 No Growth 



Growth. 



Salt. 



Molar Cone. 

 No Growth. 



Growth. 



HgCh. 

 CdCl 2 . 

 CeCl 2 . 



AlCla. 

 PbCl 2 . 

 C0CI2. 



FeCU. 

 FeCl 2 . 

 CuCl 2 . 

 ZnCl 2 . 



.00001 



.0001 



.0001 



.0005 



.001 



.000005 



.00005 



.00005 



.0001 



.0005 



T1C1..., 

 NiCh. . . 

 SnCU. . . 



TiCl 3 . . . 



MnCl 2 . . 

 BaCla. . . 

 CaCh. . . 

 MgCl 2 . . 

 SrCh. . . 



LiCl. ... 

 NH4CI . . 

 NaCl . . . 

 KC1 



.005 



.01 



.05 

 •25 

 •5 

 •5 

 1.0 



1.0 



1.0 

 2.0 

 2.0 



.001 



• 005 



.025 



• I 

 •25 

 •25 

 •25 



•5 

 •75 



1.0 



1.0 



23 salts studied we found a concentration which caused more rapid 

 growth than occurred in the plain pepton solution, the stimulating 

 salts including not only K, Na, NH 3 , Li, Sr, Mg, Ca and Ba, but 

 such toxic salts as those of Ti, Sn, Ni, Pb, Ce and Hg. The stim- 

 ulating concentrations with the latter salts were of course exceed- 

 ingly low (.00005 molar in the case of Pb, .00001 molar in the 

 case of Ce, .000005 niolar in the case of Hg) while with K and Na 

 .25 molar concentrations were stimulating. It is very possible 

 that stimulating concentrations of the other eight salts could have 

 been established by more exhaustive study. 



143 (1890) 

 A ten-year-old strain of fibroblasts. 



By ALBERT H. EBELING (by invitation). 



[From the Laboratories of The Rockefeller Institute for Medical Re- 

 search, New York City.] 



A strain of fibroblasts, obtained from the heart of a chick 

 embryo on January 17, 19 12, has completed the tenth year of its 

 life in vitro. On April 19, 1922, our incubators contained about 

 60 cultures which represented the 1906th generation of the con- 

 nective tissue cells. Their growth is as rapid as during the past 



