m\ 



the crlls (lisinlcj^ralin<» williiii the I'rn^mciil. H ii i-rows •'•") •'*') 

 ^'^^i '•'; has rcccnlly shown Hy cstahlisliiiiL; an acli\'c currenl 

 ill tlu' haiif^iiij* drop culture of Fixed (issue ci'lls. I)y wash- 

 ing I'onlinuousiy (lie phisnia eiol wilii a sliH'am ol' sei'um. 

 Iheso slinudalin«« substances Iroin the (lisinlcgi'atiiij* cells 

 arc washed away, thi- degencralion of llie central portion 

 ol" tlie fragment is delayed as also is the migration and 

 multi|)lication of tlie cells. On the contraiy Iym|)h()i(l cells 

 from the spleen under the same conditions migrate entirely 

 out as lymplioid cells and the whole Fragment oF splei-n 

 disappears. In the simple lianging droj) culture, such a 

 complete dissipalioji of tlie cells never occurs from the 

 spleen Fragments. Tlie migration of these cells is increased 

 by the flowing serum The stimulating substances accord- 

 ing to Burrows are properly speaking the same as the 

 growlh-])romoting substances in the embryonic tissue juice. 

 Besides these stimulating substances Found in the em- 

 bryonic juice, in disintegrating tissue cells, things seem to 

 indicate, that there is something in the mass of tissue, 

 which controls the growth and proliferation of the cell 

 individuals. It is ol)served here, that the activating substances 

 in the embryonic tissue juice are not the only factor neces- 

 sary for the growth and multiplication of the isolated tissue 

 cell. This stimulus which initiates the cell (li\ision. is prob- 

 ably not of environmental nature, but is produced within 

 the cytoplasm of the cells and Iransjiorted within the cyto- 

 plasm directly from cell to cell. If this is true, and if the 

 proliferation of the cell is controlled by the i)ulk of tissue, 

 we would expect to find a Kind of rhythmic setting in 

 of cell divisions in a i)iece of growing tissue in vitro. 



^Vhat I am trying to discovei- in this study of tissue cul- 

 ture, is whether w c ai'e dealing with more or less indc- 

 pendant cells or with a piece of tissue obeying the laws 

 of regeneration, i. e. colonies oF cells, in direct dependance 

 u|)on one anothei". as is the case in organisms. 



