156 



The U'chni(|iic of ninkin;^' tissue ciilliircs was supposed 

 to solve this (|U('sli()ii. Slc'i)s towards llu' solulion ot the ipics- 

 tion by this lechni(|ii(' have not been niatlc so far. 



Most investigators are |)i-one to approaeli llie |)r )l)leni of 

 the tissue eullure loo exclusively from a jjaeleriologieal point 

 of view. People use the tei'uis -pure eultui'e of tissue cells 

 in the same meaning as llu\v sj)eak of pure euiliu'es of 

 bacteria or ])aramccia. Peoph* nowadays are most inclined to 

 consider the tissue cells in vitro as cultures of indejjeiide.nl 

 cell individuals. 



Long ago I planned experimetils endeavoui'ing to solve 

 this problem. The fii'st thing wliich had lo be done was to 

 see if it was possible to obtain growth and mullijjlication of 

 one single isolated tissue cell in vitro; in other words lo sec 

 if it was possible to obtain a colony of pure fibroblasts from 

 one single fibroblast, as colonies of bacteria can be ol)lained 

 from one single bacterium. 



In order to get a suspension of living, uninjured tissue 

 cells foi" the experiments, it was necessary lo deveh^p special 

 methods. In the plasma culture, the tissue cells are connected 

 by means of the fil)rin threads in the clot and furthermore 

 the cells are intimately adherent to one another by proto- 

 plasmatic anastomoses. 



A method for isolating single individuals of fibroblasts 

 has been worked out by Rous and Jones ^'^'). The plasma 

 cultui'es of fibroblasts were digested by means of trypsin and 

 a suspension of tissue cells was obtained. This method did 

 not prove to be suitable for the purpose as a large i)crcen- 

 tage was killed and several cells remained connected to one 

 another as cell colonies. 



A new technique was therefore devised. The fibrin 

 thread connections were eliminated by cultivating the fibro- 

 blasts in a fluid dro]) of embryonic tissue juice with Ihe ad- 

 dition of extremely fine cut cotton threads serving as a sii[)- 

 port for the cell growth, and substituting the fibrin mesh- 

 work. 



