158 



1 1 hab not hi'on possibk" U) ohscrve Ihe division and proli- 

 Icralion ol" an isolated cell, lliuugh hundreds of cells have 

 been sludietl with this object in \ie\v. (irowlh by prolileralion 

 has been observed only when a iiuniber of cells were in 

 close contact in a culture. These observations lead to the 

 question as to whether intercellular contact is essential to the 

 cells for their growth and mulliplication. and what signifi- 

 cance the contact has in growth and inullijjlieation of Ihe 

 cells. 



It would l)e interesting to discover, as a supplenienlary 

 experiment to the above, how excised pieces of different 

 location within the tissue culture, behave in res])ect to their 

 ability to multiply when transplanted to a fresh medium. 

 For this reason experiments were undertaken to demonstrale 

 how the different parts of a culture grew and multij)lied. 



Before discussing the problem, it will be well to desci"ibe 

 the other methods by which the attempt was made to de- 

 termine whether isolated cells are able to multi]ily. The 

 results of the experiments just mentioned may have been 

 due to a technical error. Anyway it has to be taken in con- 

 sideration that it is not impossible thai the manipulations 

 may injure the cells, despite signs which seem to indicate 

 perfect vitality. 



^^ hen ordinary cultures were cut in two halves and trans- 

 ferred to a fresh medium, it was frequently noled Ihal llie 

 cells began to grow out first from the centre of the cut 

 edge of the culture, that is to say from the i)oinl at which 

 the cells were most crowded, and only a little later on from 

 the periphery. This has also been noted by Carrel*, l-rtmi 

 the observation it might be deduced that the central i)ail of 

 the culture has a greater ability to jiroliferatc than the 

 peripherial part, where the cells are more scattered. Some 

 experiments were undertaken to see how minute Ihe frag- 

 ments of a piece of tissue from a culture could be and 

 retain the ability to multiply when transplanted to a la- 



*) Carrel, A., Personal cominunication. 



