187 



\\c ma}' summarize Ihc results of the experiments des- 

 cribed in this chapter in tlie following way: 



It is endeavoured to prove, that the tissue cells in the 

 in vitro culture, are not to be compared wilh the bacterial 

 culture. The tissue cells are not independent individuals, 

 growing as such. — Each cell is an integral part of the 

 entire mass of tissue. How small bits of tissue or how many 

 cell individuals that are necessar}' for a growth and a 

 multiplication has not yet been determined. One cell is, at 

 any rate, not able to retain and regenerate a tissue in vitro. 



It was also found, that a fragment of tissue, containing 

 a few and scattered cell individuals, is not able to regenerate 

 in vitro. 



The anastomosis or protoplasmic connection between 

 the tissue cells, plays a vital role for the continuation of the 

 life of the cells. This is rather well known from certain 

 tissues within the organism nnd now also found to be the 

 case in the cells in vitro. 



The ex]Kn'iments seem furthermore to indicate, that 

 periodical stimulating impulses of some kind, are ^iroduced 

 within the cells of the tissue and transported from cell to 

 cell throughout the intercellul.-ir bridges causing the division 

 of a large number of cells. Which cells these are, where these 

 stimuli originate and of what nature these stimuli are, we 

 do not yet know. It is conceivable to consider the cell 

 division as the ultimate result of a general progressive 

 development of a chain of tissue cells, representing various 

 phases of the supposed stimulus or substance, which causes 

 the cell division. 



In cultures of fibroblasts, belonging to an old strain, it 

 was found, that the cell division set in rhythmically, so that 

 at one time a large number of cells divided, and at other 

 times there were very few or none. This seems to indicate., 

 that in a piece of tissue or in a portion of growing fibro- 

 blasts in a culture, several or many cells are influenced by 

 the same principle or stimulus. 



