TISSUE-CULTURE IN VITRO 



119 



slow and that they could be maintained for several days 

 without transplanting. He cut out a small square on a relatively 

 large culture the proliferating activity of which was very 

 slow. The prohferation immediately became very active 

 around the wound, which healed rapidly. This proliferation 



5 W 



20 30 



UO 50 



FIG. 26. INDEX OF CICATRIZATION AS A FUNCTION OF 

 THE AGE OF THE PATIENT 



ceased as soon as cicatrization was complete. In short, there 

 is an almost absolute identity with the biological phenomenon 

 of cicatrization in vivo^ and we are faced with the same 

 problems. How is this proliferation started and how is it 

 stopped? This is a most important point, for it is one of the 



