CARCINOGENESIS 



immature ones are at the left. The arrows within the cells 

 represent the concepts of dependence and of competition. The 

 arrows between the cells represent many stages and cells in 

 transition. 



In this diagram, cell A represents the toti-potential fer- 

 tilized ovum. Immediately following fertilization, the mech- 

 anisms for reduplication and for special functions become 

 activated, and this is indicated by the arrows from the cell food 

 to the functions. Both mechanisms have increased in size. 



FERTILIZED 

 OVUM 



D -MECHANISM FOR CELLULAR REDUPLICATION 

 O -MECHANISM FOR SPECIAL FUNCTIONS 

 !S^-C ELL- FOOD 



Figure 2. 



The first special system to become functional is the one repre- 

 sented by the circle labeled F. As the products of its reactions 

 become quantitatively significant, some of these metabolites are 

 used to catalyze and initiate the next sequence of reactions, as 

 depicted by the arrows labeled 7 and 2. The ultimate charac- 

 teristics of the differentiated cells are predetermined by the 

 particular system of reactions which is nurtured in the first few 

 generations of cells. If, in a given cell, the H function is the 

 first one to be stimulated, as indicated by arrow 7, the subsequent 

 course of events in descendants of this cell will follow the upper 



683 



