Histological Analysis of Radiation Effects 



165 



quantitatively by classifying and counting all the cells in care- 

 fully selected young areas. The cell counts are plotted as per- 

 centages against time after beginning treatment, and thus a chart 

 is obtained of the response of a given tumor to a given type of 

 treatment. ^^ 



C D 



FIG. 1. Diagrammatic Representation of the Four Cell Categories Found in 



Most Epithelial Tumors 



viable cells. 



A: Resting cell | 

 B: Mitotic cell | 

 C: Differentiating cell 1 

 D: Degenerating cell \ 

 T: Symbolizes the tumor bed, i.e., the vessels, stroma, and cells surrounding the 

 tumor strands. 



lonviable cells. 



Changes in the cell population of young tumor foci are the 

 result of direct and of indirect effects of radiation. The direct 

 effects concern mainly resting and dividing cells. After a tran- 

 sient mitotic inhibition, resting cells may break down on attempt- 

 ing division, they may differentiate according to their type and 



