ARTICLES 



611 



necessary to produce a definite change in the rate of growth 

 of the tumour cells are known. 



It is a pleasure to record my thanks to Prof. A. W. 

 Porter, F.R.S., for his unfailing kindness in criticism and help 

 in the mathematical treatment appended herewith. 



APPENDIX 



li N = the number of cells in the growing stage at any time t 

 n = the number of cells in the dividing stage at any time t 



Dividing Stage 



A 



Growing 

 Stage 



