IT ELUCIDATES CELL-DIVISION 7 



body have been isolated in crystalline form : they are 

 the extractives, kreatin and xanthin, and individual 

 cells divide in response to them according to the 

 amount of each substance absorbed by the cell. 



It will be shown that cell-proliferation depends upon 

 cell-death, and this affords an explanation of the cause 

 and origin of benign tumours. "Development" is a 

 basis of physiology; and since the multiplication of 

 human cells is due to chemical agents, as is shown by 

 this method, one cannot but suppose that the facts 

 learnt may lead to the explanation of points connected 

 with the growth of the embryo. 



One of the foundations of pathology is the phenome- 

 non of "healing," which is caused primarily by the 

 proliferation of certain cells. The causes of this 

 proliferation have been ascertained for the first time 

 by this method, and the ultimate chapters of this 

 book will describe proofs that these causes are now 

 known. If the finger is cut, or if disease gains a 

 footing in any part of the body, an attempt is made 

 by the tissue-cells to proliferate and to heal the injury; 

 but up to now no one has known why this proliferation 

 took place or how it was caused. This mystery is now 

 elucidated: The knowledge that cell-proliferation in 

 the body is due to chemical exciters, of reproduction 

 (auxetics) is, we think, the beginning of an innovation 

 which must lead to developments of practical value. 



The effect of any given substance, so long as it is 

 soluble, can be tested on many individual human cells 

 and the results watched. I fear that we, personally, 

 have only been able so far to try the effects of auxetics, 



