320 THE CAUSE OF HEALING 



xanthin. Hitherto it has been generally supposed that 

 the cell-proliferation of healing is due to some inherent 

 propensity on the part of the cells to divide; but now 

 it is clear, from in-vitro experimentation, that these 

 cells divide when they absorb a definite quantity of a 

 chemical agent, and two of these auxetics are kreatin 

 and xanthin, w r hich are contained in the remains of 

 dead tissues. When a tissue is damaged anywhere, 

 cell-death is occasioned, and the dead cells liquefy. 

 The products of this death have as constituents the 

 extractives kreatin and xanthin, and we know that the 

 neighbouring living cells must absorb the liquefied 

 remains of their dead neighbours, for it has been shown 

 that the diffusion of substances into living cells is a 

 physical process over which the cells themselves can 

 exercise no control. When a tissue is damaged, there- 

 fore, the direct result of that damage will be to make 

 the neighbouring living cells reproduce themselves in 

 response to kreatin and xanthin, and bring about the 

 cell-proliferation of healing. 



Here, then, is the solution of the first part of our 

 problem. We now know the nature of the physiological 

 cause of the cell-proliferation of healing, and we submit 

 that this knowledge reveals a fresh vista in pathology. 



But it must not be supposed that kreatin and 

 xanthin are the only agents contained in the remains 

 of dead tissues which cause cell-reproduction. They 

 are two of the active principles which we have so far 

 succeeded in isolating. It is probable that there are 

 others; in fact, we know that there must be. Supra- 

 renal extract will induce divisions very readily, and the 



