CHAPTER XV 



THE PROOF THAT THE REMAINS OF DEAD TISSUES AND 

 GLOBIN CONTAIN THE CAUSES OF THE CELL- 

 PROLIFERATION OF HEALING AND OTHER CELL- 

 REPRODUCTION- EXPERIMENTATION in VIVO CON- 

 FIRMS in-vitro OBSERVATIONS THE CAUSE OF 



BENIGN TUMOURS 



THE foregoing experiments show that some of the 

 causes of human cell-division are now known. On 

 the stage of the microscope white corpuscles can be 

 made to undergo the stages of cell-division in direct 

 response to certain chemical agents, two of which have 

 been isolated, and which can be employed in crystalline 

 form to induce cell-division. What is far more im- 

 portant, however, is the source whence these chemi- 

 cal substances are derived. They are contained in the 

 soluble remains of dead tissues. Another source of the 

 cause of cell-division is in globin, which is derived 

 from the decomposition of haemoglobin. 



It should be remembered that so far the experimen- 

 tation has been confined to testing the action of the 

 active substances and the sources of them on individual 



333 



