302 ON GROWTH AND OVERGROWTH 



were necessary to counteract opposing forces are freed and 

 become thus capable of diversion from their purpose, or, again, 

 where stimulation from without results in increased assimilation 

 and storage of nuclear and cell material which now from any 

 condition cannot be utilized in the performance of specific 

 function. 



6. In either case the cells will continue to proliferate so long 

 as the primary modification of physical relationships or the 

 primary stimulus continues to act, so long as there is adequate 

 nutriment, and so long as the tensions exerted upon the cells 

 do not become excessive. 



7. Provided that these conditions are observed, the greater 

 the amount of cell proliferation, the greater is the tendency for 

 certain at least of the newly formed cells to be projected from 

 the relations proper to cells of the tissue giving them origin, the 

 less will be the opportunity for such cells to carry on their 

 primordial function, and the greater the liability to proliferation. 



8. The longer the cells are diverted from their proper extrinsic 

 functions to proliferative activity, the greater the momentum 

 acquired by them to continue performing the proliferative act 

 until the functional activities become largely suspended and the 

 " habit of growth " is set up. 



9. When this habit of growth is inaugurated the cells can 

 continue to grow and multiply in the complete absence of those 

 conditions which initiated their proliferation in the first place, 

 and we obtain that purposeless functionless cell growth char- 

 acteristic of the true tumour. 



10. According to the stage of cell development in which this 

 habit becomes impressed upon the cell, so do we have the various 

 grades of benign and malignant tumour formation. 



APPLICATION OF THEORY 



How now does this theory apply itself to the possible microbic 

 origin of at least certain forms of malignant and other tumours ? 

 It applies itself thus : According to this theory, microbes and 

 their products may be one of the causes originating localized 

 cell proliferation in the first place, provided that (1) they bring 

 about stimulation rather than irritation, or irritation of so mild 

 a type that the cells are stimulated to an increased metabolism 



