ABNORMAL GROWTH. TUMOURS 273 



multiplying epithelial cells ; an attempt at repair, or to 

 form internal scar-tissue. But, on the other hand, not 

 infrequently the stroma acts as widely spreading malignant 

 tissue, and even to the extent of almost crushing out the 

 malignant epithelial cells. 



The foregoing suggestions are admittedly superficial, 

 and deal with the significance of tumour-formation rather 

 than with the actual exciting agency, or agencies at work. 

 Our own belief may, however, be repeated, that tumour- 

 formation is abnormal growth, a morbid process which may 

 be excited by several diverse agencies ; and that these 

 probably all act by causing an initial breach of cellular 

 continuity whereby cell-arrest is broken. There can be no 

 normal growth without Arrest and Control in ceflularly- 

 continuous organisms ; no cell species or animal species 

 could be maintained but for these factors, and they are the 

 handmaidens of Continuity. 



IS 



