2 30 ON GROWTH AND OVERGROWTH 



se £an be shown that a succession of forms can be made out, 

 hosing imperceptibly from conditions within the cells which 

 bet'iot possibly represent the stages in the life-history of some 

 s0 ^cellular parasite to others, which the parasitologists regard 

 tha^dicating stages in the life-history of one or other microbic 



;- — the histological evidence that cancer is due to parasites 

 t ur jmes, to say the least, singularly frail. 



I shall not, however, now take up these various arguments 

 and endeavour to weigh their value ; rather I would attempt 

 to approach the matter from a different point of view, would 

 seek to determine the relationship of malignant to other forms 

 of growth in the organism, and from a study of this relationship 

 would endeavour to determine whether we are justified in holding 

 this advanced view in regard to the parasitic origin of malignant 

 growths. 



Tumoues Benign and Malignant 



I would in the first place ask : Can we draw a fine between 

 tumours which are essentially benign and tumours essentially 

 malignant ? The answer to this question is an unhesitating 

 " No." If we understand by malignancy the property of local 

 invasion of surrounding tissues, together with that of the forma- 

 tion of new growths of like nature in distant organs — the other 

 associated properties being subsidiary to these two — then all 

 growths which we classify as true tumours may take on malignant 

 properties. Even so highly differentiated and (ordinarily) 

 benign a neoplasm as the chondroma 1 may exhibit metastases. 

 It is true that very often the assumption of malignant properties 

 indicates and follows a change in the morphological characters 

 of the tumour or parts of the same. Thus the lipoma, 2 as such, 

 is not malignant, but portions of a lipoma may take on a more 

 embryonic character, and the rapidly growing simpler cell forms 

 may infiltrate surrounding tissues and may lead to metastases. 

 Nevertheless, we have no doubt that this sarcomatous tissue is 

 the direct outcome of the cells forming the primary lipoma. 

 There is no question that here the lipoma has taken on malignant 

 characters. It can scarcely be questioned, also, that malignancy 

 is not a primary but a superadded property of the tumour, that 



1 [A tumour composed of cartilaginous tissue.] 

 8 [A tumour composed of fat-cells. 



