300 ON GROWTH AND OVERGROWTH 



extent that even when these cells take on cancerous proliferation, 

 and their descendants penetrate into the deeper tissues away 

 from the conditions which affected their progenitors they still 

 retain well-marked evidences of their acquired characters, and 

 they produce, not a columnar-celled, but a squamous epithelial 

 cancer. I fail to see how such cases can possibly be explained 

 unless we accept this principle of what we may term the inheritance 

 of acquired characters by the individual cells of the organism. 

 Pathologists in general freely accept this as the explanation of 

 the occurrence of primary squamous-celled epitheliomata in the 

 uterus and the gall-bladder. Apparently, so far as I have seen, 

 the significance of these tumours, as indicating an important 

 property of the cancer cell, has not been hitherto realized. 



It is nowadays almost needless to point out that to explain 

 immunity we are forced to admit a similar well-marked inheritance 

 of acquired characters by various cells of the organism. And so 

 I urge that in connexion with cancers and with tumours in 

 general these facts may be applied to the elucidation of tumour 

 growth. When cells have for long been subjected to those 

 modified conditions under which they multiply actively and 

 rapidly, then, provided the stimulus or cause of this state acts 

 over a sufficiently long time, the cells take on the "habit of 

 growth." They continue to proliferate in a purposeless manner 

 long after the factors which started the process have ceased to 

 act. Their growth and proliferation is no longer inhibited by 

 the performance of specific functional activities ; it becomes 

 wholly independent of the needs of the organism, and the more 

 extreme this independence of growth and the more the cells 

 lose the signs of their primordial function, the more malignant 

 the growth. Provided that there is adequate nutrition it matters 

 little where these cells find themselves ; they grow for them- 

 selves. Assimilation and mitosis are the two cell functions 

 retained and impressed upon them. They have cut adrift from 

 the old relationships and tensions which determined the primor- 

 dial activity of the parent cells. They have reverted from the. 

 specialized structure impressed upon them by that primordial 

 activity, as by heredity, until but a trace of that structure is left. 

 They assume the form common to cells undergoing mitosis, a 

 form we term embryonic, and that because this is the form 

 characterising actively proliferating cells in the embryo. This 



