CONCLUSION 



merits to disprove it, and replace it with something better. 

 Nevertheless (whatever the results of further research) 

 I believe that the general concept of the importance of the 

 population dynamics of mesenchymal cells must be accepted. 

 I hope, too, that I have been able to show how the type of 

 somatic mutation that must be postulated to account for the 

 physiological aspects of immunity grades smoothly into those 

 concerned with the appearance of auto-immune disease and 

 some of the proliferative diseases of the mesenchymal cell 

 system. 



It is only a minor step then to bring the picture into rela- 

 tion with the somatic mutations that are basic to our under- 

 standing of neoplastic disease. I know that in stressing 

 somatic mutation and clonal selection in cancer I am going 

 counter to the general trend of thought amongst experi- 

 mentalists in the field. But I have a basic scepticism of the 

 laboratory model when it fails to conform to clinical ex- 

 perience. As physicians, surgeons, and radiologists, all our 

 practical thinking about cancer is based implicitly on an 

 acceptance of somatic mutation as the origin of the process. 



It is probably fair to say that in many respects, these 

 lectures are superficial in their approach, making no attempt 

 to face the real problems of immunity and cancer which lie 

 in the nature of mutation and the way genetic changes are 

 translated into their phenotypic expression. The approach 

 that I have used has led to a rather simple picture in terms 

 which are not those of chemistry and physics, but of biology. 

 And it is an article of my scientific faith that there is intrinsic 

 virtue in simplicity, if it aids understanding without doing 

 violence to the facts of observation and experiment. 



REFERENCES 



Abercrombie, M., Heaysman, J, E. M. & Karthauser, H. M. (1957). 



Exp. Cell Res. 13, 276. 

 Armitage, p. & Doll, R. (1954). Brit. J. Cancer, 8, i. 

 Armitage, p. & Doll, R. (1957). Brit. J. Cancer, 11, 161. 



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