Future of Infectious and Malignant Diseases 
in a state of ecological bliss which cannot be upset by wild 
applications of drug therapy and attempts at eradication, then 
control of infectious diseases will improve even in the face of 
possible invasion by extraterrestrial micro-organisms. 
If, on the other hand, folly prevails, man may have looked too 
long into the abyss and, as Nietzsche has warned, the abyss 
may start looking into him. 
MALIGNANT DISEASES 
**, . . because there are times when the fate of a man is not like a 
game of chess dependent on skill, but like a lottery.” 
ILYA EHRENBURG: People and Life, 1891-1921 
It is difficult to predict the future of malignant disease because 
of the simple but important fact that the cause of cancer in man 
is essentially unknown. We may only speculate within the 
scope of our present knowledge on the aetiology of malignancy 
in general and then attempt to indicate the pathways of 
preventive or therapeutic approaches which appear most 
promising for the future. 
It is quite clear that the cause of cancer is multi-factorial, and 
there are two principal ways in which these local clusters of 
fast-growing cells can acquire characteristics which enable them 
to become malignant. 
(1) Acquisition of malignant characteristics from within: the cell 
constituents which are responsible for the specific function of the 
cell are changed by an event that acts upon the cell without 
adding a new constituent. This is illustrated in Fig. 2a, where 
the house at the top represents a normal organism or cell which 
is struck by lightning and then changes its character. Tumours 
caused by chemical carcinogens, physical carcinogens, and 
“spontaneous events”? of unknown origin belong to this group. 
(2) Acquisition of tumour cell characteristics from without: the 
normal cell is invaded by one or more macromolecules which 
alter the cell sufficiently to allow it to acquire the characteristics 
ofa tumour. As Fig. 2b indicates the invader may be likened to 
a ghost which enters a house, inhabits it, and changes its 
character. It is clear that the “invading’”’ macromolecules may 
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