2 Sir Charles Harington 



compounds that are curative of experimental tuberculosis 

 and leprosy; in this instance there is clear evidence that the 

 drugs, which are quite innocuous to the infecting organisms, 

 confer on the monocytes of the host the power of inhibiting 

 the growth of these organisms, thus exercising their effect by 

 reinforcing the natural defence mechanisms of the host. The 

 discovery of these drugs again was a totally unexpected out- 

 come of the line of research that was being pursued. 



All this means that the life of a chemist working in chemo- 

 therapy is apt to consist of long periods of unexciting work, 

 punctuated if he is fortunate by occasional successes; even 

 these successes however, whilst practically satisfying, may 

 well be intellectually disappointing, since they will very likely 

 bear little or no relation to the thought that he has put into 

 his research. 



By emphasizing as I have done the uncertainties and lack 

 of fundamental knowledge that bedevil chemotherapy I must 

 appear to have painted a very gloomy picture of the subject. 

 If this is so, it is certainly not because I wish to say anything 

 in disparagement of its importance. On the contrary, my 

 object is to analyse the difficulties that we face, and which are 

 particularly discouraging to chemists, in the attempt to see 

 how they may be overcome. 



It might be argued that in spite of all that I have said the 

 situation is not unsatisfactory. New and effective chemothera- 

 peutic agents continue to be discovered and the range of 

 diseases brought under control increases. But so long as we 

 cannot explain the reason for our successes we must remain 

 scientifically dissatisfied, and there is one biological pheno- 

 menon, namely drug resistance, which makes the situation 

 much less favourable than it appears even from a strictly 

 utilitarian point of view. We can hardly be easy about a state 

 of affairs in which it is reported that in many hospitals over 

 50 per cent of the strains of staphylococci causing infections 

 have become resistant to penicillin, even though we now have 

 other antibiotics with which they can be controlled; nor is 

 the encouraging emptying of our tuberculosis sanatoria cause 



