associated with smoking — the average smoker loses about 

 eight years of life through indulgence as compared with the 

 non-smoker. Other agents, such as motor-vehicle exhaust, 

 are probably also involved in lung cancer. The detection 

 and elimination of carcinogenic substances should not be 

 beyond our capabilities — the virtual absence of cancer in 

 non-industrialized communities (e.g. feudal Japan) shows 

 that cancers are diseases of civilization. Similarly, coronary 

 thrombosis appears to be definitely aggravated by stress 

 present in life in large communities: there is almost cer- 

 tainly some clot-causing substance released into the blood 

 during the disease, and this has yet to be identified. But 

 it would be possible to considerably reduce living stress 

 by limiting the sizes of urban populations to perhaps 50,000 

 or so, with adequate space allowed between buildings for 

 gardens. According to recent work on the arthritic dis- 

 eases (notably by Burnet in Australia), the basic reason 

 for these is a breakdown of the normal immunity mech- 

 anism of the body. The white blood cells, instead of at- 

 tacking only foreign bacteria, attack body cells — apparently 

 because the cell surfaces receive some chemical substance 

 making them "foreign" to the white cells. Blood from 

 arthritics has been found to contain pain-causing sub- 

 stances, and the tendency to these diseases is inherited. 

 Their cure seems to lie in chemotherapy involving the neu- 

 tralization of substances generated in error by the body 

 itself: the further study of this problem is also likely to 

 lead towards successful methods of tissue transplantation, 

 since this is limited at present by the immune reaction. 

 Mental and nervous diseases are not today regarded as 

 impossible of treatment with success. Parkinson's disease 

 — a serious neuro-muscular disorder — is now treatable by 



