The illusion that man can become resistant to them and that their presence in the organism becomes harmless is equivalent to thinking that one can become resistant to a bullet which crosses the heart. A concept as fundamental as it has always been known is that of prevention. 'Prevention is better than cure' and 'better be safe than sorry' are part of popular wisdom. Prevention in strict terms is that which prevents the occurrence of a harmful situation. The cash turnover which the disease ensures is enormous, and those involved in the business do not see favourably something which can in any way slow down their activity. A sentence perhaps erroneously attributed to the Latin historian Sallust reads 'faber est suae quisque fortunae', which, translated, means that 'everyone is the architect' of their fate. The system had the advantage of being easy to use, scarcely invasive and repeatable without contraindications.