ABSTRACT
For ‘bibliographical’ convenience, in the following chapter the human organism has been divided along the same lines as in the scientific fields devoted to it. Studies on ageing reveal significant variabilities between individuals, which lead researchers to narrow their field of endeavour and, thus, specialise in their research work. It is well to recall that, no matter how convenient this may be, such a functional division is entirely artificial, for humans constitute a whole in which each organ is always needed. Recognising the vital connections between the nervous, hormonal and metabolic systems, any local alteration of these functions, whether mental or organic, unavoidably has an effect on the functioning of the organism as a whole.
