ABSTRACT
The knowledge of present-day medicine has been obtained by studying diseases and the consequent effect of therapeutic methods upon them. The principal aim of medical research is to determine which factor (or factors) causes a particular disease. It may be a chromosomal aberration, a bacterium or a virus, or a certain life-style or life conditions. Ideally, the mechanism by which the causal factor affects the body is mapped so that methods can be developed by which the influence of the causal factor is prevented or lessened, or its effect on the body reduced.
