A close relationship is found to exist between the external world and the internal system of man. 'Siddhas' maintain that the structure of the human body is a miniature world in itself. Body temperature is maintained by the consumption of water & food and breathing. Life force is given by the element ether. The fine shape of the body is given by earth through bones, tissues, muscles, skin, hair etc. Water is represented by blood, secretions of the glands, vital fluid etc. Fire gives motion, vigour and vitality to the body while helping with digestion, circulation and simulation besides respiration and the nervous system. Above all, ether also determines the characteristic of man's mental and spiritual spheres.