 We now turn to the psycho-physiological meaning of the breathing exercise. Ordinarily, we breathe sixteen to seventeen times per minute, which we do unconsciously or involuntarily. This is because under ordinary circumstances, breathing is controlled by the autonomic nervous system. Neurophysiologically, the center where breathing is controlled is found in the hypothalamus, in the mid-brain. The autonomic nervous system is so-called because it functions independently of our will. Zen breathing is a shift from unconscious, involuntary breathing to conscious, voluntary breathing. This means that Zen meditation is a way of regulating the unconscious-autonomic order of our being. Psychologically, counting the breath trains the unconscious mind and neurophysiologically, it trains the involuntary activity of the nerves that control the function of the various visceral organs. Here we find a reason why Zen recommends abdominal breathing. Nerves are bundled in the upper part of the abdominal cavity, and the abdominal breathing exercise stimulates this bundle. As it does so, parasympathetic nerves still the mind.