Just as the influence of the Mental States over the Physical Conditions has been shown to operate by means of the Sympathetic Nervous System (controlled of course by the Subconscious Mind), so the influence of Physical Conditions over Mental States may be explained in physiological terms. In order to understand the reaction of the Body upon the Mind, we have but to recall the fact that the Subconscious Mind is the builder and preserver of the very brain-cells which are used by the Conscious Mind in manifesting thought. And also, that the entire Nervous System, both Cerebro-Spinal as well as Sympathetic, is really under the control of the Subconscious Mind so far as growth and nourishment is concerned. The very brain and nerve-centers in and through which is manifested thought, feeling, emotion, and will, are nourished by the Sympathetic System, and are hurt by anything affecting the latter. The Sympathetic System joins all parts of the organism so closely together that trouble in one part is reflected in other parts. Just as depressing thoughts will cause the organs to function improperly, so will the improper functioning of an organ tend to produce depressing thoughts. Herbert A. Parkyn, M. D., well states the action and reaction of Mind and Body, as follows: "A tree is much like a human being. Give it plenty of fresh air, water and a rich soil, and it will flourish. In the same degree in which it is deprived of these does it wilt, and _the first part of the tree to wilt when the nutrition becomes imperfect is the top_. This is owing to the force of gravity; the blood of the tree, the sap, having to overcome this force of nature when nourishing the highest leaves. The blood of man is also affected by this same force, and the moment a man's circulation begins to run down, owing to stinted nutrition, we find that the first symptoms of trouble appear in the head.... The brain failing to receive its accustomed amount of blood, such troubles as impaired memory, inability to concentrate the attention, sleeplessness, nervousness, irritableness, the blues and slight headaches develop; and the impulses sent all over the body becoming feebler, the various organs do not perform their functions as satisfactorily as usual. The impulses to the stomach and bowels becoming weaker and weaker, dyspepsia, or constipation, or both, soon follow. As soon as these, the main organs of nutrition, are out of order, nutrition fails rapidly and more 'head symptoms' develop. Every impulse of the muscular system leaves the brain, and the strength of these impulses depends upon the nutrition to the brain centers controlling the various groups. As the nutrition to these centers declines, the whole muscular system, including the muscles of the bowels, becomes weaker and the patient complains that he exhausts easily. The impulses for elimination becoming weaker, waste products remain in the circulation, and any of the evils, which naturally follow