But if none of the senses has ever developed, my brain can receive no impression whatever; it cannot have even the stimulus of memory. Hence conscious mind cannot be, except as some sense-channel or channels have been opened to carry thought material to the brain. So far as we know today, in this world, mind is absolutely dependent upon the sense organs and the brain--upon matter--for existence. THE SYMPATHETIC NERVOUS SYSTEM Associated with the central nervous system by connecting nerves--but located outside of it in various parts of the body--are groups of nerve-cells (gray matter) and their fibers, forming what we call the _sympathetic nervous system_--the direct connecting link between mind and body. The _central nervous system_ is the director of all conscious action of the body; the _sympathetic_ orders all unconscious action. The beating of the heart, the contraction of the blood-vessels, hence the flowing of the blood, the processes of digestion, the functioning of the glands, are all directed by the sympathetic. In other words, the _central nervous system_ normally controls the movements of the voluntary muscles; the _sympathetic_ controls those of the involuntary muscles. The quick blush, the sudden paling of the cheeks, the start of fear, the dilated pupils of fright are the direct result of the action of involuntary muscles under control of the sympathetic system. The stimulus is received by the central nervous system; the fibers connecting the central and the sympathetic systems carry the message quickly to the latter, which immediately respond by ordering contraction or expansion of involuntary muscles. So tears flow, we breathe freely again or we quake and tremble, our pupils widen or contract, the heart beats suffocatingly, or seems almost to stop. The _sympathetic system_, as the name implies, is influenced by suggestions from the emotions rather than from the intellect. We might say that it is controlled by the "feeling mind" rather than the thinking mind, for intellect cannot influence it in the least. The wise nurse, who knows something of the laws of the mind, soon realizes that the _sympathetic nervous system_, rather than physical disability, causes many indigestions, headaches, diarrheas, dry mouths, chills; is responsible for much nausea, much "exhaustion," etc. When she has had wider experience she finds that almost any known physical disorder can be unconsciously imitated by the suggestible patient, whose sympathetic nervous system causes physical reactions to respond to the feelings of a sick mind. Let the nurse remember, however, that is it not for her to decide whether the disorders from which her patient suffers are of physical or nervous origin. It is for her, on the other hand, to study her patient's mentality and reactions, and to become expert in reporting symptoms of nervous as well as of physical significance. CHAPTER IV RELATION OF MIND AND BODY