*Summary.*—The nervous system is able to control, coördinate, and adjust the different organs of the body through its intimate connection with all parts and through a stimulus (the nervous impulse) which it supplies and transmits. Nervous impulses, excited by external stimuli, follow definite paths and cause activity in the different parts of the body. All such pathways are through the central nervous system. In reflex action the impulses are mainly through the spinal cord, but to some extent through the bulb, pons, and midbrain. In voluntary action they pass through the cerebrum—a condition that leads to important modifications in the results. The cerebrum, in addition to controlling the voluntary movements, is able to establish the necessary conditions for secondary reflex actions, such as walking, writing, etc. Although certain of the divisions of the nervous system exercise special functions, all parts of it are closely related. Exercises.—1. Give the function of each of the parts of a neuron. 2. State the purpose of the nervous impulse. 3. Show that the exciting cause of bodily action is outside of the nervous system and, to a large extent, outside of the body. 4. Describe the arrangement that enables stimuli outside of the body to cause action within the body. 5. Describe a reflex action and show how it is brought about. 6. Distinguish between afferent, efferent, and intermediate neurons. 7. Draw diagrams showing the impulse pathways in voluntary and in reflex action. 8. What purposes are served by the sympathetic neurons? 9. Describe the method of control of the circulatory and digestive processes. How do reflex actions protect the body? 10. Compare voluntary and reflex action. In what sense are all the activities of the body reflex? 11. In what sense is walking voluntary? In what sense is it reflex? 12. How does secondary reflex action lessen the work of the nervous system? 13. State the special functions of the nerves, ganglia, spinal cord, bulb, cerebellum, and cerebrum. 14. State the importance of the formation of correct habits. [Fig. 143] Fig. 143—Nerve board for demonstrating nerve pathways. PRACTICAL WORK *To demonstrate Nerve Pathways.*—A smooth board, 2x6 ft., is painted black, and upon this is drawn in white a life-size outline of the body. Pieces of cord of different colors and lengths are knotted to represent mon-axonic and di-axonic neurons. These are then pinned or tacked to the board in such a manner as to represent the connections in the different kinds of nerve pathways. Fig. 143 shows such a board with connections for a reflex action and a voluntary action of the same muscle.