*Habit versus Self-control.*—The power of self-control, already emphasized for its importance in the economical expenditure of the nervous energy, is of vital importance in its relation to the habits of the body. Self-control is the chief safeguard against the formation of bad habits and is the only means of redemption from such habits after they have once been formed. The persistent cultivation of the power to control the appetites and the passions, as well as all forms of activity which tend to injure the body or debase the character, gives a tone to the nervous system which increases the self-respect and raises the individual to a _higher plane of life_. The worst habits _can_ be broken and good ones formed in their stead, if only there is sufficient determination to accomplish these results. Failure comes from not having the mind thoroughly "made up" and from not having, back of the desire to do better, "the strong will of a righteous determination." *Effects of External Conditions.*—While the inner life and habits have most to do with the hygiene of the nervous system, a certain amount of attention may properly be given to those conditions outside of the body which affect directly or indirectly the state of this system. Noise, disorder, and confusion act as nervous irritants, but quiet, order, and system have the opposite effect. There is, therefore, much in the management of the office, factory, schoolroom, or home that has to do with the real hygiene of the nerves as well as with the efficiency of the work that is being done. The suppression of distracting influences not only enables the mind to be given fully to the work in hand, but actually prevents waste of nervous energy. Although the responsibility for securing the best conditions for work rests primarily with those in charge, it is also true that each individual in every organization may contribute to the order or disorder that prevails. *Social Relations.*—In considering the external conditions that affect the nervous system, the fact must not be overlooked that man is a social being and has to adjust himself to an established social order. His relations to his fellow-men, therefore, affect strongly his nervous condition and theirs also. For this reason the best hygiene of the nervous system is based upon _moral_ as well as physical right living. Along with the power of self-control and the maintenance of a correct nervous poise, there should be a proper regard for the welfare of others. On account of the ease with which one individual may disturb the nervous state of another, those social forms and customs which tend to establish harmonious relations among men are truly hygienic in their effects, and may well be carried out in spirit as well as "in letter."