The Nervous System.--The smooth working of the bodily machine is due to another set of structures which direct the working of the parts so that they will act in unison. This director is the nervous system. We have seen that, in the simplest of animals, one cell performs the functions necessary to its existence. In the more complex animals, where groups of cells form tissues, each having a different function, a nervous system is developed. _The functions of the human nervous system are:_ (1) _the providing of man with sensation, by means of which he gets in touch with the world about him;_ (2) _the connecting of organs in different parts of the body so that they act as a united and harmonious whole;_ (3) _the giving to the human being a will, a provision for thought._ Cooperation in word and deed is the end attained. We are all familiar with examples of the cooperation of organs. You see food; the thought comes that it is good to eat; you reach out, take it, raise it to the mouth; the jaws move in response to your will; the food is chewed and swallowed. While digestion and absorption of the food are taking place, the nervous system is still in control. The nervous system also regulates pumping of blood over the body, respiration, secretion of glands, and, indeed, every bodily function. Man is the highest of all animals because of the extreme development of the nervous system. Man is the thinking animal, and as such is master of the earth. REFERENCE READING FOR THIS AND SUCCEEDING CHAPTERS ON HUMAN BIOLOGY ELEMENTARY Hunter, _Laboratory Problems in Civic Biology_. American Book Company. Davison, _The Human Body and Health_. American Book Company. Gulick, _The Gulick Hygiene Series_. Ginn and Company. Overton, _General Hygiene_. American Book Company. Ritchie, _Human Physiology_. World Book Company. Sharpe, _Laboratory Manual in Botany_, pages 218-225. American Book Company. ADVANCED Halliburton, _Kirk's Handbook of Physiology_. P. Blakiston's Son and Company. Hough and Sedgwick, _The Human Mechanism_. Ginn and Company. Howell, _Physiology_, 3d edition. W. B. Saunders Company. Schafer, _Textbook of Physiology_. The Macmillan Company. Stiles, _Nutritional Physiology_. W. B. Saunders Company. Verworn, _General Physiology_. The Macmillan Company. XIX. FOODS AND DIETARIES _Problems.--A study of foods to determine:--_ _(a) Their nutritive value._ _(b) The relation of work, environment, age, sex, and digestibility of foods to diet._ _(c) Their relative cheapness._ _(d) The daily Calorie requirement._ _(e) Food adulteration._ _(f) The relation of alcohol to the human system._ LABORATORY SUGGESTIONS