Vital resistance of the body is not determined by the degree of external cleanliness nor by the perfect sanitary condition of the environment. However, it can never be said that Chiropractic does not believe in cleanliness. Chiropractic, of all the sciences, lays great stress on hygiene and sanitation. Our greatest teacher in all things is Nature and if there is any one thing that Chiropractic insists upon more than any other, it is that we live according to the laws of Nature and the closer we live to Nature, the more normal will be our functions. When we study the laws of Nature, we find the secret of sanitation. Everywhere in Nature we find laws in operation which result in the destruction of waste material and in the purification of the environment. From the standpoint of common decency we are interested in sanitation or cleanliness, yet an immaculately clean environment will not result in perfect health or in the cure of dis-ease. The streets and alleys of the city may be kept clean and in a sanitary condition, yet the inside of the homes may be filled with filth. So the environment of man may be in a perfect condition so far as sanitation is concerned, yet the body may be filled with all kinds of poison and refuse. Sewerage System of the Body The human body is a machine which performs certain functions and in order that these functions be performed there is a constant process of activity; this means that the tissues which make up the body are being constantly worn out the same as the part of any other machine. This necessitates a constant process of repair. In order that this process of reparation be carried on, new material must be added to the machine; this is done by means of food. The food is taken into the mouth and properly masticated and mixed with the secretions of the glands of the mouth; it is then carried through the esophagus into the stomach. Here other digestive juices are added to it and thoroughly mixed by the vermicular motion of the stomach until the process of gastric digestion is completed; then this chyme, as it is now called, passes into the small intestines, where other secretions are added and chemical changes are brought about until this process of intestinal digestion is completed. This product is given the name of chyle.