"But the liver oxidation of other toxic substances is impaired in the meantime so that they get past the liver to the tissues, where they may do injury. Some of these toxins are excreted unoxidized by the kidneys. There are three ways of accounting for this condition: (1.) The oxidation capacity of the liver is limited. The physiological limit of alcohol ingestion is that amount which taxes the oxidation capacity of the liver to its limit. When thus taxed all other toxic substances including uric acid and the xanthin bodies pass through the liver unoxidized to appear in the urine. (2.) The presence of alcohol in the blood, through its toxic action upon the liver cells, impairs the hepatic oxidation capacity and thus permits toxic substances to pass unoxidized. (3.) A combination of these conditions may represent the real situation. It is hardly conceivable that the relation of alcohol to the liver activity is not covered in the hypotheses above formulated. "We may therefore accept it as practically demonstrated by the researches of Beebe, Hunt, and others that the oxidation of alcohol in the liver is simply one of the defensive activities of that organ, _i. e._, it is a protective oxidation and belongs strictly in the same category with the oxidation of uric acid, xanthin bodies, leucin, tyrosins, and the amido acids. "The next question which arises is, why does the liver select alcohol first and oxidize that substance to the exclusion of other toxic substances up to the oxidation capacity? The answer is probably to be found in the chemical composition of alcohol. "It oxidizes very easily, much more so than any of the other toxic substances which gain access to the liver. Its early oxidation may be due to this fact alone, or in part to an actual selection on the part of the liver. Another question of importance: Is the energy liberated in the oxidation of alcohol in the liver available for the use of the muscles, nervous system, or glands? "If this question is answered affirmatively, then alcohol is a food. If negatively then alcohol is not a food. Let us reason together. All body oxidations may be classified in two groups: (1.) _Active oxidations_ which take place in the active tissues--muscles, nervous system, or glands--and take place incident to action. It is under the perfect control of the nervous system and is proportional to normal activity. (2.) _Protective oxidations_ which take place in the liver. This class of oxidation processes is wholly independent of the usual tissue activity and is proportional to the ingestion of toxic substances and quite independent of muscle action, brain action, or gland action, other than liver action.