Much of the food taken into the body is burned to supply energy and heat. This burning is called oxidation. When food is burned, or oxidized, either in the body, or out of it, three things are produced, carbon dioxide (_carbonic acid gas_), water and ashes. These are waste matters, and must be expelled from the body, or they will clog up the various organs, as the ashes and smoke of an engine would soon put its fire out if they were allowed to accumulate in the furnace. It is the duty of the lungs to pass the carbon dioxide out to the air. With every breath exhaled, this poison gas, generated in the body through the oxidation of food, passes from the system. With every breath inhaled the life-giving oxygen is taken into the body; providing that the person is not in a close room from which the fresh air is excluded. Any substance taken into the body which interferes with the reception of oxygen into the blood, and with the giving off of carbon dioxide from the same is a dangerous substance. _Alcohol is such a substance._ It has already been stated that it is the duty of the little red corpuscles in the blood to take up oxygen in the lungs, and carry it to every part of the body, and upon the return passage to the lungs to convey the _debris_, or used-up material, from the tissues, called carbon dioxide gas. A little vapor and ammonia accompany this gas. The action of alcohol upon these little corpuscles, or carriers of the blood, is to somewhat harden and shrivel them, so that they are unable to take up and carry as much oxygen as they can when no injurious substance is present in the blood. In consequence of this, the blood can never be so pure when alcohol is present, as it may be in the absence of this agent. The following is taken from _The Temperance Lesson Book_, by B. W. Richardson, M. D.:--