Q. _What is the FUEL of the BODY?_ A. _Food is the fuel of the body_; and the _carbon of the food_ mixing with the _oxygen of the air_, evolves heat in the same way that a fire or candle does. Q. _Why is EVERY part of the BODY WARM?_ A. As the capillary veins run through every part of the human body, and the combustion of blood _takes place in the capillary veins_, therefore _every part of the body is warm_. Q. _Why does RUNNING make us WARM?_ A. When we run, _we inhale air more rapidly_; and the rapidity with which we inhale air _fans the combustion of our body_, as a pair of _bellows_ quickens the flame of a common fire. Q. _How does INHALING AIR RAPIDLY make the body feel WARM?_ A. As the combustion of the blood is _more rapid_, (in consequence of the introduction _of more oxygen from the air_), therefore _the blood is more heated_, and every part of the body is warmer also. Q. _Why does HARD WORK produce HUNGER?_ A. Because it produces _quicker respiration_; by which means a _larger amount of oxygen is introduced into the lungs_, and the _capillary combustion increased_. Hunger _is the notice_ (given by our body) to remind us, _that our food-fuel must be replenished_. Q. _Why does SINGING make us HUNGRY?_ A. Singing _increases respiration_; and as _more oxygen_ is introduced into the lungs, _our food-fuel is more rapidly consumed_. Q. _Why does READING ALOUD make us feel HUNGRY?_ A. Reading aloud _increases respiration_; and as _more oxygen_ is introduced into the lungs, _our food-fuel is more rapidly consumed_. Q. _Why do we feel MORE HUNGRY in the DAY-TIME than in the NIGHT-TIME?_ A. As we _breathe more slowly during sleep_, therefore, less _oxygen_ is introduced into the lungs _to consume our food-fuel_. Q. _Why do we need WARMER CLOTHING by NIGHT than by DAY?_ A. 1st--Because the _night is generally colder_ than the day. 2ndly--As our _respiration is slower_, our _animal combustion is slower also_; in consequence of which, _our bodies are more cold_. Q. _Why do we PERSPIRE when very HOT?_ A. The pores of the body are _like the safety valves of a steam-engine_; when the heat of the body is too great, the combustible gas and grease _flow out in perspiration_, instead of _burning in the blood_. Q. _Why do persons feel LAZY and averse to exercise, when they are HALF-STARVED or ILL-FED?_ A. _Animal food_ contains great nourishment, and produces a desire for _active occupations_; but when the body is not supplied with strong food, this desire for muscular action _ceases_, and the person grows slothful. Q. _Why have persons, who follow HARD OUT-OF-DOORS OCCUPATIONS, more APPETITE than those who are engaged in SEDENTARY pursuits?_ A. Hard bodily labour in the open air _causes much oxygen to be conveyed into the lungs by inspiration_; the combustion of the food is carried on quickly; _animal heat increased_; and need for nutritious food more quickly indicated _by craving hunger_.