Energy is obtained almost solely from the combustion of fats and sugars, proteids being reconverted into albumin, and then broken down to obtain their carbon for combustion, the nitrogen being expelled, but proteids are essential for the building of the tissues themselves, the stones of the furnaces which burn up carbohydrates and fats.
The time taken in the digestion of foods was first studied through a wound in the stomach of St. Martin, a Canadian. Experiments were made with various well-masticated foods, and with similar foods placed unchewed, into the stomach through the wound, the latter experiment being carried out by millions of people at every meal, by a slightly different route.
Boiled food is more easily digested than fried or roasted (the frying pan should be anathema to a neuropath); lean meat than fat; fresh than salt; hot meat than cold; full-grown than young animals, though the latter are more tender; white flesh than red; while lean meat is made less, and fat meat more digestible, by salting or broiling. Oily dishes, hashes, stews, pastries and sweetmeats are hard to digest. Bread should be stale, and toasted crisply _right through_. The time, compared with the thoroughness of digestion, is of little importance, as it varies widely within physiologic bounds.
Most people fancy that the more they eat the stronger they become, whereas the digestion of all food beyond that actually needed to repair the waste due to physical and mental effort consumes priceless nerve energy, and weakens one. The greater part of excessive food has literally to be _burnt away_ by the body, which causes great strain, mainly on the muscles. The question is not: "How much can I eat?" but: "How much do I need?"
"We know how dismal the world looks during a fit of indigestion, and what a host of evils disappear as the abused stomach regains its tone. Indigestion has lead to the loss of battles; it has caused many crimes, and inspired much sulphurous theology, gloomy poetry and bitter satire."--Hollander.
The nervous dyspeptic suffers no marked pain, but often feels a "sinking", has no appetite, and cannot enjoy life because his stomach, though sound, does not get enough nerve-force to run it properly.