DIGESTION
"We may live without poetry, music and art;
We may live without conscience, and live without heart;
We may live without friends, we may live without books,
But civilized man cannot live without cooks."
The human digestive system consists of a long tube, in which food is
received, nutriment taken from it as it passes slowly downwards, and from
which waste is discharged, in from sixteen to thirty hours afterwards.
Six glands pour saliva into the mouth, where it should be--but how rarely
is--mixed with the food, causing chemical changes, and moistening the bolus
to pass easily down.
The acid Gastric Juice, of which a quart is secreted daily, stops the
action of the saliva, and commences to digest the proteins, which pass
through several stages, each a little more assimilable than the last.
The lower end of the stomach contracts regularly and violently, churning
the food with the juice, and gradually squirting it, when liquified to
Chyme, into the small intestine. If food is not chewed until almost
liquified, the gastric juice cannot act normally, but has to attack as much
of the surface of the food-lump as possible, leaving the interior to
decompose, causing dyspepsia and flatulence.
Most people suppose the stomach finishes digestion, but it only initiates
the digestion of those foodstuffs which contain nitrogen, leaving fats,
starches and sugars untouched.
By an obscure process, the acid chyme stimulates the walls of the bowel to
send a chemical messenger, a Hormone through the blood to the liver and
pancreas, warning them their help is needed, whereupon they actively
secrete their ferments.
The secretion of the pancreas is very complex. It carries on the work of
the saliva, and also splits insoluble fats into a soluble milky emulsion.
Fats are unaffected in the mouth and stomach, which explains why hot,
buttered toast, and other hot, greasy dishes are so indigestible. The
butter on plain bread is quickly cleared off, and the bread attacked by the
gastric juice, but in toast or fatty dishes, the fat is intimately mixed
with other ingredients, none of which can properly be dealt with. Always
butter toast when cold.
To continue: The secretion of the pancreas also contains a very active
ferment, which, on entering the bowel, meets and mixes with another ferment
four times as powerful as gastric juice, which completes the digestion of
the proteids.
Meantime, the secretions of Lieberkühn's glands (of which there are immense
numbers in the small intestine) are further aiding the digestion of the
chyme, while the liver (the largest and most important gland in the body)
sends its ferments, and the gall-bladder its bile, which further emulsifies
the fatty acids and glycerin until they are ready to be absorbed.
The chemically-changed chyme is now termed Chyle, and is ready to be
absorbed by the minute, projecting Villi.
The fatty portion of the chyle is absorbed by minute capillaries and
ultimately mingles with the blood, which may look quite milky after a fatty
meal.
The remaining food is absorbed by the blood capillaries in the villi, and
passes to the liver for filtration and storage.
The large bowel has Lieberkühn's glands, but not villi, and is relatively
unimportant, though most of the water the body needs is absorbed from here.
How food becomes energy and tissue we do not know. The tissues are
continually being built up from assimilated food, and as constantly being
burnt away, oxygen for this purpose being extracted from the air we inhale,
and carried via the blood to every corner of the body. The ashes of this
burning are expelled into the blood and lymph, and carried out of the body
by the kidneys, lungs, skin and bowels. The product of the burning is the
marvel--Life; the extinction of the fire is the terror--Death.
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?"
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