[pg 56]
CHAPTER XI
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 provide saliva to 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 and out of the body.
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.
[pg 57]
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.
[pg 58]
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 [pg 59] 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?"