The Journey Down The Food Tube


Categories: THE FOOD-FUEL OF THE BODY-ENGINE
Sources: A Handbook Of Health

The Flow of Saliva and Appetite Juice. We are now ready to start

some food-fuel, say a piece of bread, on its journey down our food tube,

or alimentary canal. One would naturally suppose that the process of

digestion would not begin until the food got well between our teeth;

but, as a matter of fact, it begins before it enters our lips, or even

before it leaves the table. If bread be toasted or freshly baked, the

mere smell of it will start our mouths to watering; nay, even the mere

sight of food, as in a pastry cook's window, with the glass between us

and it, will start up this preparation for the feast.



This flow of saliva in the mouth is of great assistance in moistening

the bread while we are chewing it; but it goes farther than this. Some

of the saliva is swallowed before we begin to eat; and this goes down

into the stomach and brings word to the juices there to be ready, for

something is coming. As the food approaches the mouth, a message also is

telegraphed down the nerves to the stomach, which at once actively sets

to work pouring out a digestive juice in readiness, called the appetite

juice. This shows how important are, not merely a good appetite, but

also attractive appearance and flavor in our food; for if this appetite

juice is not secreted, the food may lie in the stomach for hours before

the proper process of digestion, or melting, begins.



The Salivary Glands. Now, where does this saliva in the mouth come

from? It is poured out from the pouches of the cheeks, and from under

the tongue, by some little living sponges, or juice factories, known as

salivary glands.[2]





All the juices poured out by these glands, indeed nearly all the fluids

or juices in our bodies, are either acid or alkaline. By acid we

mean sour, or sharp, like vinegar, lemon juice, vitriol (sulphuric

acid), and carbonic acid (which forms the bubbles in and gives the

sharp taste to plain soda-water). By alkaline we mean soap-like or

flat, like soda, lye, lime, and soaps of all sorts. If you pour an acid

and an alkali together--like vinegar and soda--they will fizz or

effervesce, and at the same time neutralize or kill each other.



The Use of the Saliva. As the chief purpose of digestion is to prepare

the food so that it will dissolve in water, and then be taken up by the

cells lining the food-tube, the saliva, like the rest of the body

juices, consists chiefly of water. Nothing is more disagreeable than to

try to chew some dry food--like a large, crisp soda cracker, for

instance--which takes more moisture than the salivary glands are able to

pour out on such short notice. You soon begin to feel as if you would

choke unless you could get a drink of water. But it is not altogether

advisable to take this short cut to relief, because the salivary juice

contains what the drink of water does not--a ferment, or digestive

substance (ptyalin), which possesses the power of turning the starch

in our food into sugar. As starch is only very slowly soluble, or

meltable, in water, while sugar is very readily so, the saliva is of

great assistance in the process of melting, known as digestion. The

changing of the starch to sugar is the reason why bread or cracker,

after it has been well chewed, begins to taste sweetish.



This change in the mouth, however, is not of such great importance as

we at one time thought, because even with careful mastication, a certain

amount of starch will be swallowed unchanged. Nature has provided for

this by causing another gland farther down the canal, just beyond the

stomach, called the pancreas, to pour into the food tube a juice which

is far stronger in sugar-making power than the saliva, and this will

readily deal with any starch which may have escaped this change in the

mouth. Moreover, this sugaring of starch goes on in the stomach for

twenty to forty minutes after the food has been swallowed.



Starchy foods, like bread, biscuit, crackers, cake, and pastry, are

really the only ones which require such thorough and elaborate chewing

as we sometimes hear urged. Other kinds of food, like meat and

eggs--which contain no starch and consequently are not acted upon by

the saliva--need be chewed only sufficiently long and thoroughly to

break them up and reduce them to a coarse pulp, so that they can be

readily acted upon by the acid juice of the stomach.



Down the Gullet. When the food has been thoroughly moistened and

crushed in the mouth and rolled into a lump, or bolus, at the back of

the tongue, it is started down the elevator shaft which we call the

gullet, or esophagus. It does not fall of its own weight, like coal down

a chute, but each separate swallow is carried down the whole nine inches

of the gullet by a wave of muscular action. So powerful and closely

applied is this muscular pressure that jugglers can train themselves,

with practice, to swallow standing on their heads and even to drink a

glass of water in that position; while a horse or a cow always drinks

up-hill. This driving power of the food tube extends throughout its

entire length; it is carried out by a series of circular rings of

muscles, which are bound together by other threads of muscle running

lengthwise, together forming the so-called muscular coat of the tube.

By contracting, or squeezing down in rapid succession, one after

another, they move the food along through the tube. The failure of these

little muscles to act properly is one of the causes of constipation and

biliousness. Sometimes the action of the muscles is reversed, and then

we get a gush of acid, or bitter, half-digested food up into the mouth,

which we call heart-burn or water-brash.



The Stomach--its Shape, Position, and Size. By means of muscular

contraction, then, the gullet-elevator carries the food into the

stomach. This is a comparatively simple affair, merely a ballooning out,

or swelling, of the food tube, like the bulb of a syringe, making a

pouch, where the food can be stored between meals, and where it can

undergo a certain kind of melting or dissolving. This pouch is about the

shape of a pear, with its larger end upward and pointing to the left,

and its smaller end tapering down into the intestine, or bowel, on the

right, just under the liver. The middle part of the stomach lies almost

directly under what we call the pit of the stomach, though far the

larger part of it lies above and to the left of this point, going right

up under the ribs until it almost touches the heart, the diaphragm only

coming between.[3] This is one of the reasons why, when we have an

attack of indigestion, and the stomach is distended with gas, we are

quite likely to have palpitation and shortness of breath as well,

because the gas-swollen left end of the stomach is pressing upward

against the diaphragm and thus upon the heart and the lungs. Most cases

of imagined heart trouble are really due to indigestion.



The Lining Surface of the Stomach. Now let us look more carefully at

the lining surface of the stomach, for it is very wonderful. Like all

other living surfaces, it consists of tiny, living units, or body

bricks called cells, packed closely side by side like bricks in a

pavement. We speak of the mucous membrane, or lining, of our food

tube, as if it were one continuous sheet, like a piece of calico or

silk; but we must never forget that it is made up of living ranks of

millions of tiny cells standing shoulder to shoulder.



These cells are always actively at work picking out the substances they

need, and manufacturing out of them the ferments and acids, or alkalies,

needed for acting upon the food in their particular part of the tube,

whether it be the mouth, the stomach, or the small intestine.





The Peptic Juice. The cells of the stomach glands manufacture and pour

out a slightly sour, or acid, juice containing a ferment called

pepsin. The acid, which is known as hydrochloric acid, and the

pepsin together are able to melt down pieces of meat, egg, or curds of

milk, and dissolve them into a clear, jelly-like fluid, or thin soup,

which can readily be absorbed by the cells lining the intestine.[4]



You can see now why you shouldn't take large doses of soda or other

alkalies, just because you feel a little uncomfortable after eating.

They will make your stomach less acid and perhaps relieve the

discomfort, but they stop or slow down digestion. Neither is it well to

swallow large quantities of ice-water, or other very cold drinks, at

meal times, or during the process of digestion. As digestion is largely

getting the food dissolved in water, the drinking of moderate quantities

of water, or other fluids, at meals is not only no hindrance, but rather

a help in the process. The danger comes only when the drink is taken so

cold as to check digestion, or when it is used to wash down the food in

chunks, before it has been properly ground by the teeth.





Digestion in the Stomach. Although usually a single, pear-shaped

pouch, the stomach, during digestion, is practically divided into two

parts by the shortening, or closing down, of a ring of circular muscle

fibres about four inches from the lower end, throwing it into a large,

rounded pouch on the left, and a small, cone-shaped one on the right.

The gullet, of course, opens into the large left-hand pouch; and here

the food is stored as it is swallowed until it has become sufficiently

melted and acidified (mixed with acid juice) to be ready to pass on into

the smaller pouch. Here more acid juice is poured out into it, and it is

churned by the muscles in the walls of the stomach until it is changed

to a jelly-like substance.



Digestion in the Small Intestine. The food-pulp now passes on into the

small intestine, where it is acted upon by two other digestive

juices--the bile, which comes from the liver, and the pancreatic

juice, which is secreted by the pancreas.



The liver and the pancreas are a pair of large glands which have budded

out, one on each side of the food tube, about six inches below where the

food enters the small intestine from the stomach. The liver[5] weighs

nearly three pounds, and the pancreas about a quarter of a pound.



Of these two glands, the pancreas, though the smaller, is far more

important in digestion. In fact, it is the most powerful digestive gland

in the body. Its juice, the pancreatic juice, can do everything that any

other digestive juice can, and do it better. It contains a ferment for

turning starch into sugar, which is far more powerful than that of the

saliva; also another (trypsin), which will dissolve meat-stuffs nearly

twice as fast as the pepsin of the stomach can; and still another, not

possessed by either mouth or stomach glands, which will melt fat, so

that it can be sucked up by the lining cells of the intestine.



What does this great combination of powers in the pancreas mean? It

means that we have now reached the real centre and chief seat of

digestion, namely, the small intestine, or upper bowel. This is where

the food is really absorbed, taken up into the blood, and distributed to

the body. All changes before this have been merely preparatory; all

after it are simply a picking up of the pieces that remain.



In general appearance, this division of the food tube is very

simple--merely a tube about twenty feet long and an inch in diameter,

thrown into coils, so as to pack into small space, and slung up to the

backbone by broad loops of a delicate tissue (mesentery). It looks not

unlike twenty feet of pink garden hose.



The intestine also is provided with glands that pour out a juice known

as the intestinal juice, which, although not very active in digestion,

helps to melt down still further some of the sugars, and helps to

prevent putrefaction, or decay, of the food from the bacteria[6] which

swarm in this part of the tube.



By the time the food has gone a third of the way down the small

intestine, a good share of the starches in it have been turned into

sugar and absorbed by the blood vessels in its wall; and the meats,

milk, eggs, and similar foods have been digested in the same way.



There still remains the bulk of the fats to be disposed of. These fats

are attacked by the pancreatic juice and the bile, and made ready for

digestion. Like other foods, they are then eaten by the cells of the

intestinal wall; but instead of going directly into the blood vessels,

as the sugars and other food substances do, they are passed on into

another set of little tubes or vessels, called the lymphatics. In

these they are carried through the lymph glands of the abdomen into

the great lymph duct, which finally pours them into one of the great

veins not far from the heart. Tiny, branching lymphatic tubes are found

all over the body, picking up what the cells leave of the fluid which

has seeped out of the arteries for their use and returning it to the

veins through the great lymph duct.



All these different food substances, in the process of digestion, do not

simply soak through the lining cells of the food tube, as through a

blotting paper or straining cloth, but are actually eaten by the cells

and very much changed in the process, and are then passed through the

other side of the cells, either into the blood vessels of the wall of

the intestine or into the lymph vessels, practically ready for use by

the living tissues of the body. It is in the cells then that our food is

turned into blood, and it is there that what we have eaten becomes

really a part of us. It may even be said that we are living upon the

leavings of the little cell citizens that line our food tube; but they

are wonderfully decent, devoted little comrades of the rest of our body

cells, and generous in the amount of food they pass on to the blood

vessels.



As the food-pulp is squeezed on from one coil to another through the

intestine, it naturally has more and more of its nourishing matter

sucked out of it; until, by the time it reaches the last loop of the

twenty feet of the small intestine, it has lost over two-thirds of its

food value.



The Final Stage--the Journey through the Large Intestine. From the

small intestine what remains of the food-pulp is poured into the last

section of the food tube, which enlarges to from two to three inches in

diameter. It is known as the large intestine, or large bowel. This

section is only about five feet long. The first three-fourths of it is

called the colon; the last or lowest quarter, the rectum, the

discharge-pipe of the food tube. The principal use of the colon is to

suck out the remaining traces of nourishing matter from the food and the

water in which it is dissolved, thus gradually drying the food-pulp down

to a solid or pasty form, in which condition it collects in a large S

shaped loop of the bowel just above the rectum, until discharged.



The Waste Materials. By the time that the remains of the food-pulp

have reached the middle of the large intestine, they have lost all their

nutritive value and most of their water. All the way down from the upper

part of the small intestine they have been receiving solid waste

substances poured out by the glands of the intestines; indeed, the bulk

of the feces is made up of these intestinal secretions, not, as is

generally supposed, of the undigested remains of the food. Ninety-five

per cent of our food is absorbed; the body-engine burns up its fuel very

clean. The next largest part of the feces is bacteria, or germs; and the

third and smallest, the indigestible fragments and remainders of food,

such as vegetable fibres, bran, fruit skins, pits, seeds, etc. Hence the

feces are not only worthless from a food point of view, but full of all

sorts of possibilities for harm; and the principal interest of the body

lies in getting rid of them as promptly and regularly as possible.



It can easily be seen how important it is that a habit should be formed,

which nothing should be allowed to break, of promptly and regularly

getting rid of these waste materials. For most persons, once in

twenty-four hours is normal; for some, twice or even three times in the

day. Whatever interval is natural, it should be attended to, beginning

at a fixed hour every morning.



Constipation, and how to Prevent It. Constipation should not be

treated by the all too common method of swallowing salts, which will

cause a flood of watery matters to be poured through the food tube and

sluice it clean of both poisons and melting food at the same time,

leaving it in an exhausted and disturbed condition afterwards; nor by

taking some irritating vegetable cathartic, generally in the form of

pills, which sets up a violent action of the muscles of the food tube,

driving its contents through at headlong speed; nor by washing out the

lower two or three feet of the bowel with injections of water; although

any or all of these may be resorted to occasionally for temporary

relief. A very large portion of the food eaten is sucked out of the food

tube into the blood vessels, passes through a large area of the body,

and is poured out again as waste through the glands of the lining of the

lower third of the bowel. Constipation, therefore, is caused by

disturbances which interfere with these processes all over the body,

not only in the stomach and bowels. Its only real and permanent cure is

through exercise in the open air, sleep, and proper ventilation of

bedrooms, with abundance of nourishing food, including plenty of green

vegetables and fresh fruits.



The Appendix and Appendicitis. The beginning of the large bowel, where

the small bowel empties into it, is the largest part of it, and forms a

curious pouch called the cecum, or blind pouch. From one side of

this projects a little wormlike tube, twisted and coiled upon itself,

from three to six inches long and of about the size of a slate pencil.

This is the famous appendix vermiformis (meaning, wormlike tag),

which is such a frequent source of trouble. It is the shrunken and

shriveled remains of a large pouch of the intestine which once opened

into the cecum, and was used originally as a sort of second stomach for

delaying and digesting the remains of the food. The reason why it gives

rise to so much trouble is that it is so small--scarcely larger than

will admit a knitting-needle--and so twisted upon itself that germs or

other poisonous substances swallowed with the food may get into it,

start a swelling or inflammation, get trapped in there by the closing of

the narrow mouth of the tube, and form an abscess, which leaks through,

or bursts into, the cavity of the body, called the peritoneum. This

causes a very serious and often fatal blood poisoning.



Fortunately, appendicitis, or inflammation of the appendix, is not a

very common disease, causing only one in one hundred of all deaths that

occur; and these are mostly cases that were not treated promptly. Yet,

if you have a severe, constant pain, rather low down in the right-hand

corner of your abdomen, and if, when you press your hand firmly down in

that corner, it hurts, or you feel a lump, it is decidedly safest to

call a doctor and let him see what the condition really is, and advise

you what to do.





FOOTNOTES:



[1] The term salts includes, as will be explained later, a large

number of substances, like ordinary table salt, baking soda, and the

laxative salts.



[2] There are three pairs of these: one just below the ears and behind

the angles of the jaw, known as the parotid; one under the middle of

the lower jaw known as the submaxillary; and a small pair just under

the tip of the tongue, called the sublingual. These glands have grown

up from the very simplest of beginnings. At first there was just a

little pocketing or pouching down of the mucous lining, like the finger

of a glove; then a couple of smaller hollow fingers budded off from the

bottom of the first finger; then four smaller fingers from the bottom of

these; and so on, until a regular little hollow tree or shrub of these

tiny tubes was built up, all discharging through the original hollow

stem, which has now become what we call the duct of the gland. Every

secreting gland in the body--the stomach (or peptic) glands, the

salivary glands, the liver, the pancreas--is built up upon this simple

plan. The saliva and the juice of the pancreas and that of the liver

(bile) are alkaline, as are also the blood and most juices of the body.

The stomach juice is acid, as also are the urine and the perspiration.



[3] It is wonderfully elastic and constantly changing in size,

contracting till it will scarcely hold a quart when empty, and

expanding, as food or drink is put into it, until it will easily hold

two quarts, or even a gallon or more when greatly distended, as by gas.



[4] If you take some pepsin which has been extracted from the stomach of

a pig or a calf, melt it in water in a glass tube, then drop one or two

little pieces of meat or hard-boiled white of egg into it, you can see

them slowly melt away like sugar in a cup of coffee. If you add a few

drops of hydrochloric acid, the melting will go on much faster; and if

you warm up the tube to about the heat of the body, it will proceed

faster still. So nature knew just what she was doing when she provided

pepsin and acid and warmth in the stomach.



[5] The liver and the bile are more fully described in chapter XVII.



[6] Tiny plant cells, known also as germs, which cause fermentation,

decay, and many diseases.





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