The San Francisco call., 1903-12-17
INSTRUCTIVE JTUDEuC
By YNOIEDAsGIs!NN AND
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lolysis) and the ferment (ptyalin) to
which it is due were discussed in the
/ last article
The food mass, then, as it passes
from the mouth by being swallowed
and enters the stomach through the
esophagus. is changed in that part of
its starch which has been converted
into sugar Thus far the proteids and
the fats are unchanged. In the stom-
ach, however. the food mass becomes
mixed with the gastric juice. Now the
gastric juice has the power to change
proteid matter into peptone. The i'm
portance of this will be understood
when il is stated that mere proteid
cannot pass through the walls of the
alimentary tube. but that peptone can
do so just as water soaks through
sponge.
The peDtone as quickly as it is
formed sOaks through the walls Of the
stomach and. is collected by the tiny
blood tubes (capillaries). which wind
their minute coils just under the sur
face Of both stomach and intestines.
During the interval of gastric digestion
the band of muscular fiber called the
pylOrus from a Latin word meaning
"gatekeeper') remains tightly closed.
After a time the pyIorus opens and al
lows the food mass to enter the intes-
tines The food mass consists at this
time Of starch, converted starch-that
is. sugar proteid-part of which has
been changed to peptone and fats,
which thus far are unchanged.
In the intestine the food meets with
number of important and powerful
ferments. the bile from the liver, the
amyIOpsin Cstarch converter), trypsin
(peptone maker) and steapsin (fat
emulsi1er) from the pancreas and the
invertin and other ferments of the in
testinal fluid. The combined effect Of
these engines or ferments is to con-
vert the remainder of the starch into
sugar. to change the rest of the pro-
teids into peDtOne and to convert the
fats into an emulsion. An emulsion is
merely a separation of a fat into very
minute drops.
The absorption Of these matters in
the intestine is a peculiarly interesting
and beautiful process. The inner sur
face of the intestine is covered with
minute structures known as Will. These
Will average about One-f1ftieth of an
inch in diameter and are set close to-
gether. giving to the surface an ap-
pearance like a fine plush or velvet.
Each villus is made of epitheIiaI cells.
like tower built of bricks. And the
duty of each individual cell is to alb
sorb from the food the digested pro-
ducts-sugar, peptone and emulsion
as soon as they are made.
Inside of each of these tiny towers
or Will there is a complex coil Of blood
vessels and little bulb-like bodies called
lacteals The blood vessels of each viii
lus are, of course, part of the general
blood stream. The lacteals combine into
larger and larger trunks and finally
empty their contents into the great
blood tubes near the heart. Their ac-
! tivities viii be more fully explained
when we come to discuss the lymphatic
system, of which they are a part
Now, the little eDithelial cell which
covers the villus is the real worker.
Each cell passes the sugar absorbed
over to the blood vessels and turns the
fats absorbed over to the lacteals. The
peptones absorbed by the epithelial
cells are taken up part by the blood
vessels (capillaries) and part by the
lacteals all three, sugars, peptones and
fats, thus finding their way finally into
the blood stream.