Western Reserve chronicle. [volume] (Warren, Ohio) 1855-1921, 1870-08-10
IFrom the Herald Of Health.I
STUDIES IN LOGY.
BY PROF. T. H. HUXLEY.
Tie Function Of AIImentatiOn.

Ahe function OF AlimentaJlOh.
The great tsourceof gain to the blood,
and, except the lungs, the only chan
mel by which altogether new materi-
al is introduced into that fluid, is the
alimentary canal, the tOtality of tine
operations of which constitutes the
function of Authorization. 1t will be
useful to consider the general nature
and results of the performance Of this
function before studying its details.
A man daily takes into his mouth,
and thereby introduces into his ALI
mentary canal, a certain amount OF
solid and liquid food, in the shape of
meat, bread, butter, water, and the
/ like. The amount Of chemically dry,
solid matter, which must thus be ia
ken into the body, If a man Of aver
age size and activity is neither to lose
nor to gain i'm weight, has been found
to be about 5000 grains. In addition
/ to this his blood absorbs by the lungs
about 10000 grains of oxygen gas,
making a grand total of 5000 grains
/ Tor nearly two pounds and three-quar-
/ tens avOirdupOis) of daily gain Of dry
/ solid and gaseous matter.
The weight Of dry solid matter pass
! ed out from the alimentary canal does
not on the average, amount to more
/ than one-tenth OF that which is taken
/ into It, or 500 grains. By no other
channel does any appreeiable quantity
of solid matter leave the body. 1t fol
lows, therefore, that in addition to the
lO, 600 grains Of oxygen, 7,20O grains
of dry solid matter must pass out OF
the body in the other, or gaseous and
LIQUID secretiOns. Further, as the
general composition of the body re-
mains constant, it follows either that
the elementary constituents of the
solids taken into the body must be
identical with those OF the body itself;
or that, in the course Of the vital pro-
cesses, the food alone is destroyed, the
/ substance Of the body remaining un-
changed; or, finally, that both these
alternatives hold good and that food is
partly, identical with the wasting sub
stance ofthe body and replaces it; and,
partly, differs from the wasting sub
] stance, and is consumed without re-
placing it.
AS a amatter of fact, all the substan.
/ ces which are used as food come un-
der one of four heads. They are eth
er what may be termed PrOteids, or
they are Fats, or they are Amyloids,
or they are Minerals. - #Hf1 L
/ PrOteids are substances analogous in
composition to Protein, and contain
| the four demonstration, hydrogen,
oxygen, and nitrogen, sometimes uni
| ted with sulphur and phosphorus.
Under this head come the Gluten
/ Of flour; the Albumen of white Of
| egg, and OF blood serum; the Fibrin
of the blood; the SyntOnin, which is
| the chief constituent of muscle and
/ flesh, and Casein, the chief cOnstitu-
ent Of cheese while Gelatin, which
is obtained by boiling from cOnnec-
tive tissue, and Chondrin, which may
/ be produced in the same way from
cartilage, may be considered to be out
| lying members of the same group.
Fats are cOr0pOsed of carbon, hydro
gen, and oxygen only, and contain
more hydrogen than is enough to
form water if united with the Oxy-
gen which they possess.
All oils and vegetable and animal
fatty matters come under this divis-
ion.
Amyloids sre substances which also
consist of carbon, hydrogen, and oxy-
gen only. But they contain no more
hydrogen than is Just sufficient to pro-
duce water with their oxygen. These
are matters known Is Starch, DeX-1
trine sugar, and Gum.
1t is the popularity of the three
groups of foOd-stuffs just mentioned
that they can only be obtained (at any
rate, at PRESENT. BY the activity OF liv-
ing beings, ,whether animals or plants,
so that they may be conveniently
termed vital fOOd-stuffs.
Food-stuffs of the fourth class, on
the other hand, or Minerals, are to be
procured as well from the notifying
as the living world. They are water,
and salts Of sundry alkalies, earths,
and metals. To these, in strictness,
oxygen ought to be added, though, |
as it is not taken in by the alimentary
canal, it hardly comes within the or
dinRTy acceptatiOn Of the word food. |
In ultimate analysis, then itappears |
that vital food-stuffs contain either
three or four of the elements: carbon !
hydrogen. oxygen, and nitrogen; that
mineral fOod-stuffs are water and salts. !
But the human body, in ultimate
analysis, also proves to be composed |
of the same four elements, plus water, |
and the same saline matters as are |
found in food.
MOIE NlAn AAAAsa III 6uD1AAANG NeAAA \
serve permanently for fOOd-thatis is to |
say, can prevent loss of weight and |
change in the general composition OF /
the bOdy-unless it contains certain 4
amount Of protein in the shape Ofalbu- /
men, fibrin, syntOnin, or casein.-l
While, on the other hand, any sub
stance which contains protein in
readily assimilable shape, is eompe
tent to act as permanent vital food
stuff
q The human body, as we have seen,
contains q large quantity of protein 4
in one or other of the four forms which
have been enumerated, and, there
fore, it turns out to be an indispensa-
BILE condition, that every substance
which is to serve permanently as food
must contain a sufficient quantity Of
the most important and complex COM
pOnent of the body ready made. 1t
must also contain q sufficient quanti-
ty of the mineral ingredients which
are required. Whether it contains
either fats or amylOids, or both, or is
devoid of both, its essential power Of
supporting the life and maintaining
the weight and composition Of the
body remains unchanged.
The necessity of constantly renew
ing the supply of protein arises from
the circumstance that the secretion Of
urea from the body land consequently
the loss OF nitrOgen) goes on eontinu-
ally, whether the body is fed or not;
while there is only one form in which
nitrogen (et any nate, in any consid-
cradle quantity can be taken into the
blood, and that is in the form Of So
luton of protein. If protein be not
supplied, Therefore, the body must
need waste, because there is nothing
in the food competent to make good
the loss Of nitrogen.
On the other hand, if protein be
supplied, there can be no absolute me-
eessity for any other but the mineral
fOOd-stuffs, because protein contains
carbon and hydrogen in abundance n
and hence is competent to give origin
to the other great products of waste,
carbOnie acid and water.
In fact, the final results Of the Oxi-
dstion OF protein are carbOnic acid, /
water, and sInnioniai and these, as
we have seen are the final shapes Of
the waste products Of the human econ
Omy.
From what has been said it becomes
readily ineligible that, whether an
animal be herbiverousior carniyorous, ]