On the Nature of the Gastric Juice, and the Changes it Effects on
Nitrogenized and Unnitrogenized Food. By II. Bence Jones, M. D.,
A.M. Cantab., F. R. S., Physician to St. George’s Hospital.—On the
5th of March, 1849, breakfast having been taken at eight A. M., on
boiled beef, bread, and spring water, at 9.45, by position and voluntary
effort, about a pint of substance was ejected. The first ounces were
scarcely acid to the taste; the last portion was most intensely acid.
The whole quantity was thrown on a filter, and a clear, yellowish-
brown liquid passed through. This clear liquid was intensely acid to
test paper. It coagulated slightly on the addition of nitric acid and
heat. The cold acid caused a deepish yellow color and a coagulum,
which appeared partly to be soluble by heat, and precipitable by cool-
ing. The specific gravity = 1008.2.	504.1 grains, evaporated in vacuo
over sulphuric acid, evolved a small quantity of gas.
Residue-}-basin — 549.3 grains.
basin = 505.0	“
March 15th.—Residue ... = 44.3 grs. = 8.8 per cent.
The residue was yellowish, semi-transparent, took ihe impression of
the nail, smelt of musk and sugar! ! When mixed with cold distilled
water, it became ropy, and very adhesive. The solution was highly
acid. The taste was sweet, acid, bitter, nauseous. A few drops of the
solution, with sulphate of copper and liquor potassse, gave an intense
blue, with a trace of purple; and the reduction of the oxide of copper
was very rapid, excessive, and red.
In this bottle you see this gastric juice. Here is its strong acid re-
action on litmus, and here you see the rapid reduction of the oxide of
copper. The food being bread, it is probable that some of the sugar
was formed in the process of fermentation, and not produced altogether
in the stomach.
This gastric juice, then, is a highly acid fluid secreted by the stomach.
It consists—1, of water and free acid; 2, of salts; 3, of non-nitrogenous
organic substances; 4, of albuminous or nitrogenized substance. Of
these substances, the most important is the free acid. WThat acid, it
has not yet been determined. Hydrochloric, phosphoric, acetic, lactic,
and butyric acids have each been said to exist in the gastric juice. The
hydrochloric and phosphoric are mineral or inorganic acids. The rest are
organic acids,—possibly arising from starch, sugar or fat, or other compo-
nents of the non-nitrogenized part of our food. Thus these organic acids
might be formed; but whence can the inorganic acids come? Hydrochloric
and phosphoric acids exist only in the food and blood, combined with so-
da, potash, or lime; as in common salt, phosphate of soda, or phosphate
of lime. To set free the acids, the alkalies must be separated. If one
equivalent of hydrochloric acid is set free in the stomach, one equiva-
lent of soda must be set free in the blood. The greater the quantity of
acid in the stomach, the greater the quantity of alkali in the blood, and
the more alkaline the serum must become. Whether this is effected
by galvanic action, nervous action, or muscular action, is at present al-
together unknown. Those who say anything, say it is by vital action.
Whatever may be the nature orseatof the decomposing force,—whether
galvanic, nervous, or muscular,—whether in the cells of the epithelium
of the stomach-tubes, or in the muscular structure,—we cannot admit
that inorganic acid can be poured into the stomach without an equiva-
lent quantity of alkali being set free in the blood, when digestion is
completed, the acid is re-absorbed with the food, and the alkalescence
of the blood must be altered in the opposite direction. When the sto-
mach is empty, there is little, if any acid there then. When food is
taken, the quantity of acid begins to increase, and gradually reaches the
greatest amount poured out; and then by absorption, or by escape through
the pylorus, the quantity of acid begins to decrease, until the stomach
is again empty.
For the purpose of keeping up a constant supply of at least one in-
organic acid, man has been led at all times, and in all circumstances, to
seek for salt, as necessary to his existence. What the influence of
chloride of sodium undecomposed, and of other salts, is on the solu-
bility of albumen or starch, has not yet been sufficiently determined.
The next most important constituent of the gastric juice, after water
and acid, is the albuminous substance. Its exact nature is not known.
I cannot consider it as epithelium. It is far more likely to be a sub-
stance like diastase; not albumen, not epithelium, but a peculiar albu-
minous substance. Its exact composition is not known; but probably
it is a substance undergoing changes which it can communicate to other
contiguous substances. It was precipitated by a weak alcohol from
infusion of pig’s stomach, by Wasman, and he called it pepsin; it re-
quires re-examination.
The non-albuminous organic substances in the gastric juice, are the
organic acids and fatty substance ; the latter probably exists in a very
small quantity. This complex gastric juice cannot act precisely in the
same way on two classes of substances so very different as nitrogen-
ized and non-nitrogenized food.
Firstly. The. action of the Gastric Juice on the Nitrogenized substan-
ces in the Food.—The fine state of division of the food, the smallness
of its amount, the constant muscular motion of the stomach, and the
temperature of the body—these all assist the solution of the fibrin, al-
bumen, or casein. Strong acids very easily dissolve these albuminous
substances, and the dilute acid of the stomach, in consequence, perhaps,
of some influence of the nitrogenized pepsin, or animal diastase (?), is
made to act as energetically on the albuminous food, as strong acid
would do. In this action there is nothing vital; it takes place as well
out of the body as in it. The elements of the albumen cannot be con-
verted so as to form water, salts, sugar or fat. There is no formation
of incipient albumen. If you please to call solution, reduction or com-
bination of water with the substance dissolved, you may say the albu-
men is reduced ; to me it is far more simple and quite as comprehensi-
ble to speak of it as a process of solution, and as nothing else.
Secondly. On the Action of the Gastric Juice on JJon-J\'itrogenized
Food, Starch, Sugar, Fat, fyc.—Starch is perfectly insoluble in water
and in dilute acids, but by the action of dilute acid, it easily undergoes
a change, by which it is rendered soluble. The action of strong sul-
phuric acid on starch, and the formation of sugar thereby, is probably
well known to you already; but there is no strong acid in the sto-
mach.
The relation of starch to British gum, or dextrine, or, as it has been
called, soluble starch, is also well known to you. There are many
ways of changing the insoluble starch into soluble dextrine. One very
perfect method has been practiced in France, of treating the starch, at
the temperature of 100° Fahr., with dilute hydrochloric or oxalic acid,
and thus dextrine is readily formed. There is no doubt that the tem-
perature and dilute hydrochloric acid in the stomach effect the same
conversion as you see has been effected in this flask; further action of
the acid and heat, converts the dextrine into sugar. It has been said,
that the starch is acted on by the alkaline saliva, but directly the saliva
reaches the stomach, it must be neutralized by the gastric juice.
On the Action of the Gastric Juice on Sugar.—The ready solubility
of sugar in water requires no illustration. A portion of the sugar
which is taken as such, or is formed from starch in the stomach, with-
out doubt passes into the blood as sugar; but it appears to me highly
probable, from Fremy’s experiments, that a portion is changed into
some of the vegetable acids. The acetic and lactic acids may thus be
formed, and these, in part, perhaps may become lactates and acetates of
soda in the blood. And we know, from direct experiment, what hap-
pens to vegetable acid salts injected into the blood, or taken into the
stomach ; they are oxydized or burnt, giving heat and carbonic acid
salts, which pass off in the urine. All free vegetable acids are proba-
bly changed partly into carbonic acid in the blood. Thus, then, proba-
bly the progress of a grain of starch may be traced. It forms, first,
dextrine; secondly, sugar; thirdly, vegetable acid; fourthly, carbonic
acid.
The ascending conversion of sugar into albumen cannot be admitted
until it is proved. There is not an experiment which renders such a
change probable.
The descending conversion of sugar into fat, a substance also con-
taining no nitrogen,—that is, of one kind of non-nitrogenized substance
into another kind belonging to the same class,. is most fully proved.
Bees fed on crystallized sugar made wax, and animals form more fat
than the food they are fed with contains; but this fat is not formed in
the stomach, and therefore does not concern us now. The changes
take place in the minute textures of the body, and not in the stomach.
On the Action of the Gastric Juice on Fat and Oil.—How is fat
made soluble at the temperature of the body ? Is oil absorbed ? The
following is an experiment by Tiedemann and Gmelin. A dog was
fed for four days on butter; three hours after the last meal he was
killed.
a. Stomach, contained butter, and the contents were very acid. b. Small
intestine contained butter and bile, and was acid strongly, c. The caecum
contained butter, d. The rectum contained butter, e. The chyle was very
milky, and cleared with ether, f. The blood of the vena cava inferior con-
tained much fat. g. The urine was thick; filtered, butter soluble in alcohol
was left on the filter. They add: “One of our pupils, who likes fat,
has frequently found it in his urine.” This has also sometimes been
observed after cod-liver oil. Oil and albumen form an emulsion slightly
soluble in water; but the pancreatic fluid and the bile are generally
considered as the agents which make the fat and oil of the food soluble.
Lastly, the phosphates and sulphates of soda, chloride of sodium, are
soluble in water. The earthy phosphates are dissolved by the hydro-
chloric acid. Even silica, in minute quantity, is contained, dissolved in
water, and hence these salts pass into the blood.
The formation of the gastric juice is certainly no chemical process,
but its action is entirely chemical, though it is aided by the motion which
the muscular coat of the stomach produces ; and muscular contraction
is as distinct as sensation from chemical action. Nor can the absorp-
tion of the dissolved substances be altogether considered as a vital action.
It i.s certainly subject to the laws of the diffusion of one liquid into an-
other, to the laws of endosmosis, or diffusion through a membrane, and
to capillary action. This subject, alone, might occupy me for many
lectures; it belongs more to my colleague, the lecturer on physiology,
than to me. I pass on, therefore, to the next subject, the formation of
blood from the absorbed food, the assimilation of the food to the blood,
How is it that the blood keeps its composition ? The food is dissolved,
and then absorbed, and the blood somehow makes it into blood; some-
how preservesits own composition. What, then, is this blood, chemi-
cally ? how does it differ from food in composition?—Lon. Lancet.