end (a) towards which its motion sets. The
pressure being equal in all directions, a portion
of the fluid escapes backwards through its
aperture (</). This retrograde course is,
pro tanto, a current ; and one which will
be continually lengthened by the advance of
the septum along the remainder of the
tube. And the slow successive movement of a
series of such septa would establish two con-
tinuous currents in the liquid ; a peripheral of
advance, and a central of return.*
Fig. 244.
Diagram to illustrate the effects of peristalsis in a
closed tube containing liquid.
a, Closed end of the tube ; b, perforated septum,
moved towards a, and causing the peripheral cur-
rents indicated by the arrows, in the same direction ;
c, quiescent mass of liquid, giving origin to d; rf,
central current, prolonged from the corresponding
arrow, and passing through the perforated septum.
The existence of two such currents would
be little affected by the membranous nature
or peculiar shape of the human stomach.
Even comparative inactivity of the cardiac
pouch would not prevent their occurrence, as a
consequence of pyloric peristalsis. While very
moderate contractions of this sluggish part
would accurately define the axis and its cur-
* The following description so well supplies the
interval between such a model tube and the human
stomach, that I cannot refrain from quoting it.
" The muscular action of a fish's stomach consists of
vermicular contractions, creeping slowly in continu-
ous succession from the cardia to the pylorus, and
impressing a twofold gyratory motion on the con-
tents ; so that, while some portions are proceeding
to the pylorus, others are returning towards the
cardia." (Owen's Hunterian Lectures, vol. ii. p. 236.).
314
STOMACH AND INTESTINE.
rent, as that curved line which unites the car-
diac and pyloric apertures (a, fig. 245.).
Fig. 245.
Diagram to show the general direction of movement
impressed on the semifluid food in the digesting
stomach.
a, real axis of the stomach, uniting its cardiac
and pyloric apertures ; b, situation of the abnormal
opening in St. Martin's case. (The arrows corre-
spond to the peripherial current of advance, which is
effected by peristalsis ; and the central current of
return, which is reflected from the preceding at
the pylorus.)
(2.) The observations of Dr. Beaumont are
as follows*: "The bolus, as it enters the
cardia, turns to the left, passes the aperture,
descends into the splenic extremity, and fol-
lows the great curvature towards the pyloric
end. It then returns in the course of the
smaller curvature, makes its appearance again
at the aperture in its descent into the great
curvature, to perform similar revolutions.
These revolutions are completed in from one
to three minutes; the bulb of the thermometer
invariably indicates the same movements."
He is careful to add, that there is an admix-
ture of the ingesta, which implies that the
movement is not simply a revolution ; for that,
if this were the case, " the central portions
would retain their situation, until the outer or
chymified part had passed into the duode-
num.'^
Now in order to render the movement
thus observed perfectly compatible with
that above deduced, we have but to recollect
the situation of the aperture from which the
inspection of St. Martin's stomach was made.
This was at the left extremity of the organ
(, jig. 245.). Whence it is obvious, that
any backward movement along the real
axis (a), connecting the two orifices of the
stomach, would be so near to the superior
curved border, and so far from the point of
view, that Dr. Beaumont could scarcely have
avoided imputing to it the course which he has
done. While, since every part of the stomach
would be occupied by one or other of the two
currents, the mutual interference of these at
* Op. cit. p. 101.
t This admixture he ascribes to a triturating or
agitating motion, which is partly gastric, partly re-
spiratory. But the existence of the circulating
movement described sufficiently proves that this
mixture was inherent to the process, and not (as
his supposition would imply) a result of its disturb -
their borders must gradually cause an uniform
diffusion of the various alimentary matters
moving with them. And finally, the reflec-
tion of one current into the other at the
pylorus, insures an equal contact of all the
semifluid food with the surface of the mucous
membrane; since those portions of the in-
gesta which occupy the axis of the stomach
during one moment, are destined to move
along its periphery during the next.
3. In the later stage of digestion, the move-
ment seen in the Dog's stomach soon after
death differs from the preceding.
The cardiac extremity appears even less
active than before ; and the longitudinal
shortening of the organ is also less marked.
The chief visible commencement of contrac-
tion is at the same place where it was for-
merly increased, and where it now forms a
deep constriction or hour-glass contraction.
After this constriction has continued a short
time, it sends onwards towards the pylorus a
rapid peristalsis, which appears nearly to ob-
literate the tube in its course, and ends by
engaging the muscular ring of this valve. A
slight relaxation closely follows this peristal-
sis ; and is succeeded by a complete dilata-
tion of the pyloric sac. Lastly, the hour-
glass contraction itself sometimes disappears ;
and an interval of about two minutes precedes
the repetition of the whole process. Often,
however, the constriction remains until the
peristalsis recommences.
Dr. Beaumont's observations * again seem
to supply the counterpart to this description.
He states that, when chymification has ad-
vanced, the motion is quicker. And on attempt-
ing to pass a thermometer tube towards the
pylorus, it is stopped by a stricture f, which is
situated about three or four inches from this
aperture. A forcible contraction is first per-
ceived ; but in a short time, there is a gentle
relaxation, when the bulb passes without dif-
ficulty, and is then drawn forcibly towards
the pyloric end for three or four inches. It
is then released, and forced back with a spiral
motion for the same distance, when it seems
to be again obstructed by the stricture. But
if pulled up through this, it moves freely in the
cardiac portion, mostly inclining towards the
splenic extremity. The repetition of the con-
traction is preceded by an interval of about
three minutes, during which the food revolves
as in the previous stage.
It is scarcely necessary to point out, that
when the almost obliterated pyloric tube is
filled by the tightly grasped thermometer bulb,
no axial current can possibly be produced by
the peristalsis. The pylorus having con-
tracted, and its pouch relaxed, the contrac-
tility of the whole organ would determine a
rush of fluid around the bulb; and this would
be reflected from the valve into the axis of the
* Op. cit. pp. 102. 104.
f The similar narrowing seen in the digesting
stomach of animals has been called the " transverse
band" ; a term which is objectionable, inasmuch as it
implies the presence of a special structure that does
not reallv exist.
STOMACH AND INTESTINE.
315
tube. We should thus get two currents,
which, at least in situation, would be identical
with those produced by the peristalsis of the
succeeding interval.
Action of the pylorus. The structure of the
pylorus (TTv\(opb y portce custos) has already
been described. As regards its action, it is
obviously the sphincter of the stomach. As
such, it has been supposed to possess a kind
of selective power ; by virtue of which it
contracts against the food in the earlier stage
of digestion, but subsequently relaxes to per-
mit the passage of the chyme. This view,
however, appears to me very doubtful.
In the empty stomach, the pylorus is
generally open, and readily* allows of the
passage of bile from the duodenum. In the
early stage of digestion, it is firmly shut ; and
retains the contents of the organ against
gravity, or even against such a manual pressure
as readily expels them from the cardia.
But just as in the second stage of gastric
digestion, it is plain that the valve does not
undergo any sudden or great relaxation, for
such would allow the passage of a large quan-
tity of the moving and semifluid food, much
of which would be still crude and undigested
so the very gradual diminution*!*, noticed by
Beaumont in the early stage, renders his in-
ference, that, even from the first, chyme
is constantly passing into the duodenum
very probably correct. J Supposing this to
be the case, it is evident that the action of
the pylorus must be very similar at both these
periods. And after numerous and careful
observations on this part of the Dog's stomach
towards the close of its digestive act, I have
never yet been able to substantiate any de-
finite relaxation of the pylorus ; or any but an
inconsiderable oozing of chyme at the time of
that active peristalsis which has been described
above. Hence I prefer to regard the passage
of the chyme as produced by that great increase
of force which the contractions of the pyloric
sac acquire at this period; a cause which
appears so sufficient, that it seems scarcely
justifiable to assume any additional one. The
supposed relaxation of the pylorus seems also
contradicted by a remark of Beaumont's, that,
even at the end of the process, when the
passage of chyme is greatly accelerated, the
above contractions still continue.
In short, instead of a relaxed pylorus,
through which a moderate peristalsis urges
a selected portion of the food, it appears
* Bile is almost always found in the empty
stomach of Dogs and Cats. (Compare Beaumont,
pp. 86, 87.)
t The diminution due to absorption would pro-
bably be at first compensated by the addition of
gastric juice.
| According to Magendie (Op. cit. p. 91.), the py-
lorus of the Horse is always found open, and is pro-
bably relaxed during life. It is only thus one can
explain the well-known fact, that the quantity of
food taken by this animal at an ordinary meal has
a bulk which amounts to four or five times that of
its distended stomach. Indeed, water has been
found in its caecum six minutes after being swal-
lowed. (Coleman in Abernethy's PhysiologiCiil
Lectures, p. 180.)
the state of this aperture during the close of
gastric digestion is that of a contracted valve,
through which the tolerably uniform chyme
is being strained in small quantities, at fre-
quent intervals, by a comparatively violent
muscular contraction.* Hence the separa-
tion of the chyme from the other contents
of the stomach seems to be effected by a pro-
cess somewhat analogous to a coarse filtra-
tion, aided by pressure.
How little the pylorus could reject the
" crude " portions of the tolerably homo-
geneous chyme, to transmit its more fluid or
dissolved constituents, is shown by the facility
with which indigestible substances of various
shapes and sizes pass into the duodenum.
Of these we can only say, that it is probable
they are generally carried through the con-
stricted pyloric sac and valve by a very forcible
peristalsis.f The weight and solidity of many
such masses allow them to remain some time
in the cardiac pouch, perhaps lodged behind
the transverse constriction which separates this
from the pyloric sac. Both of these circum-
stances often defer their passage to the later
stage of digestion. Smaller substances, how-
ever, sometimes traverse the whole canal in
so short J a space of time, that it is diffi-
cult to avoid believing that they leave the
stomach very shortly after entering it.
But while we may thus regard the pyloric
valve as exerting but one and the same action
during the whole period of gastric digestion,
we shall find it difficult to substitute any
other theory of its action for that local
appreciation or selection which we have
attempted to refute. Its contraction is ac-
companied by that of the whole muscular coat
of the stomach ; of which the pylorus forms,
apparently, but a terminal thickening. And
of the only two other facts which are co-
temporaneous in their occurrence and dura-
tion viz., the presence of food, and of gastric
juice the first affords little explanation ;
while the second is more likely to be another
effect of the cause, whatever it may be, which
excites that co-ordinate muscular action in
which the pylorus appears to play an im-
portant, though simple, part.
It is interesting to observe how little the
action of the pylorus is connected with any
stimulus other than a gastric one. The flow
of bile into the fasting stomach may perhaps
be regarded as a passage, such as this janitor
might well concede to a fluid which is not
only harmless, but recrementitious. But in
* It is scarcely necessary to add, that the mecha-
nism of such an act does not require that the cardia
should be, however momentarily, the stronger valve
of the two. For the force of an obliterating peri-
stalsis would beat first almost spent upon the pylorus
towards which it sets. While that of a weaker con-
traction would be chiefly expended upon the py-
loric sac. And the residual force of both would
chiefly dilate the yielding and quiescent large ex-
tremity.
t A peristalsis, the energy of which it is pro-
bable that they themselves increase.
J Thus the author has known peas traverse the
canal in two hours.
316
STOMACH AND INTESTINE.
the obstructed canal, faeces pass through it
from the duodenum with equal facility, al-
though the stomach soon resents their pre-
sence by vomiting ; an act which seems
generally to imply a shut pylorus. And
Magendie* has observed, that the gases of
this upper portion of the intestine can be
made to pass the valve with equal facility ;
while those distending the stomach excite its
contraction.
Under ordinary circumstances, whatever
be the period during which the contents of
the stomach sojourn in its cavity, or the
movements they experience at this time, they
are finally propelled onwards into the duo-
denum.
Sometimes, however, they take a backward
course ; and pass through the oesophagus, to
re-enter the mouth, and be expelled from this
cavity. Such a reversal of their normal
direction occurs in the acts of eructation,
regurgitation, and vomiting. These acts,
however they may differ in their details, must
(a priori) agree in the conditions of their oc-
currence. They require a relaxation of the
cardia, a closure-)- of the pylorus, and a com-
pression of the stomach. The latter of these
three requirements may either be the result
of the contractions of the organ itself, or may
be effected by an external or independent
pressure.
In simple eructation or belching, part of
the gaseous contents of the stomach are
ejected from the mouth. This act generally
occurs towards the close of digestion, and in
dyspeptic individuals ; the quantities of gas
thus evolved being often very considerable.
In what way the cardia is opened, or how far
the evolution of large quantities of these aeri-
form fluids in the stomach may not contribute
to render it patulous, is at present very doubt-
ful. But the intermittent character of the
occurrence certainly looks unlike a mere leak-
age of an aeriform fluid. While the frequency
with which the human stomach contains gases,
and the completeness with which the cardia
resists their expulsion in vivisected animalsj,
increase the difficulty of such a supposition,
and, so far, tend to confirm that of a tem-
porary relaxation of this aperture. The di-
rect agent of the expulsive act seems equally
uncertain. The contractions of the stomach
seem quite sufficient to account for it. And
there is certainly no violent abdominal pres-
sure. But such mobile fluids would scarce
require a remarkable effort. While, as far as
can be judged, the act appears to coincide with
the period of expiration.
An examination of that voluntary eructa-
tion which most persons can accomplish, may
perhaps strengthen the conjecture, that some
* Op. cit. p. 83.
j- Of course this closure need only be comparative :
that is, the mere resistance of the contents of the
stomach to compression would suffice to determine
their passage through the more relaxed of its two
orifices.
J As in Magendie's observations, elsewhere al-
luded to.
slight abdominal pressure is a constituent of
the ordinary act. Here, by a kind of twitch-
ing * action of the oesophagus, which is ac-
companied by a sensation that is referred to
the upper portion of this tube, air is intro-
duced into its interior; and is then expelled,
with a considerable sound, by a well-marked
movement of expiration, during which the
glottis appears to be at least partially closed.
And the expulsion of the air artificially intro-
duced is often accompanied by that of a por-
tion which was previously contained in the
stomach itself. So that involuntary and vo-
luntary eructation may be said to merge into
each other, t
In the act of regurgitation, more or less of
the liquid contents of the stomach are returned
into the mouth. This act closely resembles the
preceding, of which it often appears to be an
accidental complication ; a small portion of
liquid being carried upwards, along with an
eructation of gas. In other instances, how-
ever, the liquid is unaccompanied by elastic
fluid ; and rises so quietly, that it is only per-
ceived on reaching the fauces and back of the
tongue, where its acid taste causes it to be at
once recognized. It is probable that the pro-
cess which effects this expulsion is similar to
that of eructation. If we could conjecture
any difference, it would be, that the abdominal
pressure plays a less important part.
The act of vomiting differs from both of
the preceding : not only in the miscellaneous
character of the matters which it can expel
from the stomach, and in the greater energy
with which it is effected; but also in the fact,
that a pressure extrinsic to the organ itself
here forms what is, at any rate, the chief agent
of the process.
This abdominal pressure, which has been
before alluded to, we shall now proceed to
describe.
In those ordinary movements of respiration
which are executed chiefly by the diaphragm
and abdominal muscles, the bulk or capacity
of the belly is little affected. For during the
act of inspiration, the descent or contraction
of the former, exactly coincides with the relax-
ation of the latter muscular structures ; while
during that of expiration, the compression
which these exercise is neutralized by the re-
cession or ascent of the now relaxed dia-
phragm. Hence the moveable viscera of the
belly themselves evade all pressure ; and
merely transfer a very slight force from the
anterior to the upper wall of the cavity, or
vice versa. But if, while the diaphragm re-
mains depressed and contracted, the abdo-
* This is often called a deglutition of air, although
the movement is utterly unlike that of swallowing.
f Thus the dyspeptic poor Avho crowd the out-
patient rooms of hospitals, sometimes eructate so
voluntarily, and even ostentatiously, that the act
really seems to be done, not so much to expel gas
from an over-distended stomach as to attract com-
miseration. And it is said that, in polite Chinese
circles, a chorus of eructations at the end of a
banquet formally acquaints the host with the re-
pletion of his grateful guests.
STOMACH AND INTESTINE.
317
minal muscles be also brought into vigorous
action, the whole force of either of these
two muscular strata may be regarded as com-
pressing the viscera within the abdominal
cavity. And since many of these viscera are
hollow organs, which enclose moveable con-
tents, and communicate with the exterior of
the bod}, such a forcible pressure will expel
the contents from their interior, so soon as
their terminal orifices are thrown open;
whether by their relaxing spontaneously, or
yielding to any superior force. In this way,
the contraction of the walls of the belly plays
an important part in the acts of defaecation,
micturition, and parturition, as well as in that
of vomiting.
Now in the three former of these acts, the
intermittent abdominal pressure does but assist
those more continuous expulsive contractions
which are effected by the muscular walls of the
hollow viscera themselves. And supposing
that the cardia were open, and the pylorus
shut, it is obvious that either pressure on the
stomach, or contraction of its walls, would
alike tend to expel its contents.
Careful observation of the act of vomiting
in any of the higher animals will show that it
is always assisted by the abdominal pressure.
And the vivisections which many experi-
menters have practised, agree in carrying this
investigation further ; and in stating, that
this pressure, which ordinarily results from
simultaneous contractions of the diaphragm
and abdominal muscles, may be due solely to
the latter*, (as is normally the case in
Birds f ), or to the former, or even to an
inconsiderable compression exerted by the
lower ribs upon the epigastric region.^
While the solitary observation of Maingault <J,
which affirms the occurrence of vomiting in
the absence of all such pressure, stands ex-
pressly contradicted by the Committee of
the French Academy appointed to report
upon his Memoir.
But whether the stomach really contracts
during the act of vomiting, and if so, what
is the amount of assistance which it thus af-
fords this process, are questions which, long
the object of physiological controversy, can
even now scarcely be regarded as decided.
On the one hand, there are not wanting
experiments, which show that the act of
vomiting may be effected without the aid of
any gastric contractions whatever. Among
such we may specially adduce the vivisection
practised by Magendie ||, in which a Pig's
bladder was substituted for the stomach of
a living Dog, and was subsequently emptied,
bv vomiting, of a large part of its contents.
Such a result conclusively proves that gas-
tric contractions are not essential to the
physical act of vomiting, however frequently
they may take a part in the process. And
* Magendie, Sur le Vomissement, pp. 22. 37, 38.
f Krimer in Horn and Xasse's Archiv. 1816.
J Bulletin de la Facultede Medecine, 1813. No. 10.
p. 481. et seq.
Sur le Vomissement Paris, 1813.
II Op. cit. p. 18.
that inactivity of the stomach, which has
been directly observed by many * physio-
logists in the artificial vomiting of vivisected
animals, has been all but actually seen in the
living human -j- subject.
On the other hand, the observations in
which a muscular contraction of the stomach
has been seen to concur in this act, are even
more numerous than the preceding. The
amount of such contraction seen appears to
have varied, having sometimes been so slight
as to be scarcely visible. In all instances, it
has specially engaged the pyloric extremity of
the organ: and, in most, it is described as
either circular J, and alternating with relaxa-
tion; or peristaltic, like that found in the di-
gesting stomach, independently of all vomiting.
And though an anti-peristaltic movement is
detailed by Haller and others, yet so far as I
can find, this doctrine, which is expressly con-
tradicted by the observations just referred to,
rests only on one or two vague descriptions
of Wepfer, Rudbeck, and Schwartz.
From these very brief allusions to both
sides of this conflicted question, the author
has been careful to eliminate every statement
which does not refer to actual facts. And
the reader must recollect, that not only
does the stomach offer few obstacles to such
direct observations |j, but that some of those
summed up in the above statements, are ren-
dered additionally trustworthy by being results
quite at variance with the theories of their
observers ; while others have been confirmed
by very frequent and careful repetition.^
Hence, on the whole, I think we must con-
clude as follows: The act of vomiting is es-
sentially, and perhaps sometimes solely, the
result of powerful abdominal pressure on the
contents of the stomach. It implies a pa-
tulous cardia. The abdominal pressure which
effects it, often coincides with, and is aided
* Bayle, Wepfer, Chirac, Baciaccus, Senac,
Schwartz, and (especially) Magendie.
t Lepine, Bulletin de* r Academic de Medecine,
vol. ix. p. 146. In this case, which has been strangely
misquoted by many English authors, the stomach
was protruded from a wound in the belly. It con-