INTERNATIONAL MEDICAL MONOGRAPHS
rDR. LEONARD HILL, F.R.S.
General Editors | DR WlLUAM BULLOCH
WALTER B. CANNON, A.M., M.D.
GEORGE HIGGINSON PROFESSOR OF PHYSIOLOGY
NEW YORK : LONGMANS, GREEN & CO.
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TO THE MEMORY OF
PROFESSOR HENRY PICKERING BOWDITCH
IS GRATEFULLY DEDICATED
THIS ACCOUNT OF RESEARCHES BEGUN
UNDER HIS INSPIRATION
GENERAL EDITORS' PREFACE
THE Editors hope to issue in this series of International Medical
Monographs contributions to the domain of the Medical Sciences
on subjects of immediate interest, made by first-hand authorities
who have been engaged in extending the confines of knowledge.
Readers who seek to follow the rapid progress made in some
new phase of investigation will find herein accurate information
acquired from the consultation of the leading authorities of
Europe and America, and illuminated by the researches and
considered opinions of the authors.
Amidst the press and rush of modern research, and the multi-
tude of papers published in many tongues, it is necessary to find
men of proved merit and ripe experience who will winnow the
wheat from the chaff, and give us the present knowledge of their
own subjects in a duly balanced, concise, and accurate form.
In this the first volume of the series Professor Cannon deals with
the Mechanical Factors of Digestion. Professor Cannon initiated
the method of studying the movements of the bowels by means
of the Rontgen rays, and all subsequent researches have been
based on his discoveries. We confidently expect that this valu-
able monograph, containing the fruit of many years' work, will
prove of the greatest interest and help to those seeking to under-
stand a subject which is of the first importance in Practical
RESEARCHES conducted by the writer and his collaborators in
the Physiological Laboratory of Harvard University during the
past ten years form the basis of this book. In describing these
researches, the related work of other investigators has also been
incorporated, and although the exposition of the subject is not
intended to be encyclopedic, the whole presents an account of
the mechanical activities of the alimentary canal as they are
now known and understood. The plan here followed runs the risk
of emphasizing unduly a single series of investigations ; but, on
the other hand, it has the advantage of offering mainly direct
testimony rather than secondary interpretation.
Most of the original accounts of the experiments in the Harvard
Physiological Laboratory have appeared in American journals
devoted to the medical sciences. Much of the material which
now appears in Chapters XIV. and XV. has not previously been
published, except in brief notes in the Proceedings of the American
The hope of everyone who has tried to extend the boundaries
of knowledge is that others will soon take up the work where he
has dropped it ; and if this book should by chance stimulate
further investigation, its most cherished object will have been
WALTER B. CANNON.
GENERAL FEATURES OF THE MOVEMENTS OF THE ALIMENTARY
CANAL, AND METHODS OF INVESTIGATION
Functions of the gastro-intestinal movements -Propelling food, mixing
food and secretions, exposing digested food for absorption Uni-
formity of structure of canal Uniformity of action Peristalsis
Extrinsic control Methods of studying the movements ; fistulae,
exposure under warm salt solution, X rays Details of X-ray
procedure - - - ... . 1 7
THE MOVEMENTS OF MASTICATION AND DEGLUTITION
Movements of mastication : Duration Comminuting effects Co-opera-
tion with saliva Dental pressures Effects of mastication on later
digestive processes 8 II
Movements of deglutition : Discharge theory of swallowing Movements
of the mouth parts Pressure developed Experiments of Kronecker
and Meltzer X-ray observations of deglutition in various animals
Differences with different consistencies of food - - 11 19
THE NERVOUS CONTROL OF DEGLUTITION
Histological basis for the observed variations in deglutition Sensory
areas for deglutition Nervous control of buccal and pharyngeal
muscles Innervation of the oesophagus Two ways by which the ^0?
vagi effect oesophageal peristalsis ; primary and secondary peristalsis
Effect of vagus section A tertiary peristalsis - 20 31
CONDITIONS AFFECTING THE ACTIVITIES OF THE CARDIA
Nature of the cardia Normal state Degree of tonicity Action after
deglutition Nervous control Effects of vagus section Spasm of
the sphincter Rhythmic oscillations of contraction and relaxation
Effects of acid in the stomach Regurgitation of gastric contents
in man - - 32 44
THE MOVEMENTS OF THE STOMACH
Nature of the gastric reservoir Its relation to the activities of the small
intestine Anatomy of the stomach: its musculature Position of
the normal stomach, and the question of gravity drainage Change
in shape of stomach during digestion Peristalsis of the gastric tube
Function of the cardiac sac Two views of gastric peristalsis, with
reference to the pyloric vestibule Functions of the vestibule to
churn and expel the chyme- -Rate of gastric peristalsis, and
conditions affecting it - - . 45 53
THE EFFECTS OF STOMACH MOVEMENTS ON THE CONTENTS
Adaptation of the stomach to a changing amount of contents without
change of pressure Intragastric pressure : different in the cardiac
and pyloric ends Theory of the circulation of gastric contents
X-ray observations of the motions of the food Churning of the
food in the pyloric end Immobility of the food in the cardiac sac
Superficial digestion of this food Application to man Churning
mechanism in the pyloric vestibule Importance of this mechanism
for admixing gastric juice, continuing gastric secretion, promoting
absorption, triturating and expelling chyme - - 59 70
THE STOMACH .MOVEMENTS IN RELATION TO SALIVARY
DIGESTION, AND GASTRO-ENTEROSTOMY
Salivary digestion in the stomach : Conditions in the cardiac end of the
stomach favourable Difference in sugar percentage in two ends of
the stomach Effect of giving liquid food, and small amounts
Importance of salivary digestion - 71 74
Movement of food after gastro - enterostomy : Futility of gastro-
enterostomy as a drainage operation Food near pylorus more fluid
and under more pressure than elsewhere in the stomach Food
leaves by the pylorus rather than by stoma even if pylorus narrowed
Conditions for circulation of food Obstructive kinks of the gut,
and means of avoiding them Compensation for disturbed course
of the food Superiority of pyloroplasty 74 83
THE PASSAGE OF DIFFERENT FOODSTUFFS FROM THE
X-ray method of studying gastric discharge Consideration of defects of
the method Objections to other methods The discharge of fats
The discharge of carbohydrates The discharge of proteins Com-
parison of the carbohydrate and protein discharge The discharge
when carbohydrate or protein is fed first, and the other second
The discharge when mixtures are fed : protein-fat, carbohydrate-
protein, carbohydrate-fat - 84 95
THE ACID CONTROL OF THE PYLORUS
Stomach emptied progressively by occasional opening of the pylorus
Inadequate explanation by mechanical conditions in stomach or
intestine Explanation by chemical conditions The failure to
recognize the two factors concerned in gastric discharge The facts
to be explained Theory of the control of the pylorus by opposite
action of acid above and below Evidence that acid in the vestibule
opens the pylorus, and in the duodenum keeps the pylorus closed 96111
THE CORRELATING FUNCTIONS OF THE PYLORUS, AND
SOME CONDITIONS AFFECTING IT
Importance of the pylorus in correlating gastric and intestinal secretory
and digestive processes Explanation of the differential discharge of
the different foodstuffs The peculiar discharge of fats Passage of
water through the stomach The discharge of egg-white Influence
of hyperacidity on gastric discharge Influence of consistency of
food ; of the presence of hard particles Influence of gas in the
stomach Influence of heat and cold The effects of some patho-
logical conditions ; intestinal injury, irritation of the colon, absence
of gastric secretion - 112 129
THE MOVEMENTS OF THE SMALL INTESTINE
Importance of the small intestine Co-operation of mechanical factors
Rhythmic segmentation ; various types, occurrence in different
animals, functions, its relation to " pendulum movements "
Peristalsis ; nature of the peristaltic wave, combined peristalsis and
segmentation Relation of peristalsis to end-to-end and lateral
intestinal union Peristalsis in the presence of intestinal obstruction
Question of antiperistalsis Peristaltic rush ; its probable function
Course of food in the small intestine Rate of passage of different
foodstuffs through the small intestine - - 130 147
THE MOVEMENTS OF THE LARGE INTESTINE
Relations of stomach and caecum in herbivores Functions of the caecum
and proximal colon Antiperistalsis in the proximal colon (cat)
The changes when food enters the colon Antiperistalsis of the colon
in other animals than the cat The question of antiperistalsis in the
human large intestine Antiperistalsis with reference to the ileo-
colic sphincter, with reference to the passage of material from colon
to ileum The distal colon ; tonic constrictions Movement of the
contents Defaecation Conditions preceding the act in man - 148 163
AUSCULTATION OF CASTRO-INTESTINAL SOUNDS
Early observations on alimentary sounds Rhythmicity characteristic
of the movements of the canal Method of recording sounds Sounds
produced by the stomach Sounds produced by the small intestine
Sounds produced by the large intestine Other auscultatory
observations Use of the method - 164 17
THE INTRINSIC INNERVATION OF THE GASTRO-
Nature of peristalsis in the small intestine Evidence of local control
The "law of the intestine" : contraction above, relaxation below, a
stimulated point Nature of the rhythmic contractions Their
dependence on nervous connections Importance of the refractory
period for the rhythm Conditions governing peristalsis and
rhythmic contraction - - 178 185
Peristalsis and antiperistalsis in the large intestine The local reflex
Nature of antiperistalsis Origin of antiperistaltic waves in a
pulsating tonus ring Relation to internal pressure - - 185 190
Nature of gastric peristalsis Similarity to antiperistalsis of the colon
Explanation of gastric waves by experimental conditions in the
large intestine Gastric antiperistalsis - - 190 194
Myenteric reflex Its presence throughout the alimentary canal Co-
existence with other waves moving forward or back Importance of
the tonic state for these waves - - 194 196
|,'THE EXTRINSIC INNERVATION OF THE GASTRO-
INTESTINAL TRACT j
Origins of the extrinsic nerves Innervation of the stomach Effects of
vagus stimulation Immediate atony after vagus section, and later
recovery Nature of vagus action Psychic tonus Ineffectiveness
of vagus section during digestion Receptive relaxation of the
stomach Inhibition of gastric tonus by splanchnic influences The
question of sensations arising in the stomach ; visceral pain
Hunger - 197204
Extrinsic innervation of the small intestine : Effects of vagus stimulation
Effects of splanchnic stimulation Effects of severing these nerves
Elimination of vascular influences - - - 204 205
Extrinsic inner vation of the large intestine : Lumbar and sacral supply
Crossed innervation Effects of nerve section Defalcation - 205 207
Inner vation of the sphincters : Pylorus Ileo-colic Internal anal
sphincter Rule of sympathetic innervation - - - 207 209
DEPRESSIVE NERVOUS INFLUENCES AFFECTING GASTRO-
Influence of asthenia on gastro-intestinal movements Effects of nerve
section on the phenomenon - . 210 211
The nature of post-operative paralysis Effects of etherization, of
exposure, of cooling, and of manipulation Local and reflex
paralysis Local paralysis from manipulation Reflex paralysis via
the splanchnic nerves Importance of distinguishing the two sources
of inactivity - - 211 217
Influence of emotional states Inhibition of gastric peristalsis and of
intestinal movements Course of inhibitory impulses Importance of
mental states favourable and unfavourable to digestion - 217 220
Publications from the Laboratory of Physiology of Harvard University
bearing on the Mechanical Factors of Digestion 221
Index ........ 223
THE MECHANICAL FACT
GENERAL FEATURES OF THE MOVEMENTS OF THE ALIMENTARY
CANAL, AND METHODS OF INVESTIGATION
SINCE the digestive tube is an enfolded portion of the body
surface, food taken into it is not in the body, but is merely
enclosed. The chief functions of digestion are to render the
food serviceable, and to give it a consistency suitable for passage
through the wall of the tube into the body. The region in which
occur the final preparations for entrance of the food into the
body is the small intestine. There the enzymes are found that
finish the work begun by the enzymes of the mouth and stomach.
In the small intestine also the digested material is mainly
absorbed. Indeed, this long, narrow portion of the alimentary
tract may rightly be regarded as the very centre of digestive
and absorptive activity, with a preparatory reservoir, the
stomach, containing accumulated food, which it delivers gradually
to the small intestine, and with a terminal reservoir, the colon,
ready to receive accumulating waste.
The two general factors of digestion, the chemical and the
mechanical, which work towards the absorption of the food, are
intimately interrelated. Although our consideration of the
activities of the canal will lay emphasis on the mechanical
factors, we must not fail to keep in mind the chemical agencies
which they accompany and with which they co-operate. The
mechanical factors have the functions of mixing the food with
the secretions poured out upon it, of exposing the digested food
to the absorptive wall, of propelling the food from one region of
digestion or absorption to another, and finally of discharging the
waste. These functions are of great import to the body, for the
2 THE MECHANICAL FACTORS OF DIGESTION
food, if conducted too slowly along the tube, may suffer harmful
decomposition ; and if forced on too rapidly, it will fail to be
properly digested, and will in large measure be lost. We may
expect to find, therefore, that the rate of passage through the
different parts of the tube is nicely adapted to the speed of the
The neuro-muscular structures by which the mechanical
functions of digestion are performed are singularly uniform
throughout the tube. They consist of two muscular coats
the circular coat nearer the lumen of the tube, and the outer
longitudinal coat. The latter may be lacking in small areas,
especially in the region of the stomach. Between these two
muscular layers is a primitive nerve plexus Auerbach's or the
myenteric plexus. At the beginning of the tube, and at its end,
striped muscle prevails, but except at these extremities the
musculature is of the smooth variety. Smooth muscle is charac-
terized by the relative slowness and the rhythmicity of its con-
tractions, and by its ability to exhibit rhythmic activities at
various levels of sustained shortening, or tonus. The great
importance of these characteristics will appear as we consider
further the functions that are performed by this smooth muscle
and its nerve plexus.
In accordance with uniformity of neuro-muscular structure,
the canal presents uniformity of mechanical action. In the
course of digestion the food is subjected to an orderly series of
sequentially related processes ; what occurs in an advanced
region is more or less dependent on what has occurred in a
region previously traversed. The food, therefore, must be moved
always onward. The continued progress of the food is accom-
plished in the main by peristaltic waves rings of constriction
which sweep slowly along limited extents of the canal. These
waves are an expression of the neuro-muscular arrangements in
the wall. Although, as we shall see, the peristalsis of the
stomach and proximal colon is somewhat different from that of
the small intestine, we need not restrict the term to any particular
region. In all parts of the canal, therefore, peristalsis is the
most characteristic mechanical activity that affects the digestive
The manner in which peristalsis operates varies in different
parts. Where digestive juices are lacking and absorption does
not occur, as in the oesophagus, the waves press the food onward
MOVEMENTS OF THE ALIMENTARY CANAL 3
with rapidity. On the other hand, where digestion and absorp-
tion can take place, rapid progression is prevented by sphincters ;
and the recurring peristaltic waves passing over the food toward
closed sphincters serve to mix the food with the digestive juices,
as in the stomach, or to expose the food to the absorbing mucosa,
as in the ascending colon. In the long course of the small
intestine, where there are no sphincters to oppose peristalsis,
peristaltic activity is less noteworthy than in the other regions,
and the mixing and churning functions are performed by a special
method the rhythmic contraction of the circular fibres which
knead the intestinal contents without causing any considerable
progression. The advancement of the contents in the small
intestine, however, is effected by the peristaltic wave. In all
regions of the digestive tube, therefore, this wave is to be seen
as the means of conveyance.
The muscles at the beginning and at the end of the canal are
under voluntary control. Thus we can determine what food
shall be taken into the tube, and when, and we can, within limits,
govern the discharge from the tube. The great mid-region,
however, is normally automatic, and free from voluntary inter-
ference. The active stomach, for example, can be removed
from the body and placed in a moist chamber, where its contrac-
tions will continue for an hour or more. These automatic
structures are, nevertheless, subject to influences from the
central nervous system which augment or diminish their inherent
activity. The important relations which exist between the
alimentary tract and the central nervous system have only
recently been ascertained, as new methods of research have brought
forth the clear evidence. We shall see that disturbances arise
if the extrinsic innervation is removed, and that disturbances
may arise also because the extrinsic innervation is present.
The sensitiveness of the alimentary canal to operative inter-
ference has been the chief difficulty in past investigations of
the digestive process. The stomach and intestines, energetically
active during the height of digestion, are prone to cease their
activities suddenly when the abdomen is opened, a striking
change, likened by Meltzer to the hush that falls upon a company
when a stranger appears at the door. Of course, under these
circumstances the normal movements of the canal cannot be
studied. The famous physiologist, Johannes Miiller, testified
that he had never seen clearly the peristaltic movements of the
THE MECHANICAL FACTORS OF DIGESTION
stomach. For centuries the priests and the butchers, who
watched the entrails of their sacrificed victims, knew as much as
the physicians about the mechanical factors of digestion. Only
as methods were devised which maintained more or less perfectly
the normal conditions of the digestive organs were the natural
activities slowly ascertained.
Among the methods employed to preserve so far as possible,
or to simulate during investigation, the usual surroundings of
the alimentary canal, the fistula is the oldest. Through an
opening between the lumen of the canal and the body surface,
registering apparatus has been introduced which indicated the
movements of the region. Fistulas made at different distances
along the tube have also been used to study the rate of advance-
ment of the food and the degree of its alteration as it passed from
one stage to another in digestion. At best, however, the fistula
permits only an inferential judgment of the mechanical agencies
at work in a narrowly localized portion of the canal, a portion,
furthermore, which may be disturbed by the adhesions due to
Less disturbing than the fistula method is the direct intro-
duction of registering apparatus through the mouth. Thus the
time relations of changes of pressure in the pharynx, the oesoph-
agus, and the two ends of the stomach, have been obtained,
and conclusions have been drawn as to the activities that pro-
duced the pressures.
A method giving more direct information than either of the
foregoing methods is that introduced by v. Braam-Houckgeest, 1
which consisted in opening the abdominal cavity of the anesthe-
tized animal in a bath of physiological salt solution at body
temperature. If the temperature of the solution is sustained
and active digestion is in process, the normal movements of
the stomach and intestines can be directly observed. The
method involves such serious operative interference, however,
that with some animals (e.g., the rabbit 2 ) the usual gastric peri-
stalsis suffers profound and lasting nhibition. The effects of
the movements on the food, and the rate at which the food is
advanced, cannot be readily ascertained in the salt bath.
All physiological processes observed under conditions rendered
unnatural by the exigencies of the method employed must be
subject to standardization by the results of studies made under
more natural conditions. None of the methods above described
MOVEMENTS OF THE ALIMENTARY CANAL 5
preserve strictly the normal state of an animal digesting its food
in its usual manner. When the X rays were discovered, a new
means of investigating the alimentary tract was provided, which
permitted observations to be made without interfering with
the animal to any disturbing degree. This means of research
was suggested to me, when a medical student, by my teacher
of physiology, Professor H. P. Bowditch, in the autumn of
1896. The results obtained by use of the X rays prove that,
in order to reveal the natural activities of the digestive organs,
the older methods must be used with extreme care. When such
care is exercised, however, those methods can be safely employed
to confirm and supplement the X-ray observations. Most of
the data which will be hereafter presented have been secured
by study of the deeply hidden alimentary canal by means of
the X rays.
The method consisted in giving animals food thoroughly
mixed with subnitrate of bismuth,* and observing the shadows
cast by the X rays on a fluorescent screen. Thus the dense
bismuth powder, uniformly mixed with the food that fills the
stomach, throws the dark shadow of the stomach contents on
the screen, and the changes in the shape of the outline reveal
the movements of the organ. That the addition of bismuth
subnitrate to the food produces no peculiar effects on the move-
ments has been proved by finding no noteworthy differences
when other heavy salts, as, for example, barium sulphate, is
mixed with the food. 3 Clinical studies on man by Schule also
indicate that subnitrate of bismuth in the food does not inter-
fere with normal gastric motility, 4 and observations by Cook
and Schlesinger show that bismuth oxychloride passes through
the digestive tube at the rate of charcoal. 5
The animal most commonly used in the laboratory investiga-
tions was the cat. Confirmatory observations, however, have
been made on the dog, rabbit, guinea-pig, white rat, and on
man. For studying the conditions in the cat, deprivation of
food for twenty-four or thirty hours previous to the feeding was
usually necessary, in order to make certain that the digestive
* A few of the animals unaccountably died after being observed. Cases of
death or severe poisoning in man after the administration of large doses of
subnitrate of bismuth have been reported in Germany and the United States.
As the subnitrate of bismuth may to some extent be chemically changed in the
stomach, Hertz has advocated the use of bismuth oxychloride, which is un-
affected by either the gastric or the intestinal juices. (See Hertz, Contiipithn
and Allied Intestinal Disorders, London, 1909, p. 335.)
6 THE MECHANICAL FACTORS OF DIGESTION
tube was empty. A dose of castor-oil, administered about twelve
hours before the feeding, gave still further assurance that only
the digestion of food mixed with the bismuth salt would be
observed. The animals were either permitted to eat voluntarily
from a dish, or were placed on the animal -holder and fed from
a spoon, usually with little or no difficulty. The amount of food
given varied between 25 and 50 c.c., except where uniform
amounts were given for special purposes. One or two grammes
of the bismuth powder produced a dim shadow of the stomach
within which could be clearly seen the darker forms of any food
containing a larger amount of the substance. Four or five
grammes, mixed with 25 c.c. of food, were needed to see the
passage of the food from the pylorus.
The animal-holder consisted of a framework supporting a
sheet of black rubber cloth. The frame was made of two side-
pieces, each 80 centimetres long and 2-5 centimetres square,
connected at either end by blocks 2-5 centimetres thick,
12-5 centimetres wide, and 16 centimetres long. The rabber
cloth, which sagged for the comfort of the animal, was fastened
by strips of wood to the inner surface of the frame. Through the
side-pieces were holes 0-6 centimetre in diameter, and 5 centi-
metres apart. The legs of the animal were secured by leather
nooses ; the leather passed down through one of these holes and
up through another, in which it was made fast byforcing a pointed
peg into the hole with it. The cat's head was held by two
adjustable pegs, one on either side of the neck, which were con-
nected above. The advantage of this holder lay in its comfort-
ableness for the animal, and in the ease of feeding which it per-
mitted in case artificial administration of food became necessary.
For seeing the regular movements of the stomach, the animal
was tied back downward, with the fore -paws in nooses at either
side, and the hind-legs stretched out and fastened to the holder
in such manner as to permit the body to lie slightly turned
towards the right side. This position was also favourable for
watching the course of food through the oesophagus. The
movements of food in the intestines could be readily observed
with the animal lying directly on the back. Female cats lay on
the holder sometimes for periods of an hour or more without
making attempts to break away or manifesting signs of dis-
comfort. In marked contrast was the behaviour of the male
cats ; almost without exception they showed signs of anxiety .
MOVEMENTS OF THE ALIMENTARY CANAL 7
or rage when fastened down. The important effects on digestion
arising from these different ways of reacting to the novel sur-
roundings will be described later.
The animal-holder was supported on a leaden surface in which
a hole was cut only sufficiently large to permit the body of the
animal to be illuminated by the X rays. Below the holder,
at a distance of 30 centimetres between the anode and the
animal, was placed the tube generating the rays. The tube was
so surrounded by lead that none of the rays could reach the
observer. The observations were conducted in a dark room.
All light from the tube and from the machine which generated
the electric discharge was shut off from the observer by drapings
of black cloth. Thus in an open fluorescent screen placed on
the animal's belly, the shadows could be observed simultaneously
by more than one person. Over the screen was fastened a layer
of lead glass. On transparent tissue paper laid over the glass
the outlines of the gastric and intestinal contents could be traced,
and thus records of the conditions at various times in the course
of digestion could be preserved. In case of doubt as to the
accuracy of the tracings, an electric light momentarily flashed
on the tracing before the tissue paper was removed from the
screen permitted the outlines drawn on the paper to be compared
with the shadows, and the records thus verified.
By use of the X rays the rate of passage of food through the
oesophagus, the speed of gastric peristalsis and its rhythm, the
oscillating contractions of the small intestine, the peculiar anti-
peristalsis of the large intestine, the rapidity of discharge of
gastric contents into the duodenum, the time required for material
to be carried to the colon, and all the influences external and
internal that affect these processes, can be observed continuously
for as long a time as the animal remains in a state of peace and
contentment. The results of these observations we shall now
begin to consider.
1 v. Braam-Houckgeest, Arch. /. d. Ges. PhysioL, 1872, vi., p. 203.
2 See Auer, Am. J. Physid., 1907, xviii., p. 359.
3 Cannon, Am. J. Physid., 1904, xii., p. 388.
4 Schule, Ztschr. f. Klin. Med., 1896, xxix., p. 07.
5 Hertz, loc. cit., p. 335.
THE MOVEMENTS OF MASTICATION AND DEGLUTITION
THE MOVEMENTS OF MASTICATION.
THE freedom of movement of the lower jaw permits a wide
variety of relations between the upper and lower rows of teeth.
They can be brought together, separated, or pressed with a
sliding motion one row upon the other either forward and back-
ward or from side to side. The up and down motion is essential
to the use of the biting front-teeth; the side to side motion is
more useful in the later process of chewing. The tongue and
cheeks act like the hopper of a mill, and force the food between
the grinding facets until it is broken or torn into fragments of
proper size for swallowing.
The duration of mastication varies with appetite, with age,
the demands of business, the quantity of food in the mouth,
and especially with the nature of the food whether fluid or
gummy, moist or dry, crisp or tough. The amount of mastica-
tion given any food is related to the readiness with which a mass
is comminuted, insalivated and gathered into a bolus, and is
not related to the degree of salivary digestion. Thus soft, starchy
food is little chewed, whereas hard or dry food, not starchy
in nature, may require much chewing before ready to be
The effect of the mechanical treatment in the mouth is the
production of a semi-fluid mush in which there are likely to be
particles of varying size. Lehmann has reported that when he
chewed different substances, such as beef, macaroni, potato,
and raw apple, until the impulse to swallow came, some of the
substance was already in solution; and of the rest, by far the larger
amount was reduced to particles less than 2 millimetres in
diameter. 2 Such jcomminution must result in an enormous
MASTICATION AND DEGLUTITION 9
increase in the surface exposed to the action of digestive enzymes,
and thereby promotes the rapidity of their action. The observa-
tions of Lehmann have been confirmed by Fermi and by Gaudenz.
In the mushy mass, however, Gaudenz found 3 particles over
7 millimetres in diameter, and he states that the largest normally
swallowed do not exceed a diameter of 12 millimetres. For
determining the proper grade of fineness of the food, the tongue,
the teeth, the gums and cheeks, make the needed investigation.
If some particles in the bolus as it is carried backward in the
mouth are too large, they are returned for further mastication.
The secretion of saliva, which softens the hard particles in
the food, and with its ptyalin starts the digestion of starches,
is also promoted by the movements of mastication. According
to Gaudenz, 4 the weight of the material in the mouth when ready
to be swallowed varies in man between 3-2 and 6-5 grammes,
and of this, if the food has been chewed for twenty or thirty
seconds, 1 or 1-5 grammes may be saliva.
The mass suitable for normal mastication has an average
volume of about 5 c.c. Not all animals chew the food as finely
as man commonly chews it. The dog and cat swallow pieces
of meat so large that apparently the oesophagus must have
difficulty in conveying them, and yet these animals seem to have
no instinct to divide this food into smaller and more readily
manipulated fragments. The large lumps are merely moved
about in the mouth until they are coated. with saliva, and are
then forced backward into the gullet. In man, also, food may
be swallowed in such haste that it is barely covered with the
saliva which usually lubricates the passage through the oesoph-
agus. Masses 10 or 12 millimetres in diameter may thus
enter the stomach with little evidence that the teeth have in
any way affected them. The ability to bolt food in unbroken
masses can doubtless be cultivated ; and a person who has made
himself an expert in this act can probably push downward bigger
masses than those just mentioned.
The pressure exerted in the process of mastication may be /
surprisingly great. The pressure which the molars, for example,
are capable of exerting, as determined by a spring dynamometer,
may be as high as 270 pounds. 5 With a direct thrust the crush-
ing-point of cooked meats has been found to vary between
15 and 80 pounds ; of candies, between 30 and 110 pounds ; and
of various kinds of nuts, between 55 and 170 pounds. The figures
10 THE MECHANICAL FACTORS OF DIGESTION
for meats may be considerably less if the jaws grind from side
to side. The teeth then bite through cooked tongue when the
pressure is only 1 or 2 pounds, and through tough round of beef
when the pressure is about 40 pounds. Saliva is a further aid
to mastication if starchy food is being chewed. Thus soft bread
is not bitten through even with 60 pounds direct pressure, but
hardens to a solid mass. If the bread is softened with a little
saliva, it is easily masticated with a pressure of 3 pounds. 6
Before the saliva is well mixed with the food, however, the high
pressure may have to be applied a large number of times to-
X^reduce the mass to bits.
Breaking the food into fine fragments and mixing it thoroughly
with saliva, so that it might be sufficiently moist to be swallowed,
were formerly regarded as the most important results of mastica-
tion. Recent researches have revealed less obvious results.
The voluntary act of chewing has been found to have much
significance for the proper initiation of gastric digestion. During
mastication substances of pleasant taste are brought in contact
with the gustatory organs of the tongue and cheeks, and odours
released from the separated food rise to the olfactory region of
the nose, and through the pleasurable sensations aroused by
. these stimulations the gastric juice is reflexly started flowing,
in preparation for gastric digestion. 7 Not only in laboratory
animals, but also in human beings, this remote effect of pleasurable
sensation in the taking of the food has been demonstrated.
Hornborg and others have reported cases of gastric fistula in
children, in whom an active secretion of gastric juice was observed
when agreeable food was chewed, whereas the chewing of in-
different material was without influence. 8 As has been proved
by the experiments of Pawlow and Edkins, this initial " psychic
juice " may be a prime condition for continuance of gastric
secretion. We shall see that it may also be the prime con-
dition for the co-ordination of gastric and intestinal digestive
Still another remote effect which may result from the chewing
of agreeable food is the development in the stomach of a con-
dition of tonic contraction, a state of sustained shortening of
the circular muscles which nicely adapts the capacity of the
organ to the contents, whatever the amount swallowed. The
peristalsis of the stomach, which churns the food with the gastric
juice and pushes the chyme onward into the duodenum, is
MASTICATION AND DEGLUTITION 11
dependent on the tension developed in the muscular wall as a
result of its tonic state.
Although these secretory and motor activities of the stomach
are not, as we are aware, directly subject to voluntary control,
they are capable of being profoundly influenced, favourably or
unfavourably, by the character of the experiences, agreeable or
disagreeable, that attend the process of mastication. And these
experiences we can to some extent determine for ourselves.
THE MOVEMENTS OF DEGLUTITION.
The movements of deglutition, in common with many other
physiological processes, were explained by the older physiolo-
gists on anatomical grounds. Thus, Magendie 9 divided the act
into three parts, corresponding to the anatomical regions of the
mouth, pharynx, and oesophagus. The muscles of each of these
divisions were regarded as the active agents in propelling the
The function of moving the mass to the pharynx was variously
ascribed to the tongue itself, to the mylo-hyoid muscles swung
beneath the tongue, and to gravity. For the action of the second
part, the movements of the pharynx, there was more unanimity
of opinion, since the constrictors, especially the middle and
lower, were evidently concerned. The passage of a swallowed
mass along the oesophagus was, until 1880, ascribed solely to
peristalsis. In that year, Falk and Kronecker, 10 who had
studied the movements of the mouth and pharynx in degluti-
tion, advanced the theory that the act is accomplished by
the rapid contraction of the muscles of the mouth, and that
cesophageal peristalsis is of secondary importance.
The sudden discharge involved in Falk and Kronecker's
theory requires the temporary closure of all the exits from the
mouth except that into the oesophagus. That there is such a
closure anyone can observe to some extent in himself. When
the food has been sufficiently masticated, it is gathered in a
depression on the dorsum of the tongue, in readiness for swallow-
ing. The tip and sides of the tongue, pressed against the teeth
and hard palate, shut off the possibility of escape forward and
laterally we can swallow with the mouth open, but not with
the tongue relaxed. Since the paths of respiration and degluti-
tion cross just above the larynx, respiration is now reflexly
12 THE MECHANICAL FACTORS OF DIGESTION
stopped. A quick contraction of the mylo-hyoid muscles
suddenly presses the tongue upward against the hard palate,
and by a contraction of the hyo-glossus the organ is drawn
backwards. At the same time, by action of the palato-
pharyngeus muscles, which form the posterior pillars of the
fauces, the pharynx is drawn to a narrow cleft, and against
this narrow opening the soft palate is pulled by contraction of
the levator palati. 11 Thus exit into the naso-pharynx is pre-
Now, as the tongue rises and slips inward, it acts as a piston,
and drives the bolus first against the downward-sloping soft
palate, next against the back wall of the pharynx, then on
between the pharyngeal wall and the posterior surface of the
epiglottis, the tip of which lies in contact with the tongue's
base. 12 Thus far the top of the oesophagus has been kept
closed by pressure of the larynx against it. Immediately the
hyoid bone and the larynx are lifted and brought together,
and the epiglottis is pressed back till it shuts the laryngeal
aperture. As soon as the hyoid and larynx are lifted they are
pulled forward, and thus the oesophagus is opened. Meanwhile
the tip of the epiglottis slips downward along the back wall of
the pharynx, pushing the bolus, probably with a final quick
impulse, into the gullet. Then all the structures return to their
resting posit ons. Of course, this sequence of movements
occurs with precipitate suddenness, and can be known only by
most careful analysis.
Falk and Kronecker found that during the initiation of the
act of swallowing the closed buccal cavity showed a manometric
pressure of 20 centimetres of water. They found that the same
pressure appeared also in the oesophagus, but not in the stomach.
The pressure developed in the mouth was considered sufficient,
therefore, to force food quite through the oesophagus without
the aid of peristalsis. Confirmatory evidence for the theory
that the descent to the stomach is rapid was found in the common
experience that cold water can be felt in the epigastric region
almost immediately after being swallowed. And, further,
autopsies have shown that, when strong acids pass through the
gullet, they corrode areas only here and there, and not the entire
mucous membrane, as would be the case were the acid pressed
slowly to the stomach by peristalsis.
During the same year, in confirmation of the above results,
MASTICATION AND DEGLUTITION 13
the well-known experiments of Kronecker and Meltzer 13 were
reported. A rubber balloon, connected by a tube to a recording
tambour, was placed in the pharynx, and another balloon,
similarly connected, was introduced a varying distance into the
oesophagus. When water was swallowed, the increased pressure
on the pharyngeal balloon was instantly transmitted to the
first tambour, which recorded a rising curve on a rotating drum.
Almost immediately thereafter the cesophageal balloon was
compressed, and its tambour recorded a curve below the first.
After a varying number of seconds, according to the distance
below the pharynx at which the balloon was placed, a second
rise of pressure in the oesophagus was registered. The first
indication of increased cesophageal pressure was explained as
due to the sudden discharge of food past the balloon ; the second
curve was explained as due to a peristaltic wave which swept
more slowly along the tube.
To demonstrate that the first rise of pressure registered from
the oesophagus resulted from the rapid squirting of liquid from
the mouth, Meltzer devised another experiment. A strip of
blue litmus-paper was placed opposite the side openings at the
lower end of a stomach-tube. Attached to the paper was a
thread which ran through the tube to the upper end. The
tube was now passed into the lower end of the oesophagus,
and an acid drink swallowed. If only a half-second elapsed
after the beginning of deglutition, the litmus-paper, when
pulled away from the side openings, was found reddened by the
From these observations, Kronecker and Meltzer concluded
that liquids and semi-solids are not conveyed down the oesoph-
agus by peristalsis, but are forcibly squirted into the stomach,
by the rapid contraction of the muscles of the mouth, before the
muscles of the pharynx or the oesophagus have had time to
contract. For this purpose the mylo-hyoids alone are sufficient,
since the middle and inferior constrictors of the pharynx can be
sectioned without in the least interfering with the act. Indeed,
Meltzer has recently shown 14 that the musculature of the entire
cervical oesophagus can be wholly removed from a dog, and
that the animal thereafter is able to drink milk and water quite
normally even when the bowl is placed on the floor, and the
fluid must be forced into the thoracic oesophagus against gravity.
If the function of swallowing can thus be performed by the
14 THE MECHANICAL FACTORS OF DIGESTION
pressure developed in the mouth, the succeeding peristaltic
wave is of use merely to gather any fragments that may have
adhered to the wall in the rush of food through the oesophagus,
and to carry this meagre load to the stomach.
According to Kronecker and Meltzer, 15 the human oesophagus
may be divided functionally into three parts : a cervical part
6 centimetres long, a middle part 10 centimetres long, and the
lowest part of uncertain length. These three parts contract
in succession, 1-2, 3 and 6 seconds respectively, after degluti-
tion begins ; but each part, according to Meltzer, contracts as
a unit, simultaneously throughout its length. The duration
of the contraction is more prolonged in the lower thoracic section
than in the upper thoracic or the cervical section. The human
oesophagus, according to this view, would undergo three pro-
gressive sectional contractions not peristaltic in nature.
To determine whether the cardiac sphincter offered any
resistance to a rapid passage of food into the stomach, Meltzer
made use of another method. 16 If a stethoscope is placed over
the epigastrium during the swallowing of liquids, a sound can
be heard six or seven seconds after the rise of the larynx. The
sound is ascribed to the passage of the swallowed mass, liquid,
and air, through the tonically contracted cardia. In a few cases
a sound is heard immediately after swallowing, a result which
has been explained as probably due to insufficiency of the
cardia.* These phenomena led Kronecker and Meltzer to modify
their previous views. They now maintained that the swallowed
mass is not squirted directly into the stomach, but is checked
a short distance above the cardia. There it remains until over-
taken by the succeeding peristaltic wave, about six or seven
seconds later, when it is pressed onward into the stomach.
The methods employed in these carefully-conducted ex-
periments were possible sources of error. The presence of one
or more balloons and a stomach -tube in the oesophagus may
properly be regarded as disturbing to normal deglutition. What
can be done by the organism, while compensating for disturbing
experimental conditions, may not be the normal action of the
*, Hertz has suggested (Brit. M. J., 1908, i., p. 132) that the first sound is
caused by the impact of fluid against the posterior pharyngeal wall, for it is
louder in the prone than in the supine position. Since it can invariably be
heard in the neck region, it seems not to fit the occasional character which
Meltzer gave it. The second sound, Hertz states, is like a trickle in the
upright and like a squirt in the horizontal posture. It corresponds to the final
disappearance of the swallowed mass into the stomach.
MASTICATION AND DEGLUTITION 15
same organism in a more natural state. Furthermore, although
Kronecker and Meltzer themselves declared that their results
were true for liquids and semi- solids only, and admitted that a
dry bolus could not be shot down the gullet, yet the use of
the terms " liquid," " swallowed mass," and " bolus," easily,
leads to the inference that their results are true for the swallow-
ing of food of all consistencies.
With the purpose of studying the rate of movement of solids,
semi-solids, and liquids, in the normal oesophagus, Mr. A. Moser
and I undertook, in the autumn of 1897, observations on various
animals by means of the X rays. Thus anaesthesia could be
dispensed with, no operative interference would be required,
only the food itself would be present in the gullet ; in short, the
animal could swallow its food under quite natural conditions.
Observations were made on the long neck of the goose, on the
cat, dog, horse, and man. In watching the process of swallowing
in the goose, the neck of the animal was extended by a tall
pasteboard collar, which in no way compressed the gullet. A
bolus of corn-meal mush placed in the pharynx was seen to
descend slowly and regularly. About twelve seconds elapsed
while the bolus was moving through 15 centimetres of the
oesophagus. Careful records indicated a slight slowing of the
movement as the bolus descended. A syrup which, when mixed
with bismuth subnitrate, still dropped quickly from the end of
a glass rod was used as a liquid mass. This liquid, fed through
a pipette, also passed slowly and regularly down the oesophagus,
clearly by peristalsis. The rate was about the same as for solid
food. In the bird, therefore, peristalsis is the only movement,
without regard to the consistency of the food. The quick
propulsion of liquids from the mouth does not occur. In the
absence of this action a greater reliance on gravity is observed.
As the mouth is filled the head is raised, and the fluid, after
trickling into the oesophagus, is carried onward by peristalsis.
It is of interest to note that, when the mylo-hyoid muscles are
paralyzed in a mammal, the animal raises the head in swallowing, _
after the manner of birds.
In observations on the cat and dog, gelatine capsules con-
taining the bismuth powder or shreds of meat wrapped about it
were used as more or less " solid " food. For soft solids a mush
of bread and milk was selected, so fluid as to be easily drawn up
into a large-bore pipette, and yet so viscid as to retain the
16 THE MECHANICAL FACTORS OF DIGESTION
bismuth powder in suspension for a long period. After trying
a number of other methods, we finally decided that a simple
mixture of milk and bismuth subnitrate, shaken in a test-tube
and immediately drawn into a pipette, was the most satisfactory
means of supplying a liquid mass.
Solid food passed down the entire oesophagus of the cat and dog-
by peristalsis. In the cat the rate was uniform to the level of
the heart ; about four seconds were required for the passage.
In the lower section, from the heart to the stomach, the rate was-
distinctly slower. The distance was less than one- third the
entire canal, yet the time spent in this part was six or seven
seconds, or three-fifths of the entire time of the descent. In the
dog the solid bolus was quickly discharged into the oesophagus.,,
and descended rapidly for a few centimetres, sometimes nearly
to the base of the neck. Thereafter the rapidity was diminished ;.
yet no pause was observed the bolus simply moved more slowly.
Unlike the cat there was no slackening of speed below the level
of the heart, and without change of rate, therefore, the mass was
passed into the stomach. Four or five seconds were required for
the descent from larynx to cardia.
Semi-solids were carried in the dog and cat much as the solids
were carried. The only difference observed was a slightly more
rapid passage along the upper oesophagus in the cat. Liquids
were forced into the tube at a more rapid rate than the solids and
semi-solids. In the cat only 1-5 or 2 seconds were required for
the liquid to pass from the laryngeal to the mid-heart level. 17
Then, after a pause which lasted from a few seconds to a minute
or more, the oesophagus apparently contracted above the liquid,
and pushed it slowly into the stomach. Sometimes the peristaltic
wave seemed to be started by a swallowing movement, though
the exact course of the contraction could not, naturally, be
directly observed. In the dog, liquids were evidently squirted
for some distance along the cesophageal tube. To free the tube
from any disturbing tension or compression, the head of the
animal was released from the holde: and held in the hands.
Sometimes the liquid descended rapidly as far as the heart, at
other tunes no farther than the base of the neck. Without a
pause it then passed on with perfect regularity and entered the
stomach. Meltzer has reported direct observations of the oesoph-
agus of the anesthetized dog, and states that swallowed
liquids are projected rapidly a varying distance along the tube,
MASTICATION AND DEGLUTITION 17
the distance depending on the quantity swallowed, the force of the
swallowing movement and the degree of contraction of the
lower oesophagus. 18 When the liquid ceased its rapid flight,
instead of being promptly moved onwards, Meltzer states that
it suffered a considerable delay before a peristaltic wave arrived
and forced it along. This discrepancy between Meltzer's and our
observations was probably due to anaesthesia, which is known to
interfere greatly with oesophageal peristalsis ; for Meltzer has since
reported that objects present in the thoracic oesophagus of the
unanaesthetized dog are at once carried into the stomach without
the aid of any peristaltic wave started by the act of swallowing. 19
This peristalsis of local origin, which Meltzer has denominated
" secondary peristalsis," would account for the continuous pro-
gress of a swallowed bolus even when it has been projected deep
into the oesophagus by the forceful movements of the mouth.
The influence of consistency of food was further demonstrated
in a very simple way by our observations on the horse. A bolus
made from masticated hay or grain can be seen or felt passing
along the horse's oesophagus at the rate of 35 or 40 centimetres
per second. Even a mixture of bran and water, thin enough to
run easily through the fingers, was not carried faster than the
hay or grain. But liquids were shot along the gullet much too
rapidly to be accounted for by any peristaltic activity. Anyone
who will place his hand under the lower jaw of the horse while the
animal is drinking will find in the energetic contraction of the
mylo-hyoids a sufficient explanation of the rapid passage of water
through the oesophagus. The rate is more than five times as
rapid as that of solids and semi-solids.
X-ray observations of deglutition in the human being revealed
the same conditions that we found in the horse. Gelatine
capsules were seen descending steadily and regularly at a rela-
tively slow rate from the region of the pharynx to a point below
the heart. A semi-solid consisting of a mush of bread and milk
was traced over the same course, and it had nearly the same rate
of progression as the solid. In both cases the swallowed material
was evidently pushed onward by peristalsis. The X-ray observa-
tions of Lessen on persons who swallowed potato soup confirm
our conclusion that the passage of semi-solids through the
oesophagus is not sudden. 20
According to the X-ray studies of Hertz, solids pass along the
human oesophagus slowly, no matter what the position of the
18 THE MECHANICAL FACTORS OF DIGESTION
body ; the time required when the solids are well lubricated
varies between eight and eighteen seconds, but a dry bolus may
remain above the cardia many minutes. 21
We found no evidence of the contraction of the oesophagus in
three sections, as Kronecker and Meltzer reported. If the
oesophagus contracts in sections, with an interval of two or three
seconds between the contraction of adjoining sections, we should
expect a checking of the progress of the swallowed mass at each
stage. The steady progress of the bolus, as we observed it,
does not harmonize with the view that successive long stretches
of the oesophagus undergo each a single contraction simulta-
neously throughout its length. Schreiber, 22 who has studied
the contractions of the human oesophagus with the method used
by Kronecker and Meltzer, was also unable to find a separation
of the tube into three sections, each with its own time for con-
traction. Instead, his curves revealed the existence of a con-
striction registered gradually later as the recording apparatus
was placed gradually deeper in the oesophagus. This moving
constriction can be explained only as a peristaltic wave. As in
our observations on the cat, Schreiber found in man that peri-
stalsis was rapid in the upper oesophagus, and much slower in the
Although Schreiber showed that the first rise in Kronecker
and Meltzer's records could be obtained when the oesophagus
above the recording balloon was closed, or when the swallow
was " empty," the possibility of rapid passage of a bolus through
the oesophagus was not thereby excluded.
Our X-ray observations on the swallowing of liquids in the
human being are quite in accord with Kronecker and Meltzer's
contention. Water holding bismuth subnitrate in suspension
was drunk by the subject, and at each swallow the liquid was
projected rapidly through the pharynx and well down into the
thoracic oesophagus before it was lost to view. Hertz was able
to trace the passage of bismuth salt suspended in milk all the
way to the stomach in fourteen normal persons. After having
been " shot rapidly down the greater part of the oesophagus," the
fluid was forced slowly into the stomach. Between four and
eight seconds were required for the entire process, and of this
time about half was spent in going through the cardia. In the
head-down position fluids ascended the oesophagus at approxi-
mately one-third the rate of descent in the upright position. 23
MASTICATION AND DEGLUTITION 19
Mikulicz became convinced by repeated cesophagoscopic exam-
inations that not only is the resting tube in the thoracic region
wide open and filled with air, but that, owing to the elasticity
of the lungs, the pressure prevailing is slightly less than atmo-
spheric. 24 Doubtless this condition, if generally present in man,
is highly favourable to the projectile passage of liquids from the
mouth to the region of the cardia.
We may conclude that the act of swallowing varies in different
animals and with different consistencies of food. In various
mammals studied by means of the X rays, solid and soft mushy
foods were invariably carried down by peristalsis ; in the horse
and man, liquids were forcibly discharged along the oesophagus
by the quick contraction of muscles of the mouth, and even in
the dog and cat liquids descended for some distance faster than
more viscid masses. Whether liquids invariably descend to the
stomach at a rapid rate doubtless depends, as Meltzer has sug-
gested, on the amount swallowed, the force of the swallowing
movement, and the degree of contraction of the gullet. Since
two of these three factors are under voluntary control, it is quite
possible that mammals needing for any reason to propel liquids
rapidly through the oesophagus would in that necessity be able
to do so.
1 See Fermi, Arch. f. Physiol., 1901, Suppl., p. 98.
2 Lehmann, Sitzunjsb. d. Phys.-Med. Ges. zu. Wurzburj, 1900, p. 41.
3 Gaudenz, Arch. f. Hyg., 1901, xxxix., p. 231.
4 Gaudenz, loc. cit., pp. 238, 242.
5 Black, Dent. Cosmos, 1895, xxxvii., p. 474.
6 Head, Dent. Cosmos, 1906, xlviii., p. 1191.
7 Pawlow, The Work of the Digestive Glands, London, 1902, p. 50.
8 Hornborg, Skand. Arch. f. PhysioL, 1904, xv., p. 248.
9 Magendie, Prlcis JKllmentaire de Physiologie, Paris, 1817, ii., p. 58.
10 Falk and Kronecker, Arch. f. PhysioL, 1880, p. 296.
11 Einthoven, Hdb. d. Laryngol. u. Rhind., Vienna, 1899, ii., p. 53.
12 See the radiographic study by Eykmann, Arch. f. d. ges. Physiol., 1903,
xcix., p. 521.
13 Kronecker and Meltzer, Arch. /. Physiol., 1880, p. 446.
14 Meltzer, Proc. Soc. Exper. Bid. M., New York, 1907, iv., p. 41.
15 Kronecker and Meltzer, Arch. f. Physiol., 1883, Suppl., p. 341 ; Meltzer,
N. York M. J., 1894, lix., p. 389.
16 Meltzer, Centralbl. f. d. Med. Wissensch., 1883, p. 1.
17 Cannon and Moser, Am. J. Physiol., 1898, L, p. 440.
18 Meltzer, J. Exper. M., 1897, ii., p. 463.
19 Meltzer, Proc. Soc. Exper. Bid. M., New York, 1907, iv., p. 36. Also for
rabbit, see Zentralbl. f. Physiol., 1906, xix., p. 993.
20 Lossen, Mitth. a. d. Grenzgeb. d. M. u. Chir., 1903, xii., p. 363.
21 Hertz, Brit. M. J., 1908, L, p. 131.
22 Schreiber, Arch. f. exper. Path. u. Pharmakol., 1901, xlvi., p. 442.
23 Hertz, loc. cit., p. 131.
4 Mikulicz, Mitth. a. d. Grenzgeb. d. M. u. Chir., 1903, xii., p. 596.
THE NERVOUS CONTROL OF DEGLUTITION
As the word implies, the oesophageal tube is merely a " food-
carrier," serving to transmit nutriment quickly from the first
digestive region to the second. The variations in the rate of
transmission in different animals and in different parts of the
oesophagus of the same animal can be explained by differences
in histological structure. Thus the uniform slow peristalsis of
the goose is performed by an oesophagus composed entirely of
smooth muscle. The change from rapid to slow peristalsis near
the heart region in the cat's oesophagus corresponds to a change
from striated to smooth muscle in the structure of the wall.
The absence of any similar slackening of speed in the lower
thoracic region of the dog is accounted for by the absence of the
change of structure the dog's oesophagus is composed of striated
muscle throughout. The more rapid contraction of striated
muscle compared with smooth muscle gives a reason for the
bolus reaching the dog's stomach in four or five seconds, instead
of requiring nine seconds or more as in the shorter oesophagus
of the cat. The slow contraction of the lower portion of the human
oesophagus, noted by Kronecker and Meltzer, and by Schreiber,
is explained by the fact that this portion is composed, like the
oesophagus of the cat, of smooth muscle. 1 These distinctions are
important for our understanding of the action of the oesophagus
in relation to its inner vation.
The process of swallowing transfers the food from the short
region in which it is subject to voluntary control to that exten-
sive region in which the digestive processes are automatically
managed without affecting consciousness or being disturbed by
whims of the will. Not until the waste from the swallowed food
appears at the terminus of the canal does direct voluntary
interference again become possible. Indeed, the region at the
THE NERVOUS CONTROL OF DEGLUTITION 21
start where we can do as we wish with the food is only that
concerned with mastication ; as soon as swallowing begins, the
bolus slips suddenly into the grip of a train of reflexes from which
there is normally no recall. Like other reflex mechanisms, the
arrangements for swallowing involve afferent paths and efferent
paths. The remarkable provisions for efficient action, especially
in the oesophageal region, make the innervation of deglutition
The origins of the afferent impulses, which start the series
of reflexes, have been studied in different animals ; :and variations
have been found in their locations, just as variations were found
in the rate of passage along the oesophagus. The areas at which
the impulses can be started have been classified into the most
sensitive area or " chief spot " for initiating the swallowing
reflex, and accessory spots, of less sensitiveness, from which the
reflex is not so readily aroused. According to the careful in-
vestigations of Kahn, 2 the chief spot in each animal is found in
the natural path from mouth to oesophagus ; the accessory spots
lie in out-of-the-way places, into which, however, small particles
of food may be driven. Thus in the dog and cat the chief spot
is an area on the back wall of the pharynx, opposite the posterior
opening of the mouth cavity an area supplied by the glosso-
pharyngeus nerve. Accessory spots are present on the upper
surface of the soft palate, supplied by the glosso-pharyngeus and
the second branch of the trigeminus, and on the dorsal face and
base of the epiglottis, supplied by the superior laryngeal nerve.
In monkeys the chief spot is in the tonsillar region, and accessory
spots appear at the entrance to the larynx, on the back and
base of the epiglottis, and on the wall of the pharynx.
These spots were found by touching the mucous membrane of
the mouth and pharynx here and there until the reflex occurred.
The chief spots are extraordinarily sensitive to mechanical
stimulation, and the reflexes which they call into activity are
unusually indefatigable. Wassilieff, for example, was able by
touching one point in the mucous membrane to evoke in succes-
sion fifty acts of deglutition. 3
Accurate observations on man as to the most sensitive areas
for inducing the deglutition reflex have not been made, though in
all probability the back wall of the pharynx and areas near the
base of the tongue, when touched by foreign bodies, will evoke
the movements. The perfect reflex character of deglutition, and
THE MECHANICAL FACTORS OF DIGESTION
its absolute dependence on incoming impulses from special spots
in the mouth and pharynx, was clearly demonstrated by Wassilieff.
He swallowed a small sponge moistened with cocaine, and imme-
diately drew the sponge back by means of a thread attached to
it. The ability to swallow was for some minutes entirely lost,
and the saliva, which was abundantly secreted, had to be ex-
pectorated. Just as there must be a sensitive region to be
stimulated, so likewise there must be an object to stimulate it.
We need only to swallow several times in rapid succession, until
no more saliva is present in the mouth, to observe how impossible
the act becomes in the absence of a peripheral stimulus. Under
normal conditions of ingesting food, the sensitive spot can be
stimulated either by liquid buccal contents flowing back upon it,
when involuntary swallowing occurs, or by more or less solid
food-masses being voluntarily pushed over the base of the tongue
and into the pharynx.
The region of the central nervous system to which the afferent
impulses travel is, according to Marckwald, 4 situated in the floor
of the fourth ventricle, above the centre of respiration. From
this centre of deglutition in the medulla pass out the motor
impulses, which, distributed by a variety of nerves, produce the
remarkably rapid and orderly sequence of movements that give
the bolus its initial push and continue it on its course. By the
hypoglossus nerve impulses pass to the tongue, by the third
branch of the trigeminus to the mylo-hyoid, by the glosso-
pharyngeus and the pharyngeal branch of the vagi to the muscles
of the pharynx, and by several vagus branches to the entire
length of the oesophagus. We can readily understand into what
a chaos all this wonderfully co-ordinated mechanism is thrown
by the incidence of bulbar disease.
We shall now turn our attention to the important part played
by the vagi in the nervous control of the cesophagus. According
to Kahn, 5 the innervation of the thoracic portion of the
cesophagus is the same in the cat, dog, and monkey merely
the cesophageal branches of the vagi which enter the wall of the
tube just above the hilus of the lungs. Still other branches,
however, enter the wall near the diaphragm. To the neck
region, in all three animals, the recurrent laryngeus supplies
motor fibres in the dog and cat only to the lower portion, but
in the monkey to the whole extent of the cervical oesophagus.
Other branches of the vagi, as well as fibres from the cervical
THE NERVOUS CONTROL OF DEGLUTITION 23
sympathetic, are distributed directly to the upper portion of the
tube in the neck region. Stimulation of the sympathetic fibres
produces no obvious effect. Stimulation of the vagus nerve on
either side causes strong simultaneous contraction of the entire
oasophagus. Clearly the vagi are the motor nerves of the gullet.
There are several ways, however, in which they cause an order!} 7
peristaltic wave to progress along the tube.
In 1846, Wild reported experiments which showed that if the
O3sophagus is divided, or merely has a thread tied tightly about
it, the peristaltic wave is definitely blocked at the point of inter-
ference. From this observation he drew the conclusion that
oesophageal peristalsis is due to a series of reflexes starting in
the mucous membrane of the oesophagus itself a series at once
stopped by any interruption of the continuity of the tube. 6
This conclusion was accepted without qualification until 1876,
when Mosso published experiments which indicated the possi-
bility of central origin of the peristaltic wave. He used the
methods of Wild, but placed a small wooden ball in the oesophagus
below the point where the tube had been transected. When a
wave, started by a swallowing movement, had traversed the
upper section, it did not stop at the point of incision, but in due
time reappeared below, and carried the ball to the stomach.
Continuation of the wave across an open space led Mosso to a
conclusion opposite that of Wild viz., that oesophageal peri-
stalsis is originated step by step in the central nervous system.
The discrepancy between Wild's and Mosso's observations
and inferences had no explanation until Meltzer, in 1899, repeated
the experiments, and was able by varying the conditions to obtain
one result or the other, as he pleased. The key to the situation
lay in recognizing the effect of anaesthesia. In very deep anaes-
thesia water can be introduced into the mouth, and no deglutition
will follow. When anaesthesia is slightly less deep, reflex contrac-
tions of buccal and pharnygeal muscles occur, but they are not
followed by oesophageal peristalsis. With still less deep anaes-
thesia a peristaltic wave follows a swallow if material is pressed
into the gullet from the mouth, but fails if the swallow is empty.
It therefore fails also beyond a compressed or incised region.
With very light anaesthesia the entire process occurs quite
normally, and the wave will pass an interruption in the con-
tinuity of the tube. According to Meltzer's results, Wild ob-
served conditions which appear in deep anaesthesia, and discovered
THE MECHANICAL FACTORS OF DIGESTION
the reflex peristalsis which can originate in the oesophagus itself.
Mosso, on the other hand, who studied the conditions in light
anaesthesia, discovered the central origin of the procession of
ossophageal peristalsis, which normally prevails. 7
Two mechanisms are therefore present to control the course
of a bolus along the gullet. One mechanism requires only a
single afferent impulse to start it, the impulse arising usually
at the chief or most sensitive spot in the mouth or pharynx.
This ingoing impulse spreads in the centre for deglutition, and
in proper order evokes the series of nervous discharges which
precipitate the rapid sequence of contractions in the mouth and
throat, and move the annular constrictions along the oesophagus,
which constitute normal deglutition. The continuity of the
gullet is not necessary for the progress of this form of peristalsis,
but its nervous control is especially sensitive to anaesthetics.
Meltzer suggests calling this the higher reflex mechanism, which
gives rise to " primary peristalsis." The other mechanism
consists of a succession of reflexes, each provided with an afferent
path which leads to a motor discharge to the region immediately
above. Thus the bolus by its very presence would cause a con-
traction which would press it downwards to the stomach. This
accessory mechanism is dependent on the integrity of the
oesophageal tube, and, although requiring the presence of both
vagus nerves, is more resistant than the higher mechanism to
anaesthetics. It has been called the lower reflex mechanism,
and its activity " secondary peristalsis." 8
The observations of Kronecker and Meltzer on the innerva-
tion of deglutition were concerned with influences affecting the
process through its central control. When a series of swallowing
movements were made, as in drinking a glass of water, they
found that the peristaltic wave appeared only after the last
swallow. Thus each act of deglutition can not only rouse its
own oesophageal contraction, but can at the same time inhibit
the appearance of an oesophageal contraction in process of being
roused by a previous swallow. On the other hand, if a peristaltic
wave has just been started when another swallow is taken, this
first wave is not stopped by the second swallow, nor is there a
superposition of a second wave on the first. The second motor
discharge is only sent out after the contraction following the
first discharge has been completed. There is, then, here a clear
refractory phase which prevents continuous contraction of the
THE NERVOUS CONTROL OF DEGLUTITION 25
cesophageal muscles. The inhibitory mechanism Kronecker and
Meltzer were able to bring into action by exciting the glosso-
pharyngeal nerve ; whereupon the strongest stimuli to degluti-
tion were without effect. That the glosso-pharyngeus exercises
a tonic inhibitory influence* is indicated by the effect of cutting
it : the oesophagus enters a tonic contraction which may persist
for more than a day. 9
Although oesophageal peristalsis resembles in appearance
gastric and intestinal peristalsis, nevertheless the waves passing
along the gullet, unlike those of the rest of the alimentary canal,
have come to be regarded as due exclusively to impulses arriving
by way of the vagi. Thus, Meltzer 10 states : " It is now generally
assumed that the orderly progress of the peristalsis in the oesoph-
agus is exclusively of central origin." More recently Starling 11
has declared : " The orderly progression of the peristaltic wave
along the walls of the tube (oesophagus) is dependent on the
integrity of the branches of the vagus nerve, by which the
medullary centre is united to the gullet. Division of these nerves
destroys the power of swallowing."
The evidence that oesophageal peristalsis is managed through
the vagi is found, as we have seen, in the anatomical distribution
of the nerves to the tube, and, as just indicated, in the effect
of cutting these nerves. Thus secondary peristalsis was entirely
abolished, Meltzer observed, as soon as the vagi were severed ;
and the material introduced was no longer moved downward. 12
This stasis of food in the oesophagus after vagus section was,
indeed, recorded by Keid as long ago as 1839. 13 Keid's observa-
tions were quoted by Volkmann, 14 and Volkmann's article has
been repeatedly referred to by recent writers as authority for
the failure of deglutition after severance of the vagi.
In enunciating the doctrine that extrinsic innervation of the
cesophagus is the necessary condition for activity, two important
considerations seem to have been overlooked first, the difference
between the immediate effects of vagus section and the later
possible recovery of a normal state ; and, second, the muscular
structure of the lower fourth or fifth of the tube, which, as we
have noted, is composed in many animals largely or entirely
* The reader will recall that the glosso-pharyngeus has been reported as the
afferent nerve for the initiation of swallowing. Possibly the observation of
Kitajew (Jahresb. il. d. Fartschr. d. PhysioL, 1908, p. 151), that weak stimulation
of this nerve inhibits deglutition, while strong stimulation causes frequent and
strong contractions of the oesophagus, gives a clue to the discrepancy.
26 THE MECHANICAL FACTORS OF DIGESTION
of smooth fibres, well supplied with a myenteric plexus, and
resembling in all essentials the muscular wall of the stomach
and intestine. In 1906 I had occasion to observe that there
may be for some time after vagus section a total absence or
notable inefficiency of gastric peristalsis, with a subsequent
remarkable restoration of function. The local mechanisms,
at first inert after removal of vagus influence, later prove able
to continue gastric peristalsis in an almost normal manner. 15
If it is possible for the stomach thus to recover from a primary
paralysis, may not the oesophagus, at least that part of it similar
in all essential respects to the stomach structure, be able to-
recover likewise from a primary paralysis ?
An answer to the question was found by severing in the cat.
the lower fourth of whose oesophagus is supplied with smooth
muscle, the two vagus nerves* the right below the origin of
the recurrent laryngeal, the left in the neck and subsequently
studying by means of the X rays the movements of the food in
the oesophagus. An account of a typical case will present the
Two days after section of the right vagus nerve, the left was
cut, but just before the second operation meat wrapped about
some bismuth subnitrate was seen moving regularly along the
oesophagus and into the stomach. The next day finely ground
meat was fed ; it was carried normally through the cervical
portion of the tube, but promptly stopped at the top of the
thorax. As bolus after bolus was swallowed, the thoracic
oesophagus became filled with a distending mass. Continuous
observation for forty-five minutes revealed no sign of activity
in the gullet, and no food entered the stomach.
On the day following the second day after severance of the
left vagus nerve nothing of the accumulated mass was found
in the oesophagus. Now a spoonful of mush mixed with sub-
nitrate of bismuth was given. It was quickly passed to the
top of the thorax, and in four minutes it was spread, apparently
by rhythmic changes of pressure due to respiration, as a long,
slender mass even to the diaphragm. During another four
minutes the mass lay without being further affected. Then a
second spoonful of the mush was given. When this new material
was pressed into the thoracic oesophagus, the lumen was enlarged
to almost twice its former diameter. Immediately a con-
striction of the cesophageal wall occurred at the level of the lower
half of the heart. This constriction moved toward the stomach,
* In all operations the animals were, of course, under complete general
THE NERVOUS CONTROL OF DEGLUTITION 27
and was followed by others that also moved downward.
The first waves failed to drive food through the cardia ; the
food slipped back through the moving ring. Later waves, how-
ever, were more effective, and pushed food into the stomach.
The remnant of the mush in the gullet was now extended again
in a slender strand. During ten minutes more of continuous
observation, no further change was seen. The next morning
there was no food in the cage and none in the oesophagus. The
waste was in the large intestine.
On the third day the animal took three spoonfuls of the food,
which filled the thoracic oesophagus to stretching. Imme-
diately, at the level of the lower half of the heart, a constriction
appeared that passed downward, causing as it moved a marked
bulging of the tube in front. Some of the food surely escaped
backward through the advancing ring. This wave was immedi-
ately followed by a second, starting from the heart level, and
pushing downward in a manner similar to the first. The second
wave forced food into the stomach. The remnant became
extended to the diaphragm ; but only after four minutes did
another ring start at the heart level, and push the lower end of
the column into the stomach. Again the remnant was extended
to the diaphragm. Except occasional deep stationary con-
strictions, at the heart level, there was no change for eight
minutes. Then a ring formed just above the diaphragm, and
pushed food into the stomach ; and another ring, immediately
above, cut off the lower end of the remaining mass, and likewise
forced this bit of food through the cardia. The rest of the
cesophageal accumulation was now but a slight strand in the
upper thoracic region. For thirty- eight minutes of observation
it remained unmoved in that situation.
On the seventh day the thoracic oesophagus was filled, through
a rubber tube, with thin starch paste (3 grammes to 100 c.c.
water) mixed with bismuth subnitrate. At once after the in-
jection, one constriction after another formed in rapid succession,
each cutting off the extremity of the repeatedly extended mass
and moving it through the cardia. As judged by gently feeling
the larynx, there was no swallowing in this process ; the action
was a local response to the presence of material in the lower
gullet. Thus, by repeated reductions from below, the column
of food was gradually carried away until only a slender remnant
was left. This was slowly moved below the heart, but there it
stayed for half an hour. " At the end of that period a small bit
of meat, with bismuth subnitrate adherent, was fed. The meat
moved smoothly through the cervical region, but stopped at
the top of the thorax. Now the slender mass below was
gathered together and swept into the stomach. Sixteen
minutes were required for the meat to come to the level of
THE MECHANICAL FACTORS OF DIGESTION
the lower half of the heart. Again nothing interpretable as a
constriction was seen in the thoracic oesophagus above the
heart. Below the heart, however, the meat, which had been
separated into two pieces, was carried by peristalsis into the
Twenty-three days later the animal was again given starch
paste as before, with the same results. While there was still
a considerable amount of the paste above the heart level, swallow-
ing movements were caused by tickling the larynx. Most
careful scrutiny showed no sign of the passage of a wave over
the food in the upper thoracic region.
In the foregoing record of the gradual recovery of function in
the lower oesophagus, several points stand out significantly :
1. Immediately after operation, and for twenty-four hours
at least thereafter, it is easy to gather evidence of complete
paralysis of the oesophagus. In one instance during this first
period food was observed stagnating in the gullet for five hours,
and in another instance for seven hours, after feeding. But
evidently in the cat a distinction must be made between this
primary paralysis of the whole oesophagus after bilateral
vagotomy, and a secondary recovery of certainly the lower
half of the thoracic portion.
2. After a return of peristaltic activity in the lower oesophagus,
an important factor for arousing that activity seems to be the
stretching of the oasophageal wall. A slender mass spread along
the tube may lie for some time unmoved ; the addition of a
second mass, which causes a stretching of the wall, results in
the instant appearance of circular constrictions and peristaltic
movements. And, similarly, after repeated reductions have
rendered the strand of food more attenuated, it lies for longer
periods unaffected by oesophageal contractions. The reaction
of the oesophageal wall to the presence of a stretching mass is
a local reaction, occurring without centrally initiated movements
of deglutition. In this respect it is similar to movements of
the alimentary canal below the cardia. The lower oesophagus
seems to become more responsive to the presence of contained
material as time elapses, for the material is driven into the
stomach with increasing rapidity, and even slender masses are
sufficient cause for peristalsis. Apparently the recovery of
activity is due to a restoration, in some manner, of the capacity
for exhibiting tension when stretched a capacity ordinarily
maintained by vagus influences, but intrinsically developed when
THE NERVOUS CONTROL OF DEGLUTITION 29
those influences are lost. This, however, is a fundamental
matter which we must deal with later.
3. A difficulty in forcing food through the cardia explains
to some extent the slower emptying of the gullet during the
first days after operation. That the cardia of the cat offers
an obstacle to easy passage into the stomach after bilateral
vagotomy, is proved by the fact that strong peristaltic waves,
so strong as to produce a very marked bulging of the tube in
front of them as they advance, have failed to force food into
the stomach. Indeed, three days after cutting the second vagus
nerve I have seen almost exactly the same repetition of deep
constrictions and vigorous peristaltic movements in the lower
oesophagus as occur in the small intestine in case of obstruction. 16
The opposition at the cardia was also noted when in these
animals attempts were made to pass a tube into the stomach.
4. Throughout these observations a marked contrast was
noted between the activity of the lower half of the thoracic
oesophagus and the persistent inactivity of the upper half.
Absence of peristalsis from the region above the heart was
as true a month after the second vagus was severed as it
was during the first twenty-four hours. Is there any difference
of condition between these two parts of the thoracic oesophagus
which might account for their difference of action after vagus
section ? Leaving one recurrent laryngeal nerve, as we know,
still provides innervation for the cervical oesophagus ; but cutting
off all vagus supply, except one recurrent laryngeal, destroys
the extrinsic innervation of the gullet between the base of the
neck and the cardia. In this thoracic region the oesophagus is
provided with two kinds of muscular fibres. A histological
examination of the oesophagus of the animal on which were
made the detailed observations reported above showed that
the musculature of the upper half of the thoracic region was
composed predominantly of striped fibres, whereas the muscula-
ture of the lower half, over which peristalsis continued after
vagus section, was composed almost wholly of unstriped fibres.
Since the difference between the cervical oesophagus, which acted
normally, and the upper thoracic oesophagus, which failed to act,
was that the former had in all cases a recurrent laryngeal supply,
while the latter had no outside nerve connection, the conclusion
is justified that that part of the tube which is composed of striped
muscles fibres is paralyzed when vagus impulses are removed from
30 THE MECHANICAL FACTORS OF DIGESTION
it. The general conclusion, however, that the entire oesophagus
is put out of action by severance of the vagi must be modified.
That part of the tube which is composed of unstriped muscle is,
like other similar parts of the alimentary canal, capable of quite
perfect peristaltic activity without the aid of extrinsic nerves.
The validity of these conclusions was confirmed by observa-
tions on the rabbit and the monkey (rhesus). In the rabbit no
cesophageal peristalsis was seen at any time after severance of
the second vagus nerve, although one animal was kept alive and
examined from time to time for two weeks after the operation.
In the monkey, on the other hand, the results were similar to
those in the cat. Three hours after the second vagus was sec-
tioned, mashed banana mixed with subnitrate of bismuth,
swallowed by the monkey, was at once carried to the upper
thoracic oesophagus, where it rested. More banana forced some
of the mass in the gullet to the level of the heart. As soon as it
reached beyond this level, the food was promptly separated and
carried slowly into the stomach. There was no evidence of
obstruction at the cardia. For further assurance the animal was
etherized, the right vagus also severed in the neck, the left
thoracic wall widely opened, and the oesophagus watched directly,
as water was introduced through a tube into the cervical portion.
Where the vessels of the left lung crossed the gullet, peristaltic
waves appeared, and moved slowly downward until they went
out of sight behind the diaphragm. The point where the waves
were first seen was marked by making a deep cut, and the animal
was then killed. The oesophagus of the rabbit longest observed
and the oesophagus of the monkey received careful histological
examination. Striped muscle, almost exclusively, was seen
throughout the length of the rabbit's oesophagus. The part
of the monkey's oesophagus above the cut the part which was
paralyzed was composed entirely of striped fibres ; the part
below the cut had only a few scattered striped fibres, the rest
was all smooth muscle.
Mosso's observations revealed an cesophageal peristalsis of
central origin, distinguished by Meltzer as primary peristalsis.
Wild's studies disclosed a reflex oesophageal peristalsis of
peripheral origin, the secondary peristalsis of Meltzer. To these
two varieties, which require vagus support, must be added a
third, which can be seen when a portion of the oesophagus is
supplied with smooth muscle. The peristalsis of this portion,
THE NERVOUS CONTROL OF DEGLUTITION 31
like peristalsis below the cardia, is capable of autonomy. In
many cases which I have observed, it has been sufficient without
vagus support to clear the oesophagus of any ordinary food
which had been carried into the thoracic segment. And, as we
have already noted, the rapid contraction of the muscles of
the mouth are able to discharge fluid food into this region, where
independent peristalsis is possible.
1 Oppel, Lehrb. d. Vergl. Mik. Anat., 1898, ii., pp. 142, 146.
2 Kahn, Arch. f. Physid., 1903, SuppL, p. 386.
3 Wassilieff, Ztsch. f. Bid., 1888, xxiv., pp. 39, 40.
4 Marckwald, Ztschr. f. Bid., 1889, xxv., p. 46.
5 Kahn, Arch. f. Physid., 1906, p. 361.
6 Wild, Ztschr. f. rat. Med., 1846, v., pp. 101, 113.
7 Meltzer, Amer. J. Physiol. , 1899, ii., p. 270.
8 Meltzer, Zentralbl. /. Physiol., 1905, xix., p. 995 ; Proc. Soc. Exper. Biol.
M., New York, 1907, iv., p. 35.
9 Kronecker and Meltzer, Monatsber. d. konigl. preussisch. Akad. d. Wis-
sensch. zu Berlin, 1881, p. 100.
10 Meltzer, Am. J. Physid., 1899, ii., p. 266.
11 Starling, Recent Advances in the Physidogy of Digestion, Chicago, 1906,
12 Meltzer, Zentralbl. f. Physid., 1905, xix., p. 994.
13 Reid, Edinb. M. and 8. J., 1839, Ii., p. 274.
34 Volkmann, Wagner's Handworterb. d. Physid., 1844, ii., p. 586.
15 Cannon, Am. J. Physid., 1906, xvii., p. 429.
16 Cannon and Murphy, Ann. Svrg., 1906, xliii., p. 522.
CONDITIONS AFFECTING THE ACTIVITIES OF THE CARDIA
THE thickened band of circular smooth muscle at the junction of
the oesophagus with the stomach the cardiac sphincter, or
cardia has the function of preventing the passage of material
from the stomach back into the oesophagus. Normally we are
quite unconscious of the nauseating odour and the highly dis-
agreeable taste of the gastric contents, and for this pleasant
security the closed cardia is largely responsible. As aids in estab-
lishing the barrier between the stomach and the gullet, the sharp
angle between the two structures, acting like a valve, and the
close grasp of muscle layers in the diaphragm, have been men-
tioned. 1 Evidence will indicate, however, that these accessory
agencies must be regarded as relatively insignificant compared
with the tonus of the sphincter.
That the cardia is normally closed has been observed in various
ways ; by introducing a finger into the oasophagus from the opened
stomach, by direct inspection from below, and by inspection from
above through an oesophagoscope. The closed condition can also
be inferred from the stoppage of swallowed liquids in the lower
gullet until a peristaltic wave arrives and presses them through.
Although the contracted state of the sphincter seems continuous,
it is capable of exhibiting an alternating increase and decrease
a phenomenon known to Magendie early in the last century. 2
Two activities of the cardiac sphincter, therefore, are to be dis-
tinguished-^-a persistent contracted state or tonus, and at times,
superposed on this, rhythmic alternation of contraction and re-
laxation. In these two manifestations the smooth muscle of the
cardia is like the smooth muscle of other parts of the alimentary
canal, to be considered later.
The tonic contraction is itself variable in intensity, and can be
increased or decreased by a number of conditions. Usually, in a
CONDITIONS AFFECTING THE CARDIA 33
state of rest, the tonus is not high. The common ease of passage
through the sphincter has been observed by several investigators.
Mosso noted that a small wooden ball, attached to a thread,
could be withdrawn from the stomach without meeting any con-
siderable resistance. 3 On the cesophageal side, v. Mikulicz
observed in man that such slight pressure as 2 to 7 centimetres of
water was sufficient to drive air or water into the stomach. As
a rule the necessary pressure was less than that of a column of
fluid which would fill the thoracic oesophagus. 4
As already stated, a sound can be heard by listening over the
region of the cardia, six or seven seconds after liquids have been
swallowed. This sound is due to the swallowed material, liquid
and air. being pressed through the tonically contracted sphincter.
Sometimes this sound is heard immediately after swallowing a
result which Meltzer has attributed to a weakly contracted
cardia, because, among other reasons, he observed it in
consumptives who easily regurgitated gastric contents while
Even the slight contraction that normally prevails in the resting
cardia can be reduced by nervous influences. During repeated
deglutition, for example, the sphincter becomes more and more
relaxed as the number of swallows increases, and may be so com-
pletely relaxed that no sounds are heard as the fluid passes through
into the stomach. 6 In the rabbit with opened abdomen the cardia
can be seen to enlarge slightly with each swallowing "movement :
and if the stomach is filled with air, an act of deglutition is accom-
panied by the release of air into the oesophagus through the
patulous sphincter. As the peristaltic wave descends, it pushes
the air downward, and only when the escaped volume is restored
to the stomach does the cardia close. This relaxation of the
terminal sphincter as a peristaltic wave approaches admirably
illustrates the general law that opposed muscles normally act, not
in opposition, but in harmony a law that Meltzer emphasized
in this connection. 7
Following the relaxation of the cardia and the passage of the
swallowed bolus, there is a prompt contraction. This contrac-
tion, as Kronecker and Meltzer observed, is much more intense
and lasts longer, the longer the series of swallowing movements
that have preceded.
The nervous path by which the cardia is affected in the process
of swallowing is by way of the vagi. Impulses along these nerves
34 THE MECHANICAL FACTORS OF DIGESTION
cause, not only the relaxation of the sphincter, but also the sub-
sequent increase of tone. The two effects can be separated by
varying the rate and intensity of stimulation. 8 During vagus
stimulation in the neck region Langley observed relaxation, and
when stimulation ceased, strong contraction of the sphincter.
By giving small doses of atropine, he was able to eliminate the
motor fibres and produce pure inhibitory effects. 9 Langley 10 has
also reported that the cardiac sphincter is relaxed when adrenalin
is given ; and as the effect of adrenalin is an indicator of the
presence and function of sympathetic nerve fibres, the conclusion
is justified that the cardia has a sympathetic supply which causes
I have already stated that severance of both vagus nerves
causes in the cat a temporary increase of tone in the cardiac
sphincter (see p. 29). This observation is in accord with the
observations of Bernard, 11 Schiff, 12 and Kronecker and Meltzer, 13
that cutting both vagi in the neck is soon followed by strong
contraction of the lowest part of the oesophagus. But they are
not in accord with the observations of Krehl, 14 that after vagus
section the cardia is patulous ; nor are they in accord with Katsch-
kowsky's 15 assumption to the same effect. It may be that this
conflict of evidence can be explained by the temporal factor.
Thus Sinnhuber 16 concludes, from a critical review of the litera-
ture and from his own experiments, that, though cutting the vagi
may cause the cardia to enter a cramp-like contraction, this is
only a temporary state. Starck 17 also does not believe that vagus
section produces any lasting hindrance to the passage of food
through the cardia. In my experience, the increased tonus of
the cat's cardia after bilateral vagotomy usually does not persist
as a considerable obstacle, and the forcing of food into the
stomach by cesophageal peristalsis becomes in time not difficult.
But there have been a few instances in which there was continued
trouble in passing a tube into the stomach ; the oesophagus in
these cases suffered a marked dilatation, and became filled with
food which was not removed.
Other conditions affecting the tonic contraction of the cardia
have been reported by v. Mikulicz. 18 For example, in his obser-
vations on a patient he noted that, when the region of the cardia
had been irritated mechanically or chemically, the pressure re-
quired to force fluid into the stomach was increased. It was
higher for cold drinks and for carbonated water than for warm
CONDITIONS AFFECTING THE CARDIA 35
water.* These differences in resistance to the passage of different
fluids through the cardia were seen also in the dog, but they
disappeared when the vagi were cut.
From the stomach side the passage of air into the oesophagus
occurs by eructation, according to Kelling, 19 whenever intragastric
pressure rises to about 25 centimetres of water. A still easier
regurgitation is indicated by the observation of Kronecker that
when, after repeated " empty " swallowings, the dog's stomach
has been rilled with air, the least motion suffices to cause the air
to pass back into the oesophagus. 20 Deep anaesthesia, in Kelling's
experience, abolishes this ready relaxation of the sphincter, and
then the stomach may be inflated to bursting before the air will
Most of the evidence thus far presented indicates a relatively
low degree of tonic contraction of the cardiac ring. This con-
dition is not one that assures the retention of gastric contents in
the stomach during digestion, which is the normal function of
the sphincter. As we shall see, however, a special local and auto-
matic arrangement exists by which the cardia is more firmly
closed while gastric digestion is in progress. Before regarding
this mechanism for locking the food in the stomach, we must
consider the second activity of the cardia previously mentioned
its rhythmic contractions.
The rhythmic oscillations in the contraction of the cardia, as
already stated, were known to Magendie nearly a century ago.
These variations of contraction, according to Schiff, are not actu-
ally localized at the cardia, but result from a ring of constriction
moving up and down the lower oesophagus and periodically in-
volving the cardia. 21 Schiff 's observations were made on dogs
and cats. In 1860, Basslinger described rhythmic pulsations of
the cardia in the excised stomach of the rabbit, 22 a phenomenon
sometimes designated as " Basslinger's pulse." The cardia of the
normal rabbit Kronecker and Meltzer 23 found usually quiet, but
in a freshly bled rabbit they saw the spontaneous movements
described by Basslinger.
If Schiff's conception of peristalsis and antiperistalsis in the
* In this connection the observation by Kronecker and Meltzer (Arch. /.
PhysioL, 1883, Suppl., p. 355) may be cited, that carbonated water produces
strong persistent spasm of the oesophagus, which cannot be inhibited by subse-
quent deglutition. This peculiar effect they did not investigate further. A
distressing cramp is at times experienced in the region of the cardia, which is
at once relieved when accumulated gases are released from the stomach. The
observations may be significant in relation to cardiospasm.
36 THE MECHANICAL FACTORS OF DIGESTION
lower oesophagus is correct, any regurgitation of gastric contents
could take place only slowly and to a slight extent ; but if, as
Magendie stated, a true diminution of the contracted state occurs,
leaving an easily forced passage, gastric contents might be forced
backward suddenly and throughout the gullet. The difference
between the views of Magendie and Schiff, and the possibility
that, after all, their and Basslingers observations might have
resulted, as Kronecker and Meltzer's study suggests, from ab-
normal conditions, made it desirable to investigate the action of
the cardia under more natural conditions.
In 1902, during an attempt to see the movement of particles
of food in the stomach when the gastric contents were fluid,
I noted repeated regurgitation from the stomach into the
oesophagus. 24 The fluid consisted of 100 c.c. of thin starch paste
mixed with 5 grammes of subnitrate of bismuth. It was given
by stomach-tube. The animal lay comfortably on a holder,
unanaesthetized, and was examined by means of the X rays. The
regurgitation was unattended by any signs of nausea or retching,
and when the animal was lifted from the holder she acted quite
as a cat normally acts. The periodically lessened contraction of
the cardia would therefore appear to be a natural phenomenon.
Since the fluid, on emerging from the stomach, at once passed
quickly up the oesophagus to the level of the heart, or even to the
base of the neck, it is clear that Magendie 's conception was correct,
and that SchifFs idea of an oscillating peristalsis and antiperistalsis
in the lower oesophagus must be discarded. In fact, no one who
has studied the oesophagus directly has ever seen antiperistaltic
waves in it.
Each regurgitation, as I watched them, was followed at once
by a peristaltic wave which pushed the escaped material back
again into the stomach. Soon after it was thus restored, the
cardia again relaxed and it again rushed out, only to be restored
to the stomach by another peristaltic wave. Thus the process
continued. The peristaltic wave was seldom started by volun-
tary deglutition, but was of the secondary order, stimulated by
the presence of the material in the oesophagus.
Kegurgitation and restoration of the fluid may thus recur
fairly periodically for twenty or thirty minutes. The periods are
shorter at first than later. In the following figures are shown
the time taken by these periodic movements when a large cat was
given 180 c.c. of fluid boiled starch at 3.20 p.m. The figures
CONDITIONS AFFECTING THE CARDIA 37
under " Out " indicate the moment when the fluid emerged into
the oesophagus ; those under "In," when the last of the fluid
disappeared into the stomach.
Out, In. Out. In.
3-21 6 3-2112 3-2219 3-2228
17 24 44 51
32 38 23 2 23 8
48 54 21 29
22 2 22 8 43 49
The regurgitation continued thus, but became gradually less
frequent. Twenty minutes after the first observation, appearance
and disappearance were as follows :
45 8 4516
During the eighteen minutes of observation that followed, the
food emerged only three times.
In this instance there was a fairly rhythmic appearance of food
in the oesophagus, beginning at the rate of four times a minute,
gradually falling to three and two times a minute, and ceasing
almost entirely soon after a rate of about once per minute was
Two questions are suggested by these observations : Under
what circumstances do the regurgitations occur ? and, Why,
once begun, do they cease ?
In answer to the first question-, the fluidity of the gastric con-
tents must be regarded as a prime factor in the regurgitations.
When the food escapes into the oesophagus, it escapes quickly in
a thin stream. If the stomach is full of more or less gross frag-
ments of food, it is quite conceivable that a slight weakening of
the contraction of the cardia would not permit such semi-solid
material to pass. A second factor in the regurgitation is intra-
gastric pressure. Into the stomach of the cat that furnished the
records given above was introduced on one occasion 60 c.c. of
the fluid starch, with no regurgitation during the next five
minutes ; 60 c.c. more was introduced, with no regurgitation during
the five minutes that followed ; then 60 c.c. more was introduced,
making in all 180 c.c., and regurgitations at once began and con-
tinued. In order to demonstrate the rhythmic relaxations of the
cardia, therefore, the gastric contents must be fluid, and must
38 THE MECHANICAL FACTORS OF DIGESTION
be under sufficient pressure to pass through the cardia when its
At first it seemed that fluidity and pressure were the only
factors concerned. The cessation of the regurgitations might
then be explained by a slow accommodation of the stomach to
the volume of its contents, or by the escape of material into the
duodenum until the intragastric pressure was insufficient to press
the fluid through the only slightly relaxed cardia. These explana-
tions, however, are not adequate. Kelling has shown that,
within limits, intragastric tension is readily adjusted to varying
amounts of food, and that for this adjustment only a few moments
are required ; 25 the normally rapid adjustment of intragastric
tension, therefore, would not explain the cessation of the regurgita-
tions after their continuance for twenty or thirty minutes. And
observations on the intestinal contents of animals in which the
regurgitations have ceased have shown only a small amount of
the fluid starch in the intestine. A diminution of intragastric
pressure does not, therefore, account for the disappearance of the
Since the repeated escape of fluid food into the oesophagus
is dependent on a periodic lessening of the contraction of the
cardia and on an intragastric pressure sufficient to force the
gastric contents through the weakened barrier, and since intra-
gastric pressure probably does not materially diminish at the
time when the regurgitations cease, the explanation of the
cessation must lie in a change at the cardia. Either the rhythmic
relaxations might be stopped, or the tonus of the sphincter might
be increased. With an increased tonus the cardia might, of
course, still undergo rhythmic contractions and relaxations, but
on a level so much higher than before that the intragastric
pressure would now be unable to overtop it. Thus the cardia
would perform its normal function of preventing the passage of
food backward into the oesophagus during the process of gastric
What new conditions developed in the stomach during
digestion might affect the cardia ? The conditions might be
of two orders, mechanical or chemical : the actual stretching
of the stomach might cause closure of the cardia, as Magendie
suggested ; or the new secretion poured out by the stomach
during digestion might, with its acid reaction, have that effect.
As we have learned, the rhvthmic relaxations of the cardia are
CONDITIONS AFFECTING THE CARDIA 39
made manifest only as the content of the stomach is increased.
And, furthermore, the gastric wall does not become more stretched
by any material increase of the contents, as the food lies in the
stomach during twenty or thirty minutes. The stopping of the re-
gurgitations is therefore not explained by increase of intragastric
pressure. Is the chemical agency, acid in contact with the gastric
mucosa, capable of changing the contraction of the sphincter ?
Evidence will be presented later showing that, if acid is con-
tinuously injected into the duodenum close beyond the pylorus,
that sphincter can be kept closed for an unlimited period.
Indeed, this response of the pylorus to the acid illustrates a
general law of the alimentary tract, that a stimulus causes a
contraction above the stimulated point. And just as acid
beyond the pylorus keeps the pylorus closed, so likewise acid
in the stomach (beyond the cardia) may keep the cardia closed.
Thus an essential condition for digestion in the stomach, the
presence of acid, would itself automatically hold a barrier against
a return of the contents into the oesophagus.
That a marked acidity of the gastric contents does promptly
check regurgitation through the cardia is proved by such ob-
servations as the following :
A cat with an empty stomach was given by stomach-tube
200 c.c. fluid starch with 10 grammes bismuth subnitrate at
2.55 p.m. The regurgitations occurred as follows :
Out. In. Out In.
2-56 1 2-5611 2-5838 2-5849
16 28 58 5910
57 8 5718
3-0035 3-01 2
29 39 0115 25
48 60 44 54
5812 5822 02 2 0212
At this time no food had passed through the pylorus. The
contents of the stomach were now as much as possible removed
(about 180 c.c. ). The reaction was very faintly acid. Fresh fluid
starch was added to make 200 c.c., and then 4 c.c. of 25 per cent,
hydrochloric acid was mixed with the fluid, making approxi-
mately a - 5 per cent, acidity, which is normal for carnivora.
The fluid was then reintroduced into the same animal at
3.12 p.m., with the following results :
3.13 45 3-1353
40 THE MECHANICAL FACTORS OF DIGESTION
The fluid passed from the stomach into the oesophagus these
two times in a very thin stream. Thereafter there was no
regurgitation whatever during ten minutes of observation.
The cardia was now holding tightly enough to retain gastric
contents amounting to 220 c.c., although previous to the acidifi-
cation it did not withstand the pressure of 200 c.c.
This observation has been repeated on normal animals and
on an animal whose splanchnic nerves had previously been
severed, with the same results.
The effect of acid in the stomach on the tonus of the
cardia can be demonstrated also in the anaesthetized operated
A cat was etherized and also given subcutaneously 1 c.c.
of 1 per cent, morphine sulphate in order to maintain uniform
anaesthesia. When the animal was thoroughly anaesthetized,
the spinal cord was pithed below the brachial region, the stomach
exposed, and a tube tied into the cardiac end by means of a
ligature encircling the organ. Another tube was introduced
through the cervical oesophagus as far as the upper thorax, and
tied in place. Each tube was connected by rubber tubing with
a long upright thistle tube. Warm physiological salt solution
was now introduced until the level in each tube was 9 centi-
metres above the cardia. At once the fluid in the resophageal
tube began to disappear and reappear at fairly regular intervals,
precisely as in the X-ray observations on regurgitation.
After the rhythmic regurgitation had proceeded for several
minutes the salt solution was removed. It was replaced by a
similar solution containing 0'5 per cent, hydrochloric acid,
poured into the thistle tube connected with the stomach. The
acidulated salt solution was added until it rose 19 centimetres
above the cardia. For several minutes it stood at that point,
with no relaxation of the sphincter. The stomach was now
compressed, and the fluid rose 33 centimetres above the cardia
before the sphincter relaxed. The fluid that then passed into
the 03sophagus was immediately pushed back into the stomach
by peristalsis and held there. Pressure again applied to the
stomach forced the column of salt solution to 42 centimetres
above the cardia before relaxation again occurred. No rhythmic
regurgitation was observed.
Now the acidulated salt solution was removed from the
stomach and replaced by 1 per cent, sodium bicarbonate, poured
into the stomach-tube until 9 centimetres above the cardia.
Almost immediately regurgitations began, and continued
rhythmically during ten minutes of observation.
CONDITIONS AFFECTING THE CARDIA 41
The closure of the cardia by intragastric acidity can be
registered graphically by connecting the oesophageal tube,
described in the foregoing experiment, with a recording tambour.
The regurgitations into the oesophagus cause the writing lever
of the tambour to rise, and as the regurgitated fluid is carried
back into the stomach the lever falls. Fig. 1 presents a record
of such regurgitations. The glass tube tied into the cardiac
end of the stomach was short, and connecting it with a thistle
tube was a piece of rubber tubing. Through the rubber tubing
a hollow needle was introduced into the gastric cavity. Thus
the stomach was not disturbed in the subsequent experimental
manipulation. During the period indicated by the broad black
line at A, sufficient hydrochloric acid (2 c.c.) was introduced
FIG. 1. RECORD SHOWING CESSATION OF RHYTHMIC REGTJRGITATIONS OF
FLUID FROM THE STOMACH INTO THE (ESOPHAGUS ON ACIDULATION OF
The upstroke of the larger oscillations represents the outflow, and the down-
stroke the return of the fluid to the stomach by oesophageal peristalsis.
The small oscillations are due to respiration. The time is marked in half-
through the needle into the stomach to render the salt solution acid
to 0-5 per cent. After one more regurgitation the cardia closed.
The question now arises as to whether the effect of the acid
on the cardia is a local effect, or mediated through the vagus or
splanchnic nerves. That regurgitations continue after splanchnic
section, and may be caused to stop by rendering the gastric
contents acid, has already been noted. The task of eliminating
the vagus nerves is more difficult, because, as we have learned,
only the lowest few centimetres of the oesophagus remain capable
of peristalsis after vagotomy, and this portion did not give
clear records of a restoration of regurgitated fluid into the
stomach. The effect of the acid can be tested, however, by
observing the intragastric pressure required to open the cardia
before and after the acidulation of the fluid.
A cat with the vagus nerves severed several days previously
was prepared for observation in the manner above described.
42 THE MECHANICAL FACTORS OF DIGESTION
Warm salt solution was poured into the thistle tube connected
with the stomach until the pressure was 14 centimetres, rising
to 19 centimetres during inspiration. Only then did the cardia
relax. A second determination resulted in the same figures.
The salt solution, which proved to be neutral, was now re-
moved and replaced by the same solution containing 0'5 per
cent, hydrochloric acid. The acid fluid was poured into the
tube tied into the stomach until the pressure was 17 centimetres
(rising to 22 centimetres during inspiration) before the cardia
relaxed. The fluid was now removed and immediately again
poured into the stomach ; this time the pressure rose to 1 9 centi-
metres (24 and 25 centimetres during inspiration) before the
cardia opened. Another immediate repetition gave 21 centi-
metres rising to 26 and 27 centimetres, as threshold pressures.
In a fourth trial the pressure was raised to 53 centimetres, and
the sphincter gave way only when still more fluid was poured
into the tube.
In this experiment, as well as in those in which regurgitations
were observed and registered, a more or less prolonged latent
period intervened between the application of the acid and its
full effect in closing the cardia. But the fact that the liminal
pressure gradually rose in this instance, and finally became
almost four times as great with acid gastric contents as it was
with neutral gastric contents, proves that the effect of the acid
is not produced through extrinsic nerves, but by the local reflex
in the wall of the gut. This result has been confirmed by similar
observations made immediately after pithing the lumbar and
thoracic cord and severing the vagus nerves.
Does not the prolonged period of regurgitation observed
when fluid starch was given (frequently twenty or thirty minutes
after its introduction) indicate that the acid mechanism of the
cardia is rather defective ? In considering this question, we should
remember that boiled starch has very little effect in exciting
the flow of gastric juice, 26 and that the cardia therefore probably
exhibits relaxations for a much longer period when fluid starch
is given than when foods more favourable to gastric secretion
The fluid character of the boiled starch is also unfavourable
to the early closure of the cardia, for the acid secreted is not
kept in contact with the wall of the stomach, but is diffused
into the fluid ; and each movement of the fluid to and fro between
stomach and oesophagus serves to mix the secreted acid with
CONDITIONS AFFECTING THE CARDIA 43
the total contents. For this reason it was impossible to get
consistent results in attempting to determine the acidity of the
gastric contents under these circumstances. When the food is
less fluid, the acid reaction of the contents of the cardiac end of
the stomach is found solely on the surface, near the mucosa, for
a considerable period after digestion has commenced. Under
these circumstances the conditions for closure of the cardia are
A return of material from the stomach to the oesophagus in
dogs has been reported by Kast. 27 Lycopodium spores intro-
duced through a gastric fistula into the stomach often appeared
after half an hour at an oesophageal fistula in the neck. This
reversed movement of material in the oesophagus was not
attended by any retching or vomiting. To test whether this
return from the stomach might be true of human beings, eleven
patients were given, after supper, lycopodium spores carefully
enclosed in a gelatine capsule. As a further precaution, the
capsule was enveloped in a wafer, and was then quickly swal-
lowed with the aid of water. In six of the eleven cases spores
were found in the mouth washings next morning, and in none
of these were any spores found in mouth washings taken one
or two hours after the capsule was swallowed. It is altogether
probable that in the positive cases the cardia must have relaxed
to permit the exit of material into the oesophagus. Thereafter
the fluids bearing the very fine seeds may have been slowly
spread toward the mouth by alterations of pressure due to
respiration and the heart-beat, much as swallowed material is
spread through the paralyzed gullet. Indeed, with a weakened
cardia, the descending diaphragm, by pressing on the stomach
while lessening intrathoracic pressure, could pump fluid from
the stomach towards the mouth. Kast suggests that the dis-
agreeable taste and the coating of the tongue in gastric dis-
turbance may result from the adhesion to its rough surface of
partly digested bits of food, leucocytes and epithelial cells that
have come back from the stomach. This suggestion gains
interest in connection with our discussion of the acid closure of
the cardia, for the coated tongue appears especially in cases of
abnormal fermentation of gastric contents which results from
deficient hydrochloric acid. This is preciselv^feJte^c^njdi^ion for
a relaxed cardia.
Although the evidence points to the acid^onTyofp^e^ t-dj&
^2^*&tMWffii, 1 1 (V '<e
44 THE MECHANICAL FACTORS OF DIGESTION
through a local reflex, we must not forget that the cardia is
nevertheless under the influence of extrinsic nerves, and that
in abnormal states these nerves may cause the sphincter to
relax, and permit regurgitation of food that is acid. The
common regurgitation of gases may be due to their effect in
keeping the acid contents away from the stomach wall in the
region of the cardia. Then, as the cardia relaxes and permits
the regurgitation of gas, acid fluid may also escape before the
sphincter again closes. All these conditions, however, cannot
be regarded as normal. Normally, after we have swallowed
our food and the automatic processes of the stomach have begun
to work their changes in it. one of the automatisms the acid
closure of the cardia has the function of preventing a back-
ward escape of the gastric contents into the mouth. If in the
performance of this important function a slip occurs, and the
contents start to escape, the secondary peristalsis of the gullet
is able, as we have seen, to bring to the cardia important aid.
1 See His, Arch. f. Anal., 1903, p. 347 ; and Sinuhuber, Ztschr. f. Idin. Med.,
1903, 1., p. 118.
2 Magendie, Precis Elementaire de Physidogie, Paris, 1817, ii., pp. 77, 78.
The original report was made in 1813.
3 Mosso, Untersuch. z. NaturL d. Mensch. u. d. Thiere, 1876, xi., p. 347.
4 v. Mikulicz, Mitth. a. d. Grenzgeb. d. M. u. Chir., 1903, xii., p. 596.
5 Mcltzer, Berl. Bin. Wchnschr., 1884, xxi., p. 448.
6 Kronecker and Meltzer, Arch. f. Physid., 1883, Suppl.. p. 358.
7 Meltzer, Arch. /. Physid., 1883, p. 215.
8 v. Openchowski, Centralbl. f. d. med. Wissensch., 1883, xxi., p. 540.
9 Langley, J. Physid., 1898, xxiii., p. 407.
10 Langley, J. Physid., 1901, xxvii., p. 249.
1 Bernard, Compt. rend. Soc. de BioL, Paris, 1849. i., p. 14.
12 Schiff, Lerom snr la Physidogie de la Digest ion, Florence and Turin, 1867,
i., p. 350 ; ii., p. 377.
13 Kronecker and Meltzer, Arch. /. Physid., 1883. Suppl., p. 348.
14 Krehl, Arch. j. Physiol., 1892, Suppl., p. 286.
5 Katschkowsky, Arch. /. d. ges. Physiol., 1901, Ixxxiv., pp. 29, 30.
6 Sinnhuber. Ztschr. f. Idin. Med., 1903, 1., p. 117.
17 Starck, Munchen. med. Wchnschr., 1904, Ii., p. 1514.
8 v. Mikulicz, Mitih. a. d. Grenzgeb. d. M. u. Chir., 1903, xii., p. 584.
9 Kelling, Arch. f. Uin. Chir., 1901, Ixiv., p. 403.
20 Kronecker, article " Deglutition," Dictionnaire de Physidogie (Richet),
Paris, 19CO, iv., p. 744.
- 1 Schiff, loc. tit., ii., p. 333.
2 Basslinger, Untersuch. z. Saturl. d. Mensch. u. d. Thiere, 1860, vii., p. 359
3 Kronecker and Meltzer, Arch. /. Physid., 1883, Suppl., p. 347.
!1 Cannon, Aw. J. Physid., 1903. viii., p. xxii.
5 Kelling. Ztschr. f. Bid., 1903, xliv., p. 234.
Pawlow, The Work of the Digestive Glands, London, 1902, p. 97.
27 Kast, Berl. Uin. Wchnschr., 1906, xliii., p. 947.
THE MOVEMENTS OF THE STOMACH
THE function of the stomach as reservoir, ready to receive
within a short period a generous provision of food, and arranged
to deliver this food to the intestine during a much longer period,
in proper amount and at proper intervals, has already been
mentioned. This reservoir, however, is itself a place of active
digestion. In it the ptyalin of saliva can continue to act for an
hour or more, if the amount of food taken is large. And the
peptic digestion peculiar to the stomach is an important pre-
liminary to the completion of proteolysis by the action of trypsin
and erepsin in the intestine. Even in vitro the course of tryptic
digestion is more rapid and more intense if it has been preceded
by peptic digestion ; l while erepsin, incapable by itself of attacking
most natural proteins, must await the changes wrought by the
other enzymes before it can become effective. The sequence of
action of these ferments in an order which gives greatest efficiency
is only one of many instances of remarkable interrelations in
the digestive canal. 2 Besides being a receptacle for ingested
food, therefore, the stomach is also the seat of important pre-
paratory stages of digestion. In promoting these digestive
changes, the other mechanical activities of the stomach play their
part, by churning together food and secretions. And when this
process has proceeded to a proper stage, they propel the altered
food onward for further digestion, as rapidly as the duodenum
is ready to receive it. The functions of acting as reservoir,
and of mixing and propelling the food, are performed by different
parts of the organ.
The anatomy of the stomach with reference to its varying
form has been carefully discussed by Cunningham. 3 Since he
has considered the relation between the structure of the organ
and its physiological alterations of shape, we can safely follow
46 THE MECHANICAL FACTORS OF DIGESTION
in the main his description. Two portions are to be distin-
guished a cardiac and a pyloric portion. The demarcation
between the two appears on the lesser curvature as a notch or
angular depression the " incisura angularis."
The fundus is separated from the rest of the cardiac portion
by an imaginary line passing around the stomach from the
cardiac orifice to the opposite point on the greater curvature.
In man it is defined as the part lying above a horizontal plane
passed through the cardia. That part of the cardiac portion
lying between the fundus and the incisura angularis (called
by His the " body " of the stomach 4 ) has,
when full, a tapering shape. This shape
is, as we shall later learn, of considerable
significance for the origin of gastric peri-
The pyloric portion, to the right of
the incisura angularis, is divisible into
the pyloric vestibule and the pyloric
canal. The canal, which in man is about
7 SC oF EMA THE 3 centimetres long, is a region more or
STOMACH. less tubular in form, but always so con-
At C is the cardia ; tracted as to be clearly marked off from
F, fundus ; IA, inci- ,, , ., , m i , ., v i
sura angularis ; B, t ne vestibule. The vestibule lies between
body ; PC, pyloric ^ ne incisura angularis and the pyloric canal,
canal ; P, pylorus. *_J .
and in the resting stomach is usually
pouched into the greater curvature. The term " antrum
pylori," meaningless because of its varied uses, we shall discard.
The wall of the stomach consists of three coats, but our
interest centres on the activities of the muscular coat. The
muscles are arranged in an outer longitudinal layer, a middle
circular layer, and a set of inner oblique fibres. The longitudinal
fibres continue those of the oesophagus, and, radiating over
the cardiac end, become more marked along the greater and
lesser curvatures than on the ventral and dorsal surfaces. Over
the pyloric portion they lie in a thick uniform layer terminating
almost wholly at the pylorus. The circular fibres, arranged in
rings at right angles to the curved axis of the stomach, form
a complete investment. Toward the pyloric end they become
gradually more numerous, and around the pyloric canal they
form a very well defined stratum, increasing in thickness towards
the duodenum, and at the duodeno-pyloric junction forming
THE MOVEMENTS OF THE STOMACH 47
the strong pyloric sphincter. The sphincter is clearly separated
from the circular coat of the duodenum by a distinct septum of
connective tissue an interruption of continuity with physio-
logical significance. At the incisura angularis is another special
thickening of the circular fibres, called by early writers the
" transverse band." The oblique fibres start from the left of
the cardia, and pass as two strong bands along the anterior part
of the dorsal and ventral surfaces, giving off fine fasciculi to the
circular layer ; towards the pyloric portion they gradually
disappear. It is probable that these bands have an interesting
function only recently suspected.
In 1898, Dr. F. H. Williams and I made observations on the
changes of form of the normal human stomach during digestion. 5
We found that while early in gastric digestion, when the subject
was standing, the greater curvature might reach several centi-
metres below the umbilicus (the pylorus being then considerably
above this level), in the later stages, as the stomach shortens,
the pylorus becomes the lowest point. The changes suggested
that the contraction of the longitudinal and oblique fibres between
the two fixed points, cardia and pylorus, resulted in a tendency
for the lumen to take a more nearly straight course between the
two orifices. 6 X-ray observations by Morton and Hertz 7 on
seventeen healthy young men show that in the vertical position
the greater curvature lies from 1 to 12 centimetres below the
umbilicus. Nothing is stated regarding the amount of gastric
contents in these cases, an important consideration, as we have
seen. After an extensive X-ray study of the shape and position
of the stomach, Holzknect 8 has declared that the " normal "
human stomach is one in which the pylorus is the lowest point.
The same view was expressed by Pfahler, who, after X-ray ex-
amination of thirty-one healthy persons, declared that the
essential point of the normal stomach is that " the pylorus be
on a level with the lower pole."* Although both Holzknect
and Pfahler admit that the normal stomach is relatively rare,
they support their opinion by the argument that the stomach
is a reservoir, that a reservoir should always be placed higher
than its outlet, and that therefore the " normal " stomach is
always set above the pyloric outlet as its lowest point.
The view expressed by Holzknect and Pfahler is in agreement
with an unfortunate conception of the emptying of the stomach
which has in the past prevailed among some surgeons, who have
THE MECHANICAL FACTORS OF DIGESTION
assumed that the stomach is emptied by gravity drainage. We
need not do more than note in passing that in the obviously
normal stomach of the dog or cat the pylorus is nearly the highest
point when the animal is in the standing position, and that the
so-called " normal " human stomach could remain satisfactory
for gravity drainage only so long as a person holds the upright
position or lies on his right side. A shift to the left side upsets the
nice hydraulic arrangement, for it places the pylorus at the highest
point of the stomach, and then how can the contents pass out ?
The essential fallacy in
the idea of gravity drain-
age from the stomach results
from a failure to regard
the pressure relations in <
the abdominal cavity. The
weight of the alimentary
canal, as such, is approxi-
mately that of water. The
food swallowed or under-
going gastric digestion has.
approximately the weight
of water. The pressure in
any part of the inactive
alimentary canal, as Weis-
ker proved, 10 is due to the
weight of the overlying ab-
dominal organs. If the
canal is inactive, therefore,
the food is as if surrounded
by water. Water resting in water is, of course, in exact equi-
librium. And even when the body is in the upright position ,
and a large artificial opening connects the stomach and
the intestine, water will not run out : " because of the hydro-
static relations in the abdomen, gravity can have no effect." n
" Drainage " in the common usage of that term is therefore
impossible. That the food may move onward through the
alimentary canal, muscular contraction is necessary to create
a difference of pressure.
The muscular activity of the stomach is exhibited differently
at the two ends. Near the middle of the body of the stomach
(at 1 to 6, Fig. 3) peristaltic waves take their origin, and course
FIG. 3. OUTLINES OF AN ALMOST IN-
STANTANEOUS RADIOGRAPH OF THE
STOMACH (CAT) DURING DIGESTION.
= cardia; P = pylorus. At 1, 2, 3, 4,
and 5, are indentations due to a series
of constriction rings (peristaltic waves)
passing towards the pylorus.
THE MOVEMENTS OF THE STOMACH
towards the pylorus. The region above 1 to 6 usually exerts
merely a tonic grasjLon its contents, and does not display peri-
stalsis. By a study of the pressure at various parts of the
stomach in man, Moritz 12 and v. Pfungen 13 inferred that the
cardiac end of the stomach must be quiet, and that the motor
functions were performed mainly by the pyloric end. The
same conclusion was earlier expressed by Leven. 14 Not until
the X rays were used, however, was the evidence of the way in
FIG. 4. TRACINGS OF THE SHADOW CAST BY THE STOMACH (CAT), SHOWING
CHANGES IN THE SHAPE or THE ORGAN AT INTERVALS OF AN HOUR
DURING THE DIGESTION OF A MEAL.
which the two regions of the stomach perform their separable
functions clear and decisive.
The significance of these two physiologically distinct regions
is indicated by outlines of the shadow of the stomach made at
regular intervals during digestion (see Fig. 4).* Comparison of
these tracings shows that as digestion proceeds the change of
form in the pyloric portion is relatively slight. The first region
to decrease in size is that part of the body of the stomach over
which the waves are passing. As food is discharged into the
intestine, the circular muscle of this middle region of the stomach
* For a more complete series, see Cannon, Am. J. Physiol., 1898, i., pp. 370-
50 THE MECHANICAL FACTORS OF DIGESTION
contracts tonically until (Fig. 4, 2 and 3) a tube is formed, with the
full cardiac pouch at the upper end, and the active pyloric portion
at the other. Along the tube shallow peristaltic waves still
continue. Now the radiating fibres at the cardiac end begin
to squeeze the contents into the tubular portion. This process,
accompanied by a slight shortening of the tube, continues until
the shadow cast by the contents is almost obliterated (Fig. 4,
6 and 7). The waves of constriction moving along the tubular
portion press the food onward as fast as they receive it from the
contracting cardiac pouch, and when the pouch is at last emptied
they sweep the contents of the tube into the vestibule. There the
operation is continued by deeper constrictions, till finally nothing
but a slight trace of food in the cardiac end is to be seen.
On the basis of this description of the changes in the cat's
stomach, Cunningham has examined post mortem the form of
the organ in man, and has found not infrequently a similar
tubular part extending from the middle of the body to the
pylorus, and distinctly separable from the saccular cardiac end.
X-ray observations in man reveal the same conditions. In
accordance with these facts, Cunningham has suggested the
term " cardiac sac " and " gastric tube " to designate these two
portions of the stomach.
Concerning the action of the cardiac pouch or sac, little more
need be stated. Since it lies close beneath the diaphragm, it is
exposed to repeated gentle pressure with each respiration. Since
the upper border of the sac is moved more than the lower border,
the contents must be slightly kneaded by the alternate contrac-
tion of the diaphragm and the muscles of the abdominal wall. 15
The function of the stomach as a reservoir serving out its
contents a little at a time, so that the intestinal digestive pro-
cesses are not overwhelmed by the sudden arrival of a great mass
of material, is at first performed by the entire organ, but later is
chiefly performed by the cardiac sac. The advantage thus
secured to the intestines can be claimed also for the stomach
itself. For, as the foregoing description indicates, and as experi-
ments to be described later will prove, the stomach mixes its
secretion with the food in the busy vestibule over which, through-
out the period of gastric digestion, constriction waves are con-
tinuously running ; and the cardiac sac, an active reservoir,
presses out its contents little by little as the churning mechanism
in the pyloric end is ready to receive them.
THE MOVEMENTS OF THE STOMACH 51
Concerning gastric peristalsis two views have long been held.
According to the older view, which still has its supporters, 16
the stomach is completely divided at the transverse band by
each recurrent wave, and the vestibule then contracts simul-
taneously in all parts in a systolic manner. According to the
newer view, developed by recent research, the waves sweep
from their origin to the pylorus, and do not partition the stomach
into two chambers. Since the conception of the course of gastric
peristalsis affects in an important way the conception of its
functions, we may profitably consider the evidence presented
in support of the two views.
Beaumont, in his famous experiments on Alexis St. Martin,
observed how a thermometer tube introduced through the fistula
was affected by the motions of the stomach, and drew the follow-
ing conclusions : " The circular or transverse muscles contract
progressively from left to right. When the impulse arrives at
the transverse band, this is excited to more forcible contraction,
and, closing upon the alimentary matter and fluids contained in
the pyloric end, prevents their regurgitation. The muscles of
the pyloric end, now contracting upon the contents contained
there, separate and expel some portion of the chyme." 17 In
close accord with this description of the movements of the human
stomach is the account given by Hofmeister and Schutz of the
activities of the excised stomach of the dog. 18 The stomach,
which was placed in a moist chamber kept at body temperature,
remained active for from sixty to ninety minutes. A typical
movement of the organ consisted of two phases. In the first
phase a constriction of the circular fibres started a few centi-
metres from the cardia, and passed towards the pylorus. As
the constriction proceeded, it increased in strength until a
maximum was reached about 2 centimetres in front of the vesti-
bule. This annular contraction, called by Hofmeister and
Schutz the " preantral constriction," closed the first phase.
Immediately thereafter the strong transverse band contracted
and shut off the vestibule from the remainder of the stomach.
Immediately a general contraction of the muscles of the pyloric
end followed. Kelaxation began at the transverse band, and
progressed slowly towards the pylorus. Moritz, 19 who studied
gastric movements by introducing recording balloons into the
dog and man, and Ducceschi, 20 who used the same method in
the dog, found marked alterations of the pressure in the pyloric
52 THE MECHANICAL FACTORS OF DIGESTION
end, which were not transmitted to the cardiac end. They
inferred, therefore, that the pyloric end, separated from the
remainder of the stomach, had its own distinct systole and
diastole. By introducing the gastroscope through fistulas in
dogs and men, Kelling noted so great a narrowing in the region
of the transverse band that large pieces of food (lumps of bread)
were lying before it. 21 Inference as to the functioning of the
transverse band was drawn by Schemiakine, who, while watching
through a fistula at the pylorus, noted that the food was not
continuously present there, but came in separate allotments. 22
Kaufmann's experimental evidence that vagus stimulation pro-
duced complete contraction of the band may be added. 23 And
more recently Auer has reported that in the rabbit, when ex-
trinsic nerves have been severed, gastric peristalsis is empha-
sized at the transverse band by a deep constriction, which
divides the stomach, and that thereupon the vestibule contracts
as a whole in a typical systole. 24
As some of the foregoing evidence definitely proves, the
circular muscle at the beginning of the pyloric portion is capable
of powerfully contracting and completely dividing the gastric
lumen. Indeed, in my first observations on the stomach I saw
the organ thus divided after I gave the animal apomorphine or
mustard to induce vomiting. 25 But what the stomach is capable
of doing is not proof of normal functioning. Obviously, in my
observations unnatural stimulation was employed. Is not the
same true also of the other observations supporting the concep-
tion of complete separation of the cardiac and pyloric portions ?
Beaumont admitted that the thermometer tube which he used
was an irritant. " If the bulb of the thermometer," he wrote,
" be suffered to be drawn down to the pyloric extremity, and
retained there for a short time, or if the experiments be repeated
too frequently, it causes severe distress, and a sensation like
cramp, or spasm, which ceases on withdrawing the tube, but
leaves a sense of soreness or tenderness at the pit of the stomach." 26
Perhaps a gastroscope in the stomach might have a similar effect.
Even a rubber sound introduced into the human stomach
becomes, according to Moritz, a source of irritation. 27 Of course,
inferences drawn from study of the excised stomach and from
the movements of food seen through a fistula must be standard-
ized by observations made under more natural and more instruc-
THE MOVEMENTS OF THE STOMACH 53
I have less hesitation in suggesting that complete division of
the stomach at the transverse band is the result of unnatural
stimulation because of my own experience. Many times I have
carefully watched with the X rays gastric peristalsis in human
beings, monkeys, dogs, cats, white rats, and guinea-pigs, 28 and
although the waves moving into the pyloric half of the vesti-
bule have at times almost obliterated the lumen, I have never
seen such deep constrictions at the beginning of the pyloric
portion. The systole of the vestibule in the rabbit I have noted
in one instance, but I have also watched in the rabbit's stomach
continuous peristalsis, running from the middle of the organ to
the pylorus, as in the other animals, without any obliteration of
the gastric lumen.
The observation that peristaltic waves run all the way to
the pylorus first reported in May, 1897 29 was immediately
confirmed by the X-ray studies of Koux and Balthazard 30 on
frogs, dogs, and human beings. Recently, with greatly improved
methods, Kastle, Bieder, and Rosenthal 31 have obtained in-
stantaneous radiographs of the human stomach, and have com-
pletely substantiated our early contention that the pyloric end
is normally not separated from the rest of the stomach, and that
the waves are continued over the vestibule.
The importance of a correct conception of the movements of
the pyloric portion lies in its significance for our understanding
of the functions of this part of the stomach. If the transverse
band completely closes the lumen, and the vestibule then under-
goes a systolic contraction, the function of this portion must be
mainly one of expelling the food into the duodenum.* On the
other hand, if the waves sweep without interruption over this
region, deepening as they go, they may have two functions
that of expelling the food, if the pylorus opens ; and that of
^nixing the foocl with the gastric juice, if the pylorus remains
closed. Because observations under normal conditions support
the latter conception of the activity of the vestibule, we are
warranted in concluding that it has a more important function
than that of merely expelling gastric contents into the intestine.
After summarizing the description given by Hofmeister and
Schutz, Ewald, for a priori reasons, declared : " I cannot accept
* Calculation shows that the volume of the two parts of the moderately
filled stomach of the dog is such that if at each " diastole " the vestibule. were
filled, and at each " systole " it forced the contents into the duodenum, the
stomach would be emptied within two minutes 1
54 THE MECHANICAL FACTORS OF DIGESTION
this view. The plain fact that the pyloric portion secretes a
strongly digesting fluid . . . proves it to be an important part for
the peptonizing function of the stomach." 32 The account of
the remarkable manner in which the pyloric portion performs
this function must be deferred until we consider the effects of
gastric movements on the contained food.
When an animal is examined with the X rays immediately
after receiving a meal which fills the stomach, there appears
within a brief interval a slight annular constriction near the
beginning of the vestibule, which moves slowly to the pylorus.
This is followed by several waves recurring at regular intervals
in the same region. Two or three minutes later very slight con-
strictions appear near the middle of the body of the stomach,
and, pressing deeper into the greater curvature, course towards
the pyloric end. Since the waves are repeated rhythmically,
the circumference in which they start must pulsate. And since
the time required for the waves to go from the source to the pylorus
is longer than the interval between pulsations, several waves
are always seen on the stomach at the same time.
When a wave sweeps round the bend into the vestibule, the
indentation made by it increases. As digestion proceeds, the
constrictions in the region of the vestibule grow still stronger,
and finally, when the stomach is almost empty, they may, as
they come near the pylorus, completely divide the cavity. At
all times, in the close neighbourhood of the pyloric canal, the
circular and longitudinal muscles, both of which are here strongly
developed, probably co-operate to decrease simultaneously in
all directions the terminal segment of the stomach. Certainly
there is a fairly quick change from a rounded, bulging mass of
food, in front of the advancing ring, to a much smaller mass,
just before the wave disappears at the pylorus (compare 2 and 3,
Fig. 4). 33
Gastric peristaltic waves do not pass on to the duodenum,
but stop at the pylorus. This separation of the two regions is
probably to be accounted for by the interruption in the con-
tinuity of the circular fibres just beyond the pyloric sphincter.
The rate of recurrence of the waves varies in different animals.
In the cat it ranges from four to six waves per minute ; in the
dog the rate is about four per minute ; and in man about three.
Age apparently has little influence on the rate. The number
of waves per minute in kittens about six weeks old was within
THE MOVEMENTS OF THE STOMACH
the limits of variation noted in adult animals. Under given
conditions the rhythm is remarkably regular. I have many
times been able to tell within two or three seconds when a minute
has elapsed, simply by observing the undulations as they passed
a selected point.
A slower recurrence of the gastric waves when fat was fed
than when bread-and-milk mush was fed suggested that there
might be characteristic rates for different foodstuffs. Ob-
servations at different intervals after feeding different foods
gave the following results : 34
5 to 5-4
The average rate of peristalsis increases from fats to proteins
and from proteins to carbohydrates, and the rate most frequently
observed varies in the same direction ; but the differences are so
slight and the variation with any given food so great as to make
it improbable that each foodstuff produces a characteristic rate.
As a result of my first observations on the stomach, I stated
that in normal conditions gastric peristaltic waves are con-
tinuously running, so long as food remains in the organ. 35
Hundreds of observations made since that time on various
animals mainly on cats, but also on dogs, guinea-pigs, and
white rats as well as records from human beings, 36 have con-
firmed the conclusion that peristalsis continues uninterruptedly
until the stomach is swept clear of its contents.* The number
of waves during a single period of digestion is larger than might
at first be supposed. In a cat that finished eating, at 10.52 a.m.,
15 grammes of bread, the waves were running regularly at
eleven o'clock. The stomach, examined and found active every
half-hour, was not empty until after six o'clock. At the average
rate for carbohydrate food (5-5 waves per minute), approxi-
mately 2,300 waves passed to the pylorus during that single
digestive period. When proteins or fats are fed, the stomach
is emptied more slowly than when equal amounts of carbohydrates
are fed. 37 Although the average rate of gastric peristalsis, as
* The rabbit offers an exception to this general statement.
56 THE MECHANICAL FACTORS OF DIGESTION
we have seen, is slower for proteins and fats than for carbo-
hydrates, the differences are so slight that the slower rate does
not compensate for the longer residence in the. stomach. When
equal amounts of protein, fat, or carbohydrate, are fed, therefore,
a much larger number of peristaltic waves, and consequently
a much greater expenditure of energy in the contraction of gastric
muscle, is required by the proteins and fats than by the carbo-
hydrates, before the stomach is emptied.
In some animals I have watched, the waves were repeated
less frequently as gastric digestion proceeded ; but records made
at intervals during seven hours, after feeding different foods,
showed no constant direction of variation. No general state-
ment, therefore, regarding the tendency of the waves to vary
in rate as the stomach is being evacuated, can safely be ventured.
The condition for the appearance of gastric peristalsis has
received relatively little attention. According to Edelmann,
who studied the stomach by means of a balloon introduced into
the organ, the movements are temporally related to the secretion
of gastric juice. Furthermore, he states that neutralization or
dilution of the gastric juice results in cessation of the movements,
which are restored only when the contents become again strongly
acid. 38 In the experiments of Hedblom and myself, the feeding
of acid food was attended by especially deep and rapid peristaltic
waves ; the rate was usually slightly faster than six waves per
minute. 39 And the feeding of fatty food, which inhibits gastric
secretion, was in my experience usually attended by relatively
shallow gastric waves. 40 Although there is this evidence of
concomitant variation of acid gastric contents and peristalsis,
it is not proof that the waves are the result of an acid stimula-
tion. Indeed, I have observed deep and strong peristaltic
waves in the stomach when the contents were strongly alkaline. 41
And, furthermore, peristalsis starts immediately, when food is
introduced into an empty stomach, if only the organ is at the
time in a state of tonic contraction. The secretion of gastric
juice does not occur with such promptness. The causal relation
does not exist, I believe, between secretion and peristalsis but
between these two and a common antecedent factor. A dis-
cussion of this matter must, however, be deferred until later.
A modification of the normal movements of the stomach is
seen when vomiting occurs. Vomiting can be induced by irrita-
tion of the gastric mucosa, or by stimulation of centres in the
THE MOVEMENTS OF THE STOMACH 57
medulla, or, as Valenti has recently shown, by the excitation
of a well-defined region between the pharynx and the top of the
oesophagus. 42 The centrifugal impulses pass through the vagi,
dilating the cardia. These impulses also cause dilation of the
cardiac end of the stomach, while increasing the tonus of the
pyloric region. X-ray observations on cats given apomorphine
subcutaneously, or mustard by stomach-tube, 43 correspond
closely with Openchowski's description of the appearances of the
exposed stomach during emesis. The first change is the total
inhibition of the cardiac end of the stomach, which becomes a
perfectly flaccid bag. This is followed, when apomorphine has
been given, by several deep contractions that sweep from the
mid-region of the organ towards the pylorus, each of which
stops as a deep ring at the beginning of the vestibule, while a
slighter wave continues. Finally, in all cases, a strong con-
traction at the angular incisure completely divides the gastric
cavity into two parts. Although waves continue running
over the vestibule, the body of the stomach and the cardiac
sac are fully relaxed. Now a simultaneous jerk of the
diaphragm and the muscjes_of the abdominal wall shoots the
contents out through the relaxed cardia. As these jerks are
repeated, the gastric wall seems to tighten around the remnant
of contents. Once during emesis I saw an antiperistaltic con-
striction start at the pylorus and run back over the vestibule,
completely obliterating the cavity, but stopping at the angular
incisure. In the process of ridding the gastric mucosa of irri-
tants, therefore, the stomach plays a relatively passive role.
1 Fischer and Abderhalden, Ztschr. f. physiol. Chem., 1903, xl., p. 216.
2 See Cannon, " The Correlation of the Digestive Functions," Boston
M. and 8. J., 1910, clxii., p. 97.
3 Cunningham, Tr. Roy. Soc., Edinb., 1906, xlv., p. 9.
4 His, Arch. f. Anat., 1903, p. 350.
5 See Williams, The Rontgen Rays in Medicine and Surgery, New York, 1901,
pp. 360, 365, 370.
6 Cf. His, loc. cit., p. 362, Figs. 1 to 4 ; and Bettmann, Phila. Month. M. J.,
1899, i., p. 133.
7 See Hertz, Quart. J. Med., 1910, iii., p. 375.
8 Holzknecht, Berlin, klin. Wchnschr., 1906, xliii., p. 128.
9 Pfahler, J. Am. M. Ass., 1907, xlix., p. 2069.
10 Schmidt's Jahrb., Leipz., 1888, ccxix., p. 284.
11 Kelling, Arch. f. d. Verdauungskr., 1900, vi., pp. 445, 456.
12 Moritz, Ztschr. f. Bid., 1895, xxxii., p. 359.
13 v. Pfungen, Centralbl. f. Physiol., 1887, i., p. 220.
14 Leven, Traite des Maladies de VEstomac, Paris, 1879, p. 16.
58 THE MECHANICAL FACTORS OF DIGESTION
15 See Cannon, loc. cit., p. 373.
16 See Boldireff, Internat. Beitr. z. Path. u. Therap. d. Ernahrungsstor., 1910,
17 Beaumont, Physiology of Digestion, Plattsburgh, 1833, p. 115.
18 Hofmeister and Schutz, Arch. f. exper. Path. u. Pharmakol., 1885, xx., p. 7.
19 Moritz, loc. cit., p. 362.
20 Ducceschi, Arch, per la Sc. Med., 1897, xxi., p. 134.
21 Kelling, Arch. f. Ttlin. Chir., 1900, Ixii., p. 22.
22 Schemiakine, Arch, des Sc. Biol., St. Petersb., 1904, x., p. 170.
23 Kaufmann, Wien. med. Wchnschr., 1905, lv., p. 1582.
24 Auer, Am. J. PhysioL, 1908, xxiii., p. 170.
25 Cannon, Am. J. PhysioL, 1898, i., p. 374.
26 Beaumont, loc. cit., p. 114.
27 Moritz, loc. cit., p. 369.
28 See Cannon, Am. J. PhysioL, 1898, i., p. 367 ; 1902, viii., p. xxii.
29 Cannon, Science, June 11, 1897, p. 902.
30 Pvoux and Balthazard, Compt. rend. Soc. de Biol., Paris, June, 1897, xlix.,
pp. 704, 785 ; and Arch, de PhysioL, 1898, xxx., p. 90.
31 Kastle, Rieder, and Rosenthal, Miinchen. med. Wchnschr., 1909, Ivi.,
p. 281 ; also Arch. Rontgen Ray, 1910, xv., p. 3.
32 Ewald, Lectures on Digestion, London, 1891, p. 67.
33 See Hertz, loc. cit., p. 381.
34 Cannon, Am. J. PhysioL, 1904, xii., p. 392.
35 Cannon, Am. J. Physiol., 1898, i., p. 367.
36 Cannon, Am. J. PhysioL, 1903, viii., p. xxii ; 1905, xiv., p. 344.
37 Cannon, Am. J. Physiol., 1904, xii., p. 393.
38 Edelmann, Dissertation (Russian) abstracted in Jahresb. u. d. Fortschr. d.
Physiol., 1906, xv., p. 119.
39 Hedbiom and Cannon, Am. J. Med. Sc., 1909, cxxxviii., p. 518.
40 Cannon, Am. J. Physiol., 1907, xx., p. 315.
41 Cannon, Am. J. PhysioL, 1907, xx., pp. 298, 299.
42 Valenti, Arch. f. exper. PathoL u. Pharmakol., 1910, Ixiii., p. 136.
43 Cannon, Am. J. Physiol., 1898, i., p. 373.
THE EFFECTS OF STOMACH MOVEMENTS ON THE CONTENTS
WHATEVER the amount of food sent to the stomach, the organ
has a wonderful ability to adapt itself with precision to the
volume of the contents. Even during the short time of a single
digestive period the body of the stomach may contract from
a large conical sac, many centimetres in circumference, to a
narrow tube little larger than a loop of intestine. Furthermore,
during this alteration in size the pressure remains practically
uniform. The change in the opposite direction, from smaller
to larger capacity, Kelling 1 proved could occur within a minute
or two without noteworthy increase of intragastric pressure.
Thus, when he introduced into the stomach of a dog 240 c.c.
of material, the pressure was 7-6 centimetres of water ; and when
this amount was increased to 460 c.c., the pressure was only
7 centimetres. Since he failed to find persistence of pressure
regulation in deep anaesthesia, Kelling inferred that it was a
reflex adaptation. More recently, Sick and Tedesko 2 have
proved, however, that the excised stomach, kept alive in warm
oxygenated Ringer's solution, is able to adapt itself to increase
of volume by an intrinsic relaxation, especially in the cardiac
end, so that there is no marked increase of pressure. Observa-
tions which I have made on cats entirely confirm the results of
both Kelling and Sick ; and I have also seen the excised stomach
gradually contract, as the contents were decreased, and main-
tain continuously the pressure that existed before the decrease.
The mechanism by which the stomach becomes so remarkably
adjusted to its contained volume may exist, therefore, within
The nature of the adjustment in the stomach wall is not yet
clearly explained. Mere relaxation of the tonic contraction of
the gastric muscle, according to Griitzner, would not account
60 THE MECHANICAL FACTORS OF DIGESTION
for the great changes in the capacity of the stomach without
attendant alterations of intragastric pressure. 3 Miiller, 4 working
under Griitzner's direction, compared the relaxed muscle fibres
in the full stomach and the contracted fibres in the empty
stomach of the frog and salamander. He found that, whereas
the length of the relaxed fibres was not more than three times
that of the contracted, the circumference of the full stomach
was five times that of the empty. The discrepancy he explained
as due to a rearrangement of the fibres : the musculature of the
full stomach was composed of only two or three layers of fibres,
while the contracted stomach had from fifteen to twenty layers.
How the fibres can thus slip by one another and still maintain
continuous pressure, and how, once dissociated, they are restored
to the multiplex composition of the contracted state is not
Another adjustment required by the filling of the stomach is
that of the abdominal muscles to the enlargement of the ab-
dominal contents. According to Kelling, the abdominal contents
of the dog may be increased 100 per cent, by a single meal.
Obviously, if the muscles of the abdominal wall do not relax,
intra-abdominal pressure must increase a result which might
produce serious circulatory disturbances. As the stomach is
filled, however, the muscles are relaxed, and in consequence the
pressure within the abdomen is not affected by taking food.
Apparently this adaptation of the abdominal muscles is a reflex
originated in the stomach or intestines ; for when air or salt
solution is injected into the peritoneal cavity, the pressure is at
once increased. 5
The figures given for intragastric pressure vary somewhat
with different observers, and, as might be expected, the pressures
are different in the less active cardiac end, holding the food in
tonic grasp, and in the more active pyloric end, undergoing
repeated compression by peristaltic waves. We have already
learned that these waves, as they move along the pyloric vestibule,
press gradually deeper into the contents. The pressure, there-
fore, should be greater at the pylorus than elsewhere in the
stomach. Actual measurement of the pressure in the cardiac and
pyloric ends of the human stomach have been made. Von Pfungen
introduced into the stomach of a boy who had a gastric fistula
8 centimetres to the left of the mid-line a rubber balloon, and
found that intragastric pressure near the fistula was upward from
THE EFFECTS OF STOMACH MOVEMENTS 61
19 centimetres of water, whereas directly in front of the pylorus
the pressure was 162 centimetres of water. 6 By means of an
intragastric bag passed down the oesophagus, Moritz studied the
pressures in the two ends of the stomach in a normal individual.
Although his figures are lower than v. Pfungen's, they show
a similar difference between the cardiac and pyloric portions.
The usual pressure in the cardiac end varied between 6 and
8 centimetres of water, while in the pyloric end there were
rhythmic recurrences of pressure amounting in some instances
to 38, 40, and even 60 centimetres of water, though as a rule
ranging from 20 to 30 centimetres. 7 The results obtained by
Sick, who used the method of Moritz, were confirmatory
7 to 16 centimetres pressure in the cardiac end, contrasted with
25 to 42 centimetres in the pyloric end. 8
The methods used in these experiments are not above criticism.
The presence of the experimenter's tube, especially in the pyloric
vestibule, where deepening peristaltic constrictions narrow the
lumen, may have prevented to some extent a free movement of
the contents, and may have thus unnaturally increased the
pressure in that region. Also the balloon may have stimulated
unusually strong contractions in the pyloric portion, and in
that way increased the difference between the pressures in the
two ends of the stomach. Yet the results obtained are what
might be expected from greater depth of the constrictions as
they approach the pylorus, and this concurrent evidence dis-
tinctly indicates that towards the pyloric exit the intragastric
pressure becomes considerably greater than it is near the less
active fundus. This conclusion is confirmed by the manner in
which chyme is discharged into the duodenum. In my X-ray
observations, whenever the chyme was permitted to emerge,
I saw it spurted through the pylorus and shot along the intestine
for several centimetres. The same testimony to the efficacy of
pressure at the pylorus is given by investigators who have
watched the gastric discharge through a duodenal fistula.
The absence of peristalsis over the cardiac sac, and the presence
of gradually deepening peristaltic constrictions in the pyloric
vestibule, have important practical consequences. Before con-
sidering them, however, we shall review what is known of the
O ' '
effects of gastric movements on the contents of these two parts
of the stomach.
A difference in the activities of the two ends of the stomach
62 THE MECHANICAL FACTORS OF DIGESTION
might have been inferred from old observations on the appear-
ance of the food in the cardiac and pyloric portions. In 1814,
Home described two parts of the stomach of the dog, " that
next the cardia the largest, and usually containing a quantity
of liquid in which there was solid food, but the other, which
extended to the pylorus, being filled entirely with half-digested
food of a uniform consistence." 9 Twenty years later Eberle
reported that, when the stomach of a dog is carefully opened
during digestion, the surface of the mass in the cardiac end shows
signs of digestion, but the interior of the mass remains unchanged,
whereas the contents of the pyloric end are throughout uniformly
mushy and fluid. 10 Many years later, Ellenberger and his
students demonstrated that, for several hours after eating, the
digestive processes in the two ends of the stomach of the horse
and the pig were quite different, and that different foods fed
successively were found, not uniformly mixed, but arranged
in strata. 11
These excellent observations were for a long time obscured
by Beaumont's description of the circulation of the food in the
human stomach, a description so circumstantial and detailed
as to present all the semblance of exactness. " The bolus as it
enters the cardia," Beaumont wrote, " turns to the left ; passes
the aperture ; descends into the splenic extremity ; and follows
the great curvature towards the pyloric end. It then returns,
in the course of the small curvature, makes its appearance again
at the aperture, in its descent into the great curvature, to perform
similar revolutions." 12 That Beaumont's conclusions were based
on the movements of a thermometer tube introduced through
a fistula, and on the appearance of particles of food in the gastric
contents as they passed the fistulous opening, was not criticized.
Yet, as we now know, the irritation by the thermometer tube
produced abnormal contractions, and the course which the par-
ticles took when out of the observer's sight could not be fairly
It is easily possible to test experimentally the validity of
Beaumont's inferences by watching with the X rays the move-
ments of pieces of food prepared to throw a black shadow in a
dimly outlined stomach. For this purpose I made little paste
pellets of bismuth subnitrate, with starch enough to preserve
the form, and gave them with the customary food, containing
relatively much less of the bismuth salt. These pellets, when
THE EFFECTS OF STOMACH MOVEMENTS 63
partly dried, did not disintegrate in the stomach during the
gastric digestion of soft bread. Several times I was fortunate
in finding two of the little balls in the axis of the body of the
stomach, and about a centimetre apart. As a constriction wave
approached them, both moved forward, but not so rapidly as the
wave. Now, when the constriction overtook the first ball, the
ball moved back towards the fundus through the moving con-
stricted ring, in the direction of least resistance. The wave then
overtook the second ball, and it also passed backward to join its
fellow. At the approach of the next wave they were both pushed
forward once more, only to be again forced backward, one at
a time, through the narrow orifice. But as the waves recurred
in their persistent rhythm, the balls were seen to be making
progress an oscillating progress towards the pylorus ; for
they went forward each time a little farther than they retreated.
This to-and-fro movement of the pellets was in no way inter-
rupted in the region of the transverse band, which is additiona
good evidence that normally it does not divide the stomach into
two parts. In the pyloric vestibule, where the peristaltic waves
were deep, the oscillations were more marked than in the body
of the stomach. On different occasions from nine to twelve
minutes elapsed while the balls were being pushed from where
the waves first affected them to the pylorus ; on the way, there-
fore, they must have been churned back and forth by approxi-
mately a half -hundred constrictions. 13
In the cardiac sac no signs of currents were visible. Balls
which lay in this region immediately after the food was ingested
kept their relative positions until the sac began to contract, and
then moved slowly towards the pyloric end. The immobility
of the food in the cardiac sac was also proved by feeding first
5 grammes of bread and bismuth subnitrate, then 5 grammes of
bread alone, and finally 5 grammes of bread with the bismuth
salt again. The first stratum lay along the greater curvature
and extended into the pyloric vestibule, the third stratum spread
along the lesser curvature, and the second rested between.
Tracings of this stratification of the contents were made on trans-
parent paper. Ten minutes after peristalsis began, the strati-
fication had entirely disappeared towards the pyloric end of the
stomach, but in the cardiac end, after an hour and twenty
minutes, the layers were still clearly visible. 14
These X-ray observations on the stratification of the gastric
64 THE MECHANICAL FACTORS OF DIGESTION
contents are in fair agreement with the observations of Ellen-
berger and Goldschmidt on the horse, which have since^been
confirmed by Scheunert. 15 They do not present the arrangement
so uniformly simple as Griitzner has described it. 16 He fed in
succession foods differently coloured, and, after digestion had
continued for an hour or more, killed the animal, froze the stomach
with its contents, and then made sections of it. Frogs and toads,
rats, cats, and dogs, served as subjects for the investigation.
As in the X-ray experiments, he reports that the first food was
pushed along the greater curvature by the later masses, but it
was also spread outwards from the greater curvature, in the form
of a thin layer, which prevented the later masses, lying within,
from coming into direct contact with the secreting mucosa.
Thus, whenever new food was given, it nested in the midst of
the food already present, just as described by Eberle in 1834.
In the pyloric end, Griitzner found that after digestion began the
strata soon became broken and warped.
Direct study of the motions of the food in the stomach, there-
fore, wholly discredits the account given by Beaumont ; not
even when the contents are fluid does circulation occur. On
the other hand, the motions observed offer a complete explana-
tion of the difference in the gastric contents at the two ends of
the stomach as described by Home and Eberle. Anyone can
readily verify the basic observation which first indicated the
separate functions of the cardiac and pyloric ends. The food
in the centre of the cardiac sac has the same appearance after
an hour and a half of gastric peristalsis that it had when ingest ed,.
but the contents of the pyloric vestibule, which the waves have
been churning, are changed to the consistency of thick soup.
The absence of any motions in the contents of the cardiac
sac suggested that the food during its stay there has little oppor-
tunity to become mixed with the gastric juice, and thus to undergo
peptic digestion. The truth of this supposition was easily
proved experimentally by feeding a slightly alkaline food, and
later testing the reaction of the contents in various parts of the
A cat which had been without food for fifteen hours was given
18 grammes of mushy bread made slightly alkaline with sodium
carbonate. One hour and a half after the cat had finished eating
she was killed, and the stomach exposed by opening the abdomen.
A very small hole was then made in the wall of the cardiac sac r
THE EFFECTS OF STOMACH MOVEMENTS 65
and another similar hole was made in the pyloric vestibule.
By means of a glass pipette food was extracted first from the
periphery of the cardiac sac ; this food was slightly acid. The
cleaned pipette was then introduced 2*5 centimetres into the
contents of the sac ; the food thus extracted gave the original
alkaline reaction. Specimens of the fluid contents near the
pyloric end, taken from various depths, were all strongly acid. 17
These observations on the cat I repeated on the dog. They
have been completely confirmed by Heyde working with Griitzner.
Rats, rabbits, guinea-pigs, and cats, were fed by Heyde with
different kinds of food mixed with acid indicators, and were
killed at different intervals after eating. The stomachs were
carefully removed and frozen ; sections were made through the
frozen contents, and the altered colour of the indicators revealed
at once the extent of acidification. The inner layers of the
food in the cardiac end retained for hours a neutral or weakly
alkaline reaction ; only the outer layers were slightly acidified
and digested. 18
As we have already learned, the functional difference between
the cardiac and pyloric ends of the stomach is the same in man
as in the dog, the cat, and other experimental animals. Does
a corresponding difference prevail between the character of the
contents in the two ends of the human stomach ? Does the
mass of food in the quiet cardiac sac remain long unmixed with
gastric juice while that in the pyloric end is intimately churned
by the peristaltic waves ? These questions have been considered
by Sick, 19 who, using a specially-devised stomach-tube, removed
samples of the contents from the cardiac or pyloric end at will.
The subjects took a semi-fluid test-meal, and then swallowed
a cachet containing carmine or charcoal. After a given time the
stomach-tube was introduced, first into the pyloric, and later
into the cardiac end. In spite of the semi-fluid gastric contents,
and in spite of exercise by the subjects during the interval of
digestion, the pyloric part of the stomach remained wholly free
from the colouring material for fifteen or twenty minutes indeed,
in some cases for almost twenty-five minutes while the cachet
had meanwhile dissolved and liberated its contents into the food
of the cardiac end. Gradually, after thirty or forty minutes,
the carmine powder appeared near the pylorus. Sick also found
a difference in the consistency of the contents in the two portions
of the stomach : in the pyloric end a thin fluid was present,
66 THE MECHANICAL FACTORS OF DIGESTION
homogeneous in character ; in the cardiac end a lumpy, rather
coherent mass. He concluded, therefore, that in the human
stomach, even when the food is somewhat fluid, an important
difference exists between the physical and chemical nature of the
contents of the two ends, and that only slowly does a com-
plete mixture take place. This conclusion is supported by the
experiments of Prym, 20 who has furthermore emphasized the
significance of this differential treatment of the food for the
clinical examination of gastric contents. Evidently, if the con-
tents are not a uniform and homogeneous mixture, not only
may the stomach-tube give wrong testimony regarding the
conditions in the organ, but the food even when expressed as a
whole may be equally deceptive.
The application to man of the facts determined for animals
has been criticized by Hertz, who has declared that gas in the
fundus of the human stomach (gas is practically always present)
causes the oesophagus to discharge new food either on or slightly
below the upper surface of the stomach contents, and thus not
into the centre of the mass in the cardiac sac. He has also
suggested that the delay in the appearance of the colouring
materials (carmine and charcoal) in the pyloric end, noted by
Sick, was due to their first floating on the surface of the contents,
whence they could become only gradually incorporated. 21 Of
course the question of the stratification of the food is really
not involved in a consideration of the mechanical effects of
peristalsis in one end of the stomach, and mere tonic contraction
in the other end. Hertz seems not to have given due weight
to the statement of Sick that about three-fourths of his subjects
were reclining on the right side, nor has he offered any explana-
tion of the difference in the consistency of the food from the
two parts of the stomach, which Sick reported. Certainly the
greater size of the human stomach does not cause it to act differ-
ently on the food than do the stomachs of dogs and cats, for,
as already stated, Ellenberger and Goldschmidt proved that
there was no general mixture of the gastric contents in the horse
during several hours after the ingestion of food. The main argu-
ment of Hertz seems to be based on the assumption that gastric
contents are so fluid as to be the medium of rapid diffusion.
Experiments to be described later show that diffusion does
indeed occur even in viscous gastric contents, and that when
the contents are of a thin, fluid consistency the diffusion may
THE EFFECTS OF STOMACH MOVEMENTS 67
be rapid. After an ordinary generous meal, however, with a
satisfactory variety of food, the gastric contents, as the autopsy-
room demonstrates, may not be fluid, but a thick and mushy
mass. In such a mass diffusion currents must be slow. Indeed,
the currents described by Beaumont, resulting from the move-
ments of the gastric wall, could hardly occur. Under such
circumstances, therefore, the evidence points to the same effects
on the food in the two ends of the human stomach as are found
The supposed value of the circulation of the food in currents
running throughout the stomach, as described by Beaumont,
lay in the means it offered for bringing the contents of the
stomach near to the secreting gastric mucosa, and thus per-
mitting the gastric juice to exert more readily its action.
Although my X-ray observations did not support Beaumont's
description of a mixing current moving along the greater and
lesser curvatures, they nevertheless showed that in the pyloric
vestibule and the region just before it an admirable mechanism
exists for bringing all of the food into intimate contact with the
mucosa in that region. Evidently, when a constriction occurs,
the mucous surface enclosed by the ring is brought close around
a narrow isthmus of food or chyme lying in the axis of the stomach.
Now, as this constriction passes on, fresh areas of the mucosa
are continuously pressed inward to form the little orifice. And
at the same time, as the constriction moves, a thin stream of
the gastric contents is continuously forced back through the
orifice. The result of this admirable mechanism, indicated by
the oscillating pellets, is that every part of the mucosa of the
pyloric portion is brought near to every bit of food a large number
of times before the food leaves the stomach.
It is well known that the mucosa of the pyloric portion of the
stomach does not secrete hydrochloric acid, although it does
secrete pepsin. Yet the contents of this region, all observers
agree, become uniformly acid in reaction soon after gastric
digestion begins, and remain thus until the stomach is emptied.
We must assume, therefore, that the acid-pepsin secretion is
pressed onward from the surface of the contents of the cardiac
portion, by the gentle waves of peristalsis in that region, and
gradually mixed into the contents of the vestibule. Meanwhile,
however, the deep waves approaching the pylorus have churned
the vestibular food with the local pepsin secretion, and now,
68 THE MECHANICAL FACTORS OF DIGESTION
as the imported acid appears, proteolytic digestion can progress
rapidly. 22 Thorough mixture of the food with the secretion of
the vestibule and with the gastric juice from the body of the
stomach is therefore one of the functions of the peristaltic waves.
The resulting chyme is a soupy, homogeneous fluid, ready for
exit into the intestine.
Another function of the intimate contact of mucosa with
gastric contents in the pyloric region is that of continuing
gastric secretion. As Edkin's experiments proved, the con-
dition for the continued secretion of gastric juice, after the
initial " psychic " secretion, lies in a chemical stimulation of
the gland cells through the blood-stream. 23 The chemical
stimulant given to the blood is produced, not by the mucosa of
the cardiac end of the stomach, but by that of the pyloric end.
And the vestibular mucosa is roused to activity by the presence
of acid, peptone, or sugar solutions a presence which is re-
peatedly forced on the mucosa by the churning waves.
An associated function of the churning action in the vestibule
is concerned with absorption. Although water is not absorbed
in the stomach, glucose in concentrated solution, and proteins
which have been exposed to gastric digestion, may be absorbed
in considerable amount. 24 The mucosa of the vestibule has
many fewer glands than the mucosa of the cardiac end, where
they are placed in very close order. The absorption that occurs
in the stomach, therefore, probably takes place in the vestibule,
for there the epithelial surface is most favourable to the process.
There also gastric digestion is most advanced, and the food in
consequence is most ready for passage through the mucosa.
And, furthermore, in the vestibule the mechanical conditions
are most favourable to absorption, because the digested food is
repeatedly brought into very close contact with the mucous lining.
If the pylorus does not relax before an approaching wave, the
food is pressed into a blind contractile pouch, the only exit from
which is backward through the advancing ring of constriction.
As we have seen, the constrictions are deeper near the pylorus,
and the rings therefore are small ; consequently the food is squirted
backward through them with considerable violence. The action
of this part of the stomach on the food can be observed by means
of the little pellets which I have already mentioned. As the
slow waves push the little morsel and the surrounding soft food
up to the closed sphincter, the whole mass is squirted back
THE EFFECTS OF STOMACH MOVEMENTS 69
into the vestibule. Again and again I have seen this process
repeated until the sphincter relaxed and allowed the more fluid
parts to pass out.*
The older writers on the physiology of digestion described
a selective action of the pylorus. The region of the sphincter
was supposed to possess a peculiar sensitivity which caused it to
prevent the passage of undigested material into the duodenum.
Hofmeister and Schutz, and Moritz, have disclaimed any such
function, and have declared that solid particles are carried from
near the exit of the stomach back to the cardiac end by anti-
peristaltic waves. The action at the pylorus which I have seen,
however, was like that described by the older writers ; for during
digestion there was no antiperistalsis, and the sphincter, separa-
ting the fluids from the solids, as in the case of the hard morsels
mentioned above, caused the solids to remain and undergo a
tireless rubbing. Frequently, when several of these pellets
were given at the same time, they have all been seen in the
vestibule after the stomach was otherwise empty. There they
remained, to be softened in time by the digestive juices or to be
forced through the pylorus later, for, as is well known, solids
do pass into the intestine. 25 It seems highly probable that the
prevalence of pathological conditions in the pyloric end of the
stomach, rather than in the cardiac end, is due to the injury
which the greater activity of the pyloric end may bring upon itself.
The presence of peristaltic waves on the right half of the
stomach and their absence from the left half indicates two separate
parts of the stomach. The evidence now before us shows that
these two parts have distinct functions. The left half is a reser-
voir in which the food is not mixed with the gastric secretion,
and from which the contents are slowly pressed out into the active
right half. The peristaltic waves coursing over the right half
mix the food with the gastric juice, expose it to the mucosa of
the vestibule for absorption and for the continuance of gastric
secretion, churn the unbroken particles of food until they are
triturated, and finally expel the chyme into the duodenum.
Still other consequences of the different activities of the two
ends of the stomach are next to be considered.
* At a meeting of the Boston Society of Medical Sciences, May 20, 1902, I
demonstrated a method of showing the churning function of the stomach,
and the activities of other parts of the alimentary canal, by means of the
70 THE MECHANICAL FACTORS OF DIGESTION
1 Kelling, Ztschr. f. Bid., 1903, xliv., p. 234.
2 Sick and Tedesko, Deutsches Arch. f. Jdin. Med., 1907, xcii., p. 439.
3 Griitzner, Ergebn. d. Physid., 1904, Abth. ii 2 ., p. 77.
4 Miiller, Arch. f. d. ges. PhysioL, 1907, cxvi., p. 253.
5 Kelling, loc. cit., p. 181.
6 v. Pfungen, Centralbl. /. PhysioL, 1887, i., pp. 220, 275.
7 Moritz, Ztschr. f. Bid., 1895, xxxii., pp. 356-358.
8 Sick, Deutsches Arch. /. Idin. Med., 1906, Ixxxviii., p. 190.
9 Home, Lectures on Comparative Anatomy, London, 1814, i., p. 140.
Eberle, Physiologic der Verdauung, Wiirzburg, 1834, pp. 81, 91, 100, 154.
11 Ellenberger and Hofmeister, Arch. f. wissensch. u. prakt. Thierh., 1882,
viii. ; 1883, ix. ; 1884, x., p. 6 ; and 1886, xii., p. 126. Ellenberger and
Goldschmidt, Ztschr. f. physiol. Chem., 1886, x., p. 384.
12 Beaumont, Physidogy of Digestion, Plattsburgh, 1833, p. 110.
13 Cannon, Am. J. PhysioL, 1898, i., p. 377.
14 Cannon, Am. J. PhysioL, 1898, i., p. 378.
15 Scheunert, Arch. f. d. ges. PhysioL, 1906, cxiv., p. 64.
16 Griitzner, Arch. f. d. ges. PhysioL, 1905, cvi., p. 463.
17 Cannon, Am. J. PhysioL, 1898, i., p. 379.
18 Grutzner, Deutsche Med.-Ztg., 1902, No. 28.
19 Sick, Deutsches Arch. /. Jdin. Med., 1906-07, Ixxxviii., p. 199.
20 Prym, Deutsches Arch. f. klin. Med., 1907, xc., p. 310.
21 Hertz, Quart. J. Med., 1910, iii., p. 384.
22 v. Wittich, Arch. f. d. ges. PhysioL, 1874, viii., p. 448.
23 Edkins, J. Physid., 1906, xxxiv., p. 133.
24 v. Mering, Verhandl. d. xii. Congr. f. innere Med., 1893, p. 471 ; TobJer,
Ztschr. f. physiol. Chem., 1905, xlv., p. 206.
25 Cannon, Am. J. Physid., 1898, i., p. 377.
THE STOMACH MOVEMENTS IN RELATION TO SALIVARY
DIGESTION, AND GASTRO-ENTEROSTOMY
THE discussion of the events in the stomach has thus far shown
that the contents may rest in the cardiac end for an hour or more,
exposed to a relatively slight pressure, and unaffected by the
peristalsis of the pyloric end ; and, on the other hand, that the
contents of the pyloric end, repeatedly swept to and fro by the
passing waves, are repeatedly exposed to a pressure which
increases as the pylorus is approached. These conditions have
important bearings on the question of salivary digestion in the
stomach, and on the course taken by the food after the operation
of gastro-enterostomy. These matters we shall now consider.
SALIVARY DIGESTION IN THE STOMACH.
In stating the functions of saliva, emphasis has been laid on
its effects as a lubricant for the tongue, cheeks, and lips, and
for the food about to be sent through the oesophagus ; and as
a diluent for irritating substances taken into the mouth. Saliva
can indeed change starch to sugar ; but during ordinary mastica-
tion the short time for this chemical change has been pointed out,
and in the stomach the action of ptyalin has been supposed to
be soon stopped by the acid gastric juice.
The short time assumed for salivary digestion in the stomach
was supported by Beaumont's conception that all the food was
rapidly acidified by circulation along the gastric walls. These
mixing currents, however, as we have seen, do not exist, and
in the cardiac end, although the surface of the contents becomes
acid, the internal mass of the contents remains unchanged in
reaction. Since salivary digestion can continue so long as free
acid is absent, I suggested in 1898 that salivary digestion might
72 THE MECHANICAL FACTOKS OF DIGESTION
proceed in the cardiac sac for an hour or more without inter-
ference by the acid gastric juice. 1 This conclusion has been
supported by Oehl, 2 and by Heyde, whose experimental work
with Griitzner has been described.
Several researches have been published indicating the possi-
bility of rather extensive amylolysis in man. As long ago as
1880, von den Velden pointed out that free hydrochloric acid
does not appear for almost an hour after eating an ordinary
(breakfast, and for almost two hours after eating a full midday
meal. And, later, Hensay 3 and Miiller, 4 presented quantitative
analyses of the amounts of sugar jmd^dgxtrins jwhich might
be formed in the stomach whenlood is carefully chewed. They
found that after aTialf^our in the stomach carbohydrate food
/ was in large part made soluble by saliva, that over one-half,
I even two-thirds, of the soluble portion consisted of maltose and
of dextrins closely related to maltose, and that the remainder
\ consisted of dextrins more nearly related to starch.
None of the observers who brought forward these positive
results regarded the differences between the pyloric and cardiac
ends of the stomach. To be sure, many years ago Ellen-
berger and Hofmeister had studied the digestive processes in
the pyloric vestibule and the cardiac sac of the horse and pig, 5
and later Hohmeier reported similar studies on the rat. 6 The
cardiac end of the stomach in the horse, pig, and rat, how-
ever, is to a great extent lined with inactive pavement epithe-
lium, and with " cardia " glands, the secretion of which is not
acid. 7 A demonstration of salivary digestion in the cardiac
end of the stomach under these circumstances is not satisfactory
proof of what occurs in animals in which the secretion of the
cardiac wall is strongly acid. H. F. Day and I 8 undertook,
therefore, an investigation of salivary digestion in the stomach
of the cat, which resembles the stomach of the dog and of man,
not only in structure, but also in pouring out an active secretion
from almost every part of its surface.
Crackers, free from sugar, were powdered, weighed in uniform
amount (30 grammes), and mixed with a uniform volume
of filtered human saliva (100 c.c.). The resulting thick mush
was immediately fed in small amounts or introduced by a tube
into the stomach of the hungry animal. At the end of a half-
hour, an hour, one and a half or two hours, the animals were
quickly etherized, and the stomach excised, after the contents
SALIVARY DIGESTION 73
of the pyloric and cardiac ends had been separated by a ligature
tied around midway between them. The contents of the two ends
were at once removed, and the enzyme action stopped by boiling.
After the food had evaporated to dryness, it was powdered,
1 gramme of it was mixed with 100 c.c. of distilled water, the
mixture was allowed to stand for a half-hour, then filtered, and
the filtrate tested for sugar (as maltose) by Allihn's method.
Two factors, besides the difference between the two ends of
the stomach, had to be considered. One was the rapidity of
salivary digestion. Starchy foods vary considerably among
themselves in the rate at which they change to sugar. 9 The
material used by us was tested in vitro at 38 C., and in seven
minutes four-fifths of the amount of sugar found at the end of
an hour was already present. Under these conditions the
accumulation of the products of digestion inhibited the action
of the ferment as time passed ; nevertheless, the change was
clearly of sufficient rapidity to result in considerable amylolysis
before being checked by acid, even in the pyloric end. The
second condition to be considered was the possibility of any
agency, except saliva, that would change starch to sugar.
Control experiments, in which the powdered cracker was mixed
with distilled water, revealed only the slightest trace of any
Our examination showed that after a half-hour the contents
of the cardiac and the pyloric ends of the stomach have about
the same percentage of sugar, and that after an hour the cardiac
mass, because of continued amylolysis, contains about 80 per
cent, more sugar, in unit volumes, than the vestibular mass.
The difference is doubtless actually greater, for the food in the
cardiac end is drier than that in the pyloric end, and we ex-
amined the dried material. From an hour to two hours after
feeding, the ratio of the sugar percentages in the two parts of
the stomach begins to approximate unity again. This change
is probably due largely to diffusion of the sugar solution from
the cardiac to the pyloric contents. The possibility of this
diffusion was proved by feeding first salmon and later crackers
mixed with saliva. At the end of an hour some of the salmon
taken from near the surface in the cardiac end, fully 1-5 centi-
metres from the stratum of crackers, contained 3 per cent, as
much sugar as the crackers. This diffusion, however, did not,
in our experiments, remove to any important degree the ptyalin
74 THE MECHANICAL FACTORS OF DIGESTION
from the mass in the cardiac sac, nor did the position of the
stomach affect the differences in sugar production in the two parts.
When liquid food was given, and when small amounts of food
were given, the sugar percentages in the two parts of the stomach
were nearly the same. This observation, probably explicable
on the basis of ready diffusion, or uniform penetration of the
acid gastric juice, has important bearings, for it indicates that
the usual test-meal, small in volume and containing fluid, becomes
homogeneous in the two parts of the stomach, and that therefore
any part of it, which is taken for examination, is very like any
Much of the starch which was not changed to sugar was-
changed to dextrin, and thus, since dextrin is not readily fer-
mented, the food was possibly saved to the organism. The
especial value of this process lies in its occurrence in greatest
degree in the midst of the cardiac contents, where hydrochloric
acid, which inhibits the action of many of the organized f erments,.
does not for some time make its appearance.
We may conclude therefore that, in the early stages of gastric
digestion, after an ordinarily bountiful meal which has been
properly masticated, the contents of the cardiac end of the
stomach, although undergoing proteolysis on the surface, are
chiefly subject to the action of ptyalin ; and, furthermore, that
the contents of the pyloncT end, after a brief stage of salivary
digestion, are subject thereafter to strictly peptic changes.
Later, as the contents of the fundus become acid, the food in
the stomach as a whole receives uniform treatment.
The observations of Miiller and Hensay on salivary digestion
in man, together with the results obtained by Day and my-
self, emphasize again the importance of mastication. A large
portion of the food consists of starch. Only by mastication is
this food properly broken up so that a large surface is exposed
to the action of ptyalin. When it has been thus thoroughly in-
salivated, it will go far on the way to final digestion, while
waiting to be discharged from the stomach.
THE MOVEMENT OF FOOD AFTER GASTRO-ENTEROSTOMY.
If the pyloric canal becomes narrow or closed, or if there is-
otherwise delay in the passage of food from the stomach, the
common operation of making an artificial anastomosis, or stoma,
between the stomach and a loop of small intestine is performed,
in order to render the forwarding of the gastric contents possible
or more rapid. The assumption is that always after gastro-
enterostomy there is a change in the course which the food takes
in going from the stomach into the bowel. Two questions of
interest arise with regard to the effect of the new opening. Under
what conditions does it induce an alteration in the normal
course of the food ? And if the normal course of the food is
changed, what are the results ?
In much of the surgical literature on gastro-enterostomy, until
within a few years, the operation was conceived as a " drainage "
operation, and surgeons were careful to make the stoma at the
most dependent point in the stomach. Involved in this con-
ception are the assumptions that the stomach is a relatively
passive bag, and that the food, swallowed in a semi-solid state,
somehow becomes liquid, and by gravity runs through the new
hole into the intestine. Facts which we have already considered
prevent us from giving ready credence to these assumptions.
The stomach is not at any time during digestion in the con-
dition of a passive reservoir ; the cardiac end is exerting a
positive pressure, and, so long as food is present, the pyloric
end is the seat of continuous peristalsis. The statement has
been made repeatedly in surgical writings, that a gastro-enter-
ostomy midway in the stomach relieves the pylorus of the irrita-
tion from food and gastric juices. It seems to be assumed that
the region between the new opening and the pylorus becomes
unnecessary for digestion, and inactive. There is no reason,
however, for believing that peristalsis does not persist under
these circumstances, and that the food is not thoroughly churned
in the pyloric end in the normal manner. Although, in cases
of pyloric stenosis, gastro-enterostomy, of course, shortens the
time during which peristalsis and acid juices are present in the
pyloric end of the stomach, we should not deceive ourselves
by the supposition that the operation permits this region to
enjoy entire relief from either of these disturbing conditions.
In observations on animals in which the stomach and gut had
been artificially joined, and the pylorus externally ligated or
completely closed by sutures, I have seen the waves passing
over the pyloric end without interruption for long periods.
Our previous consideration has shown that, as the stomach
empties, the most dependent point changes its position. The
76 THE MECHANICAL FACTOKS OF DIGESTION
greater curvature of the relaxed or full stomach may indeed
reach considerably below the pylorus, but as the contents
disappear, the greater curvature rises, and the pylorus, being
more or less fixed, then becomes the lowest point.
The argument may be advanced that observations on a
normal animal do not hold good for abnormal conditions in
human beings. The claim may be made that the attachment
of the intestine to the stomach acts as a drag, keeping the stoma
at the most dependent point, and that then the stomach must
be merely a passive reservoir with its contents drained by gravity.
Or the point may be urged that when the stomach is dilated,
toneless, and flabby, it cannot act normally, and that the part
observed to be lowest when the abdomen is opened must remain so.
In this connection the ready mobility of the intestinal coils
may be mentioned. If the stomach, however, has been pur-
posely attached to a fixed portion of the gut in order to make
the stoma permanently the most dependent point, or even if
the new opening remains lowest because of pathological conditions,
we may reasonably question whether evacuation is thereby
facilitated. For in our discussion of the doctrinaire notions
of the shape of the normal stomach we learned that the hydro-
static conditions in the abdominal cavity are such that gravity
drainage is impossible that when a gastro-enterostomized
stomach is filled with water the water does not run out by itself,
even with the subject in the upright position. In other words,
material does not move along the alimentary canal unless the
pressure is greater on one side of it than on the other.
What we have learned regarding the pressure relations in the
stomach is pertinent to the present discussion. As we have
seen, peristaltic waves are continuously passing over the pyloric
end so long as food is present, and on approaching the sphincter
they become deeper and deeper until they almost obliterate
the lumen. Two results follow from this peristaltic activity.
The waves which force the food repeatedly against a closed
pylorus mix the food with the gastric juice, and churn the mixture
into a fluid chyme. The first effect of the waves, therefore, is
to render the contents of the pyloric end of the stomach more
liquid, and therefore more freely movable than the contents of
the cardiac end. The second effect of the gradually deepening
waves is that the pressure within the stomach is greater near
the pylorus than anywhere else.
The direct consequence of greater fluidity of food near the
pylorus and greater pressure on the food at that point is that
the chyme takes its normal passage through the pylorus, if the
pylorus is patent, rather than through any artificial opening.
This fact was first determined by Kelling, who performed gastro-
enterostomies on dogs by all the methods known to surgery
on the anterior and posterior surfaces of the stomach, with high
attachment of the jejunum, with low attachment of the jejunum,
by union with the ileum at any part and at the same time
made a duodenal fistula. He observed that nothing left by the
stoma, as could be determined through the duodenal fistula ;
all food, whether solid or liquid, emerged from the stomach by
way of the pylorus. 10 This observation was confirmed in X-ray
studies by J. B. Blake and myself. 11 We made openings of
various sizes and at various positions between the stomach and
intestine. When fluid boiled starch was given, this fluid, instead
of running through the stoma into the intestine, was forced out
naturally through the pylorus. Only two exceptions were
observed in our experience r one in an animal with the stoma
on the posterior wall of the vestibule close to the pylorus, and
the other in an animal with a large anterior stoma (3 centimetres
long) about halfway between the two ends of the stomach.
The food left by both exits ; but in the latter case salmon, less
fluid, went out by the pylorus alone. It was not observed passing
through the stoma at any time during four and a half hours after
In one instance the pylorus was partly occluded. A tape
was passed through the walls of the stomach in front of the
pylorus and tied ; then the gastric wall was sewed tightly over
the entrance and exit of the tape. The food still passed out
through the pylorus. In another instance a linen ligature was
tied snugly around the canal at the pyloric sphincter. A week
later liquid boiled starch was fed, and, although peristaltic
waves were continually pressing up to the pylorus, the food
was seen passing out wholly by way of the stoma. Still later,
when thick salmon was fed, the stomach was watched for the
first three-quarters of an hour, and again between two and
two and a half hours after the feeding. No food was observed
going from the stoma, but in small amounts it was passing through
the pylorus. At autopsy the ligature was found partially
embedded, and the pyloric opening was about 0-3 centimetre
78 THE MECHANICAL FACTORS OF DIGESTION
in diameter. These cases clearly show that even when the pylorus
is narrowed so as to make difficult the passage of the chyme,
the chyme is forced into the intestine by the natural way rather
than through an opening remote from the greatest pressure.
When salmon was fed, the food, with the one exception above
mentioned, was never seen leaving the stomach by the artificial
opening, if the pylorus was patent. The salmon, as a more solid
food than the starch paste, becomes, as we have seen, fluid near
the pylorus, although remaining in its swallowed condition in
the cardiac end. Naturally, a more fluid material under general
pressure should pass more readily through an opening in the
stomach than a drier and more solid mass. For this reason
alone the chyme should go out through the pylorus sooner than
the unchymified food through an opening in the middle of the
stomach. And when this difference of consistency, favourable
to the pyloric passage, is combined with greater pressure in the
pyloric region, the reasonableness of the results observed by
Kelling and by Blake and myself is manifest.
These results have been further confirmed by Tuffier 12 and
by Delbet. 13 They have received support also in observations
by Leggett and Maury, 14 who traced the course of food by means
of strings tied to little bags containing lead shot. As the
heavy weight must tend to carry the bags to the lowest point,
the occasional first exit of the string through the stoma, in
Maury's experiments, should not be wholly unexpected. The
possibility of the anastomotic opening rather than the pylorus
being at times the path of election cannot, however, be gain-
said ; recent experiments by F. T. Murphy and myself have
confirmed the earlier work with Blake in showing that occasionally
food will take the artificial before it will take the natural course.
But there is no doubt, from the wide range of evidence above
cited, that in experimental animals the natural exit of the food
is through the pylorus, and not through the artificial opening,
when both ways are offered.
The claim may again be made that the results of these experi-
ments, which were performed on animals, do not apply to con-
ditions in human beings, where the stomach and intestines are
larger structures, and permit the establishment of larger open-
ings. In this connection the experience of Berg is of interest.
In 1907 he reported the cases of two persons, who had each an
accidentally established duodenal fistula, and were losing a large
amount of food through this unnatural orifice. 15 Berg made a
gastro-enterostomy in each patient, and in one of them also
tied the pylorus. In the latter case chyme ceased to be dis-
charged. In the former case, however, it continued passing out
through the duodenal fistula. This operation on a human being
exactly corresponds to Kelling's experiments on dogs, and to
the studies by Delbet, mentioned above. The conclusion, there-
fore, may be justly drawn that, if the pylorus is patent, the
gastric contents are forced out through the natural passage
rather than through the anastomosis.
On the basis of the consideration just presented, Moynihan
has concluded that gastro-enterostomy is most efficient only
when gross mechanical obstruction exists. Under no circum-
stances, and in compliance with no persuasion, however insistent,
he has declared, is the operation to be done in the absence of
demonstrable organic disease. 16
In animals in which gastro-enterostomy had been performed,
and the pylorus had been left unclosed or only partly occluded,
Blake and I repeatedly observed a circulation of the food. The
food was forced through the pylorus, was pushed thence through
the duodenum, and driven into the stomach again through the
stoma. We have watched animals a half -hour at a time, and
over and over again at short intervals during this period food
has entered the duodenum from the pylorus, and gone through
the regular course, only to merge once more with the mass in
the stomach. Usually at these times no food was seen passing
into the intestine beyond the stoma. It was of interest and
of practical importance to observe that the food circulated most
constantly when the stomach wall was stretched by a large
amount of contents. The stretching separates the edges of the
opening to which the intestine is attached, and as the edges
separate, the intestine is drawn straight between them. Thus
it forms a flat cover to the stoma, becoming, in short, practically
a part of the gastric wall. In the stretching and flattening of
the attached coil of intestine, the entrances into the lumen of
the gut are changed to narrow slits. These slits may, indeed,
be so much narrowed by pressure applied to them from within
the stomach that they act like valves, permitting material to
enter, but preventing its escape.
The effectiveness of these " valves " we tested in the excised
stomach by tying the pylorus and filling the organ with water.
THE MECHANICAL FACTORS OF DIGESTION
As the gastric wall became stretched and the internal pressure-
increased, almost no water escaped through the stoma into the
intestine. And when the cardia was closed and the stomach,
and its fluid contents further pressed by hand, the " valves "
were still more effective in preventing leakage (see Fig. 5). Not
more than a moderate distension of the stomach after gastro-
enterostomy seems, therefore, an essential condition for effective
action of the anastomosis.
The circulation of the food above described did not in our
experiments result in the symptoms of " vicious circulation."
The animals never vomited in conse-
quence of repeated entrance of food
from the duodenum into the stomach.
Indeed, the observations of Boldireff 17
indicate that the presence of a certain,
amount of bile and pancreatic juice in
the stomach may be quite normal. And
Kaiser, after citing numerous observers-
who found bile almost invariably present
after gastro - enterostomy in human,
beings, has declared that he does not
regard its presence there unfavourably. 18 "
Retention of food in the stomach,
with subsequent repeated vomiting, such
ENTRANCES INTO THE as attends the so-called "vicious cir-
INTESTINAL LUMEN TO culation " after gastro-enterostomy, was-
associated usually, in our experiments,
with obstructive kinks and other de-
FIG. 5. DIAGRAM SHOW-
ING HOW STRETCHING
THE STOMACH IN GASTRO-
CAUSE THE ATTACHED
PART OF INTESTINE TO
BECOME ALMOST CON-
TINUOUS WITH THE GAS-
TRIC WALL, AND THE
BE CHANGED TO MERE
S, stomach; I, intestine.
monstrable obstacles to the easy passage
of the food. In the case of fatal kinking observed by us-
the trouble was invariably at the distal point of that part
of the intestine which was attached to the stomach. Sharp
turns in the intestine are normally straightened without
difficulty by the injection of material driven along by peristalsis.
When a kink forms immediately beyond the stoma, however,
this force is not at hand to straighten it, for peristaltic activity
has been abolished in the intestine proximal to the kink by
cutting the necessary circular fibres. The contraction of the
interrupted circular muscle evidently can have no other effect
than that shown in Fig. 5 i.e., a shortening of the intestinal
wall between the attachments to the stomach. The only force
tending to obviate the kink is the pressure on the food in the
stomach, which in the cardiac portion is slight. The rational
procedure, therefore, is to attach a narrow band of the distal gut
continuously to the stomach wall for several centimetres beyond
the stoma. The gut is thus kept straight throughout a distance
which permits peristalsis to become an effective force. From
clinical considerations, Kappeler has come to the same conclusion,
and has recommended fastening to the stomach wall 4 to 6 centi-
metres of both the proximal and distal loops, for the purpose of
avoiding sharp turns.
If gastro-enterostomy is performed when the pylorus is entirely
obliterated, the new opening presents the only outlet from the
stomach. Under these circumstances an important mechanism
operating normally in the duodenum may become, to some
extent, impaired. The effect of acid chyme in causing a flow
of pancreatic juice and bile is now well known. Bayliss and
Starling 19 found that the action of acid in causing a flow of
pancreatic juice and bile is not confined to the duodenum, but-
is effective in approximately the upper 60 centimetres of the
dog's intestine. It is probable, therefore, that secretin is pro-
duced at least through the duodenum and jejunum of man. If
the anastomosis is made between the stomach and the uppermost
part of the small intestine, the mechanism for the flow of these
important digestive juices would be retained.
With the pylorus closed and the stoma as the only exit, one
might suppose at first that the admixture of the chyme with
pancreatic juice and bile would be largely abolished. But that
need not necessarily be the case. Probably a certain amount of
the pancreatic juice and bile is carried into the jejunum and
ileum, and there mixed with the food. Furthermore, in our
X-ray observations on experimental animals, the food was re-
peatedly seen passing from the stoma into the proximal loop.
No sooner did it thus pass towards the pylorus than a peristaltic
wave was started which swept the food at once into the stoma
again. As the circular fibres were not complete at the stoma,
the food was not pressed past the opening into the distal gut,
but was forced into the stomach. No sooner had the wave gone
by than the food was pressed again into the proximal loop.
Thereupon a new peristaltic wave once more pushed the food
toward the anastomotic opening ; back it was pressed again,
however, when the wave reached the cut fibres. This process,
82 THE MECHANICAL FACTORS OF DIGESTION
repeatedly observed, must at least mix some of the food very
thoroughly with the digestive secretions poured into the duo-
denum. Kelling 20 has recorded a surgical case in which he
observed through a fistula a similar passage of some of the food
backwards into the duodenum from the stoma. Only a rela-
tively small part of the food, however, can be treated in this
manner, and at best this to-and-fro shifting is a poor substitute
for the process which normally mixes the juices and the chyme
in the first part of the small intestine.
The observations on the effects of gastro-enterostomy above
described affect the conclusions drawn from studies of digestion
and absorption after this operation. These conclusions are
based on figures obtained in some instances with the pylorus
patent, in other instances with it occluded. Possibly the wide
variations in the amounts of the different foodstuffs, particu-
larly fats, which have been reported as not absorbed after
gastro-enterostomy, may be explained by the degree of devia-
tion of the chyme from its normal course because of the differing
patency of the pylorus.
From the considerations suggested by our experimental work,
Blake and I concluded that the stoma should be large and near
the pylorus, that circulation of the food could be rendered less
likely by avoiding conditions which stretch the stomach, and that
kinks might be obviated by attaching several centimetres of the
distal gut to the stomach. The probability of a circulation of the
food, however, if the pylorus is left open, the non-mixture
of much of the food with the digestive and neutralizing fluids
in the duodenum, and the ever-present danger from kinks,
despite care, make the operation not an ideal one. When pyloro-
plasty is possible, these objections can be avoided. And, as
Blake and I pointed out, in accordance with our observations,
the rapid exit of food from the stomach after cutting the pyloric
sphincter is prevented by rhythmic contractions of muscle
rings in the duodenum an activity which replaces in part the
functions of the pylorus, and also mixes the food with the pan-
creatic juice and bile.
1 Cannon, Am. J. Physid., 1898, i., p. 379.
2 Oehl, Arch. Ital. de Bid., 1899, xxxii., p. 114.
3 Hensay, Munchen. med. Wchnschr., 1901, xlviii., p. 1208.
4 Miiller, Sitzungsb. d. phys.-med. Gesdlsch. zu Wiirzlurg, 1901, p. 4.
5 Ellenberger and Hofmeister, Arch. /. wissensch. u. praTct. Thierh., 1884,
vii., p. 6 ; and 1886, xii., p. 126.
6 Hohmeier, Inaugural-Dissertation, Tubingen, 1901.
7 Oppel, Lehrb. d, vergl. mik. Anat. d. Wirbelthiere, i., Der Macicn, Jena,
1896, pp. 240, 337, 346, 397.
8 Cannon and Day, Am. J. Physiol., 1903, ix., p. 396.
9 Hammarsten, Jahresb. ii. d. Fortschr. d. Thierchem., 1871, i., p. 187.
10 Kelling, Arch. /. llin. Chir., 1900, Ixx., p. 259.
11 Cannon and Blake, Ann. Surg., 1905, xli., p. 686.
12 Tuffier, La Semaine Mid., 1907, ii., p. 511.
13 Delbet, Bull, et Mini. Soc. de Chir., Paris, 1907, xxxiii., p. 1250.
11 Leggett and Maury, Ann. Surg., 1907, xlvi., p. 549.
15 Berg, Ann. Surg., 1907, xlv., p. 721.
1 6 Moynihan, Brit. M. J., 1908, i., p. 1092.
1 7 Boldireff, Zentralbl. f. Physiol., 1904, xviii., p. 457.
18 Kaiser, Ztschr. /. Chir., 1901, Ixi., p. 337.
19 Bayliss and Starling, J. Physiol., 1902, xxviii., p. 325.
20 Kelling, Deutsche Ztschr. /. Chir.. 1901, Ix., p. 157.
THE PASSAGE OF DIFFERENT FOODSTUFFS FROM THE STOMACH
IN 1901, while studying the movements of the intestines, I
observed that not only did salmon begin to leave the stomach
later than bread and milk, but that it was slower in reaching
the large intestine ; and in the report of the research I called atten-
tion to this interesting difference. A careful study of this
phenomenon, and, in general, of the manner in which the different
foodstuffs are mechanically treated by the alimentary canal,
seemed a promising basis for understanding the agencies by
which the movements are controlled. Accordingly, experiments
were undertaken, directed towards the application of the X rays
to the purposes of such an investigation. Since the method
devised has proved serviceable in a variety of directions, I shall
describe it in some detail.
Among the first essentials for simplicity of method in a study
of the mechanical treatment of foods by the stomach and intes-
tines is the employment of foods as purely protein, fat, or carbo-
hydrate, as possible. Such foods were selected. Boiled beef free
from fat, boiled haddock, and the white meat of fowl, are examples
of the proteins that were fed ; beef suet, mutton and pork fat,
are representatives of the fats ; starch paste, boiled rice, and
boiled potatoes, of the carbohydrates. A uniform amount
25 c.c. was invariably given. The food was always finely
broken or pressed in a mortar, and, if carbohydrate or protein,
was moistened with enough water to produce, as nearly as could
be judged by the eye and by manipulation, the uniform con-
sistency of thick mush. Bismuth subnitrate, 5 grammes,
thoroughly mixed with each 25 c.c. amount, rendered it opaque
to the X rays.
In all cases full-grown cats, deprived of food for twenty-four
or thirty hours previous to the experiment, served as subjects
THE PASSAGE OF DIFFERENT FOODSTUFFS 85
for the observations. The animals were either permitted to eat
from a dish, or were placed on holders and fed from a spoon,
usually with little or no difficulty, and released as soon as fed.
A half-hour and an hour after the feeding, and thereafter at
hourly intervals for seven hours, the animals were fixed in the
holders, observed, and the conditions recorded. With proper
assistance, four or five animals can be examined at one sitting.
The records consisted of outlines of the shadows of gastric and
intestinal contents traced on transparent paper laid on the fluor-
escent screen. If in any case there was doubt that all the
shadows had been recorded, an electric light, flashed momen-
tarily on the tracing before its removal from the screen, per*
FIG. 6. TRACINGS or THE SHADOWS OF THE CONTENTS OF THE STOMACH
AND INTESTINES MADE Two HOURS AFTER FEEDING, IN ONE CASE BOILED
LEAN BEEF (A), AND IN THE OTHER BOILED RICE (B).
The small divisions in some of the loops represent rhythmic segmentation.
mitted the outlines drawn on the paper to be compared with the
shadows, and the outlines thus verified.
Since the diameter of the intestinal contents varies only
slightly (see Fig. 6), the area of cross-section of the contents
may be disregarded, and the aggregate length of the shadows
taken to indicate the amount of food present. Thus by com-
, paring the aggregate length of these shadows it is possible to
judge the relative amounts of a food in the intestine of an animal
at different times after feeding, as well as the relative amounts
of different foods in a series of animals, or in the same animal in
a series of experiments, at any given interval after the food was
ingested. For example, in one case, the original record of which
is reproduced in Fig. 6, the protein in the intestine two hours
after feeding was 20 centimetres (the aggregate length of the
86 THE MECHANICAL FACTORS OF DIGESTION
masses) ; and in another case the amount of carbohydrate, at
the same time after feeding, and similarly measured, was 43 cen-
timetres. By this method the observer, without interrupting
or interfering with the course of digestion, can know when food
first leaves the stomach, the rate at which different foods are
discharged into the intestine, the time required for passage
through the small intestine, and the mechanical treatment
which the food receives. Only during the brief periods of making
the records are the animals in any way disturbed ; between
observations they rest normally and quietly, wholly unrestrained.
That the results obtained by the use of the method are not due
to individual peculiarities was proved by observing the same
animal repeatedly with different foods, and finding the results
characteristic of the food, and not peculiar to the animal.
Animals once used were not used again within three days.
The method has obvious defects : (1) The loops of intestine
are not always parallel with the screen, and the loops not parallel
do not always make the same angles with the screen surface ;
the shadows cast by the contents of the loops must therefore be
variously foreshortened. In extenuation of this defect, it may
be said that the animals were stretched on their backs, and
that the ventral abdominal wall was flattened, both by the
stretching and by the pressure of the fluorescent screen laid
upon it ; the loops therefore must have been nearly parallel
with the screen, except at short dorso-ventral turns from one
loop to another. That the foreshortening of the shadows in the
loops and turns was not a serious source of error was repeatedly
proved by tracings made before and after a rearrangement of
the loops by abdominal massage ; the tracings showed that only
slight variations in the aggregate length of the shadows resulted.
(2) By overlapping of the loops two masses of food, or parts of
two masses, may cast a single shadow. Care was invariably
taken to obviate this error by pressing apart with the fingers
loops lying close together. (3) May not the bismuth subnitrate
and the food separate, and the shadows then be misleading ?
This separation doubtless occurs to some extent in the stomach.
To test the question with reference to the intestinal contents,
which are much more important for the reliability of the method,
animals were fed the three different kinds of food, and were
killed from two to six hours after the feeding. The intestinal
mucosa was remarkably free from any perceptible separate
THE PASSAGE OF DIFFERENT FOODSTUFFS 87
deposits of the heavy powder, and the well-limited masses of
material scattered at intervals along the gut were invariably
mixtures of bismuth subnitrate and the food. Naturally, as
part of the food becomes digested, and as fluids constantly inter-
change between the intestinal mucosa and the food-remnant in
its onward movement, the relation of the bismuth subnitrate to
the food must vary ; but examination proved that the remnant
does not become fluid to a degree which prevents it from being
a vehicle for the transmission of the bismuth salt, nor, on the
other hand, does the percentage of bismuth fall until it no longer
indicates the presence of alimentary material. The changes in the
relation of the bismuth salt to the food, from absorption of food
or secretion of fluids, are clearly much less in the early stages of
intestinal digestion, when little absorption and digestive altera-
tion have occurred, than they are later. The application of
the method to the determination of the rate of discharge through
the pylorus is therefore justified only in the first two or three
hours after digestion, before much absorption has taken place.
(4) The subjective differences between observers, the personal
equation in making records, is another possible source of error.
That Magnus 1 and men working with him, and Hedblom 2 work-
ing with me, have employed the method with no essential varia-
tions from my original results indicates that the personal equa-
tion need not be great. (5) The variations in the thickness of
the food-masses at different times, and the variations in the
individual rates of absorption of the different foods, are two
other possible faults of the method. These defects, however, must
be regarded, especially in the early stages of intestinal digestion,
as relatively slight, compared with the great and characteristic
differences in the amount of food present in the intestine when
carbohydrate, fat, and protein foods, are separately fed. 3
The time during which various foods remain in the stomach
has by some perverse chance come to be regarded as an indica-
tion of their digestibility. Tables of " digestibility," based on
this conception, have long been published. Such a table Beau-
mont 4 made from observations on Alexis St. Martin, and later
Leube, 5 and Penzoldt and his pupils, 6 studied by means of the
stomach-tube the duration of gastric digestion of various foods,
and tabulated their findings. For several reasons, these figures
are not satisfactory for judging the rate at which the stomach
is emptied. The observations were made either on a pathological
83 THE MECHANICAL FACTOKS OF DIGESTION
subject or on persons whose digestive processes had been inter-
rupted by the introduction of a stomach-tube. The results,
moreover, express merely the time when the stomach was found
empty ; they give no hint as to the moment when food first
passed the pylorus, or as to the amounts, large or small, which
entered the intestine at any stage during digestion. Also, if
comparisons are to be made, the amount of food given should
be known, for a large amount will evidently remain longer in
the stomach than a small amount. Beaumont's records indicate
frequent inattention to this factor, and Leube's observations
have the same defect. Although Penzoldt and his fellow-workers
recorded the amounts, they did not give systematically the
same amounts, and the stomach therefore was not always
dealing with the same volumetric problem. Furthermore, these
investigators did not regard the consistency of the food a factor
of importance, as we shall later learn ; nor did they attempt to
simplify conditions by the use of fairly pure foodstuffs, for their
purpose was to discover how ordinary articles of diet were
treated in the stomach.
Since my purpose was to observe how different foodstuffs,
other conditions remaining as nearly as possible the same, are
treated mechanically by the stomach and intestine, I selected
foods predominantly fat, carbohydrate or protein, and fed them
in uniform amount and consistency. Differences of treatment
then might reasonably be associated with differences in the
foodstuffs. We shall first consider the results when fats are fed.
The Discharge of Fats. In selecting f^t food, particular atten-
tion had to be paid to the effect of temperature on consistency ;
a fat, mushy at room temperature, might be much too fluid at
body temperature. Care was taken, therefore, to choose fats
or fatty tissues which, when mixed with bismuth subnitrate,
presented at body temperature about the same degree of viscosity
as the carbohydrate and protein preparations.
The rate at which fats leave the stomach may be judged from
the curve of the fat-content of the small intestine (Fig. 7, dash
line), plotted from the average figures of sixteen cases of fat-feed-
ing.* The curve shows that the emergence of the fat from the
stomach begins rather slowly in eight of the sixteen cases, indeed,
nothing left during the first half-hour of digestion and continues
* The figures which this and other curves express can be found in the original
reports of the investigations.
THE PASSAGE OF DIFFERENT FOODSTUFFS
at such a slow rate that there is never any great accumulation
of fat in the small intestine. Fats almost invariably are present
in the stomach during the seven hours of observation ; in one
case an animal was killed six hours after receiving 25 c.c. of
mutton fat, and about 11 c.c. had not yet departed. The long,
low curve is characteristic. It indicates a slow discharge from
the stomach, approximately as slow as the departure of the fat
from the small intestine by absorption and by passage into the
How do the results of the X-ray method accord with other
evidence as to rate of emergence of fat from the stomach ? In
1876, Zawilski, 7 while studying the duration of the fat-stream
These and all other similar curves presented later show the average aggregate
length of the food-masses in the small intestine at the designated intervals
after feeding. These are the curves for various fat foods (dash line),
protein foods (heavy line), and carbohydrate foods (light line) sixteen
through the thoracic duct, was impressed by the length of time
necessary to complete the absorption of fat. Three animals,
fed 150 grammes of fat mixed with other food, were killed after
different intervals ; after five hours of digestion, 100 of the 150
grammes were still in the stomach, and even after twenty-one
hours 10 grammes were still there. In the small intestine the
variation in amount was only slight ; about 10 grammes were
found at five hours, and about 6 grammes at twenty-one hours.
While investigating the absorption of fatty acids, Frank 8 con-
firmed the observations of Zawilski : the fat stayed long in the
stomach, and a fairly uniform amount was present at various
times in the small intestine. And, again, in observations inci-
dental to another investigation, Matthes and Marquadsen 9 con-
90 THE MECHANICAL FACTORS OF DIGESTION
firmed the statements of Zawilski and Frank. The testimony
of different observers was thus far harmonious. Thereupon
Strauss denied that fat remains long in the human stomach. 10
His methods, however, were hardly comparable with those of
the previous investigators ; only one-fourth of the food was fat,
it was given with much liquid, the observations were few, and on
only one patient.
The results obtained by the X-ray method, therefore, agree
with, and amplify, the evidence offered by Zawilski, Frank, and
Matthes and Marquadsen. The long delay of fat in its passage
through the alimentary canal occurs in the stomach. Fat
passes from the stomach about as rapidly as the small intestine
disposes of it ; as a rule, therefore, the amount of fat in the small
intestine is fairly constant in quantity and relatively slight in
The Discharge of Carbohydrates. The rate at which carbo-
hydrates leave the stomach can be judged from the curve (Fig. 7,
light line), particularly during the first two hours of digestion.
In my first observations on the movements of the stomach,
bread was seen in the duodenum about ten minutes after feeding.
The curve representing the content of the small intestine after
feeding carbohydrates shows that this early emergence of the
starchy food from the stomach is followed by an abundant dis-
charge. In a half -hour the amount of carbohydrate present
has almost equalled the maximum for fat, and at the end of an
hour that amount has more than doubled. The abrupt high
rise of the curve to a maximum at the end of two hours indicates
the great rapidity of discharge. And as the stomach was
usually almost empty about three hours after feeding the standard
amount of carbohydrates, the slow fall in the curve during the
last four hours of observation records in the main the gradual
departure of the food from the small intestine through the
absorbing wall and into the colon.
The testimony of Penzoldt and his pupils, 11 that the delay in
discharge of carbohydrates from the human stomach is usually
not great, is in harmony with the more detailed observations on
experimental animals. That potato leaves the human stomach
rapidly, and that the gastric juice cannot attack it to any
extent, Marbaix reported 12 in 1898, and he suggested that an im-
portant question lies here. The answer to that question we must
soon consider. For the present we need only note that all the
THE PASSAGE OF DIFFERENT FOODSTUFFS 91
evidence for a rapid passage of carbohydrate food through the
pylorus is concordant. As a consequence of this rapid exit the
small intestine receives a large bulk in a relatively short time.
The Discharge of Proteins. The heavy line in Fig. 7 is a curve
plotted from the average figures for the content of the small
intestine after feeding four representative proteins in sixteen
cases. The striking feature of the protein curve during the first
two hours is its very slow rise. In nine of the sixteen cases no
food had left the stomach at the end of the first half-hour, and in
eight cases the small intestine had not received at the end of
an hour more than 4 centimetres of food.
The main portion of a diet is more likely to be composed of
carbohydrates or proteins, or of the two combined, than of fats
alone. To digest a diet consisting chiefly or even largely of fat
is an unusual task for the digestive apparatus. The mechanical
treatment of carbohydrates and proteins is therefore of more
importance practically than the treatment of the fats ; and the
fact that the stomach is more habituated to the presence of
carbohydrates and proteins in large amounts makes a con-
sideration of the differences of treatment of these foodstuffs
more significant than a comparison involving the fats.
The curves representing the carbohydrate and protein dis-
charge from the stomach are strikingly different. At the end of
a half-hour the average figures indicate that eight times as much
carbohydrate as protein has left the stomach ; at the end of an
hour more than five times as much, and even at the end of two
hours, when much carbohydrate food has probably been absorbed,
considerably more than twice as much carbohydrate as protein
is present in the small intestine.
The remarkable difference between the carbohydrate and the
protein rapidity of departure from the stomach assumes special
significance when the action of gastric juice on these two food-
stuffs is considered. That the carbohydrates, which are not
digested by the gastric juice, should begin to leave the stomach
soon after being swallowed, and should pass out rapidly into a
region where they are digested, whereas the proteins, which are
digested by the gastric juice, should be retained in the stomach
sometimes for a half-hour or more, without being discharged
in any considerable amount, indicates the presence of an
important digestive mechanism.
THE MECHANICAL FACTOKS OF DIGESTION
With the purpose of securing further evidence of the action of
this probable mechanism, various combinations of foodstuffs
were fed, and the rate of passage from the stomach studied by
the method already described.
The Discharge when Carbohydrate or Protein is Fed First. As
we have learned, when different kinds of foods are fed one after
another, the first food swallowed fills the pyloric vestibule and lies
along the greater curvature of the stomach, and the later food is
pressed into the midst of that part of the earlier food which
occupies the cardiac end. Thus, if carbohydrates are fed first
cm and proteins second, the carbo-
hydrates will be in contact with the
pylorus and will predominate in
the pyloric end of the stomach,
while the proteins will be found
in larger amounts towards the
Does the presence of proteins in
the cardiac end of the stomach
retard the exit of carbohydrates
lying near the pylorus ? Or if the
proteins are near the pylorus, does
the presence of the carbohydrates
in the cardiac end cause an early
exit ? To answer these questions,
12-5 c.c. of crackers and water, and
12-5 c.c. of boiled lean beef, each
mixed with 2-5 grammes of sub-
nitrate of bismuth, were fed in one
ITS i 1 2 3
The heavy line is the curve after
feeding moistened crackers
first, lean beef second (four
cases) ; the heavy dot line,
after feeding lean beef first,
crackers second (four cases).
The light line is the curve for
crackers alone, the light
dot line for lean beef alone
(four cases each).
series, crackers, then beef ; in another series, beef, then crackers.
The results are represented in Fig. 8. The rate of discharge
when carbohydrates were fed first should be compared with the
rate when proteins were fed first. When the crackers were near
the pylorus, the discharge for two hours was almost as rapid as
when crackers alone were given. At the end of two hours,
however, the curve ceased to follow the normal for crackers;
there was a checking of the outgo from the stomach, which is
reasonably explained by assuming that the beef by that time had
come to the pylorus in considerable amount, and was as usual
passing out slowly. On the other hand, when the beef was first
at the pylorus, the curve was in close approximation to the
THE PASSAGE OF DIFFERENT FOODSTUFFS
normal for beef during the first four hours, and after that time,
as the crackers came to the pylorus in greater amount, the curve
continued to rise, while the curve for beef alone fell. In
this combination, never during the first three hours was
there half as much food in the small intestine as when crackers
alone were fed. The presence of protein near the pylorus dis-
tinctly retarded the onward passage of carbohydrate food lying
in the cardiac end.
It is noteworthy that when beef was fed first the stomach still
contained considerable food even six hours after feeding three
hours longer than the period for carbohydrates alone. On the
other hand, when crackers were fed first,
most of the food had left the stomach
at the end of four hours only about an
hour longer than the carbohydrate
period. Since gastric peristalsis persists
while food is present in the stomach,
this experiment seems to indicate that
serving the cereal before the meat at
breakfast, and the old custom of eating
the pudding before the beef, are rational
and physiologically economic arrange-
ments. If the carbohydrate, however,
follows the protein, careful chewing, as
we have learned, will permit salivary
digestion to continue in the cardiac mass
during the period of delay.
The Discharge when Mixtures are Fed.
Inasmuch as what we eat is generally
a mixture of the various foodstuffs, it was of interest to
discover what effect combinations of the foods, from which
characteristic curves had been secured, might have upon those
curves. For this purpose, carbohydrates, fats, and proteins,
were mixed in pairs, in equal amounts, to make 25 c.c. of food,
and this mixture, with 5 grammes bismuth subnitrate, was fed,
and the results recorded.
To test the effect of mixing carbohydrate and protein on
the rate of gastric discharge, equal parts of lean beef and
crackers were given. In Fig. 9 a comparison is presented
between the treatment of the mixed foods and the same foods
fed separately. Only the changes during the first three hours
o \ i 2 3
The dash line is the curve
for equal parts of moist-
ened crackers and boiled
lean beef, the heavy
line for crackers alone,
and the light line for
beef alone (four cases
THE MECHANICAL FACTORS OF DIGESTION
" >, 1 2 3 4
The heavy line is the curve for
lean beef alone, the light line
for beef suet, the dash line for
a mixture of beef and suet in
equal parts (four cases each).
are taken for consideration, since they are most significant in
judging the rapidity with which the stomach empties. The
amount of the mixed food in the small intestine at the end of a
half-hour was nearer the carbo-
hydrate than the protein figure,
but in general, as the curves show,
a mixture of carbohydrate and
protein foods in equal parts resulted
in a rate of discharge which was
intermediate : the mixed food did
not leave the stomach so slowly as
the proteins, nor so rapidly as the
carbohydrates. This conclusion
was verified by obtaining similar
results when boiled haddock and
mashed potato were mixed and fed.
Boiled lean beef and beef suet mixed in equal amounts served
for observations on the effect of combining fat and protein.
Comparison of the curve for the mixture with the curves for the
two constituents fed separately (Fig. 10) reveals at once that the
combination is discharged more
slowly than either the lean beef or
the suet fed alone. In other words,
the presence of fat causes protein
to leave the stomach even more
slowly than the protein by itself
would leave. Feeding haddock and
mutton fat in equal parts corrobo-
rated the other observations ; after
two hours the small intestine had
only two-thirds as much of the
mixed food as of the haddock when
fed alone. The long delay in
the initial passage of salmon
from the stomach (which con-
trasted so strikingly with the rapid
discharge of bread, and suggested
the investigation) was probably due to the presence in salmon
of more than half as much fat as protein.
Mashed potato and mutton fat, and moistened crackers and
beef suet, mixed equally in each combination, were used in study-
The light line is the curve for
mashed potato, the heavy line
for mutton fat, and the dash
line for mixed potato and
mutton fat (four cases each).
THE PASSAGE OF DIFFERENT FOODSTUFFS 95
ing the effect of uniting fats and carbohydrates. In each series
of observations the passage of the mixed food from the stomach
was more rapid at first than the normal for the carbohydrate used
(see Fig. 11). Very soon, however, the fats had a retarding effect
on the outgo of the carbohydrate, so that the curve for the mixed
foods after the first hour ceased to rise, and never even approxi-
mated the height of the carbohydrate curve. We may reason- -^
ably conclude, therefore, that the addition of fat in large amount
(50 per cent.) to carbohydrate has the same effect, though not to
so great a degree, as the addition of fat to protein : the fat retards
the exit of either foodstuff from the stomach into the intestine.
The striking differences in the rapidity of discharge of different
foods from the stomach, the importance of which I need not
emphasize, can all be explained quite simply when we under-
stand the remarkable mechanism of the pyloric sphincter.
1 Magnus, Arch. f. d. qes. Physid., 1908, cxxii., pp. 210, 251, 261 ; Padtberg,
ibid., 1909, cxxix., p. 476.
2 Hedblom and Cannon, Am. J. Med. Sc., 1909, cxxxviii., p. 505.
3 Cannon, Am. J. Physid., 1904, xii., p. 387.
4 Beaumont, The Physidogy of Digestion, Plattsburgh, 1833, p. 269.
5 Leube, Ztschr. f. Uin. Med., 1883, vi., p. 189.
6 Penzoldt, Deutsches Arch. /. Uin. Med., 1893, li., p. 545.
7 Zawilski, Arb. a. d. physid. Anst. zu Leipzig, 1876, p. 156.
8 Frank, Arch. /. Physid., 1892, p. 501.
9 Matthes and Marquadsen, Verhandl. d. Cong. f. innere Med., 1898, xvi.,
10 Strauss, Ztschr. f. didt. u. physikal. Therap., 1899, iii., p. 279.
11 Penzoldt, Deutsches Arch. f. Uin. Med., 1893, li., pp. 549, 559.
12 Marbaix, La Cellule, 1898, xiv., p. 299.
THE ACID CONTROL OF THE PYLORUS
CLINICAL studies with the stomach-tube, 1 investigations through
duodenal fistulas, 2 and, as we have already seen, X-ray observa-
tions on the undisturbed subject, combine to prove that the
stomach is emptied progressively during the course of gastric
digestion, and not suddenly at the end, as some investigators
have stated. 3 The X-ray studies and the examinations through
duodenal openings have further demonstrated that the chyme
does not pass through the pylorus at the approach of every
peristaltic wave, but emerges occasionally, at irregular intervals.
The irregular opening of the pyloric passage after periods lasting
from ten to eighty seconds I noted in my first report of gastric
movements, 4 and these results were in close agreement with the
observations of Hirsch and others on dogs with duodenal fistulas,
that chyme comes from the stomach at intervals varying between
one-fourth of a minute and several minutes. 5
Both mechanical and chemical agencies have been invoked to
explain the emptying of the stomach. These agencies have been
supposed by some investigators to act in the stomach, by others
to act in the intestine.
That mechanical agencies acting in the stomach control the
exit of food has been claimed by those who believe that chyme is
discharged only after several hours of gastric digestion. They
declare that the pyloric sphincter, although able to withstand
the repeated peristaltic pressure in the earlier stages of chymifica-
tion, is overcome by the more intense constrictions in the later
stages. 6 We know, however, that a delay of several hours in
the discharge from the stomach is abnormal. The moving con-
striction rings do indeed press deeper into the gastric contents
as digestion proceeds, but this late augmentation of contraction
does not explain the normal gradual exit during earlier stages of
THE ACID CONTKOL OF THE PYLORUS 97
chymification, when wave after wave passes, with fairly uniform
depth, and yet every now and then some chyme departs. The
occasional discharge of chyme from the stomach cannot there-
fore be attributed to an occasional increase of intensity of the
The effect of mechanical conditions in the intestine on gastric
evacuation was first pointed out in 1897 by v. Mering, 7 who
found that the introduction of a large amount of milk into a
duodenal fistula checked the exit of water from the stomach.
The next year Marbaix 8 published a paper on evacuation of the
stomach as affected by a state of repletion of various parts of
the intestine. A state of repletion in the upper half of the small
intestine induced by injections through fistulas inhibited the
discharge from the stomach.* In order to cause the reflex,
however, even in the first fourth of the intestine, the injected
liquid had to occupy a considerable extent of gut. For example,
filling the gut from 10 to 25 centimetres beyond the pylorus
caused no inhibition of the discharge. But much less than
15 centimetres of continuous content is normally present in
the upper intestinal tract. The tracings of X-ray shadows
(see Fig. 6, p. 85) show that the intestinal contents are normally
disposed in separate short masses. Under natural conditions,
therefore, the extensive uninterrupted surface of contact re-
quired by v. Mering's and Marbaix's explanation, in order to
prevent a continuous outpouring from the stomach, does not
exist. As the continuous outpouring, nevertheless, does not
occur, their results do not explain the normal 'control of gastric
discharge. Von Mering's and Marbaix's contribution has been
supported, however, by Tobler's observation 9 that the rapid
inflation of a balloon in the duodenum checks the passage of
food from the stomach. This experiment, like v. Mering's and
Marbaix's, does not explain normal conditions, because, as I
have shown, 10 chyme normally gathers in the duodenum
gradually, by repeated small additions, and even when accu-
mulated lies as a slender strand which does not distend the gut.
Each strand thus formed is soon hurried forward some distance
along the tube, thus clearing the duodenum for new accumulations.
* An investigation of the motor functions of the stomach after pyloroplasty
(see Cannon and Blake, Ann. Surg., 1905, xli., p. 707) has proved that, although
the upper part of the small intestine may become filled with food, there is
no cessation of peristalsis. The effect noted by v. Mering and Marbaix is
therefore probably due to closure of the pylorus.
98 THE MECHANICAL FACTORS OF DIGESTION
Though the passage of food from the stomach may be checked
by artificially filling a long piece of the upper intestine or by
sudden distension of the gut at one point, such conditions cannot
account for any natural control of gastric discharge from the
intestinal side, because such conditions are not normally found.
The evidence, therefore, is opposed to the conception that
mechanical agencies, acting either in the stomach or in the
intestine, play an important part in controlling the normal
We turn now to a consideration of chemical agencies that have
been invoked to explain the emptying of the stomach. As long
ago as 1885 Ewald and Boas found, 11 by use of the stomach-
tube on man, that there was a considerable development of
free hydrochloric acid before the gastric contents began to be
notably diminished in amount. Where the acid may have had
its effect whether on peristalsis or on the pyloric sphincter
was not determined. Later, Penzoldt, 12 in studying the periods
during which various common foods remain in the stomach,
noted that foods delaying the appearance of free hydrochloric
acid remain longest. Verhaegen, 13 on the other hand, declared
that it matters little for the passage through the pylorus whether
the food is acid or neutral. Although Penzoldt 's careful work
was of clinical value, it is inadequate to explain the factors
in control of gastric evacuation. The varying composition
of the foods he used, the varying amounts and consistencies,
and the failure of his method to indicate the rapidity of
gastric discharge as digestion proceeds, render difficult the
drawing of exact conclusions from Penzoldt's results. In
the presence of strong opposing evidence, Verhaegen's con-
tention that neither acidity nor neutrality of the chyme has
any effect on the emptying of the stomach may reasonably
be doubted. Furthermore, his observations were made with
the stomach- tube, on only four individuals, two of whom
The first evidence of the action of chemical agencies in the
duodenum on the emptying of the stomach was brought forward
by Hirsch. In 1893 he reported 14 that solutions of inorganic-
acids left the stomach slowly, and he inferred that the slow exit
was due to the stimulating effect of the acid on the mucosa of
the duodenum. Later, Serdjukow, one of Pawlow's students,
inhibited gastric evacuation by introducing acid into the duo-
THE ACID CONTROL OF THE PYLORUS 99
denum through a fistula, 15 thus confirming the conclusion of
Hirsch. Tobler's results 16 also substantiate it.
The main defect of the above methods as means for deter-
mining the nature of the chemical control of gastric discharge is
their failure to distinguish between the two factors concerned
in emptying the stomach : one, the pressure to which the food
at the pylorus is subjected by recurring peristaltic waves ; the
other, the action of the pyloric sphincter. Not until the X-ray
method was used was it possible to watch, under normal con-
ditions, both gastric peristalsis and the exit of food through the
pylorus. Until the application of the X-ray method, therefore,
a clear distinction between the normal effects of these two factors
could not be made.
Evidently the normal exit of food might be occasional because
of occasional peristaltic constrictions, or occasional specially
strong peristaltic constrictions, pressing the gastric contents
against an easily opened pylorus ; or, on the other hand, the
occasional passage might be due to an occasional relaxation of
the pylorus in the presence of fairly uniform conditions of
Some of the investigators whose work has already been men-
tioned have, indeed, ascribed the control of gastric discharge
solely to the action of the pyloric sphincter. Marbaix, for
example, writes of the influence of the repletion of the intestine
on the closure of the pylorus. 17 His evidence for this limitation
is not clear. Von Mering, on the other hand, recognized that
intestinal repletion might check gastric discharge by stopping
peristalsis, and he resected the pylorus in order to differentiate,
if possible, between the peristaltic and the pyloric factors.*
The failure to make this differentiation is the essential flaw, for
the present analysis, in the methods of Ewald and Boas, Pen-
zoldt, Hirsch, Serdjukow, and Tobler. Their results, therefore,
while significant, cannot serve for a conclusive determination of
the control of gastric evacuation.
The evidence that under normal conditions peristaltic waves
are continuously running over the stomach, so long as food
* The possible confusion of the two factors is illustrated in Pawlow's report
of Serdjukow's experiments. He states (The Work of the Digestive Glands,
London, 1902, p. 165) that acid chyme entering the duodenum reflexly occludes
the pyloric orifice, " and at the same time reflexly inhibits the propulsive
movements of the organ (stomach)." Clearly the occlusion of the pyloric orifice
alone would account for Serdjukow's results. What is the evidence that
peristalsis also was affected ?
100 THE MECHANICAL FACTOKS OF DIGESTION
remains, has been presented in a previous chapter. In my
experience, neither ejaculation of acid chyme nor stretching of
the duodenum with food pressed through the cut pylorus (see
footnote, p. 97) has any tendency to interrupt the sequence of
waves. As remarked in the discussion of mechanical agencies
acting in the stomach, the waves do not show from moment to
moment marked variation of intensity. One of the two factors
concerned in gastric discharge the pressure in the vestibule
is therefore recurrently constant. The control of the discharge,
consequently, must reside with the other factor i.e., with the
action of the pyloric sphincter. If the sphincter holds tight, the
recurring waves churn the food in the vestibule ; if the sphincter
relaxes, these waves press the food out into the duodenum. The
pylorus is the " keeper of the gate."
The discharge from the stomach, as we now know, is occasional.
The foregoing analysis proves that this occasional discharge must
be due to occasional relaxations of the pyloric sphincter. To
explain the action of the pylorus, therefore, it is necessary to
consider agencies which maintain an intermittent closure
which usually keep the passage shut, yet open it at intervals to
allow portions of the chyme to depart. None of the researches
on the control of gastric evacuation, discussed in the preceding
pages, were definitely concerned with this intermittent closure.
Further investigation was desirable to explain the repeated
opening and shutting of the pyloric orifice.
Further investigation was necessary also to explain the striking
differences in the rate of discharge of different foodstuffs.
The facts presented in the foregoing chapter immediately raised
the question, What is the pyloric mechanism whereby carbo-
hydrates, not digested by the gastric juice, are permitted to pass
quickly into the small intestine to be digested, whereas proteins,
digested in the stomach, are there retained to undergo digestion ?
As we have learned, investigators have hitherto regarded
factors in the stomach, or factors in the intestine, as controlling
gastric evacuation. An interaction of agencies in the two
situations has not been considered. A theory based on evidence
of opposed effects from a single stimulus acting first in the
stomach and later in the duodenum I propounded 18 in 1904, to
explain the differential discharge of the different foodstuffs.
The first statement in the theory is that acid coming to the
pylorus causes a relaxation of the sphincter. Thus would be
THE ACID CONTROL OF THE PYLORUS 101
explained why the initial discharge is longer delayed when
proteins are fed than when carbohydrates are fed. Both carbo-
hydrate and protein stimulate gastric secretion in abundance,
as researches on dogs by Pawlow and his co-workers, 19 and as
clinical studies on men, have shown. Inasmuch as carbo-
hydrates do not unite chemically with the acid, free acid is at
once present in the stomach ; carbohydrates would therefore
begin almost immediately to pass through the pylorus. Pro-
teins, on the other hand, join with the acid, and thus retard for
some time the development of an acid reaction ; 20 the protein
discharge would therefore be retarded.
But acid on the stomach side of the pylorus is not the
only determinant of pyloric action. The observations of Hirsch
and Serdjukow now have their bearing. Since it has been shown
that acid in the duodenum does not stop gastric peristalsis, the
acid reflex from the duodenum must affect the pyloric sphincter.
The second statement in the theory naturally follows acid in
the duodenum closes the pylorus.
It is probable that the pyloric sphincter has normally a greater
or less degree of tonic contraction, with occasional relaxations. 21
Certainly it has a tonic contraction persistently strong for some
time after food enters the stomach. When protein, for example,
is fed, peristaltic constrictions may press the food against the
pylorus repeatedly for a half-hour or more (approximately, 150
waves) without forcing food through the orifice.
The whole theory of the acid control of the pylorus may now
be stated. The pylorus is tonically closed when food is ingested,
and remains closed against recurring pressure. The appearance of
acid at the pylorus causes the sphincter to relax. The pressing
peristaltic waves now force some of the acid chyme into the
duodenum. The acid in the duodenum at once tightens the
sphincter against further exit. The same acid also stimulates
the flow of alkaline pancreatic juice. 22 Since no inorganic acid
is normally present beyond the first centimetres of the small
intestine, 23 and since the acid reaction of the contents in this
uppermost region is replaced throughout the rest of the small
intestine by practically a neutral reaction, 24 the acid chyme
must be neutralized soon after its emergence from the stomach.
As neutralization proceeds, the stimulus closing the pylorus is
weakened ; now the acid in the stomach is able again to relax
the sphincter. Again the acid food goes forth, and immediately
102 THE MECHANICAL FACTORS OF DIGESTION
closes the passage behind until the duodenal processes have
undergone their slower change. And thus, repeatedly, until
the stomach is empty.* What is the evidence for this theory ?
As the acid of the gastric juice, according to the theory, may
have two opposing effects on the pylorus, we shall review first
the evidence that acid in the vestibule causes the pylorus to
open, and afterwards the evidence that acid in the duodenum
causes the pylorus to be kept closed.
The evidence that acid in the vestibule opens the pylorus we
shall consider under several headings, as follows :
1. Delaying the appearance of hydrochloric acid delays the
initial discharge. In terms of the above theory the quick exit
of carbohydrates is due to the early appearance of acid in the
stomach. The appearance of acid can be delayed if the carbo-
hydrates are first moistened with sodium bicarbonate. Then the
acid would first be neutralized by the alkaline food near the
secreting surface and in the churning vestibule ; and only after
some time would an acid reaction appear in considerable amount.
If the theory is correct, this postponement of the appearance of
acid should delay beyond the normal time the initial discharge
of the food.
Crackers, rice, and mashed potatoes were chosen as repre-
sentative carbohydrate foods. The rice was steamed and dried,
and the mashed potato was also dried before being used. In all
cases 1 per cent, sodium bicarbonate was added to the dried
food until a mush was made, of the same consistency as in the
standard cases. The carbohydrates thus prepared were mixed
with subnitrate of bismuth, and fed, as in the standard cases, in
25 c.c. amounts. The average figures for twelve cases in which
the three carbohydrates wet with water were fed, and the twelve
cases in which they were fed wet with sodium bicarbonate, are
represented graphically in Fig. 12.
The curves show that at the end of a half-hour there had
emerged only about one-tenth as much of the food wet with the
alkaline solution as of the same food wet with water (in six of
the twelve cases no alkaline food had left the stomach) ; at the
end of an hour, from a third to a half as much ; and in two hours,
from about a half to five-sixths as much. In other words,
* Cohnheim, in his summary of the factors controlling the discharge of food
from the stomach (Nagel's Handb. d. Physiol. d. Mensch., Braunschweig, 1907,
ii., p. 564), mentioned the theory here propounded, but stated that my evidence
for it was not convincing. It is fair to note that at that time the evidence in
a complete and detailed form had not been presented.
THE ACID CONTROL OF THE PYLORUS
there has been a marked retardation in the discharge of carbo-
hydrates wet with the alkaline solution. This result is in har-
mony with the observation by Jaworski on man, that alkalinity
of the contents delays the emptying of the stomach. 25
Sodium bicarbonate delays the appearance of acid in two ways :
it checks the secretion of the gastric juice, 26 and for a time it
unites with the acid of the gastric juice as rapidly as it is poured
out. The evidence here presented shows that experimental
conditions delaying the appearance of hydrochloric acid delay
the discharge from the stomach.
2. Hastening the appearance of an acid reaction hastens the
initial discharge. According to the theory, as already stated,
the slow passage of proteins from the
stomach is due to their union with the
acid of the gastric juice, which prevents
the rapid development of a marked acid
Evidence as to this supposition may
be secured by feeding protein food that
has previously been changed to acid
protein. Fibrin, lean beef, and fowl,
freed from fat, were chosen as repre-
sentative protein foods. They were
mixed with 10 per cent, hydrochloric
acid, and allowed to stand until changed
to acid protein. The free acid was dia-
lyzed away until test showed none present.
As the change to acid protein was accom-
panied by swelling of the original sub-
stance, the standard protein content
was to some extent preserved by feeding the acid protein in
twice the usual amount. Doubling the amount of the natural
protein notably retards the outgo from the stomach. 27 If
changing the natural to acid protein has no effect on the outgo
from the stomach, doubling the amount should likewise retard
the outgo certainly should not accelerate it.
Fibrin, fowl, and lean beef were fed as acid proteins in 50 c.c.
amounts, and with the same consistency as in the standard
cases. In Fig. 13 are presented the curves for the average
figures of the twelve cases in which these same foods were given
as acid proteins.
Hours ' 1
The continuous line i
the curve after feeding
potato, rice, an<
each) moistened with
water, and the dot-line
the same, moistened
with 1 per cent.
NaHC0 3 .
THE MECHANICAL FACTORS OF DIGESTION
The curves show that at the end of a half-hour the stomach
had discharged from five to ten times as much acid protein as
natural protein ; three to ten times as much at the end of an
hour ; and in two hours about twice as much acid protein as
natural protein. Evidently the change to acid protein and the
feeding in increased amount resulted not in slowing, but in
remarkably accelerating the exit from the stomach. According
to Moritz, Tobler, and Lang, protein discharged through the
pylorus may be merely acid protein, unaccompanied by free
hydrochloric acid. 28 In that case the protein given in these
cases is ready to leave the stomach. If any acid is secreted upon
it, free acid is at once present, and appears, therefore, earlier
CTn than when natural protein is fed. The
evidence here given indicates that, when
experimental conditions hasten the appear-
ance of an acid reaction, the discharge
from the stomach is correspondingly
3. The appearance of acid near the
pylorus closely precedes the initial dis-
charge. Although in the experimental
conditions already described the emer-
IG ' 1 ' gence of food from the stomach occurred
The continuous line is . . , j-i i
the curve after feeding as if acid were present to open the pylorus,
its presence has only been inferred ; there
has been no demonstration that acid was
present when the iirst food passed into the
duodenum. The relation between the
first development of acid and the first exit of the food should
be more exactly determined. This can be done by establishing
in the vestibule, close to the pylorus, a fistula.
A fistula holding a simple flanged cannula with a removable
plug was established in the vestibule in several cats. The cats
recovered readily from the operation, and were usually in very
good health. In order that the food could be seen with the
X rays when it first entered the duodenum, it was always mixed
with bismuth subnitrate. When potato was fed, 20 drops of
dimethylamidoazobenzol were added an amount staining the
potato orange, and showing a clearly marked change to pink
when hydrochloric acid developed. As soon as the potato was
given (usually by stomach-tube), the plug was removed from
fibrin, fowl, and lean
beef (four cases each)
as natural protein, and
the dot-line the same,
as acid protein.
THE ACID CONTKOL OF THE PYLOEUS 105
the cylinder of the cannula, and replaced by a tight-fitting glass
syringe. By pulling up the piston the thin mushy contents of
the vestibule were drawn slightly into the glass tube. Then any
change of colour could be noted. If the original orange colour
still persisted, the piston was pushed down again, and thus the
food was restored normally to the stomach. Usually such
observations were made every four minutes ; during the intervals
X-ray observations showed whether food had yet been passed
into the duodenum. When lean beef was fed, the colour-change
could not be clearly seen, and it was necessary to remove through
the cannula a sample of the vestibular contents in a small
pipette. The contents were tested for acid with Congo-red,
dimethylamidoazobenzol, and tropaolin oo.
Observations through the fistula proved that a delay in the^
appearance of acid in the contents of the vestibule is associated
with a similar delay in the passage of food from the stomach ;
that this may occur in spite of vigorous gastric peristalsis ; that
under these circumstances the introduction of a small amount
of acid near the pylorus causes immediately the exit of food
through the pylorus ; and that, whether potato or beef is fed, and
whether in the same animal the discharge begins at the usual
time or is much retarded, the first delivery of food into the
duodenum is normally preceded by the development of an acid
reaction in the vestibule.
These observations on the vestibular contents are well sup-
ported by studies of the reaction of the discharged chyme.
Tobler, London and Sulima, and London and Polowzowa, have
tested the chyme collected from a duodenal fistula close to the
pylorus. Tobler fed lean beef to his dogs. The repeatedly dis-
charged gastric contents were acid from the beginning, and con-
tinued during digestion to be "stark sauer." 29 London and
Sulima 30 recorded that when cooked egg-albumin was fed, the
discharge from the pylorus was initiated by the pouring forth of
an acid fluid. The same condition was recorded by London and
Polowzowa 31 after feeding white bread.
4. Hydrochloric acid opens the pylorus of the excised stomach.
Magnus has shown 32 that pieces of the small intestine, removed
from the body and placed in warm, oxygenated Kinger's
solution, will remain alive and, so long as the myenteric plexus
is intact, will manifest the typical activities. I have given
evidence that the mechanism in control of the differential dis-
106 THE MECHANICAL FACTORS OF DIGESTION
charge through the pylorus is independent of the central nervous
system. 33 To test whether the mechanism resides in the local
nerve plexus, the following experiment was performed :
A cat which had fasted for twenty-four hours was quickly
killed by etherization. The empty stomach was removed and
placed in oxygenated Ringer's solution (38 C). A glass tube,
with a short rubber tube and a water manometer attached, was
tied into the cardiac orifice. A small amount of O4 per cent.
HC1, made blue by the changed Congo red, was introduced through
the tube into the fundus, which was held lower than the vestibule.
The stomach was now inflated until air bubbled through the
pylorus. The rubber tube was next tightly clamped. When
the air had ceased escaping i.e., when pyloric tonus withstood
intragastric pressure the stomach was gently and slowly turned
until the acid came to the pylorus. In a moment the blue fluid
poured forth into the Ringer's solution. The pylorus had opened.
It might be supposed that the acid coming into the vestibule
caused an increased tonus of the gastric musculature, and that
thus the pyloric orifice was forced open. The manometer, how-
ever, did not show any increase of intragastric pressure. Further-
more, the stomach can be tipped so that the acid fluid enters
the vestibule, but does not come to the pylorus. This did not
lead to the driving out of more air ; the acid did not notably
stimulate contraction of the gastric wall. The opening of the
pylorus, therefore, was due to the presence of the acid.
A 1 per cent, sodium bicarbonate solution, coloured red,
similarly brought to the pylorus, did not begin to emerge for a
considerably longer time, and then usually drifted out into the
Ringer's solution as if slowly diffusing. The conclusion is
justified that in the living excised stomach acid coming to the
pylorus causes the pylorus to open.
We may sum up, therefore, as follows, the evidence that acid
on the stomach side of the pylorus signals the relaxation of the
sphincter. Moistening carbohydrates with NaHC0 3 retards their
normally rapid exit from the stomach ; feeding proteins as acid
proteins remarkably hastens their normally slow exit ; observa-
tions through a fistula in the vestibule show that an acid reaction
closely precedes the initial passage of food through the pylorus,
that the introduction of acid causes pyloric opening, and that
delaying the acid reaction causes retention of the food in the
stomach, in spite of strong peristalsis ; and, when the stomach
THE ACID CONTROL OF THE PYLORUS 107
is excised and kept alive in oxygenated Ringer's solution, the
pylorus is opened by acid on the gastric side. What, now, is
the proof that acid in the duodenum keeps the pylorus closed ?
The support for the second half of the theory, that acid in
the duodenum keeps the pylorus closed, has already been in part
suggested. As other observations to the same effect are to be
described, however, a brief restatement of the experiments
previously mentioned will not be out of place, and will serve to
bring all the evidence together.
1. Acid in the duodenum inhibits gastric discharge. In 1893,
Hirsch, as already noted, found that inorganic acids left the
stomach slowly. When he isolated the stomach, however, the
acids departed as rapidly as any other fluid. He explained this
difference by assuming that the stomach is controlled by acid
reflexes from the duodenum. Serdjukow modified Hirsch's
experiment by introducing through a duodenal fistula small
quantities of acid solutions or pure gastric juice. By repeated
injections it was possible to prevent discharge from the stomach
for an unlimited time. Tobler's observations were closer to the
normal conditions. He allowed a dog with duodenal fistula to
eat 100 grammes of lean beef. The chyme as it emerged was
caused to leave the duodenum through the artificial opening.
The stomach was thus emptied in about two hours and fifteen
to thirty minutes. The next day the dog was given the same
amount of the same kind of food, but whenever a portion of the
chyme came through the fistula from the stomach, a similar
portion of the chyme of the day before was injected through the
fistula towards the intestines. The result was that the chyme
left the stomach at considerably longer intervals, and was more
thoroughly digested. The time of digestion thus became length-
ened to three hours and three hours and a half. Tobler's
observations have been completely confirmed by Lang. 34
The experiments of Hirsch, Serdjukow, Tobler, and Lang
prove definitely that acid chyme in the duodenum checks the
outgo from the stomach. Since we now know that gastric
peristalsis is not stopped by the discharge of acid chyme, the .
effect must be due to the action on the pyloric sphincter. Acid /
in the duodenum causes pyloric contraction.
-2. Absence of the normal alkaline secretions from the duo-
denum retards gastric discharge. Pawlow has recorded that
the passage of acid solutions out of the stomach is remarkably
THE MECHANICAL FACTOKS OF DIGESTION
slower in dogs with a pancreatic fistula than in those without
one. 35 In order to test whether the discharge of normal gastric
contents is likewise retarded by a similar condition in the
duodenum, the following experiment was performed : The
larger pancreatic duct and also the bile-duct were tied so as to
prevent the flow of the secretions into the intestine. Six and
twelve days after the operation the animals were given the
standard amount of mashed potato and bismuth subnitrate
with the usual consistency. The outgo from the stomach was
determined, as before, by measuring the length of the food-
masses in the small intestine. Fig. 14 presents a comparison
of the discharge under normal conditions
and after tying the ducts. Obviously there
has been a very marked checking of the
normal rapid outgo of the potato from the
stomach ; nothing out in a half-hour, a
fourth the normal amount in an hour, and
a third the normal at the end of two
Why there should be no exit of the food
during the first half-hour is not clear, but
the very slow increase of the intestinal con-
tents thereafter from 7 '5 to 14-5 centi-
metres in the second hour of digestion, com-
pared with the increase from 10 to 31-5
centimetres in the second half-hour in the
normal state is in harmony with the ob-
servation that acid in the duodenum closes
Under normal conditions, acid in the duodenum stimulates
the secretion of pancreatic juice and bile. These alkaline fluids
must neutralize the acid chyme, for an acid reaction is not found
beyond the first few centimetres of the small intestine (see p. 101).
The neutralizing of the acid removes the stimulus keeping the
pylorus closed. If the alkaline fluids are prevented from enter-
ing the intestine, the acid is necessarily neutralized more slowly,
the pylorus is kept closed during longer periods, and the emptying
of the stomach therefore occurs at a slower rate.
3. Destroying continuity between stomach and duodenum
hastens gastric discharge. Additional evidence as to the rela-
tions between the duodenum and the pylorus in the control of
Hours i 1 2
The continuous line is
the curve after feed-
ing potato (four cases)
in normal conditions,
and the dot-line the
same, with pancreatic
and bile ducts tied.]
THE ACID CONTROL OF THE PYLORUS
gastric evacuation can be secured by setting aside the duodenum,
and causing the stomach to empty into a lower part of the gut.
The intestine was cut through about 1-5 centimetres beyond
the pyloric furrow, and again about 30 centimetres beyond.
The upper end of this separated portion was turned in and
closed with stitches ; the lower end was joined to the gut near
the ileocolic opening by an end-to-side junction. The upper end
of the main part of the intestine was now united to the small
remnant of duodenum contiguous to the pylorus. Thus the
stomach emptied, not into the duodenum, but into a piece of
the intestine, formerly 30 centimetres beyond.
After recovering from the operation, the animals were fed
shredded lean beef of standard amount and consistency. Kefer-
ence to Fig. 15 shows at once the difference
between the factor which acts inside the
stomach and the factor which acts in the
duodenum to control the pylorus. In the
normal, and in the experimental conditions
as well, there occurred the retardation of
the initial discharge characteristic of pro-
teins. Setting aside the duodenum evi-
dently did not change that. That Hours i i 2
retardation, according to the conclusions FIG. 15.
already stated, is an affair of the stomach Th ^ continuous line is
, , . , , . i n ,1 the curve after feed-
alone. And the results graphically reported
in Fig. 15 serve to confirm those conclu-
When the food begins to emerge, the
figures are suddenly quite different. In-
stead of 3 centimetres at the end of an hour, 16 centimetres ;
and twice the normal amount at the end of two hours such is
the effect of destroying the continuity between stomach and
duodenum. After the first delay (in one case no food left the
stomach for an hour), protein is poured forth at a remarkably
In considering agencies affecting the cardia, we learned that
acid in the stomach increased the tonic contraction of the
sphincter through a local mechanism. The investigations of
Magnus have shown that intestinal reflexes occur in the myen-
teric plexus. It seemed probable that merely cutting a ring
around the intestine as close as possible to the pylorus, and
ing lean beef (four
cases) in normal con-
ditions, and the dot-
line the same, with
the duodenum set
110 THE MECHANICAL FACTORS OF DIGESTION
deep enough to sever both muscular coats, would yield informa-
tion as to the path of influence from duodenum to stomach. A
ring was cut as above described, and the separated edges of the
muscular coats were then held together by only the mucosa and
the submucous connective tissue. When protein was fed there
was again the initial delay nothing out at the end of a half-
hour and this was followed by an exit almost as rapid as when
the duodenum was set aside. We may conclude that the in-
fluence from duodenum to pylorus runs through a local reflex,
mediated by the my enteric plexus. In the intestinal wall is a
local reflex, such that a stimulus causes a contraction above the
stimulated point and a relaxation below. 36 The action of acid
on the two sides of the pylorus is in exact agreement with this
so-called " law of the intestine "; the acid when above causes a
relaxation of the sphincter which is below, and the acid when
below causes a contraction of the sphincter which is above. As
we have already seen, the cardia also obeys this law.
We may sum up, as follows, the evidence that acid in the
duodenum keeps the pylorus closed. Acid in the duodenum
inhibits gastric discharge, as proved by the observations of
Hirsch, Serdjukow, and Tobler an effect, as we now know, not
due to stoppage of peristalsis, but to closure of the pylorus ; the
stomach empties more slowly than normally when the tying of
pancreatic and bile ducts prevents alkaline fluids fromneutralizing
the acid chyme in the duodenum ; the discharge of protein
becomes rapid if the pylorus is sutured to the intestine below the
duodenum, or if a ring is cut through the muscular coats im-
mediately beyond the pylorus. The effect from the duodenum
is thus a local reflex, mediated, like the local reflex of the small
intestine, by the myenteric plexus.
When all the factors concerned in the proper functioning of the
pyloric sphincter are considered, the simple control of its activity
by the action of acid above and below must be regarded as one
of the most remarkable automatisms in the body. The highly
important part which the pylorus plays seems to have been
surmised by the ancients who gave it the name, " keeper of the
gate," and called it also " rector " and " janitor Justus." How
it makes the relations between gastric and intestinal digestive
processes orderly and progressive, we shall next consider.
THE ACID CONTROL OF THE PYLORUS 111
1 Ewald and Boas, Arch. f. pcith. Anat., 1885, ci., p. 365.
2 Schiff, Physiologic de la Digestion, Florence and Turin, 1867, ii., p. 326;
Kiihne, Lehrb. d. physiol. Chem., Leipzig, 1868, p. 53 ; also v. Mering, Verhandl.
d. Cong. f. innere Med., 1897, xv., p. 433.
3 Richet, Compt. rend. Acad. d. Sc., Paris, 1877, Ixxxiv., p. 451 ; Rossbach,
Deutsches Arch. f. klin. Med., 1890, xlvi., pp. 296, 317.
4 Cannon, Am. J. Physiol., 1898, i., pp. 368, 369.
5 Hirsch, Centralbl. f. klin. Med., 1892, xiii., p. 994.
6 See Lesshaft, Arch. f. path. Anat., 1882, Ixxxvii., p. 80.
7 v. Mering, loc. cit., p. 434.
8 Marbaix, La Cellule, 1898, xiv., p. 251.
9 Tobler, Ztschr. f. physiol. Chem., 1905, xlv., p. 195.
10 Cannon, Am. J. Physiol., 1902, vi., p. 262.
11 Ewald and Boas, loc. cit., p. 364.
12 Penzoldt, Deutsches Arch. f. klin. Med., 1893, 1L, p. 535 ; 1894, liii., p. 230.
13 Verhaegen, La Cellule, 1897, xii., p. 69.
4 Hirsch, Centralbl. /. klin. Med., 1893, xiv., p. 383.
15 Serdjukow, Abstract in Jahresb. ii. d. Fortschr. d. Physiol., 1899, viii.,
16 Tobler, loc. cit., p. 198.
17 Marbaix, loc. cit., p. 273.
18 Cannon, Am. J. Physiol., 1904, x., p. xviii.
19 Pawlow, loc. cit., pp. 36, 100.
20 Danilewsky, Ztschr. f. physiol. Chem., 1881, v., p. 160.
21 See Bastianelli, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1892, xiv.,
p. 93 ; and Oser, Ztechr. f. klin. Med., 1892, xx., p. 291.
22 Bayliss and Starling, Centralbl. f. Physiol., 1901, xv., p. 682.
23 Moore and Bergin, Am. J. Physiol., 1900, iii., p. 325.
2 * Munk, Centralbl. f. Physiol., 1902, xvi., p. 33.
25 Jaworski, Ztschr. f. BioL, 1883, xix., p. 444.
28 Pawlow, loc. cit., p. 95.
27 See Cannon, Am. J. Physiol., 1904, xii., p. 409.
28 Moritz, Ztschr. /. BioL, 1901, xlii., p. 571 ; Tobler, loc. cit., p. 197 ; Lang,
Biochem. Ztschr., 1906, ii., p. 240.
29 Tobler, loc. cit., p. 197.
30 London and Sulima, Ztschr. f. physiol. Chem., 1905, xlvi., p. 215.
31 London and Polowzowa, Ztschr. f. physiol. Chem., 1906, xlix., p. 340.
32 Magnus, Arch. f. d. ges. Physiol., 1904, cii., p. 362.
33 Cannon, Am. J. Physiol., 1906, xvii., p. 429.
3 * Lang, loc, cit., p. 225.
35 Pawlow, loc. cit., p. 164.
36 See Bayliss and Starling, J. Physiol., 1899, xxiv., p. 142.
THE CORRELATING FUNCTIONS OF THE PYLORUS, AND SOME
CONDITIONS AFFECTING IT
THE great importance of the pylorus in correlating the digestive
processes of the stomach and small intestine is perhaps brought
out most impressively if we consider what would happen if the
sphincter did not perform its proper functions. Let us suppose
that it opened as soon as gastric peristalsis started.
We know from Edkins's experiments that gastric juice con-
tinues to be secreted because acid, peptone, or sugar solutions
affect the mucosa of the vestibule. Evidently, if the pylorus
opened as soon as the peristaltic waves started, they would
act merely to propel the gastric contents rapidly through the
stomach. The food, therefore, would not have time to receive
much of the acid secretion of the cardiac end, nor would even
the small amount of acid that the food might carry be churned
against the mucosa of the vestibule. That the processes in the
stomach may advance in an orderly manner, therefore, the
gastric contents must be retained until the portion in the vesti-
bule is churned to an acid chyme.
Again, if the food were allowed to depart before becoming
acid,* it could not stimulate chemically the duodenal reflex.
The pylorus, consequently, would not be held closed, and the
upper small intestine would be crowded full of food through an
uncontrolled pyloric sphincter. Furthermore, the chyme, unless
held back until acid, would not, on entering the duodenum, excite
the flow of pancreatic juice and bile. Thus, if the pylorus
relaxed at the approach of the first peristaltic wave (after meat
had been fed, for example), the food would not only emerge
wholly undigested by gastric juice, but would bear no provision
for being digested by the pancreatic juice. In order that the
* The somewhat variant case of the fats will be considered later.
CORRELATING FUNCTIONS OF THE PYLORUS 113
pancreatic juice may be caused to flow, and may have time to
become mixed thoroughly with the chyme, without being over-
whelmed by fresh discharges from the stomach, food must be
retained in the vestibule until acid in reaction.
If we grant that the vestibular contents must be acid before
being permitted to pass the pylorus, note how favourably the
stomach is arranged for the utilization of its secretions. We
have already learned that in order to open the sphincter the
acid must be at the pylorus. Clearly, if the vestibule secreted
acid, the acid would at once open the pylorus and let out the
food (meat, for example) before the gastric juice had had oppor-
tunity to digest it. But the vestibule does not itself secrete
acid. The acid and the food with an acid reaction must be
brought from the cardiac end of the stomach and thoroughly
mixed with the contents of the vestibule before the pylorus
relaxes. The necessity of importing the acid into the vestibule
insures a thorough mixing of the food with the gastric juice
before the food departs, and provides time for gastric digestion.
We can now appreciate how wonderful an arrangement the acid
control of the pylorus is an arrangement whereby the food is
held in the stomach until provision is made for the continuance
of gastric secretion, until the gastric juice has had time to act,
and until the food can bear with it the acid needed for processes
in the duodenum. In the duodenum the acid chyme stimulates
the flow of pancreatic juice and bile, and holds the pylorus closed
until this chyme has been thoroughly mixed with these digestive
fluids. This thorough mixing stops gastric digestion, injurious
to the action of the pancreatic ferments, by neutralizing the
acid. As the acid is neutralized, the stimulus holding the pylorus
closed is weakened, and then the acid in the stomach is again
effective in causing the pylorus to open.
We shall find still more reason for admiration of the pyloric
reflex when we see how exactly its acid control can be applied
in explaining the differential discharge of different foodstuffs.
The delay in the initial discharge of protein food we have already
explained as due to the union of the first acid secreted with the
protein. The continued slow exit can also be explained. The
mixing occurs only in the pyloric end ; as we know, the centre
of the mass in the cardiac end long remains unchanged in reaction.
Since the vestibule does not secrete acid, all the acidity of its
contents is due to acid pressed in from the cardiac end. But
114 THE MECHANICAL FACTORS OF DIGESTION
unchanged protein, stored in the cardiac end, is also continuously
being pressed into the vestibule. There is thus continuous
utilization of the imported acid. Since it is altogether probable
that a certain degree of acidity is necessary for opening the
pylorus, the fresh protein masses, by uniting with the acid and
thus reducing the acid reaction, would naturally diminish the
rate of exit from the stomach. That this factor is important
in checking the rapid outgo of protein food is indicated by
the quick discharge of acid proteins, which do not demand large
amounts of acid (cf. two curves in Fig. 15). Possibly also the
protein discharge continues to be slow because protein chyme
presents a greater amount of acid for neutralization than does
carbohydrate chyme. Tobler and Lang have shown that acid
protein in the duodenum will check gastric evacuation. 1
Khigine's results prove that, when 200 grammes of flesh are fed to
a dog, 50 per cent, more gastric juice is secreted during the first
four hours of digestion than is secreted in the same time when the
same amount of bread is fed. 2 The neutralizing of the larger
amount of acid in the duodenum would naturally require a
longer time, and would result in a slower rate of discharge than
would be expected when bread is fed.
In examining the effects of feeding combinations of foodstuffs,
we noted that when carbohydrate was fed first, and protein
second, the departure of the carbohydrate was not materially
checked ; but that when protein was fed first, and carbohydrate
second, the protein held back the carbohydrate. In the former
case the carbohydrate content of the vestibule did not retard
the development there of an acid reaction ; in the latter case the
protein did retard that development. This observation indi-
cates that the acid which opens the pylorus acts close to the
pylorus a conclusion which is sustained by the -effect of acid
in the excised stomach.
When carbohydrates and proteins were mixed in equal parts,
the discharge was intermediate in rapidity. This result is in
accord with other evidence, for a large proportion of protein
was present to unite with the acid secreted, and this would tend
to retard the discharge in the usual manner.
In a mixture of fats and proteins in equal parts, the presence
of fat caused the mixture to leave the stomach even more slowly
than the protein alone. This result also is in accord with the
supposition that acid opens the pylorus, for fat alone inhibits ?
CORRELATING FUNCTIONS OF THE PYLORUS 115
and fat mixed with protein notably retards and diminishes, the
flow of gastric juice. 3 Moreover, the development of an acid
reaction is checked by the union of acid with protein. Quite
naturally, therefore, this combination of foodstuffs was slowest
of all to pass from the stomach.*
Fats mixed with carbohydrates in equal amounts caused the
carbohydrates to pass the pylorus at a rate slower than their
normal. In this case the fats again retarded and diminished
secretion ; but the carbohydrates, unlike the proteins, did not
further hinder the appearance of an acid reaction. The checking
of the outgo can therefore be explained by the effect of the fats
in diminishing gastric secretion.
The evidence just presented indicates that typical variations
in the rate of discharge of proteins, carbohydrates, and fats,
and combinations of these foodstuffs, can be readily explained
by the action of acid upon the pylorus. This ability to explain
the peculiar differences in the gastric discharge of the different
foodstuffs brings additional strength to the evidence already
given that acid acting oppositely above and below controls the
The discharge of fats is peculiar, and requires special con-
sideration. In attempting to understand their prolonged slow
discharge, we must first consider their effects both in the stomach
and in the duodenum. We know that fat in the stomach does
not stimulate the flow of gastric juice. On the other hand,
according to Lintwarew, 4 fat in the duodenum, like acid, may
check the gastric discharge.
Associated with the absence of gastric secretion there is
apparently a low degree of pyloric tonus. Boldireff, for example.
has reported that, when fats are fed in considerable amount, a
mixture of pancreatic juice, bile, and intestinal secretion, flows
back into the stomach. 6 This result could not occur unless at
times the pyloric sphincter were in a relaxed state, and unless at
* An important food consisting of a combination of fat and protein is milk.
Before being coagulated, milk issues from the stomach in gushes, like water,
as we shall see later. Clearly, were not milk quickly coagulated, it would go
at once into the intestine, unchanged and not provided with acid to help rouse
pancreatic secretion. Once coagulated, however, milk leaves the stomach
., 1901, xlii., p.
d. Gesdlsch. /. Kinderheilk., 1906, p. 147), the chyme from milk is a clear
slowly (Moritz, Ztschr. /. Bid., 1901, xlii., p. 575). According to Tobler (Verh.
yellowish fluid, with the protein mostly changed to peptone. Coagulation
may be interpreted, therefore, as a conservative provision delaying the passage
from the stomach until peptonization has occurred. The slow discharge of a
fat-rich milk, after the first few gushes through the pylorus, can be explained
by the combination of fat and protein in its composition.
116 THE MECHANICAL FACTORS OF DIGESTION
times the pressure in the stomach were less than that in the
duodenum. In this connection it is of interest to recall that,
of the three foodstuffs, fats produce the slowest rate of gastric
peristalsis (see p. 55), and commonly the weakest (i.e., the
shallowest) waves. My observations do not support Cohnheim's
suggestion 6 that fat in the duodenum stops gastric peristalsis.
Fats differ from carbohydrates and proteins in very seldom
constituting the chief elements of a diet. They differ also in
npj^arousing gastric secretion. They are further peculiar in
acting by themselves in the duodenum, not only to inhibit gastric
evacuation, but also to stimulate the flow of pancreatic juice. 7
Clearly, fats do not require the secretion of gastric juice for
changes in the stomach, or for the control of their exit into the
intestine, or for the stimulation of a pancreatic secretion specially
favourable to their digestion.
Although fats have a special relation to the pyloric mechanism,
the alternative possibility of an acid control, even when fats
alone are fed, should not be overlooked. Fatty acid may be
set free in considerable amount in the stomach by gastric lipase
if the fat is fed as an emulsion. 8 A separation of fatty acid also
occurs when, in the early stages of fat digestion, pancreatic juice
enters the stomach. 9 If, at first, fats readily pass through an
easily opened pylorus, the later development of acid in fats in
the stomach might cause them to control their own discharge, like
other foods which develop an acid reaction of the gastric contents.
And in the duodenum it is noteworthy that fats are changed
with an effect quite unlike that of the other foodstuffs. Fats
cause the pancreatic juice to flow, but the pancreatic juice,
instead of diminishing the acidity of the duodenal contents,
increases the acidity by separating a still greater amount of
fatty acid. 10 Even when dissolved in bile, the fatty acids give
the solution an acid reaction. 11 To this increasing acidity of the
contents of the upper intestine, as well as to the action of fats
themselves, and the weak and sluggish gastric peristalsis which
they evoke, may reasonably be attributed the fact that fats pass
from the stomach only as fast as they are absorbed or carried
into the large intestine.
The low pyloric tonus and the inhibition of gastric secretion
conditions which attend the ingestion of fat are possibly
related through the action of the vagus nerves. Pawlow has
shown that the psychic secretion of gastric juice is due to im-
CORRELATING FUNCTIONS OF THE PYLORUS 117
pulses coming to the stomach by way of the vagi. 12 Vagus
stimulation also produces an augmentation of the contraction
of the pyloric sphincter. 13 Vagus impulses, therefore, cause the
initial flow of gastric juice the psychic secretion and they also
cause increased pyloric tonus. In the absence of one effect of
vagus stimulation, we might find the other effect also lacking.
Certainly that seems to be true for the fats. It is also a possible
explanation of several other conditions of anomalous discharge
from the stomach among them, the discharge of water and
Water begins to enter the intestine almost as soon as it enters
the stomach ; it may pass out in single gushes or continuously.
According to Moritz, who watched the process through a duo-
denal fistula, 500 c.c. of water may go from the stomach into
the intestine in thirty minutes. 14 Similar results have also been
reported by other observers who have studied the exit of
water. 15 Physiological salt solution likewise may go out
Water and salt solution are, of course, very different in con-
sistency from the foods ordinarily taken into the stomach.
Furthermore, water and salt solution neither present the con-
ditions for psychic secretion (they are not chewed with a relish,
they are swallowed rapidly, they do not satisfy appetite), nor,
once in the stomach, do they produce any considerable secretion
of gastric juice. When only 100 or 150 c.c. of water are injected,
very often not the least trace of secretion occurs. " It is only a
prolonged and widely-spread contact of the water with the
gastric mucous membrane which gives a constant and positive
result (secretion)." 17 The rapid exit of water from the stomach
would preclude the conditions which make it even a feeble
stimulant of gastric secretion. And the failure of water to excite
any noteworthy amount of gastric juice favours a rapid exit, so
far as the duodenal reflex is concerned, for the acid stimulus
closing the pylorus is thereby absent. Within the stomach,
water certainly has an effect on the pyloric sphincter very dif-
ferent from foods which evoke an abundant flow of gastric juice.
When such foods are given, scores of peristaltic waves may
sweep up to the pylorus before the sphincter relaxes ; but when
water is given, it begins to leave the stomach at once.* The
* The quick exit of water, before it is acidified, doubtless explains the
readiness with which it conveys infection.
118 THE MECHANICAL FACTORS OF DIGESTION
fact that water may pour through the pylorus in a fairly con-
tinuous stream, as rapidly as it is swallowed, points definitely
to a diminished pyloric tonus. This fact and the failure to
stimulate gastric secretion are, as I have pointed out, apparently
related to each other. In these facts may be found a
probable explanation of the rapid discharge of water from the
In the same class with water is raw egg-white. In my observa-
tions on the rate of discharge of different foods from the stomach,
I pointed out that egg-albumin formed an exception to the
general rule that protein passes out from the stomach slowly. 18
This observation is confirmed by London and Sulima's study of
dogs with a duodenal fistula. They found that raw egg-albumin
begins to pass the pylorus immediately after ingestion ; it
emerges in large gushes at intervals of four or five seconds.
These gushes are therefore too frequent to correspond to the
occurrence of peristaltic waves. For about twenty minutes the
egg-white issues from the stomach with an alkaline reaction ;
then the reaction becomes acid, and the discharge naturally is
more seldom (one to three minute intervals) and less abundant. 19
In this connection it is of interest that Pawlow found fluid egg-
white no more effective in exciting gastric secretion than an equal
volume of water. 20 Like water, fluid egg-white does not offer the
conditions for arousing psychic secretion ; and again, attending
that condition, there is a state of diminished pyloric tonus, as
evidenced by discharges through the pylorus much more frequent
than the peristaltic waves in the dog's stomach. The rapid
passage of fluid egg-white from the stomach would therefore be
* Cohnheim states that water swallowed by dogs when the stomach is full
passes along the lesser curvature, through a little channel formed there, and,
diluting only the contents of the vestibule, pours through the pylorus. After
the first few gushes the water appears at the duodenal fistula, free from gastric
contents, and almost neutral in reaction (Mi'mchen. med. Wchnschr., 1907, liv.,
p. 2582). I have some tracings made in 1898, showing how water containing
bismuth, when swallowed into a full stomach, leaves the bismuth lying along
the lesser curvature. It occurred to me then that this phenomenon in a car-
nivorous animal was not unlike the course of the more fluid food in ruminants ;
but as I had no further evidence, I did not call attention to the observation.
The strong, oblique fibres of the inner muscular coat (see p. 47) would help
to make a channel by their contraction. There is not, however, entire agree-
ment among observers on the passage of water through the stomach during
gastric digestion. Leven and Barret have found that, whereas water dis-
appears rapidly from the resting stomach, its discharge is considerably retarded
if taken with food, even with a few bites of bread (Radioscopie Gastrique et
Maladies de VEstomac, Paris, 1909, p. 75). Of course, the delay* under these
circumstances is readily explained.
COEEELATING FUNCTIONS OF THE PYLOEUS 119
explained in the same manner that the rapid outgo of water is
According to my earlier investigations, egg-white coagulated
by heat also left the stomach at a rapid rate. This observation,
likewise, is confirmed by London and Sulima. They found,
however, that, unlike fluid egg-white, the coagulated form did
not begin to leave the stomach immediately, but several minutes
after ingestion. When the gastric discharge began, its reaction
was acid. First the discharge had only fine particles of the egg-
albumin, but later these were much larger. 21 These unchanged
particles are significant, for they indicate that the acid has been
secreted more rapidly than it could unite with the compact
coagulum of the egg-albumin. 22 This failure of the acid to unite
with albumin as soon as secreted brings about the same condition
that prevails when carbohydrates are fed : there is an early
appearance of free acid in the stomach. London and Sulima
reported large amounts of free hydrochloric acid in the chyme of
coagulated egg-white. 23 On the other hand, although the chyme
of beef and fibrin is acid in reaction, it may not contain free
hydrochloric acid (see p. 104). This difference in the rapidity of
union with the acid as it is secreted would account for the differ-
ence in the rate of discharge of these proteins. The slow union of
acid with coagulated egg-white, and the resultant early appear-
ance of free acid in the stomach, explains the rapid departure of
That water does not emerge rapidly from the stomach merely
because it is fluid was shown by the observations of Moritz. 24
Weak hydrochloric acid, he found, passed out more slowly than
water, and beer passed out with even greater retardation. The
slow exit of weak hydrochloric acid can be explained by its effect
in closing the pylorus from the duodenal side. And beer, stimu-
lating gastric secretion not only by its alcohol content, 25 but also
by its bitter taste, ^ 6 must go out slowly, because of the acid con-
trol of the pyloric passage.
In connection with the acid control of the pylorus the effect of
hyperacidity may be considered. By requiring a longer time for
neutralization in the duodenum, and thereby holding the pylorus
closed for longer periods, hyperacidity might be expected to cause
a retardation of gastric discharge. In work with C. A. Hedblom,
* A very rapid exit of a rice preparation moistened with sodium bicarbonate
(which hinders gastric secretion) may be similarly explained.
120 THE MECHANICAL FACTORS OF DIGESTION
evidence on this question was obtained by feeding potato with
which had been mixed a known percentage of hydrochloric acid.
The results are represented in the curves of Fig. 16.
In comparing with the standard rate the results of feeding acid
food, it is fairer to use the second rather than the first half-hour
of the standard curve, since at the beginning of the first half-hour
digestion has not begun and no acid has yet appeared at the
pylorus, while at the beginning of the second half-hour acid chyme
is being discharged. As the curves indicate, the rate of exit is
faster than normal when the potato has an
acidity of 0-25 per cent., and slower than
normal when it has an acidity of 1 per cent.
Potato with an acidity of 0-5 per cent, is
discharged during the first half-hour about
as rapidly as the food is normally dis-
charged. The difference between the outgo
of the weakly acid (0-25 per cent.) and the
strongly acid (1 per cent.) potato is re-
markable. Note that at the end of the
first half-hour there was in the intestine
more than 2-5 times as much, and at the
end of an hour about two times as much,
of the weakly acid potato as of the strongly
acid. According to Katschkowski, a hyper-
acidity, even 0-7 to 0-8 per cent, of hydro-
chloric acid, produces a lasting spasm of
the pylorus. 27 Al chough in our experi-
ments we did not note so pronounced an
effect, we found nevertheless that the
hyperacidity caused a retardation of the
passage of food from the stomach, a result
explained by reasons already stated.
Some of the other conditions affecting gastric discharge, which
Hedblom and I studied, were the consistency of the food, the
presence of gas in the stomach, the temperature of the food, and
irritation of the colon. The results can be briefly stated.
To obtain information regarding the effects of varying con-
sistency and other mechanical factors on the gastric discharge,
observations were made on more or less viscous samples of potato
and on hard particles mixed with the food. Before diluting the
potato, it was baked, in order to drive off most of the water.
S g 8 g g
The heavy line is the
curve (for the second
half-hour) when po-
tato is fed normally ;
the light line, when
fed with 0-25 per
cent, acidity (HC1) ;
and the dash line,
when fed with 1 per
CORRELATING FUNCTIONS OF THE PYLORUS 121
Two series of observations were made. In the first series no
water was added ; the potato when mixed with bismuth sub-
nitrate and ready for feeding was very thick and doughy. In the
second series water was added until the mixture was of the con-
sistency of thin gruel. The volume fed in all cases was 25 c.c.
The results with these extremes should be compared with the
results when potato of the standard consistency (intermediate
between the extremes) is fed. As the curves in Fig. 17 (A) show
graphically, the rates of discharge of the same kind of carbo-
hydrate food, thick or diluted, are nearly the same ; indeed, the
rates of discharge do not differ among themselves enough to
A. The light continuous line is the curve for potato of standard consistency ;
the heavy continuous line, for thick, doughy consistency ; the dash line,
for thin, gruelly consistency 5 cases each.
B. The heavy line is the curve for lean beef of standard consistency ; the light
line, that for lean beef of thin, gruelly consistency.
permit any noteworthy significance to be attributed to the
The dilution of protein food might be expected to have a
different effect from the dilution of carbohydrate. If protein
food is diluted with water, evidently, in a given amount, less
protein is present to unite with acid than would be present if the
same amount were given undiluted. To test this supposition, lean
beef was fed after being shredded and mixed with water to a thin,
gruelly consistency. A comparison of the curves in Fig. 17 (B)
shows that the dilution of the protein food, and the reduction
thereby of the material uniting with the acid of the gastric juice,
tends toward a more rapid discharge of the protein from the
122 THE MECHANICAL FACTORS OF DIGESTION
The factor of consistency of protein food is important in
relation to the differing results reported by different investigators.
Thus, Cohnheim found, 28 by observations through a duodenal
fistula, that the emptying of the stomach began about fifteen
minutes after feeding a dog finely chopped meat mixed with
water, and Lang reported that the first slight discharges of gastric
contents did not occur until at least fifteen minutes after feeding
his dogs 200 grammes of fibrin. Moritz, on the other hand, who
also used the fistula method on dogs, observed that the exit of
the gastric contents began about three-quarters of an hour after
feeding 200 grammes of raw meat. My own experience with
proteins of standard consistency accords
with that of Moritz. The discrepancy
between the concordant observations of
Cohnheim and Lang and the concordant
observations of Moritz and myself is prob-
ably due to a difference in consistency of the
protein food. Certainly, my results were
well within the limits set by Moritz, and
did not show nearly so long a delay in the
first discharge of meat from the stomach as
was reported by Koux and Balthazard. 29
Few observations as to the relation be-
tween hard food-masses and gastric dis-
charge have been reported. Moritz 30 found
in experiments on a dog with a duodenal
fistula that finely chopped sausage began to
leave the stomach in forty-five minutes,
whereas coarse unchopped sausage did not
begin to leave for two hours. In my first paper on the
stomach 31 I reported that hard particles repeatedly pushed up
to the pylorus checked the outgo of food from the stomach.
Since improved methods permitted a careful testing of this
statement, Hedblom and I repeated the observations, giving
small irregular pieces of dried starch paste with the standard
In Fig. 18 the normal discharge is compared graphically with
the discharge when the same food, with hard particles added, was
fed. There is a marked retardation of the outgo of food from the
stomach when hard particles are present.
Food finely divided is sometimes fed in order to spare the
The heavy line is the
normal curve for
potato ; the light
line, the curve when
hard particles are
present in the food
CORRELATING FUNCTIONS OF THE PYLORUS 123
stomach. That results not easy to anticipate may follow was
shown by Cohnheim's observations on a dog with a duodenal
fistula. The stomach emptied itself of 50 grammes of finely
divided meat in an hour and thirty-five minutes. When the
same amount was given in large lumps, the stomach required
almost an hour longer to empty itself. The coarser meat,
however, was discharged almost entirely dissolved, whereas
nearly half of the finely divided meat emerged in unbroken
particles. As Cohnheim pointed out, the " easily digested,"
finely divided meat did indeed spare
the stomach, but it placed more work in
the small intestine. 32
The usual presence of gas in the fundus
of the human stomach has already been
mentioned. When a person reclines,
this gas of course changes location ; and
if the person lies on his back, the gas
takes a position under the anterior
surface of the stomach. That the pres-
ence of a body of gas in the stomach
might affect the exit of food has appar-
ently not been much considered. Yet
with the X rays peristaltic waves can be
seen moving over an accumulation of gas
without either churning the contents or
propelling them onward. The gas acts as
a shield, keeping the walls of the stomach away from the food.
We desired to learn how a considerable amount of gas in the
stomach might effect the discharge.
The animals were first fed the standard amount of food. Air
was then introduced into the stomach while the animals were
under observation ; thus the distension of the stomach walls
could be easily regulated. In a few instances eructations nearly
emptied the stomach during the first hour ; more air was then
introduced until approximately the original volume was restored.
The average figures for fourteen cases are compared with the
average figures for normal conditions in Fig. 19. As was to be
expected, these average figures cover a wide variation in the
effects produced by the presence of gas. In few cases, however,
was there any effect except a retardation of the discharge into
the intestine. This result has been noted repeatedly in other
k 1 2 3
The heavy line is the nor-
mal curve for potato ;
the light line, that for
potato when gas is pres-
ent in the stomach.
124 THE MECHANICAL FACTORS OF DIGESTION
instances in which gas appeared in the stomach spontaneously*
Thus, in one case in which fibrin was fed, and in which the peri-
staltic waves could be clearly seen passing over the gas in the
stomach, the discharge was as follows :
Hours after feeding .. .. . . * 1 2 3'0 4-0 5
Centimetres of fibrin when gas was present ..00 lO'O 17'0 22
Centimetres of fibrin, average of four normal cases 4 8 21 29*5 32'5 32
Such cases of spontaneous accumulation of gas seemed to be
associated with atony and enfeebled peristalsis. When the air
was experimentally introduced, however, peristalsis, when ob-
served, was normal in rate and intensity.
With peristalsis normal, how may the retardation of the dis-
charge, noted in the above experiments, be explained ? That
the distension of the stomach walls prevented them from exerting
a direct propelling action on the food was distinctly visible.
Only at one surface was there contact of the wall with the food.
Since gas slips to and fro more readily than fluid or semi-fluid
contents, it prevents the normal action of the peristaltic waves.
The retardation due to gas is a result which evidently might be
different in man and in the cat. In the upright position of man
any gas in the stomach naturally rises to the fundus, and the food
then lies in the region of active peristalsis. But in the prone
position of man gas in the stomach may interfere with peristaltic
activities quite as much as it does in the cat.
Observers who have studied the effects of heat and cold on the
motor functions of the alimentary canal have reported various
results. Liideritz 33 exposed the stomach and intestines of
rabbits in a bath of normal salt solution which was gradually
cooled. He saw no change until a temperature of 28 to 30 C. was
reached below 28 the movements gradually ceased. Oser M
states that low temperatures close the pylorus, but that higher
temperatures, up to 37 C., have no such effect. According to
Miiller, 35 low temperatures have a quieting, even a paralyzing
effect on the movements of the stomach, whereas high tempera-
tures increase gastric peristalsis. These statements accord with
the observation of Schiile, 36 and Leven and Barret, 37 that warm
water leaves the stomach much faster than cold ; but they do not
seem to accord with Miiller's own results that both hot and cold
fluids leave the stomach more slowly than fluids at body
In such studies the time required for the equalization of the
CORRELATING FUNCTIONS OF THE PYLORUS 125
ingested food to the temperature of the body is important, for
probably the temperature effects diminish as the equalization
takes place. By use of maximum thermometers, Winternitz 38
observed that thirty minutes after drinking 500 c.c. of cold water
the temperature of the gastric contents was only 0-6 C. lower
than general bodily temperature. On a patient with gastric
fistula, Quincke 39 obtained similar results when cold water was
taken, and further found that water at 40 C. reached body
temperature within ten minutes. According to Quincke, hot or
cold water reaches body temperature sooner than lukewarm milk.
As Miiller points out, the stomach is in a high degree able to bring
food of widely differing temperature quickly to the temperature
of the body, a function doubtless dependent on the central
position of the organ in the body and on the rich blood-supply in
its walls and in the surrounding structures.
Since the stimulating influence due to variations of temperature
is present for only a comparatively short interval, the influence
exerted might be correspondingly short ; but the possibility of
the effect outlasting for some time the period of stimulation must
be considered. In the following experiments to determine the rate
of discharge of hot and cold solid foods, the conditions of experi-
mentation were quite normal. Care was taken to keep the food
at the temperature stated until all had been fed.
In two cases in which the hot food was given, the potato was
kept in a dish surrounded by a large quantity of water at 50 to
55 C. during the period of feeding, and the animals were fed from
a spoon. In the other cases the food was given by means of a
syringe, and was delivered into the stomach at a temperature of
approximately 60 C. The cold food was fed in a frozen condition,
and reached the stomach in frozen lumps.
The only change from the normal in the rate of discharge of
food, hot or cold, was a slight acceleration, but this change was
so slight as to be inconsiderable. In none of the cases was there
observed any notable variation from the usual peristalsis.
In a series of X-ray observations made by C. K. Metcalf, hot
and cold applications applied from one to forty minutes to the
abdomen of healthy cats produced no appreciable alteration
in gastric peristalsis. It continued without interruption and
without measurable change of rate. These results are quite in
harmony with the statement of Lommel 40 regarding his similar
experiments on dogs. On the other hand, as Murphy and I have
126 THE MECHANICAL FACTORS OF DIGESTION
reported, 41 excessive cooling of the stomach and intestines, by
introducing cold sterile salt solution into the abdominal cavity,
may be followed by increased activity of intestinal peristalsis.
But this is a procedure causing changes of temperature in the
bowel too great to be produced by any external applications.
/" The conclusion seems justified that changes in the temperature
/ of the food do not influence, in healthy animals, for any consider-
able time, either gastric peristalsis or the rate of discharge from
I the stomach.
All the statements made thus far regarding the action of the
pylorus have had reference to conditions not attended by any
8 4 1 2 3 4 5 6
The continuous line represents the normal curve for potato ; the dot line, the
typical condition immediately following intestinal operation near the
pylorus. Gastric peristalsis was seen at every observation after the first
pathological change. When pathological states arise, however,
the normal action may be profoundly altered.
An illustration of such disturbance of the functions of the
pyloric sphincter was given in the observation made by Murphy
and myself directly after high intestinal section and suture.
Gastric peristalsis was not interfered with, but for almost six
hours after recovery from anaesthesia the pylorus remained
tightly closed against the peristaltic pressure, and did not permit
the food (potato) to pass into the injured gut 42 (see Fig. 20). As
we pointed out, there is a remarkable coincidence between the
period of delay of the discharge from the stomach and the period
required for the primary cementing of intestinal wounds.
Hedblom and I were interested to learn whether any effect on
gastric discharge could be demonstrated after causing irritation
CORRELATING FUNCTIONS OF THE PYLORUS 127
of the colon. The irritation was produced by injecting a few
drops of croton-oil into the caecum through a small median in-
cision in the abdominal wall. The operation, performed under
ether, did not cause any subsequent signs of discomfort in the
animals. The next day they were fed the standard potato, and
observed. Comparison of the standard curve for potato with the
curve representing the average figures of four cases in which the
colon was irritated (Fig. 21) shows at once noteworthy differ-
ences. Not only was the gastric discharge much slower when the
colon was irritated, but the passage of the food through the small
intestine was greatly retarded. The normal curve drops mainly
because of the passage of material into the large intestine. When
the colon was irritated, the curve failed to drop throughout eight
" >2 1 2 3 4 5 6 78
The heavy line is the normal curve for potato ; the light line, the curve after
croton-oil has been injected into the colon.
hours, whereas the normal curve begins to drop at the end of two
hours. Normally, potato begins to appear in the colon at the
end of two or three hours ; under the conditions of the present
experiment, however, it did not appear in the colon until six or
seven hours had elapsed. In all cases food was still present in the
stomach at the end of seven hours, though normally the stomach
is emptied of most of this food in about three hours.
Whether injury to the upper small intestine, and irritation of
the colon, affect gastric evacuation through an alteration of
gastric secretion has not been ascertained. There are patho-
logical conditions of the stomach, however, in which gastric
secretion is disturbed, and in which the acid control of the pylorus
certainly is in abeyance. Cohnheim has described a dog which,
128 THE MECHANICAL FACTORS OF DIGESTION
though recovering from gastric catarrh and possessed of a good
appetite, still secreted no gastric juice. When meat was fed, it
passed through the pylorus in a short time wholly undigested.
Thus the small intestine was overwhelmed with a mass of unpre-
pared material, and exposed in turn to the possibility of a
secondary disturbance of its own functions. 43
In achylia gastrica, likewise, the absence of acid does not lead
to a retention of food in the stomach ; indeed, it is likely to depart
with unusual rapidity. But evacuation in the absence of an acid
reaction is only one problem to be settled either in achylia
gastrica or in such cases of gastric catarrh as that instanced
by Cohnheim. Pancreatic secretion without the natural acid
stimulus in the duodenum needs quite as much to be investigated
As shown by these examples, only after the discovery of natural
relations is the character of disturbed relations revealed. If in
spite of disturbed relations the processes concerned continue to be
serviceable to the organism as a whole, an adaptation to the new
conditions must have occurred. The ability of organs to adapt
their functioning gradually to pathological states is well known in
many instances. This adaptation, however, must be studied by
itself as a special subject. Thus, after the normal physiology of
the pylorus is made clear, it becomes of interest to know to what
extent and in what manner disturbances in the stomach and
duodenum are attended by changes in the pyloric reflex which are
compensatory. The fact that compensations may occur is not an
argument against the normal functioning. The activities
occurring in the pathological absence of gastric juice do not affect
the great array of evidence in favour of the normal acid control of
the pylorus, just as compensated aortic regurgitation does not
prove that the semilunar valves have no function. We are
thoroughly justified, therefore, in supporting, by all the favour-
able evidence here reviewed, the conclusion that acid above opens
and acid below closes the pyloric passage.
1 Tobler, Ztschr. f. physiol. Chem., 1905, xlv., pp. 197, 198 ; Lang, Biochem.
Ztschr., 1906, ii., p. 240.
2 Khigine, Arch, des 8c. Bid., 1895, ill, p. 461.
3 Pawlow, The Work of the Digestive Glands, London/ 1902, pp. 97, 103 -
also Fermi, Arch. f. Physiol., Suppl., 1901, p. 76.
4 Lintwarew, Biochem. Gentralbl., 1903, i., p. 96.
CORRELATING FUNCTIONS OF THE PYLORUS 129
5 Boldireff, Centralbl. /. Physiol., 1904, xviii., p. 457.
6 Cohnheim, Physiol. d. Verdauung u. Ernlihrung, Bsrlin, 1908, p. 168.
7 Dolinsky, Arch, des Sc. Biol., 1895, iii., p. 424.
8 Volhard, Ztschr. f. klin. Med., 1901, xlii., p. 429.
9 Levites, Ztschr. f. physiol. Ohem., 1906, xlix., p. 276.
10 Levites, loc. cit., p. 279.
1 Moore and Rockwood, J. Physiol., 1897, xxi., p. 64.
12 Pawlow, loc. cit., p. 51.
13 Openchowski, Centralbl. f. Physiol., 1899, iii., p. 4 ; Oser (Ztschr. /. klin
Med., 1892, xx., p. 288) states that vagus stimulation completely closes the
open pylorus. See also May, J. Physiol., 1904, xxxi., p. 270.
4 Moritz, Ztschr. f. Bid., 1901, xlii., p. 584.
15 See Gley and Rondeau, Oompt. rend. Soc. de Bid., Paris, 1893, xlv., p. 517 ;
Roux and Balthazard, Arch, de Physiol., 1898, xxx., p. 90.
16 Moritz, loc. cit., p. 589 ; also Carnot and Chassevant, Gompt. rend. Soc. de
Biol., Paris, 1906, lx., p. 866.
17 Pawlow, loc. cit., p. 94.
L8 Cannon, Am. J. Physiol., 1904, xii., p. 399.
19 London and Sulima, Ztschr. f. physiol. Ohem., 1905, xlvi., p. 233.
20 Pawlow, loc. cit., p. 96.
21 London and Sulima, loc. cit., pp. 215, 220.
12 See Fermi, loc. cit., p. 59.
23 London and Sulima, loc. cit., p. 212.
24 Moritz, loc. cit., pp. 589, 590.
25 See Chittenden, Mendel, and Jackson, Am. J. Physiol., 1898, i., p. 207.
26 Pawlow, loc. cit., pp. 138, 139.
17 Katschkowski, Arch. /. d. ges. Physiol., 1901, Ixxxiv., p. 48.
28 Cohnheim, Munchen. med. Wchnschr., 1907, liv., p. 2581.
!9 Roux and Balthazard, Arch, de Physiol., 1898, xxx., p. 91.
30 Moritz, Verhandl. d. deut. Naturforscher und Aerzte, 1893, p. 25.
51 Cannon, Am. J. Physiol., 1898, i., p 359.
J2 Cohnheim, Munchen. med. Wchenschr., 1907, liv., p. 2582.
33 Liideritz, Arch. f. path. Anat., 1889, cxvi., p. 53.
34 Oser, Ztschr. f. klin. Med., 1892, xx., p. 287.
35 Miiller, Ztschr. f. didt. und physikal. Therap., 1904, viii., p. 587.
56 Schiile, Ztschr. f. klin. Med., 1896, xxix., p. 81.
37 Leven and Barret, Eadioscopie Gastrique et Maladies de VEstomac, Paris
1909, p. 73.
38 Winternitz, " Physiologic Bases of Hydro therapy," in A System of Physio-
logic Therapeutics, Philadelphia, 1902, ix., p. 41.
39 Quincke, Arch. f. exper. Path, und Pharmakol., 1888, xxv., p. 380.
40 Lommel, Munchen. med. Wchnschr., 1903, L, p. 1634.
11 Cannon and Murphy, Ann. Surg., 1906, xliii., p. 531.
42 Cannon and Murphy, loc. cit., p. 515.
43 Cohnheim, Physiol. d. Verdauung u. Erndhrung, Berlin, 1908, p. 23.
THE MOVEMENTS OF THE SMALL INTESTINE
THE longest portion of the alimentary canal is the small intes-
tine. Its relative length varies, however, in different animals,
and this variation is related interestingly to the character of the
food. Carnivorous animals as a rule have a relatively shorter
small intestine than do herbivorous animals. Thus in the cat the
tube is about three times the length of the body, in the dog four
to six times, whereas in the sheep and goat it may be more than
twenty-seven times the body-length. 1 The extensive surface
provided by this length of gut is further augmented in many
animals by the folds which project inward and form the " valvulse
conniventes." And the mucosa covering the interior of all this
surface has its area again enormously increased by being disposed
on the finger-like villi, which project inward in countless myriads
towards the lumen. Between this vast extent of mucosa and
the outer longitudinal and inner circular muscle of the intestine
lie venous and lymphatic plexuses, and the radicles of larger
vessels belonging to these two systems.
Digestive juices secreted in the mouth, the stomach, and in the
duodenum, have already accomplished marked alterations in
the food by the time it is pushed on into the ileum. Yet in this
extensive region the final changes occur, and while here the
nutritious portions of the food are almost completely digested
and absorbed. The small intestine, therefore, is the very centre
of the essential activities on which the body depends for
The mechanical factors of digestion, as we have seen, have the
functions of propelling the food, mixing it with the digestive
juices, and exposing the digested food to the absorbing mucosa.
These functions, all of them of first importance in co-operation
with digestion and absorption, are accomplished in the small
THE MOVEMENTS OF THE SMALL INTESTINE 131
intestine by two main types of activity by the peristaltic wave,
and by rhythmic contractions of the intestinal musculature.
When an animal is first fastened to the holder, after the food
has been distributed through the intestine as shown in Fig. 6,
the noteworthy condition in most or all of the loops is the total
absence of movement. If the animal remains quiet, however,
only a few moments elapse before peculiar motions appear in one
or another of the loops, or perhaps in several, and last for some
time. These motions consist in a sudden division of one of the
long, narrow masses of food into many little segments of nearly
equal size ; then these segments are again suddenly divided,
and the neighbouring halves unite to make new segments, and
so on, in a manner to be more fully described. I have called
this process the " rhythmic segmentation " of the intestinal
FlG. 22. DlAGKAM REPRESENTING THE PROCESS OF RHYTHMIC
Lines 1, 2, 3, 4, indicate the sequence of appearances in a single loop. The
dot lines represent the regions of division. The arrows show the relation of
the particles to the segments they subsequently form.
contents. 2 Further observation reveals peristalsis here and
there. These phenomena are now to be considered in detail.
Rhythmic segmentation is by far the most common and the
most interesting mechanical process to be seen in the small
intestine. The nature of the process may best be understood
by referring to the diagram, Fig. 22. A mass of food is seen
lying quietly in one of the intestinal loops (line 1, Fig. 22).
Suddenly an undefined activity appears in the mass, and a
moment later constrictions at regular intervals along its length
cut it into little ovoid pieces. The solid string* is thus quickly
transformed, by a simultaneous sectioning, into a series of fairly
uniform segments. A moment later each of these segments is
divided into two particles, and immediately after the division
* In lieu of any better short expression, " string " of food is used to designate
the long, slender mass of the contents lying in a loop of the intestine.
132 THE MECHANICAL FACTORS OF DIGESTION
neighbouring particles (as a and b, line 2, Fig. 22) rush together,
often with the rapidity of flying shuttles, and merge to form
new segments (as c, line 3, Fig. 22). The next moment these
new segments are divided, and neighbouring particles unite to
make a third series, and so on.
At the time of the second segmentation (line 3, Fig. 22) the
particles at the ends of the row are left small. Observation
shows that these small pieces are not redivided. The end piece
at A simply varies in size with each division ; at one moment it
is left small, at the next moment it is full size from the addition
of a part of the nearest segment, and a moment later is the small
bit left after another division. The end piece at B (probably the
rear of the mass) shoots away when the end mass is divided, and
is swept back at each reunion to make the large end mass again,
only to be shot away and swept onward with each recurrence of
The process of repeated segmentation thus continues, with
the little particles flitting toward each other, and the larger
segments shifting to and fro, commonly for more than half an
hour without cessation. From the beginning to the end of a
period of segmentation the food is seen to have changed its
position in the abdomen to only a slight extent. Whether this
change is a passing of the food along the loop, or a movement of
the loop itself, it is impossible to tell from the shadows on the
screen. The change of position, however, is much less con-
spicuous than the lively division and redi vision which the mass
suffers so many times from the busy, shifting constrictions.
From this typical form of rhythmic segmentation there are
several variations. Sometimes, and especially when the mass
of food is thick, the constrictions do not make complete divisions,
and are so far apart that the intermediate segments are relatively
large. Moreover, the constrictions do not take place in the
middle of each segment, but near one end. In another variety
of segmentation the food is divided, and the first divisions then
subdivided, before any reunion occurs. This form of segmenta-
tion is fairly typical for the constrictions seen in a small mass
advancing through the intestine. Sometimes the divisions occur
in the middle of a long string of food, and leave the ends wholly
A remarkable feature in the segmentation of the food is the
rapidity with which the changes take place. The simplest way
THE MOVEMENTS OF THE SMALL INTESTINE 133
of estimating the rate is to count, not the number of times the
partition of the food recurs in the same place, but the number
of different sets of segments observed in a given period. Thus
in Fig. 22 the appearances of lines 2, 3, 4, etc., would be counted,
and not merely lines 2, 4, etc. Repeated observations have
shown that the rate of division in long, thin strands of food may
commonly be as high as twenty-eight or thirty times in a minute
i.e., a change from one set of segments to another set every
two seconds, and a return of the same phase every four seconds.
In some cases the rate is as low as eighteen to twenty-three times
per minute. The larger masses seem to be associated with a
Segmentation frequently continues for more than half an hour ;
in one instance it was seen persisting, with only three short periods
of inactivity, for two hours and twenty- two minutes. At the
rate of thirty segmentations per minute, it is clear that a slender
string of food may commonly undergo division into small par-
ticles more than a thousand times while scarcely changing its
position in the intestine.
This process, thus far described as I saw it in the cat, I have seen
also in the white rat and in the dog. 3 In the white rat the changes
occurred at the rate of forty-four to forty-eight per minute ; in the
dog, sometimes at a rate between eighteen and twenty-two, at
other times between twelve and fourteen, per minute. The seg-
menting movements I have never seen in the rabbit, but, instead,
rhythmic to-and-fro shiftings of a mass along the lumen of the
gut, rapidly repeated for many minutes. In 1905 I reported
having heard rhythmic sounds in the human intestine at the
rate of seven or eight per minute, and gave reasons for believing
that this rhythm was caused by segmenting movements. 4 Two
years later Hertz was able to observe the process of segmentation
in man. " The shadow of the short length of small intestine,
at first of uniform thickness, became constricted in its centre ;
the constriction increased until the single shadow was more or
less completely divided into two. Then each half underwent a
similar division, but the two central segments of the four pro-
duced by the second division joined together. The new central
segment then divided again, the segmentation continuing, in one
case, at the rate of ten divisions in a minute and a half." 5 This
rate is approximately seven divisions per minute, which is about
the rate of the rhythmic sounds which I had heard.
THE MECHANICAL FACTORS OF DIGESTION
The process of segmentation in cats has been observed also by
Hertz 6 and by Magnus, 7 both of whom used the X-ray method ;
and it has been seen in dogs with opened abdomen by Henderson, 8
who likened the appearance to that which would be presented by
a column of large frog-hearts beating in such mutual co-ordination
that, while numbers 1, 3, 5, and 7, are in systole, 2, 4, 6, and 8,
are in diastole, and vice versa. From all this evidence, it is clear
that the process is one whose existence is thoroughly well
The appearance of the exterior of the small intestine while
this process is occurring is shown in Fig. 23. This photograph
was taken after the animal, well anaesthetized, had had its spinal
cord pithed below the brachial
region, and its abdomen opened
under warm physiological salt
solution. Active digestion was in
progress. A noteworthy feature of
the rings of constriction, which
contrast with the peristaltic wave,
is their narrowness. As these
narrow constrictions occur the re-
gion becomes pale and bloodless.
The effect of the process of rhyth-
mic segmentation proves it an
admirable mechanism. The food
over and over again is brought
into closest contact with the in-
testinal walls by the swift, knead-
ing movement of the muscles. Thereby not only is the undi-
gested food intimately mixed with the digestive juices, but
the digested food is thoroughly exposed to the organs of
absorption. Mall 9 has shown that contraction of the intestinal
wall has the effect of pumping the blood from the sub mucous
venous plexus into the radicles of the superior mesenteric vein,
thus materially aiding the intestinal circulation. Moreover,
lacteals loaded with fat will in a few moments become empty
unless the intestine is slit lengthwise so that the muscles cannot
exert compression. 10 The rhythmic constrictions, therefore,
both propel the blood in the portal circulation and act like a
heart in promoting the flow of lymph in the lacteals. This
single movement, with its several results, is another excellent
FIG. 23. A PHOTOGRAPH OF
THE SMALL INTESTINE SEG-
MENTING ITS CONTENTS.
THE MOVEMENTS OF THE SMALL INTESTINE 135
example of bodily economy. The repeated constrictions
thoroughly churn the food and digestive fluids together, plunge
the absorbing mucosa into the very midst of the food-masses,
and also, by compression of the veins and lacteals of the intes-
tinal wall, serve to deport through blood and lymph channels
the digested and absorbed material.
There is little doubt that segmentation is due to an activity
of the intestinal musculature similar to that which causes the
so-called " pendulum movement." This activity is characterized
by a gentle swaying motion of the coils, and is accompanied by
rhythmical contractions. Observers have described it variously
as shortenings and narrowings of the gut, rhythmically repeated
at nearly the same intestinal circumference ; n as alternating
to-and-fro movements of the long axis without changes in the
lumen ; 12 as local or extensive periodic contractions and relaxa-
tions mainly of the circular musculature ; 13 and as waves in-
volving both muscular coats of the intestine, and travelling
normally from above downward at a rapid rate (2 to 5 centi-
metres per second). 14 The pendulum movements have been
seen in the dog and in the rabbit and cat. 16 In the cat, Bayliss
and Starling noticed that, when the lumen of the gut was dis-
tended by a rubber balloon, there appeared rhythmical contrac-
tions, which nearly always were most marked at about the
middle of the balloon i.e. t the region of greatest tension.
The segmenting movements, of course, do involve changes in
the lumen, and they do not appear as waves. In these respects,
therefore, they do not fit certain descriptions of the pendulum
movements. Segmentation is, however, a local contraction and
relaxation of the intestinal musculature ; and its occurrence,
usually at a point midway between two rings of constriction,
where the compressed food stretches most forcibly the relaxed
circular and longitudinal muscles, indicates that it is a response
to the increased local tension.
The best known of the intestinal movements is the peri-
staltic wave. It is observed in two forms : as a slowly advancing
contraction which creeps through a short distance in a coil,
and as a swift movement sweeping without pause for much
longer distances along the canal. The first form of the wave
merely transports nutriment from one region to another near
by, thus utilizing different areas of the mucosa for secretion
and absorption ; the second form, which may glide swiftly from
136 THE MECHANICAL FACTORS OF DIGESTION
one end of the canal to the other, has the effect of clearing it of
its contents. The first form may retain the unqualified term
peristalsis ; the second may be distinguished by the term " rush-
ing peristalsis," or " peristaltic rush," as suggested by Meltzer
and Auer. 16 I
The normal peristaltic wave is slow. Its rate has been
variously stated as 1 or 2 centimetres per minute, or even
slower. 17 By most observers the wave is said to move always
in one direction from stomach to colon.
The contraction that occurs in rhythmic segmentation is
narrow, involving hardly a centimetre of the circular coat ; the
contraction that occurs in peristalsis, on the contrary, extends
along the canal for 4 or 5 centi-
metres. The difference can be
clearly seen by comparing Figs. 23
and 24. A much larger number
of circular fibres are evidently
engaged when food must be pushed
through the canal than are active
in any single segmenting contrac-
With the X rays it is commonly
impossible to see how a moving
mass of food is related to the end
of the intestine, and therefore it
is impossible to state absolutely
whether peristalsis or antiperistal-
sis is active. The relations can be
seen with the fluorescent screen only near the stomach and
near the ileo-colic valve. The evidence that advancing peristalsis
alone occurs normally is, as we shall see, so overwhelming
that we can safely assume that, when food is moving in loops
not visibly related to fixed points, it is moving onward.
When a mass of food has been subjected for some time to the
segmenting activity of the intestine, the separate segments,
instead of being again divided, may suddenly begin to move
slowly along the loop in which they lie. That this movement
is not a swinging of the coil as a whole, but a peristaltic advance
of separate rings of its circular musculature, is made probable by
the fact that the succeeding segments follow along the same
path their predecessors have taken. The advance of the little
FIG. 24. A PHOTOGRAPH OF A
PERISTALTIC WAVE ON THE
The wave was pushing material
into the colon.
THE MOVEMENTS OF THE SMALL INTESTINE 137
pieces may continue for 7 or 8 centimetres, when finally the
front piece stops or meets other food. Then all succeeding pieces
are swept one by one into the accumulating mass, which at last
lies stretched along the intestine, a solid string manifesting no
sign of commotion.
Another form of slow peristalsis is frequently observed when
the food is pushed forward, not in small divisions, but as a
large lump. The relatively long mass of food is first crowded
into an ovoid shape as the forward movement begins. The
next moment it is indented in the middle by a circular constric-
tion, which spreads it into two portions along the loop. Now
both portions may be cut in two. The whole mass is at once
swept together again, and slightly beyond its first position,
whereupon the segmenting process is repeated. Thus, with
many halts and interruptions, the food slowly advances.
A slight variation of the combined peristalsis and segmentation
just described is seen when the amount of food is greater and
extends farther along the intestine. Under such circumstances,
as the mass moves forward, there appears just in front of the
rear end, where the distension is greatest, a constriction which
separates a piece from the main body, and causes it to shoot
backward sometimes through the distance of a centimetre. The
main body meanwhile is not disturbed. No sooner has the rear
section been shot away than it is swept forward again into union
with the rest of the food, and the whole mass then advances
until another interfering constriction repeats the process.
Peristalsis may become disturbed after a surgical operation
requiring the intestine to be severed and sutured. Clinical
experience has not determined whether end-to-end or lateral
methods of uniting the divided intestine are preferable. In
favour of the lateral junction, the argument has been urged 18
that it permits conveniently a desirable large contact of serous
surfaces a condition said not to be possible in the end-to-end
union without dangerously narrowing the lumen of the canal,
and without liability of producing death of the tissues from
pressure on mesenteric vessels. The claims have been made,
also, that lateral anastomosis can be used without regard to the
size of the intestinal parts to be united, and that with it the
opening between the two intestinal ends can be made as extensive
as may be wished. On the other hand, the tendency of all
lateral unions of parts of the alimentary canal to become nar-
138 THE MECHANICAL FACTORS OF DIGESTION
rowed has been repeatedly recognized. And studies on animals
have shown that indigestible substances, such as straw and hair,
may accumulate at the point of lateral union and block the
passage. 19 Such a condition, however, has never been cited as
true of man whose diet is carefully watched after operation.
Theoretically there are possibilities of functional defect both
in the end-to-end and in the lateral union. In the end-to-end
junction two severed ends of the intestine are sewed together.
The transverse cutting of the gut destroys locally the mechanism
governing peristalsis, and under these conditions there might
be stasis of the food in the region of union. In lateral anas-
tomosis circular muscle fibres of the canal are cut the fibres
which force the food onward. Contraction of the circular
muscle singly in either one or the other of the overlapping
intestinal ends cannot then force the food onward, but must
simply shift the food over into the inactive part. For propulsion
of the contents of this region there must be a co-ordinated,
advancing contraction of the circular fibres simultaneously in
the two apposed loops. Undigested material is commonly found
as a remnant in the region of lateral junction. Is there in this
region a stasis of the normal food material ?
In order to test the possibilities of functional disturbance,
F. T. Murphy and I made intestinal sections and resections in
animals, and then united the severed gut either end-to-end or
laterally. For two reasons, the operation was performed as near
as possible beyond the delicate fold of mesentery which holds
the end of the duodenum in place : the point is fixed so that
the position of the suture can be recognized fairly accurately
in observations with the X rays ; and it is so near the stomach
that the observer does not have to wait long after feeding the
animal before the food reaches the region he wishes to study.
Observations were made on different animals one, four, seven,
and ten days after end-to-end union of the intestine. In no case
was the slightest evidence observed of stasis of the food in the
region of operation. The food was passed along that part of the
intestine as it was passed along other parts.
The results were quite different with lateral anastomosis.
Animals permitted to live ten days or two weeks showed usually
the condition already mentioned a more or less complete
blocking of the canal by accumulated hair and undigested
detritus at the opening between the apposed loops. To see
THE MOVEMENTS OF THE SMALL INTESTINE 139
whether there was a stoppage of the normal food at the anas-
tomosis, animals were operated upon and carefully fed for four
days on food with little waste. Then they were given a rather
thin boiled starch (4 grammes of starch to 100 c.c. of water),
with an admixture of bismuth subnitrate. As long as this food
was passing through the intestine, some of it was always present
at the junction. And when almost all the unabsorbed material
was in the colon, there still remained a large mass filling the
widened lumen where the coils were laterally joined. Observa-
tion the next day showed the mass still at the anastomosis.
Autopsies on these animals proved that the stasis of the food
was not due to previous accumulation of indigestible waste.
The region of junction was filled, not with hard material, but
with a pasty stuff, in physical characteristics much like that
seen ordinarily in the small intestine, and certainly capable of
easy peristaltic transportation through the gut. In these cases
the two apposed coils evidently did not co-operate to propel
the enclosed food. Any food forced through the region of union
was propelled by a push from behind, a push exerted by peri-
stalsis of the intact Wall driving new masses from time to time
into the accumulation at the junction. And when no food
remained to act as an intermedium between the accumulated
mass in the widened lumen and the pressing peristalsis of the
intact gut, there was nothing to continue the propulsion through
the common chamber, and the mass was left unmoved.
Inasmuch as stasis was not observed at any time after end-
to-end union of the severed gut, whereas after lateral anastomosis
ordinary food was stagnant in the region of junction, it is clear
that, other things being equal, the end-to-end union is preferable
to the lateral for rapid return of the normal functioning of the
canal. In time after lateral union the canal may become changed
from a crooked to an almost straight tube. 20 As such an altera-
tion takes place, possibly there occurs a restitution of the func-
tional efficiency of the joined parts. The absence of this
functional efficiency, however, certainly for some days, and prob-
ably for weeks, after the operation, renders lateral anastomosis
not an ideal procedure. The dangers of the end-to-end union,
on the other hand, have been largely obviated by recent improve-
ments in the technique of intestinal surgery.
As to the claim made for lateral anastomosis, that it permits
the opening between the two intestinal ends to be as large as
THE MECHANICAL FACTORS OF DIGESTION
desired, we must recognize that the more extensive the cutting
of the circular muscle, the greater is the interference with peri-
staltic activity ; and also, that the condition to be desired is
not so much a large opening as an opening that functions
Although our experiments led us to differ from the opinion of
Ashton and Baldy, 21 that lateral union is always desirable, we
agree with them as to the danger of allowing the blind ends of the
intestinal loops in lateral union to extend beyond the anastomotic
opening. If each extends beyond the opening, the end of the
proximal loop, in our experience, is in danger of becoming packed
with hardened waste, and the end of the distal loop is likely to
invaginate until the invaginated portion
fills the lumen in the region of the anasto-
mosis, and produces obstruction (see Fig. 25).
The blocking of the lumen in our ex-
periments, when the intestine was united
laterally, led us to make observations on
the movements of the canal in case of
obstruction. Even when the obstruction
was within 25 centimetres of the pylorus,
it did not retard the discharge of food from
the stomach. As the food collected in the
obstructed gut, there was seen in every
instance a remarkable exhibition of intestinal
activity. Ordinarily in the small intestine,
as I have stated, segmentation is a much
more common activity than peristalsis. Over and over again,
however, in these cases of obstruction, the food was pushed
toward the obstruction by repeated waves of peristalsis. Noth-
nagel reported 22 increased activity of like character above an
experimental obstruction in the small intestine of the rabbit.
The moving constrictions in our cases were evidently powerful,
for as they advanced, the walls of the canal in front were bulged
widely by the compressed contents ; and when the peristaltic
ring could no longer withstand the pressure it was causing,
the contents squirted back through the advancing ring for some
distance along the gut. No sooner had one wave passed over
the accumulated food to the point of blocking than another
would start and go over the same course again, or a series of
rhythmic contractions would occur, dividing the contents into
FIG. 25. DIAGRAM
SHOWING EFFECT OF
Too GREAT OVER-
LAPPING OF LOOPS
IN LATERAL UNION.
Proximal loop (A) im-
pacted, distal loop
THE MOVEMENTS OF THE SMALL INTESTINE 141
large segments, and sometimes separating them widely from
one another. The numbered parts in Fig. 26 are tracings of
the sequence of changes in the shadows of the food during a few
moments of observation about an hour and a half after feeding
boiled gluten-flour. Similar activities, though not so violent,
were seen an hour previous. Other cases, observed during a
longer period, showed this same vigorous squeezing and churning
of the accumulated food, alternating, however, with periods of
From these observations it is clear that, when the intestine
is obstructed, an activity is aroused which must tend to com-
FIG. 26. TRACINGS OF THE SHADOWS OF THE CONTENTS OF AN OBSTRUCTED
LOOP OF INTESTINE, SHOWING THE SEQUENCE OF CHANGES THROUGH
SEGMENTATION AND PERISTALSIS DURING A FEW MOMENTS OF OBSERVATION
ABOUT AN HOUR AND A HALF AFTER FEEDING.
In the condition represented by No. 4 there was repeated peristalsis, with
regurgitation of the food through each advancing peristaltic ring.
pensate for the obstruction, and work to obviate it. These
results support the contention made in the discussion of gastro-
enterostomy, that kinks and sharp bends in the intestine normally
have food forced through them by peristalsis. A kink was
artificially produced by turning a loop back on itself for about
4 centimetres, and sewing together the surfaces in contact.
Observation five days later proved that the food was pushed
around the very sharp bend of the tube by the vigour of the
The possibility of waves moving in either direction along the
gut anyone can readily prove by repeating Engelmann's observa-
tion on the intestine of an animal recently killed. 23 To what
142 THE MECHANICAL FACTORS OF DIGESTION
extent the conditions in reversed loops may become similar to
those in the dead animal is not known. That antiperistalsis
does not occur in the small intestine seems to be proved by
Mall's experiment 24 of reversing a portion, sewing it in place,
and then rinding that undigested material did not pass the
reversed region, but collected at the upper end. Other observers, 25
after reversing various lengths of the gut, have confirmed Mall's
conclusion that peristalsis does not reverse in the reversed por-
tion, but they have found further that thoroughly digestible
food can be pushed through reversed loops, when not too long,
without any noticeable difficulty. The addition of solid in-
digestible stuff, such as pieces of straw and bone, at once caused
stasis at the upper junction.
Opposed to the conclusion that there is no antiperistalsis of
the small intestine is the clinical evidence that in cases of in-
testinal obstruction continued vomiting of offensive decomposed
material may occur after the stomach has been repeatedly
washed the so-called " fsecal vomiting."
In relation to this conflict of evidence, our observations on
an animal with about 20 centimetres of the intestine reversed
just beyond the duodenal band are of interest. The first
observation was made six days after the operation. At the
autopsy not long thereafter, a heap of indigestible stuff was
found obstructing the canal at the upper suture. With the
X rays the food had been seen again and again leaving the
stomach. After collecting in the duodenum, it moved onward,
with occasional segmentation, through a definite course which
was traced on transparent paper. Finally it began to accu-
mulate in the region of the upper suture. About a half -hour
after ingestion the whole mass began to be tossed about by the
alternating periods of segmentation and peristalsis characteristic
of the state of obstruction. Suddenly the mass was divided near
the enlargement of the upper suture ; then the proximal portion
was moved rapidly back along the course which had been traced,
even up to the pylorus. This reversed movement of the food
was seen repeatedly with perfect distinctness. The method
used did not permit seeing the contractions of the intestinal
wall ; only the effects on the food could be observed. But if
food had been moved forward, as in this instance it was certainly
moved backward, the movement must assuredly have been
attributed to peristalsis.
THE MOVEMENTS OF THE SMALL INTESTINE 143
Further evidence of the possibility of antiperistalsis in the
small intestine has been brought forward by several observers
who, some time after the operation, have watched directly the
activities of a reversed part of the gut. More than three months
after operation, Kelling saw in the exposed intestine the contents
moved towards the colon through the reversed portion by
distinct peristaltic waves. 26 Enderlen and Hess were able to
produce downward peristalsis in a reversed loop by electrical
stimulation. 27 And after a considerable interval had followed the
reversal, Beer and Eggers, 28 and McClure and Derge, 29 reported
seeing peristaltic waves moving distinctly from the upper to the
lower junction. In time, therefore, conditions may arise which
alter the function of the intestinal wall.
The swift wave of peristalsis that may sweep over the entire
length of the small intestine in about a minute, or over extensive
reaches of the gut, was observed first by v. Braam-Houck-
geest 30 in rabbits with exposed intestines, killed by asphyxia.
The confused turnings and squirmings of the coils as the con-
traction rushes along have caused the phenomenon to be desig-
nated as " Rollbewegung " and the " vermicular wave." As
already stated, Meltzer and Auer have suggested the term " peri-
staltic rush " complete or incomplete, according as all or only
part of the small intestine is involved.
This peculiar type of intestinal activity Starling was inclined to
regard as an exaggeration of the rhythmic type 31 ; on the other
hand, Mall placed it in a class by itself and declared that its
service was to rid the intestine rapidly of irritating substances.
That this rushing wave is, however, truly peristaltic in character
was proved by the observation of Meltzer and Auer, that it
consists of a contraction preceded by a completely relaxed section
of the gut, through which the contents are rapidly driven. They
were able to evoke the phenomenon at will in rabbits by intra-
venous injections of pairs of substances producing stimulation
and inhibition of intestinal activity. The most effective pair was
ergot (stimulant) and calcium chloride (depressant). 32
Peristaltic rush probably occurs in conditions of abnormal
irritation of the gut, and may be the characteristic activity when
a purge is given. With the X rays I have seen rapjd peristalsis
produced in the small intestine by injecti .
Under normal conditions, the only simikfr^^cuir^i^^
peristalsis is that frequently observably w^lrt^f^ti^^K^^^;, ^A
144 THE MECHANICAL FACTORS OF DIGESTION
segmented in the duodenum, is carried swiftly onward through a
number of coils before being released.
Having considered the motor activities exhibited by the small
intestine, we may now turn our attention to the mechanical treat-
ment which the food receives in traversing it. As we have
learned, the chyme is not forced from the stomach by every wave
that passes over the vestibule, but only at intervals. When the
pylorus relaxes, the food, under considerable pressure, is squirted
along the duodenum for 2 centimetres or more. Careful watch-
ing of this food shows that usually it lies for some time in the
curve of the duodenum, until, with additions from the stomach,
a long, thin string is formed. While resting in this place it is
exposed to the outpouring of bile and pancreatic juice. All at
once the string becomes segmented, and the process continues
several minutes, thoroughly mixing the digestive juices with the
chyme. In this region the alternate positions of the segments
are sometimes far apart, and the to-and-fro movement of the
particles may be a relatively extensive and very energetic
swinging. Finally, the little segments are united into a single
mass, or formed in groups, and begin to move forward. Peri-
stalsis here, as already mentioned, is much more rapid than
normal peristalsis elsewhere in the small intestine. The masses,
once started, go flying along, turning curves, whisking hither and
thither in the loops, moving swiftly and continuously forward.*
After passing on in this rapid manner for some distance, the food
is collected in thicker and longer strings, resembling the strings
seen characteristically in the other loops. Towards the end of
digestion, the small masses shot out from the stomach, after a few
segmentations, may move on in the rapid course without being
accumulated in a larger mass until the swift movement ceases.
During the first stages of digestion in the cat's small intestine
the food usually lies chiefly on the right side of the abdomen ;
during the last stages the loops on the left side usually contain the
greater amount of food. In these loops the food remains some-
times for an hour or more with no sign of movement. All at once
a mass may begin to undergo division and reunion, division and
reunion, over and over again, in the manner described above as
rhythmic segmentation. After a varying length of time the
activity wanes, and the little segments are carried forward
* If this process is true also of man, the region beyond the duodenum would
naturally be " jejune."
THE MOVEMENTS OF THE SMALL INTESTINE 145
individually and later brought together, or united and moved on
as a single body, or left quietly for some time without further
change. Thus by a combined process of kneading and peristaltic
advance the food is brought to the ileo-colic valve to enter the
In studying the passage of food through the small intestine of
a woman with a fistula at the ileo-colic junction, MacFadyen,
Nencki, and Sieber, 33 noted a considerable variation in the time
between the ingestion of the food and its appearance at the fistula.
Peas, for example, arrived at the colon on one occasion two and a
quarter hours, and on another occasion five and a quarter hours,
after being eaten. Demarquay, 34 who studied a case similar, but
apparently less normal, reported also a wide variation in the time
of the first appearance of food at the fistula.
The X-ray method as I used it did not permit a statement of
the moment when the food first entered the colon ; only the first
regular observation after food had entered could be reported.
Since the observations were an hour apart, the results, except in
their negative aspect, were not as exact as could be desired. The
following figures, therefore, represent for each foodstuff the
number of cases in which, at the hours stated, a shadow was first
seen in the colon :
Hours after feeding .. ..2 3 4 5 6 7 8*
Carbohydrates (sixteen cases) 1 6 4 4 1
Proteins (sixteen cases) .. .. 12 2 72 2
Fats (sixteen cases) .. .. 23 7 2 2
This table indicates a variation similar to that observed in man.
Although the mean time after eating at which material reaches
the colon is about four hours for carbohydrates, about six hours
for proteins, and about five hours for fats, the divergence from
the mean in each of the three cases is considerable. Among the
carbohydrates used, the divergence was chiefly due to moistened
crackers, which in four instances arrived at the colon only after
five or seven hours. And among proteins, also, the divergence
was chiefly due to one food boiled haddock which reached the
colon about two hours earlier than most of the other proteins.
As a general statement, we may say that in the cat carbohydrates
reach the large intestine about one hour before fats, and about
two hours before proteins. After time is allowed for the later
* In two cases no material had reached the colon at the end of seven hours ;
they are regarded as belonging to an eight-hour class.
146 THE MECHANICAL FACTORS OF DIGESTION
start of proteins from the stomach, the probability still remains
that proteins pass through the small intestine much more slowly
than do carbohydrates, whereas fats have a rate intermediate
between the two.
The relatively rapid movement of carbohydrates through the
canal may be associated with the presence of insoluble cellulose.
Hedblom and I found that coarse, branny food stimulates gastric
peristalsis ; it also passes through the small intestine with unusual
speed. In X-ray observations on man, Hertz noted that after an
ordinary meal a shadow appeared in the caecum after intervals
varying between three and a half and five hours, with an average
interval of four hours and twenty-two minutes. 35 When a horse
eats oats, the waste may go through the much longer intestine of
that animal in less time. 36 The greater length of the small
intestine in herbivorous animals compared with carnivorous,
mentioned at the beginning of this chapter, is possibly associated
with the greater rapidity of movement of plant food and the
necessity of digesting out the valuable contents from cellulose
In experimental animals I have never seen any marked delay
in the passage of food through the small intestine except under
experimentally disturbing conditions, such, for example, as
irritation of the colon (see p. 127). Hertz has reported that, in his
observations on human beings, delay in the small intestine has
occurred only in cases of lead-poisoning. If the evacuation of the
bowels is retarded, therefore, and no obstruction of the lumen
exists, the chances are almost wholly in favour of the large
intestine as the place of retention.
1 Fermi and Repetto, Arch. f. Physiol., 1901, Suppl., p. 85.
2 Cannon, Am. J. Physiol., 1902, vi., p. 256.
3 Cannon, Am. J. Physiol., 1903, viii., p. xxi.
4 Cannon, Am. J. Physiol., 1905, xiv., p. 346.
5 Hertz, Guy's Hosp. Rep., 1907, Ixi, p. 409.
6 Hertz, loc. cit., p. 409.
7 Magnus, Arch. /. d. ges. Physiol., 1908, cxxii., p. 216.
8 Henderson, Am. J. Physiol., 1909, xxiv., p. 71.
9 Mall, Johns Hopkins Hosp. Rep., 1896, i., p. 68.
L0 Mall, loc. cit., p. 47.
Ludwig, Lehrb. d. Physiol. d. Mensch., Leipzig and Heidelberg, 1861,
11., p. 615.
12 Raiser, Beitr. z. Kennt. d. Darmbeweg. (Dissertation), Giessen, 1895, p. 7 ;
and Nothnagel, Die Erkrank. d. Darms und d. Peritoneum, Wien, 1898, i.,
Darmbewegung, p. 1.
THE MOVEMENTS OF THE SMALL INTESTINE 147
13 MalUoc. cit., p. 48.
14 Bayliss and Starling, J. Physiol., 1899, xxiv., p. 103.
5 Bayliss and Starling, J. Physiol., 1901, xxvi., pp. 127, 134.
16 Meltzer and Auer, Am. J. Physiol., 1907, xx., p. 266.
17 See Cash, Proc. Roy. Soc., 1886, xli., p. 227.
8 Kiittner, Beitr. z. klin. Chir., Tubingen, 1896, xvii., p. 505.
19 Senn, Ann. Surg., 1888, vii., p. 265 ; and Reichel, Miinchen. med. Wchnschr.,
1890, xxxvii., p. 197.
20 Edmunds and Ballance, Med.-chir. Trans., London, 1896, p. 263.
21 Ashton and Baldy, Med. News, 1891, Iviii., p. 235.
12 Nothnagel, Beitr. z. Physiol. u. Pathol. d. Darmes, Berlin, 1884, p. 28.
23 Engelmann, Arch. f. d. ges. Physiol., 1871, iv., p. 35.
24 Mall, loc. cit., p. 93.
25 See Sabbatani and Fasola, Arch. Itcd. de BioL, 1900, xxxiv., p. 195 ;
Prutz and Ellinger, Arch. /. klin. Chir., 1902, Ixvii., p. 964 ; 1904, Ixxii., p. 415.
26 Kelling, Arch. /. klin. Chir., 1900, Ixii., p. 326.
27 Enderlen and Hess, Deutsche Ztschr. f. Chir., 1901, lix., p. 240.
28 Beer and Eggers, Ann. Surg., 1907, xlvi., p. 582.
29 McClure and Derge, Johns Hopkins Hosp. Bui., 1907, xviii., p. 473.
30 v. Braam-Houckgeest, Arch. f. d. qes. Physiol., 1872, vi., p. 267.
31 Starling, Schcifer's Text-Book of Physiology, Edinburgh and London, 1900,
ii. , p. 329.
32 Meltzer and Auer, loc. cit., p. 281.
13 MacFadyen, Nencki, and Sieber, J. Anat. and Physiol., 1891, xxv., p. 393.
34 Demarquay, L' Union Med., 1874, xviii., p. 906.
35 Hertz, loc. cit., p. 410.
36 See Goldschmidt, Ztschr. f. physiol. Chem., 1887, xi., p. 299.
37 See Cohnheim, Physiol. d. Verdauung u. Erndhrung, Berlin, 1908, p. 33.
THE MOVEMENTS OF THE LARGE INTESTINE
IN carnivorous mammals digestion occurs principally in the
stomach and small intestine ; the caecum is either rudimentary or
absent. In herbivores, as a rule, either the stomach is amplified
and subdivided, as in ruminants, or, if the stomach is simple,
there is usually compensation in a large sacculated colon and
caecum. The caecum is the seat of extensive bacterial fermenta-
tion ; food rich in cellulose may remain in this region for days,
undergoing changes which result in its being utilized by the body. 1
Even when the caecum is of moderate size or rudimentary, as in
the cat, prolonged retention of the material delivered by the small
intestine is provided for in the reversed peristalsis which prevails
in the proximal colon. Food remnants may have begun to enter
the large intestine two or three hours after the food was ingested,
and they may have left the small intestine entirely empty at the
end of seven hours, and yet be found in part in the proximal colon
at the end of twenty-four hours. While stagnating in this
region, rich in bacterial flora, the contents are subjected to
fermentative decomposition, and the last bit of nutriment here
The energetic chemical processes occurring in the small intes-
tine demand a fluid medium. By the salivary and gastric glands
large amounts of fluid are poured out upon the food. This is
augmented by the secretions of the pancreas and liver and the
wall of the gut itself. Throughout the small intestine, although
water is readily absorbed, the digestive products are maintained
in a semi-fluid state. Ease of movement through the canal and
ready exposure of the food for absorption are doubtless thereby
favoured. When the large intestine is reached, however, and
practically all of the serviceable substances have entered the
body, the water is no longer necessary. In the proximal colon,
therefore, water is also removed.
THE MOVEMENTS OF THE LARGE INTESTINE 149
As the waste is crowded onward into the distal colon, it takes
on more and more the peculiar faecal consistency. According to
Roith, 2 the contents of the transverse colon in man are generally
as firm as those of the rectum. As these fsecal accumulations are
periodically pushed into the rectum they are discharged from the
body. The motor activities subserving these various functions
performed by the large intestine we shall now consider.
When, in the cat, the large intestine is full, palpation through
the abdominal wall will demonstrate that the material in the
distal colon usually consists of hard incompressible lumps, while
that in the proximal colon is so soft that the walls of the gut can
be easily pushed together. The condition of the contents in
these two regions seems to indicate a rough division of the large
intestine into two parts, and the mechanical activities of these
two parts verify the differentiation. In the descending colon
the material is gripped by persistent rings of tonic constric-
tion (see Fig. 27). In the ascending and transverse colon and
in the caecum, by far the most common movement is anti-
The first food to enter the colon from the small intestine in the
cat is pressed by antiperistaltic waves towards the cisecum, and all
new food as it enters is also affected by them. The waves follow
one after another in a series like the peristaltic undulations of the
stomach (see Figs. 28 and 32), beginning at the nearest tonic
constriction (Figs. 27 and 32). They rarely run continuously for
a long time. When the colon is full it is usually quiet. The first
sign of activity is an irregular undulation of the walls, then very
faint constrictions passing along the gut toward the caecum. As
they continue coursing over the intestine, they become deeper and
deeper until there is a marked bulging between successive con-
strictions. After these deepest waves have been running for a
few minutes, the indentations grow gradually less marked, until at
last they are so faint as to be hardly discernible. The final waves
are sometimes to be observed only in the neighbourhood of the
Such a period of antiperistalsis lasts from two to eight minutes,
with an average duration of four or five minutes. The periods
recur at varying lengths of time. In one instance a period began
at 1.38 p.m. and was repeated at 2.6, 2.34, 2.55, 3.15, and at 3.36,
when the observation ceased. In another instance a period
began at 2.43 p.m., and was repeated at 2.57 and at intervals of
150 THE MECHANICAL FACTOKS OF DIGESTION
from ten to fifteen minutes thereafter while the animal was being
The waves have nearly the same rate of recurrence as those in
the stomach ; about five and a half waves pass a given point in a
minute. This rate has proved fairly constant in different cats and
FIG. 27. RADIOGRAPH SHOWING THE REGION OF Toxic CONSTRICTIONS
(DESCENDING COLON) AND THE REGION or ANTEPERISTALSIS (TRANSVERSE
AND ASCENDING COLON).
at different stages in the process of digestion. In one case,
however, the waves passed at the rate of nine in two minutes.
The stimulating effect of rectal injections on the movements of
the small intestine has already been mentioned. Enemata have
also pronounced stimulating action on the antiperistalsis of the
colon. Usually, the almost immediate result of a rectal injection
THE MOVEMENTS OF THE LARGE INTESTINE 151
of warm water is the appearance of deep antiperistaltic waves,
which often continue running for a long period. In one case,
after an injection of 50 c.c. of warm water, the waves followed
one after another with monotonous regularity during an observa-
tion lasting an hour and twenty minutes.
Two other movements have been observed in the ascending
colon, but they are rare appearances. The first of these was a
serial sectioning of the contents, noticed in an animal given castor-
oil with the food. A constriction separated a small segment in
the caecum ; another constriction then cut ofi a segment just
above the first, and with the disappearance of the first con-
striction the two separated segments united. A third segmenta-
tion took place above the second, and the changes occurred
again. Thus the whole mass was sectioned from one end to the
other, and no sooner was that finished than the process began
again and was repeated several times. A slight modification of
this movement was observed in a colon containing very little
food. The mass was pressed and partially segmented in the
manner characteristic of the small intestine, and was thus again
and again spread along the ascending colon, and each time swept
back into a rounded form by antiperistalsis. The second of the
two movements mentioned above consisted in a gentle kneading
of the contents. This was caused by broad constrictions appear-
ing, relaxing, appearing, relaxing, over and over again in the
same place. When several of these regions were active at the
same time, they gave the food in the colon the appearance of
a restless undulatory mass. Once a constriction occurred and
remained permanently in one place, while the bulging parts on
either side of it pulsated alternately, at the rate of about eighteen
times in a minute, with the regularity of the heart-beat. Although
these phenomena are remarkable, they are not usual, and are
in no way so important as the antiperistalsis.
The passage of material through the ileo-colic valve seems to
stimulate the colon to activity. As a mass is nearing the valve
the large intestine is usually quiet and relaxed (Fig. 28, 4.00),
though occasionally indefinite movements are to be observed ; and
sometimes just before the mass reaches the end of the ileum the
circular fibres of the colon in the region of the valve contract
strongly, so that a deep indentation is present there. The
indentation may persist several minutes ; it disappears as the
muscles relax just previous to the entrance of new material. The
152 THE MECHANICAL FACTORS OF DIGESTION
mass is now moved slowly along the ileum, and is pushed through
the valve into the colon. The moment it has entered, a strong
contraction takes place all along the csecum and the beginning
of the ascending colon, pressing some of the food onward ; and a
moment later deep antiperistaltic waves (Fig. 28, 4.03) sweep
down from the transverse colon, and continue running until the
caecum is again normally full i.e., for two or more minutes.
These constrictions, passing backward over the colon, do not
force the normal contents back through the valve into the small
intestine again. I have seen hundreds of such constrictions, and
only twice have there been exceptions to this rule once under
normal conditions, when a small mass slipped back into the ileum ;
and at another time when a
large amount of water had
been introduced into the colon.
The X-ray observations on
antiperistalsis of the cat's
proximal colon which I pub-
lished in 1902 3 were confirmed
FIG. 28. TRACINGS SHOWING . iqfu hv Elliott and Barrlav-
CHANGES WHEN FOOD ENTERS THE
COLON, AND ALSO THE FIRST TONIC Smith, who studied the activities
of ^ j
4.00, the colon relaxed as food ap-
proaches in the ileum; 4.03, the men opened under warm salt
colon contracted and traversed by so l u tion. 4 They called atten-
antipenstaltic waves after the food J
has entered. tion also to a fact which had
been overlooked, that Jacobi
had reported, in 1890, colonic aniiperistalsis in the cat,
noticed incidentally during a research on colchicum-poisoning. 6
By the X-ray studies and by the investigations of Elliott and
Barclay-Smith, however, the reversed peristaltic movement of
the proximal colon was definitely established as a normal activity.
These returning waves have now been seen in the dog, 6 in the
rat and guinea-pig, and to some extent in the rabbit, hedgehog,
and ferret. 7 When a well-developed caecum exists, there may be
an interplay between its peristalsis and the antiperistalsis of the
proximal colon, as in the rat ; or, as in the rabbit, the ca3cum
may feed material into the mixing apparatus of the proximal
colon. In the herbivores which they studied, Elliott and Barclay-
Smith found that sacculation of the proximal colon was associated
with churning movements, each sacculus becoming at times the
seat of swaying oscillations. The greater the churning activity
THE MOVEMENTS OF THE LAEGE INTESTINE 153
of the proximal colon, the more marked was the sacculation of its
The colon of man is of the sacculated herbivorous, rather than
of the carnivorous type. As all observations have indicated, the
sign of a proximal colon which mixes and churns its contained
material is a uniform soft consistency of its contents. Only in
the caecum and ascending colon is this condition realized in man ;
the contents of the transverse colon, I have already stated, are
generally as firm as those of the rectum. From the nature of the
contents, Elliott and Barclay-Smith assumed that in man the
material entering the proximal colon " is still delayed by a back-
ward current, still commingled by the activity of the walls of
The support for the view that antiperistalsis occurs in the
human proximal colon is at present inferential. In cases of
caecal fistula, rectal enemata will often traverse the entire length
of the colon, and escape through the artificial opening. In these
cases also, surgeons have endeavoured to stop the faecal discharge
by transplanting the ileum into the transverse colon, and they
have found that the discharge still continues. Indeed, one case is
reported in which the ileum was sewed into the lower end of the
descending colon ; and since the discharge through the fistula in
the caecum persisted, the colon was finally cut across, and closed
immediately above the junction in order to stop the backward
transportation of material. 8 The larger amount of contents in
the proximal colon has also been considered evidence of anti-
peristalsis. Thus, Koith has found that the caecum and ascending
colon contain on an average about twice the amount of material
present in an equal length of transverse colon, and three to five
times as much as an equal length of descending colon. 9 This
observation, however, might be explained by the capacity of the
caecum being greater than any other part of the large intestine, 10
and by its possessing a very thin wall. 11 Significant X-ray
evidence has been brought forward by Stierlin, who has published
radiographs showing that the proximal colon holds part of the
food containing the bismuth salt after the rest has passed on into
the distal colon, 12 and that it retains this material longer than
any other part of the alimentary canal. These observations, I
may state, are in harmony with the conditions in experimental
animals in which antiperistalsis has been demonstrated. Stierlin
has also pointed out that the caecum is the widest part of the
154 THE MECHANICAL FACTOKS OF DIGESTION
entire intestinal canal, and that in this region the separation of
the contents in sacculi or haustra is often absent or only slightly
Although the escape through caecal fistulas of material intro-
duced distally in the colon clearly demonstrates a backward
current in the human large intestine, and although the great
volume of caecal contents and their long retention are indicative
of antiperistalsis, the phenomenon has not yet been seen in man.
Hertz has testified to having watched with the X rays the shadow
of the human colon for various periods in a large number of
individuals, without seeing antiperistalsis. Even when an enema
containing bismuth was introduced under pressure until the
whole colon was visible, he saw no sign of antiperistaltic activity. 14
Much weight should not be given, however, to this negative
evidence, for in all animals in which antiperistalsis of the colon
has been seen, its occurrence has been occasional. In observa-
tions on these animals, I have had experiences that almost
parallel those of Hertz on man. Even in experimental conditions
most annoying failure to evoke antiperistalsis was common in
my experience until the great significance of the tonus ring as a
source of the waves was realized a relation to be considered
later. Possibly when tonic contractions can be produced in the
human colon antiperistaltic waves will be revealed.
Since the circular coat of the ileum is thickened at the junction
with the colon, Keith 15 suggested, in 1903, that in most animals,
probably including man, not merely a mechanical valve, but a
true sphincter, separates the large ard small intestines. The
next year Elliott proved physiologically the existence of such a
sphincter in the dog, by showing that it was subject to special
nervous control different from that of neighbouring parts of the
intestinal tract. 16
Antiperistalsis in the colon gives new meaning and value to the
location of a sphincter or valve at the opening of the ileum. For,
inasmuch as the valve is normally competent, the constrictions
repeatedly coursing toward it force the food before them into a
blind sac. The effect on the contents must be the same as the
effect seen in the stomach when the pylorus remains closed before
the advancing waves. The confined material is pressed upon by
the approach of each constriction ; but since it cannot go onward
in the blind sac, and is, moreover, subjected to increasing
pressure as the constriction comes nearer, it is forced into the
THE MOVEMENTS OF THE LARGE INTESTINE 155
only way of escape i.e., away from the caecum through the
advancing constricted ring. About twenty-five waves in the cat
affect thus every particle of food in the colon during each normal
period of antiperistalsis. The result must be again a thorough
mixing of the contents, and a bringing of these contents into close
contact with the absorbing wall a process which has already
been variously repeated many times in the stomach and in the
small intestine. The last remnants of value in the food,
with some of the water, are here removed ; and the waste is
passed onward into the distal colon to be ejected from the
In 1894, Griitzner 17 published an observation and made an
assumption about which there has since been much controversy.
He stated that when normal salt solution, holding in suspension
hair, powdered charcoal, or starch grains, is injected into the
rectum, it is carried upward into the small intestine, and may
even enter the stomach. These experiments have been repeated
by several observers. Some have confirmed Griitzner's results ;
others have failed, after using most careful methods, to find any
evidence of the passage of the injected material back to the
stomach, and they have declared that the apparent success was
due to carelessly allowing the food of the animal to become con-
taminated with the test materials, so that these were introduced
into the stomach by way of the mouth.
By means of the X rays it is possible to see just what takes
place when a fluid is injected into the rectum. For the purpose
of determining how nutrient enemata are received and acted
upon in the intestines, I introduced in large and small amounts
thin fluid masses and thick mushy masses, in different animals.
The enemata consisted of 100 c.c. of milk, one egg, 10 to 15
grammes of bismuth subnitrate, and 2 grammes of starch, to hold
the bismuth powder in suspension. To make the thick enema, all
these were stirred together and boiled to a soft mush ; to make
the thin enema, all the parts were boiled together except the egg,
which was added after the boiled portion was cooled. The small
amount injected was 25 c.c. ; the large amount almost 90 c.c.,
about the capacity of the large intestine when removed from the
body. The animals were given first a cleansing injection, and
after this was effective the nutrient material was introduced.
In order to make sure of the observation, a control radiograph
was first taken to show no bismuth food present, and other
156 THE MECHANICAL FACTORS OF DIGESTION
radiographs were taken at varying intervals after the injection
to record the course the food was following.
When small amounts of nutrient fluid were introduced, they
lay first in the distal colon. In every instance antiperistaltic
waves were set going by the injection, and the material was
thereby carried to the caecum. When large amounts were
injected, they stopped for a moment in the region between the
second and last third of the colon, as if a constriction existed
there. Then a considerable amount of the fluid passed the point,
and the antiperistaltic waves began their action. In any case
the repeated passing of the waves seemed to have the effect of
promoting absorption, for in the region where they continued
running the shadows became gradually more dim, and finally
the bismuth appeared to be only on the intestinal walls ; in other
regions e.g., in the distal colon the shadows retained their
original intensity. Small injections were never, in my experience,
forced even partially into the small intestine ; but with the larger
amounts, whether fluid or mushy, the radiographs showed many
coils of the small gut filled with the bismuth food.
The pressure required to force the injected material beyond
the ileo-colic sphincter is probably due largely to antiperistalsis
in the colon a factor unknown to both Griitzner and his
opponents. The sphincter which is thoroughly competent for
food coming normally from the small intestine into the large is,
for some unknown reason, incompetent for a substance, even of
the consistency of thick cream, introduced in large amount by
rectum. When the valve first permits the food to enter the
ileum, the fluid pours through, and appears suddenly as a
winding mass occupying several loops of the intestine. The
winding mass is continuous from the valve to the other end ;
antiperistalsis is therefore not visible in the small intestine under
the circumstances of this experiment. The antiperistaltic waves
of the colon, however, continue running ; the proximal colon is
thus almost emptied, and the small intestine more and more
filled with food. After a short time the typical segmenting
movements can be seen in the loops, busily separating the food
into small masses and over and over again dividing and redividing
I have never seen injected material passed back from the colon
as far as the stomach ; but once, about ten minutes after an
injection of 100 c.c. of warm water, the cat retched and vomited
THE MOVEMENTS OF THE LARGE INTESTINE 157
a clear fluid, resembling mixed water and mucus. In the fluid
were two worms, still alive, commonly found in the intestine.
As material accumulates in the proximal colon, we have learned
that it is at first confined there by antiperistaltic waves. With
further accessions, however, the contents naturally must be
pressed more and more into the distal colon. In the early stages
of this accumulation, while the food lies chiefly in the proximal
part, the only activity of the muscular walls is the antiperistalsis.
As the contents extend along the intestine, a deep constriction
appears near the advancing end, and nearly separates a globular
mass from the main body of the accumulation. The contents
of the large intestine progress farther and farther from the
caecum ; meanwhile new tonic constrictions appear, which
separate the contents into a series of globular masses, which are
present chiefly in the distal colon (Fig. 27). Similar appearances
are observable in the terminal portion of the rabbit's colon, in
which deep circular constrictions separate the scybalous masses,
and push them onward by regular peristalsis. Comparing tra-
cings made at rather long intervals (forty-five minutes), I found
that as the colonic contents increased the rings disappeared from
the transverse colon, and were then present with the waste
material in the descending colon. Thus in the cat also these
rings, which seem with short observation to be remaining in one
position, are probably moving slowly away from the caecum,
pushing the hardening contents before them. The contents at
this stage are no longer fluid, and consequently they must offer
considerable resistance to a force pushing them towards the
rectum. It is an advantage to have this pultaceous material pro-
pelled in divisions rather than in a uniformly cylindrical mass,
since the fibres along the length of the mass are thereby rendered
effective. Such seem to be the functions of the persistent rings :
to form the waste matter into globular masses at the end of the
proximal colon, and to push these masses slowly onward.
The rate of progress of material through the large intestine in
man has been studied by Hertz with the X rays. He states that
the time required for each part of the colon ascending, trans-
verse, and descending is about two hours. That is, about the
same period is occupied in passing through the 2 feet of colon
between the caecum and the splenic flexure as through the
22| feet of small intestine. 18 The movements of the human
colon, however, appear to be less active at night than during the
158 THE MECHANICAL FACTORS OF DIGESTION
day. In one individual, for example, a bismuth content was
present at the end of the descending colon eight hours after being
ingested at breakfast ; but when taken at 10.30 p.m. it had reached
only the end of the ascending colon after twelve hours. The
taking of meals also is stimulating to the colon ; by making
tracings hourly after a bismuth breakfast, Hertz found that,
apart from meals, progress through the colon was slow, but that
after each meal there was perceptible advancement of the
contents. More progress occurred, for example, during the
dinner-hour than during the previous four hours. 19
According to Holzknecht, 20 who in two cases was fortunate in
seeing the activities of the human colon by means of a fluorescent
screen, the contents of one section are moved onward into an
empty distal section by a sudden push, lasting only a few seconds.
The haustral segmentation disappeared just before the advance
began, but reappeared at once when the material became settled
in the new position. Holzknecht has suggested that by three or four
such pushes, lasting about three seconds, the whole colon would
be traversed. The functions of the haustra, under these circum-
stances, would probably be concerned with increasing surfaces
for absorption, and not with propulsion of their contents.
The process of clearing the colon is in the cat a process of
gradual reduction of the material present. The first radiograph
in Fig. 29 shows the appearance of material in the colon at
3.11 p.m. Later, with a slow, sweeping movement, the gut
swung around to the position shown in Fig. 29, 3.25. At the
same time the tonic constrictions disappeared, much as the
haustral indentations disappear in man, and were replaced by a
strong, broad contraction of the circular muscle, tapering, the
contents off on either side in two cones. The region of strongest
contraction was apparently drawn downward with the rest of
the gut by a shortening of the descending colon. As the intestine
swung around, more material was forced into the rectum ; and
when the swinging of the intestine stopped, the constriction
which divided the lumen passed slowly downward, and with the
aid of the muscles surrounding the abdominal cavity pushed the
separated mass out of the canal. After the terminal mass had
thus been pushed out, the colon, with the remainder of its con-
tents, returned to nearly its former position (Fig. 29, 3.46).
About two hours afterward this remnant had been spread
throughout the length of the large intestine by means of the
THE MOVEMENTS OF THE LARGE INTESTINE 159
160 THE MECHANICAL FACTORS OF DIGESTION
slowly moving rings. Fig. 27 is a radiograph of the same colon
pictured in Fig. 29 ; the radiograph was taken at 11.50 a.m., and
at 12.15 p.m. the material in the distal colon was forced out in
the manner above described. Within three hours the remaining
portion had been spread into the evacuated region, as shown in
Fig. 29, 3.11.
The manner in which the material is spread from the region of
the antiperistaltic waves into the region of the tonic constrictions
presents a problem. During normal living new food constantly
arriving in the colon must force the old contents forward, just as
the later parts of a meal force forward the earlier parts ; there
is no doubt, however, that most of the contents of the proximal
colon may be passed onward even during starvation. The
emptying of this region, according to my observations, is never
complete ; for after considerable time has elapsed, and the large
intestine is cleared and dilated with gas, some substance is still
to be detected in the caecum and clinging to the walls of the
ascending colon, an observation which Hertz has recorded also
for human beings. 21 The only activities manifested here are the
antiperistaltic waves, and the strong tonic contraction of the
whole circular musculature shown in Fig. 28. It is clear that the
latter activity would serve to press into the transverse colon a
considerable portion of the contents of the ascending colon, and
the remnant seen clinging to the walls would be the part not thus
Twice I have seen appearances which might account for the
emptying of the first portion of the large intestine in a more
thorough manner than that above described. At one time, with-
out apparent stimulation, a strong tonic contraction occurred
along the proximal colon, which almost wholly forced out the
contents. This action seemed merely an exaggerated form of
the contraction observable after food passes the ileo-colic valve.
At another time, after a mass of food had passed through the
ileo-colic valve, after the proximal colon had contracted generally,
and the antiperistaltic waves had coursed over it in the usual
manner, a deep constriction appeared at the valve and ran
upward without relaxation nearly the length of the ascending
colon, pushing the contents before it. For an instant the wave
paused ; then the constriction relaxed, and the food returned
toward the caecum. These observations indicate that either a
general contraction of the wall of the large intestine or a true
THE MOVEMENTS OF THE LARGE INTESTINE 161
peristalsis may be effective in pressing waste matter from the
region where antiperistalsis is the usual activity into the region
where it may be carried on to evacuation.
The function of the colon during defaecation has also been
observed in the cat by Elliott and Barclay-Smith, 22 who found
complete agreement with the account given above. In man the
changes have been studied and described by Hertz, who used the
X-ray method. 23 As in the cat, a relatively long column of
faeces is passed out at one time ; Hertz's tracings show that the
entire large intestine below the splenic flexure is normally
evacuated at a single act. Thereafter, usually during the next
twenty-four hours, waste material accumulates in the distal
colon. It first stops at the junction between the pelvic colon
and the rectum, where an acute angle offers some obstruction to
progress. Then from below upwards the pelvic colon fills, and,
if more material arrives, it gathers progressively in the iliac and
descending colon. On becoming distended the pelvic colon rises,
and widens its acute angle with the rectum, thus removing the
obstruction to advancement of faecal matter. Some of this
matter now entering the rectum leads to the desire to defsecate.
The common performance of the act regularly after breakfast is
probably due, in part at least, to stimulation of peristalsis in the
colon by taking food, aided by the muscular activities that
attend arising and dressing. When these procedures do not
result in the natural " desire to defaecate," voluntary contraction
of the muscles surrounding the abdominal cavity may cause
some faeces to enter the rectum, and thus evoke the call.
When the call to defaecation has come, the further performance
of the act is accomplished primarily by increased intra-abdominal
pressure a result of voluntary contraction of the abdominal
muscles and the diaphragm. As the diaphragm contracts, the
entire transverse colon is pushed downward, and the ascending
colon and caecum are forced into an almost globular form. The
intra-abdominal pressure, as measured in the rectum during this
stage, may be from four to eight times the normal i.e., may be
between 100 and 200 millimetres of mercury. 24 The pressure
causes more faeces to enter and distend the rectum and the anal
canal. The distension of these parts now arouses reflexes which
start strong peristaltic contractions of the colon, continues the
tendency to strain with the voluntary muscles, and produces
relaxation of both anal sphincters. Although, as here described,
162 THE MECHANICAL FACTORS OF DIGESTION
the process involves voluntary factors, it is quite capable of being
performed perfectly by the spinal animal. 25
The material below the splenic flexure is in most cases thus
normally voided, and at the same time, according to Hertz's
tracings, much of the content of the ascending colon and caecum
is pushed onward into the transverse colon. The sort of
peristaltic activity of the colon that Holzknect has observed
occurs, therefore, at the time of defaecation, and results in an
advancement of the faecal contents in at least two large divisions.
If approximately nine hours are required for material to reach
the descending colon in man, the waste from food taken at eight
o'clock in the morning might be discharged at five o'clock in the
afternoon. If defaecation should occur regularly at four o'clock,
however, the waste from breakfast must be retained for another
twenty-four hours. Thus, as Hertz has pointed out, the interval
between a meal and the excretion of its residue will vary, when
the bowels are opened regularly once a day, between nine and
thirty-two hours, the period depending on the time of eating and
the time of defaecation.
The importance of responding as soon as the desire to defaecate
arises is shown by the observation that the rectum accommodates
itself to the presence of a faecal accumulation, 26 and then
does not produce the desire. If the signal is not soon obeyed
it ceases to be given ; the faeces may then remain long in the
rectum without calling forth sensations, and the defaecation
reflex be to that extent impaired. As material emerges, there-
fore, from the control of automatisms that have governed its
passage through the digestive canal, and enters the region where
voluntary interference is again possible, disturbances are likely
to arise because the automatic call for exit can be voluntarily
1 Zuntz and Ustjanzew, Arch. f. Physid., 1905, p. 403.
Roith, Merckel and Bonnet's Arbeiten, 1903, xx., p. 32.
3 Cannon, Am. J. Physid., 1902, vi., p. 265.
4 Elliott and Barclay-Smith, J. Physid., 1904, xxxi., p. 272.
Jacobi, Arch. /. exper. Pathd. u. Pharmakd., 1890, xxvii., p. 147.
Cannon, Am. J. Physid., 1903, viii., p. xxi ; Henderson, ibid., 1909, xxiv.,
7 Elliott and Barclay-Smith, loc. cit.
8 Maucaire, Cong, de Chir., Paris, 1903, p. 86.
10 ? 0it ti Mi r h ' a ', d ' 6renz 9d. d. M. u. Chir., 1908, xix., p. 40.
Luschka, Lage d. Bauchorg. d. Mensch., Carlsruhe, 1873, p. 21.
THE MOVEMENTS OF THE LARGE INTESTINE 163
11 Toldt, Sitzungsb. d. kais. AJcad. d. Wissensch., Vienna, 1894, ciii., Abth.
iii., p. 52. See also Riesinger, Munchen. med. Wchnschr., 1903, i., p. 1722.
12 JSee also tracings by Hertz (Guy's Hosp. Rep., 1907, Ixi., p. 424, Fig. 10 d ;
p. 427, Fig. 12), and by Holzknect (Munchen. med. Wchnschr., 1909, Ivi.,
p. 2402, Fig. 2 c).
L3 Stierlin, Ztschr. f. Klin. Med., 1910, Ixx., p. 392.
4 Hertz, Constipation and Allied Intestinal Disorders, London, 1909, pp. 7, 8.
15 Keith, J. Anal. Physiol., 1903, xxxviii., p. vii.
16 Elliott, J. Physiol., 1904, xxxi., p. 157.
17 Griitzner, Deutsche med. Wchnschr., 1894, xx., p. 897.
18 Hertz, loc. cit., p. 9.
19 Hertz, loc. cit., p. 18.
20 Holzknect, loc. cit., p. 2402.
21 Hertz, loc. cit., p. 418.
22 Elliott and Barclay-Smith, loc. cit., p. 283.
23 Hertz, loc. cit., p. 30.
24 Keith, Allbutt and Kolleston's Syst. of Med., 1907, Hi., p. 860.
Sherrington, Schafer's Text-Book of Physiology, Edinburgh and London,
ii., p. 851.
Hertz, loc. cit., p. 426.
AUSCULTATION OF GASTRO-INTESTINAL SOUNDS
IN reporting, in 1902, observations on the movements of the
intestines, I made note 1 of an instance of rhythmic sounds
accompanying the rhythmic movements in the small gut. It
occurred to me at that time that the sounds heard over the
abdomen might indicate the mechanical activities going on in the
alimentary canal in man, but it was not until a few years later
that my attention was strongly aroused to the interest and
possible practical value of abdominal auscultation. 2 The loud
gurgling sounds produced by the intestines were, of course,
observed and recorded centuries ago ; the descriptive designation
" borborygmus " was employed even by Hippocrates. And
Robert Hooke, in a remarkable passage written more than a
hundred years before Laennec, suggested "that it may be possible
to discover the Motions of the Internal Parts of Bodies ... by
the sound they make, that one may discover the works performed
in the several Offices and Shops of a Man's Body, and thereby
discover what Instrument or Engine is out of order, what Works
are going on at several Times and lie still at others " ; and in
support of this idea Hooke mentioned, among other instances,
the hearing of the " Motion of Wind to and fro in the Guts." 3
The suggestion that abdominal sounds may be useful in dis-
covering the works of the stomach and intestines has, however,
received but scant attention. In 1849, Hooker published an
essay, 4 in which he described variations in the frequency and
intensity of intestinal gurglings in the course of different diseases
of the digestive organs. Since that time other writers have
classified the sounds normally audible into splashings, rattling or
rustling noises, the transmitted murmurs of respiration, and the
rhythmic pulsation of the aorta. 5 These sounds, however,
according to L. Bernard, 6 are not constant over the abdominal
AUSCULTATION OF GASTROINTESTINAL SOUNDS 165
organs nor do the vibrations heard characteristically in the healthy
individual alter in pathological conditions. Even in the most
recent and most complete treatises on auscultation, the only
additional statements, so far as the gastro-enteric tract is con-
cerned, are with regard to the rubbing noises audible in cases
of inflammation, and the piping notes that can be heard when
there is intestinal stenosis. Any further notice of the facts or
possibilities of auscultation of the stomach and intestines during
digestion I have been unable to find.
As anyone can easily determine, the abdomen is not poor in
noises ; on the contrary, it is usually much richer than the thorax,
and the noises are of the most diverse character, from soft gurg-
lings to loud rumbling explosions. Any special attention to the
peculiarities of certain sounds in the general tumult audible at
the height of digestion was hardly to be expected, so long as the
nature of the motor activities of the stomach and intestines was
not well understood. The recent increase of our knowledge of
these activities, however, enables us to recognize more accurately
the relation between the movements of the alimentary canal and
the sounds these movements produce.
The most characteristic feature of the movements of the
stomach and intestines is without doubt rhythmicity. Peri-
staltic waves pass in rhythmic succession over the gastric vesti-
bule, rhythmic segmentation kneads the contents of the small
intestine, and antiperistaltic waves rhythmically follow one
another in the proximal colon.
The condition most favourable for the production of sounds in
the alimentary canal is the presence of a gas mixed with food
more or less fluid. When the food and the gas are churned
together, a sound must result. Air in fine division can be intro-
duced into the stomach by eating in combination with other food,
or by themselves, such preparations as souffles, light omelettes,
toast, or very porous bread. I have also used a thin paste of
gluten-flour and milk, thoroughly stirred with white of egg until
the mixture was frothy. Eaten with a little cream and sugar,
this mixture is not unpleasant. These preparations should not
be chewed so thoroughly as to drive much of the air from the
small cells in which it lies enclosed. When such food is eaten,
rhythmic sounds can be heard over the pyloric end of the stomach,
and later over the lower quadrants of the abdomen.
In listening to these sounds I have made use of a flat-disc
166 THE MECHANICAL FACTOKS OF DIGESTION
stethoscope, with the metal chamber 2 inches in diameter. The
flatness and weight of the metal chamber render it so stable that
it remains where placed without being held, and by the addition
of a rubber tube of sufficient length the stethoscope will reach
easily to any situation on the observer's own abdomen. For
several months I kept the stethoscope at hand near my bed, and
when not asleep used it in listening to the sounds of digestion.
At times, in the quiet of the night, it is possible to hear the sounds
without the stethoscope. Indeed, the vibrations are sometimes
so strong that they can be felt in the abdomen, or perceived like
the tactile fremitus of the chest, by placing the hand over the
region in which the sound arises.
The rhythmic sounds are not due to respiration ; they differ
from the respiratory murmurs in rate and time. Nor are they
due, as one who hears the confusion for the first time might sus-
pect, to the chance choice of a rate and the selection of such
sounds out of the confusion as correspond to that rate. Graphic
records of the sounds produced by the stomach and small intestine
have been secured, and the element of human judgment thereby
eliminated. In registering the sounds of digestion I have em-
ployed the first method used by Hiirthle 7 to register the heart-
sounds. A telephone transmitter, rendered specially sensitive
by the use of rather coarse carbon granules loosely disposed, was
connected in series with five dry cells (total electro-motive force
5-5 volts) to the primary coil of an inductorium. The secondary
coil of the inductorium was attached to platinum electrodes in a
moist chamber. Over the electrodes lay the nerve of a nerve-
muscle preparation. The contraction of the muscle raised a lever
which wrote on a smoked drum. So sensitive was this arrange-
ment that ordinary conversation could not be carried on near the
apparatus without marring the record. Sound vibrations seem
to be conducted from one point to another in the abdomen much
better than in the thorax. But when sounds not arising immedi-
ately under the transmitter caused the muscle to contract, the
recording of these muffled outlying vibrations could be largely
avoided by withdrawing the secondary coil of the inductorium to
a proper distance. In order that the observer might listen to the
sounds while they were being recorded, a telephone receiver was
arranged to be thrown into circuit at will.
The Sounds produced by the Stomach. The active end of the
stomach is the pyloric end. The food in the vestibule, as we
AUSCULTATION OF GASTROINTESTINAL SOUNDS 167
have already seen, is repeatedly compressed by peristaltic waves
moving up to the pylorus. If the sphincter does not relax as
the ring of constriction approaches, the only escape for the food
is back through the narrow advancing ring (cf. Fig. 4). Since
the waves are recurring with rhythmic regularity and the pylorus
relaxes only occasionally, the food near the pylorus must be
squeezed and regurgitated by wellnigh every constriction ring.
That the rhythmic gastric sound is caused by the escape of the
food backward through the narrow moving orifice was proved by
the following observation. A mixture of starch paste, white of
egg, and subnitrate of bismuth, stirred with an egg-beater until
frothy, was given by stomach-tube to a cat. The cat's hair had
been cut short over the pyloric region, and the skin wet with
water. When a stethoscope was applied, little gurgling explosions
could be heard at intervals of about thirteen seconds. The
animal was then examined with the X rays, and peristaltic waves
were found recurring at intervals of thirteen or fourteen seconds.
As a constriction was about to pass up to the pylorus, the noisy
X-ray machine was stopped, and the stethoscope applied. At
the proper time the characteristic sound occurred. Meanwhile no
food had left the stomach ; the sounds must have been due to
the regurgitation of the food through the advancing peristaltic
Since the pyloric end of the stomach reaches farther to the
right than any other part, it is clear that by reclining on the left
side the pyloric end will be brought uppermost. When the
stomach is so situated, the lighter food i.e., food mixed with
air will naturally rise into the pyloric end. Peristaltic waves
passing over this somewhat viscous mixture of air and chymous
food will then, for reasons already stated, produce audible
vibrations. Sounds quite distinct when a subject lay on his left
side became very weak or inaudible when he turned so that the
pyloric end was lowermost.
The stomach-sounds can best be heard after a fairly bountiful
meal in which has been included a large admixture of the food
of spongy consistency already mentioned. The subject should
lie on his left side. The disc of the stethoscope should be placed
about midway between the umbilicus and the lower end of the
sternum, and to the right of the median line. Not all persons I
have examined have exhibited the sounds. When the sounds
appear, however, they are usually loud, rattling, explosive, and
168 THE MECHANICAL FACTORS OF DIGESTION
of a characteristic quality quickly recognized after they have
once been fixed in mind. But occasionally there is only the
recurrence of a short series of pops. In some individuals the
sounds are louder and more distinct than they are in others ; and
in all the cases I have studied, the sounds, even within two or
three minutes, have varied considerably in intensity. At times
the characteristic explosive discharges last several seconds ; at
other times there is at the regular period merely a sharp, short
report. Between the moments when the typical sounds return,
one can ordinarily hear with more or less distinctness a sudden
little pop, and perhaps several, always coming at irregular
intervals. These sharp pops, which resemble the bursting of
bubbles, can be heard in all parts of the abdomen, but with
greatest frequency on the right side.
The gastric sound recurs approximately every twenty seconds.
In one individual the interval was usually from seventeen to nine-
teen seconds ; in another, about twenty-one seconds ; and in a
third, about twenty-four seconds. These rates vary, as the rate of
gastric peristalsis in the cat varies (see p. 54), at different times
in the same individual. In the first case mentioned above, for
example, the interval was occasionally twenty and twenty-one
seconds. In all lower animals, except the rabbit, that I have
examined with the X rays, peristaltic waves have been found
running over the stomach with monotonous regularity whenever,
during gastric digestion, the animal has been observed. In man,
also, gastric peristalsis probably runs in continuous rhythm until
the stomach is empty, for in one case observation during the
first four hours after a meal revealed only occasional short inter-
ruptions of the rhythmic sounds. The sounds are likely to be
thus interrupted even when they have been for some time clearly
and regularly audible. The silence may cover one, two, or even
three of the regular periods. It is noteworthy that when the
sound can be heard again it continues the previous rhythm. This
fact is illustrated by the following figures, showing the number of
seconds between successive gastric sounds about two hours after
AUSCULTATION OF GASTROINTESTINAL SOUNDS 169
The equations show that the normal periods have been pre-
served ; the peristaltic rhythm, therefore, has probably been
continuous although each wave has not produced a sound. The
sound just previous to a silent interval is likely, in my experience,
to be somewhat louder and more prolonged than is usual. This
prolonged sound may mean a discharge of food through the
pylorus, and thereby the conditions in the vestibule may be so
altered that the immediately succeeding waves can cause no
sounds until the region is again normally filled ; but I have no
evidence of this.
Fig. 30 is the copy of a record, secured by the telephone
method previously described, which shows graphically many of
the features of the stomach-sounds above mentioned. The
different heights of the separate marks indicate variations in the
intensity of the sounds. The duration of the sounds also can be
FIG. 30. GKAPHIC RECORD OF THE STOMACH - SOUNDS SECURED BY PLACING
OVER THE PYLORIC REGION A TELEPHONE TRANSMITTER ACTIVATING A
The time is marked in intervals of ten seconds.
judged ; for example, at c and e they are more prolonged than
before a. One of the intermediate pop sounds is recorded at a.
Silent intervals are indicated in the regions b, d, and/. In these
regions arrows have been placed at the points where the sounds
would have recorded if present. The regular rhythm is resumed
in continuation of the previous rhythm. The silent intervals are
not always so frequent as this record shows them ; I have one
tracing in which the marks are not only rhythmically regular,
but of almost the same height, uninterruptedly for fifteen minutes.
The evidence that the rhythmic sounds audible over the pyloric
region are due to the rhythmic recurrence of peristaltic waves
moving up to the pylorus has been presented in a comparison of
the conditions in man and in the cat. This evidence is confirmed
by observations of Moritz on himself. He introduced a stomach-
tube into the pyloric end of his stomach, and found that there
were rhythmic oscillations of the intragastric pressure in that
region. Examination of his records proves that the rate of
170 THE MECHANICAL FACTORS OF DIGESTION
gastric peristalsis, in his case also, is approximately three waves
per minute, or waves at intervals of about twenty seconds. 8
Hertz has reported 9 hearing at intervals of eighteen and twenty
seconds sounds like those I had described. In one case he states
that he heard " a series of short pops repeated with perfect
regularity every seventeen seconds for about five minutes." In
some instances, however, Hertz was unable to hear any rhythmic
sounds arising from the stomach, an observation which accords
with my own experience. When the narrowness of the peristaltic
ring of the vestibule is considered, however, the securing of
reliable auscultatory evidence of gastric movements seems not an
impossibility. The conditions for producing vibrations in gastric
contents driven through the narrow ring must be more exactly
The Sounds produced by the Small Intestine. Khythmic
segmentation, although not always present, is by far the most
common mechanical process to be observed in the small gut.
The segmenting movements have a more rapid rate than the
stomach movements. In the cat and the dog rhythmic con-
tractions of the small intestine are from three to five times as
frequent as the waves of gastric peristalsis.
Usually, on listening over the lower abdomen, especially over
the right lower quadrant, during the height of digestion, the
observer hears what seems at first only a great confusion of noises.
Without experience it is difficult to distinguish in the midst of
this tumult the rhythmic sounds of the small intestine. It is
well to listen in the night after the stomach is empty, or, better,
an hour or two before breakfast. The stomach is then producing
no sounds, and the active part of the large intestine can be
avoided by placing the disc of the stethoscope over the lower left
quadrant of the abdomen. As already mentioned, these sounds
can sometimes be heard in the quiet of the night without the use
of the stethoscope. I have heard them thus, and determined
their rate by listening at the same time to a clock ticking twice
The rhythmic sound of the small intestine is different in quality
from the gushing, explosive sound of the stomach. To be sure,
the intestinal sound is not always the same : sometimes it is a soft
rustling of fine crepitating noises ; sometimes a group of little
rattling explosive discharges, as if an exaggerated crepitation ;
and sometimes as heard through the stethoscope a rough
AUSCULTATION OF G ASTRO -INTESTINAL SOUNDS 171
rolling rumble, like miniature thunder. But after these varia-
tions in quality there remain three features of the intestinal
sounds that are fairly distinctive. First, the individual sounds
usually rise slowly to an acme of intensity and then gradually
subside ; but they may increase slowly to a maximum and
suddenly cease, or may begin loud and then gently decrease to
silence. Thus each sound may last two or three seconds or more.
The second characteristic is the persistence of the rhythm for
some time in one place ; it may be audible for a minute, or it may
last for many minutes, but it does not move away as the sound
produced by a peristaltic wave would move. The third feature
is the distinctive rate. This rate is usually one sound every seven
or eight seconds, but I have heard the sounds four or five seconds
apart, and at times ten seconds apart. This rate would occasion
from seven to twelve movements per minute. The rhythmic
contractions of the small intestine are thus from two to four times
as frequent as the waves of gastric peristalsis, a ratio correspond-
ing to that in the cat and dog. This fact and the fact that the
rhythmic sounds can at times be heard loudest in the left flank,
far from the active ascending colon, have led me to regard these
sounds as a result of the activity of the small intestine rather than
of the colon. Of course, at any one time there will be some
variation in the rate, but usually it is not great, as the following
figures, showing the number of seconds between the beginnings of
successive sounds, will indicate :
8 15 = 7 + 8
13 = 7 + 6 9
As these figures illustrate, the sound sometimes skips the
regular period, but continues the rhythm on reappearing.
In the morning, after an ample dinner the evening before, I
have heard these rhythmic sounds continue in one part of the
abdomen or another without interruption, for more than an hour
and a half. The intestinal sounds are not peculiar to the morning
hours, though they are most clearly distinguishable at that
time. After learning their qualities and rate, I have heard them
distinctly in the midst of active digestion in the afternoon and
evening. Nor are they peculiar to the left side of the body. At
times I have heard them loudest on the right side.
172 THE MECHANICAL FACTOKS OF DIGESTION
In describing, in 1902, the rhythmic sounds attending rhythmic
segmentation in a cat with opened abdomen, I stated : " As
new rings occurred the old relaxed, but apparently with tardi-
ness, for the contents gurgled as if forced through the narrowed
lumen." 10 The contraction of the circular muscle at fairly regular
intervals along the length of a mass of food cuts the mass into
segments, and the repeated splitting of these segments to form
new segments must bring about with each operation a squeezing
and shifting of the food, almost simultaneously along the whole
extent. If the food contains air, the squeezing and shifting will
result in audible rumblings and crepitations. The presence of
valvulse conniventes conceivably causes the sounds to be louder
than they would be in a smooth intestine. The rather long
duration of these sounds sometimes three seconds and more
led me to think that the process in the human body is like that
FIG. 31. GRAPHIC EECORD OF THE RHYTHMIC SOUNDS OF THE SMALL
The height of the records has been reduced to one-fourth the original size. The
time is marked in intervals of five seconds.
observable in the cat and dog, and not the simple to-and-fro
oscillation of a small bit of food observable in the rabbit.
These observations, made in 1905, have not yet been confirmed
by others. In 1907, Hertz reported his failure to hear rhythmic
sounds of the character I had described. He succeeded, however,
in observing with the X rays rhythmic segmentation in the
human small intestine, and at almost exactly the rate I had noted
for the sounds which I attributed to the segmenting move-
ments (see p. 133).
The subjective element in the auscultatory evidence for these
sounds is eliminated when they are made to record themselves.
Such a record, secured by the method already described, is
shown in Fig. 31. It is a record of sounds heard before breakfast
one morning about 9.30 o'clock. The dinner at 6 o'clock the
previous evening consisted of grape-fruit, mackerel, potato,
cucumber and tomato salad, four slices of bread and butter, and
strawberries and cream with cocoanut cakes. About 10 o'clock
AUSCULTATION OF GASTRO -INTESTINAL SOUNDS 173
in the evening four slices of bread and butter and a glass of milk
were taken. At the time this record was made the telephone
transmitter was placed on the lower left quadrant of the abdomen.
The duration of the sounds is not indicated, since the recording
muscle contracted in each case only at the climax of intensity.
The Sounds produced by the Large Intestine. Antiperistaltic
waves moving toward the caecum must press the food into a
blind pouch, and the only escape for the food must be, as in the
stomach with the pylorus closed, back through the advancing ring.
Each peristaltic wave should produce a sound, therefore, similar
in quality to that of the stomach. From the analogy of the cat
and dog, one would expect these waves to have about the same
rate of recurrence as the gastric waves. One would expect, like-
wise, that they would run, not continuously, like the gastric waves,
but for short periods, when new masses of food enter the colon from
the small intestine ; that they might appear, as in the cat, after the
injection of a large enema ; and that during the periods of activity
the waves would follow one another in a fairly regular rhythm.
The greater activity in the right lower quadrant of the abdomen
is manifested by the more frequent occurrence of sounds there
than in the left lower quadrant. At times an almost constant
succession of little popping noises and faint gurglings can be
heard in the region over the ascending colon when the region over
the descending colon is quite silent. But in spite of listening
in the region of the caecum for hours, at different times of
the day, and with my body in various positions, a uniform and
characteristic rhythm of the sounds in this region, if it be present,
has escaped me. Sounds of a coarse rumbling character, some-
what like those of the stomach but usually more prolonged, are
at times audible. These sounds were once heard recurring
regularly for a short period at intervals of about twenty seconds.
More commonly, in my experience, such irregular intervals as
these 45, 25, 35, 27, 25, 14, and 29 seconds are observable.
Inasmuch as these sounds are not clearly rhythmic, it seems
questionable whether they are produced in only one part of the
intestine. But these gurglings are heard loudest along the
ascending and transverse colon, and for that reason are probably
due to activities of the large bowel.
The absence of a regular rhythm in the repeated contractions
of the large intestine has been supported by experience with
enemata. The enemata consisted of starch and a little flour
174 THE MECHANICAL FACTORS OF DIGESTION
boiled in normal salt solution. The resulting paste was thin, yet
viscid enough to be stirred into a froth much like soapsuds.
Enemata of this kind, made frothy, were introduced at body
temperature in amounts varying between 1,500 c.c. and 2,000 c.c.
In order to avoid confusing noises from the stomach, their effects
were studied in the morning before breakfasting, and they were
usually preceded by a cleansing enema of warm normal salt
solution. If the body is kept in a horizontal position, the fluid
can be retained for a half -hour or more without difficulty. During
this time, especially if the pelvis is raised, there are repeated pains
or cramps, referred most commonly to the region of the hepatic
flexure of the colon. Sometimes the pains are referred also to
midway in the transverse, and less often to the ascending colon.
They are very distinct and quite unmistakable in their character.
It is remarkable that these recurring cramps, which are un-
doubtedly due to contractions of the intestine, are ordinarily not
felt in the descending colon, sigmoid flexure, or rectum, but are
restricted to the proximal colon, the region which, in the lower
animals, is characterized by the greatest activity.
The contractions attending the pains are not expulsive, nor
do they seem to move backward from the part in which they are
felt, for no sound is audible over the csecum either during the pain
in the hepatic flexure or after it has disappeared. The con-
tractions apparently occur again and again in the same region
without moving in either direction. In the cat I have observed
such repeated circular contractions of the proximal colon (see
p. 151), but they are not usual.
The recurrent pains ordinarily last from six to eight seconds,
increasing gradually in intensity until just before the end. They
are commonly attended by gurgling noises audible as the cramp is
passing away. The cramps have been observed succeeding one
another for nearly ten minutes at intervals varying between
nineteen and twenty-two seconds, but in my experience they are
ordinarily not so regular as this. The following figures, repre-
senting in seconds the time between the onset of successive
cramps, illustrate the usual rather irregular recurrence of the
28 39 22 43
47 35 15 42
35 15 25 40
15 50 43
23 18 40 54
41 35 25 37
AUSCULTATION OF GASTKO-INTESTINAL SOUNDS 175
From the evidence I have been able to secure by auscultation
and from sensations of cramp, it seems certain that the ascending
and first part of the transverse colon are more active than the re-
mainder of the large intestine. As we have learned, the evidence
for antiperistalsis in this more active region is not conclusive. I
have already mentioned that Elliott and Barclay-Smith found
such sacculation as occurs in the human colon associated with
emphasized churning activity of the walls of the sacculi. In repeat-
ing their observations on the guinea-pig and rabbit, I have seen
oscillating movements of single sacculi, now here, now there, or of
many sacculi at the same time, each contracting repeatedly,
squeezing out the contents of the pouch, crowding full the neigh-
bouring pouches which in turn became active, then relaxing,
filling, and discharging, again and again, till the food was
thoroughly churned. Such a process could not be attended by a
clearly marked rhythm : too many little activities are going on at
the same time. But these little activities would naturally be
attended by the continuous popping noises and the slight gur-
glings which are heard at times over the ascending colon. Is it
not likely that in man, even though antiperistalsis may occur
in the proximal colon, oscillating contractions of the sacculi
constitute the more prominent operation ?
Although auscultation has failed to bring evidence of antiperi-
stalsis in the colon, the method, as used by Hertz, has served to
indicate when material begins to pass through the ileo-colic valve.
In the morning before breakfast he heard nothing over the
caecum. The silence persisted rntil between four and four and a
half hours after breakfast, when a few quite characteristic sounds
were heard, which became louder and more frequent up to a
maximum from one to two and a half hours after they began.
Then confusions of sounds occurred because of the taking of other
meals. The first caecal sounds were found by the X-ray method
to coincide with the first appearance of a shadow in the caecum.
They seemed to be produced by the passage of fluid contents
through the ileo-colic sphincter. The presence of gas in the colon
was favourable to the production of the sounds, for they decreased
in intensity as the semi-fluid material accumulated. In auscul-
tation, therefore, we have a means of determining the rate of
passage of material through the small intestine. 11
A characteristic sound, not periodic, which is audible at times
along the transverse and descending colon is a progression of little
176 THE MECHANICAL FACTORS OF DIGESTION
crackling noises, like the breaking of minute bubbles. The sound
starts in the transverse colon, and its advance can be clearly
traced. If the disc of the stethoscope lies over the splenic flexure,
the crackling can be heard first faintly, then louder and louder,
then gradually more faintly again ; and if after the climax of
intensity there the stethoscope is changed to a position farther
along the large intestine, the sound can again be heard passing
through the same phases as before. This sound is likely to be
followed immediately by a tendency to pass gas from the bowel.
The conveyance of gas from the region of active fermentation in
the proximal colon to a place from which it can be finally voided
is apparently, therefore, a special action, and conceivably may
occur without changing the position of the firm contents of
To one listening for the first time for rhythmic abdominal
sounds, probably the most striking feature of what he hears is the
large number of sounds which are not rhythmic. Most prominent
among these irregular sounds are the sudden quick discharges or
pops, which can be heard, either singly or in a short series of three
or four, almost at all times and in all parts of the abdomen, though
most frequently on the right side. As already stated, these
reports resemble the sound of bursting bubbles. Occasionally a
continuous little gurgling can be heard for some moments,
gradually becoming less intense. Peristalsis in the small intestine
may be thus manifested.
A noteworthy characteristic of the intestinal sounds is their
alteration in intensity and frequency at different times. I have
no records showing this variation, but it has impressed itself upon
me while listening for long periods to the activities of the intes-
tines. At times there will be almost silence in the lower abdomen ;
the silence will give way gradually to an abundance of sounds,
and these in turn will subside till again only occasional sounds are
audible. The observations of BoldirefE have proved that the
alimentary canal has a periodic activity while not digesting ; 12
the intestines may also have alternating periods of increased and
decreased activity while digestion is going on.
Whether the observation of the sounds of the stomach and
intestines is to be of clinical importance will depend on whether
there are typical variations of these sounds in different diseases of
the alimentary canal. The observations here recorded, made
chiefly upon myself, were confirmed on a few other normal
AUSCULTATION OF GASTRO-INTESTINAL SOUNDS 177
individuals. No attempt was made to study the sounds produced
in abnormal conditions. Irritation in the region of the ileo-colic
junction might cause reflex spasm of the sphincter at the end of
the small intestine. Material would then cease to pass into the
colon, and csecal sounds would fail to appear. Hertz has suggested
that the presence or absence of these sounds would be serviceable
in differentiating acute appendicitis with and without peritonitis.
In cases of peritonitis of the region, he found that the sounds
disappeared as the inflammation developed. 13 Auscultation
might also be used to separate the somewhat vague expression
" motor insufficiency " into its two factors, absence of peristalsis
and pyloric obstruction. Evidently if sounds recur in regular
rhythm at the pylorus, and food remains in the stomach, the so-
called "motor insufficiency" is due, not to absence of peri-
stalsis, but to difficulty at the pylorus. Furthermore, in
such disorders as gastritis, nervous dyspepsia, atony, colic,
obstruction, and dysentery, a study of the sounds produced
by the movements of the alimentary canal, both before and after
the administration of drugs, may reveal facts important to the
1 Cannon, Am. J. PhysioL, 1902, vi., p. 259.
2 Cannon, Am. J. PhysioL, 1905, xiv., p. 339.
3 Hooke, Posthumous Works, London, 1705, The Method of Improving
Natural Philosophy, pp. 39, 40.
4 Hooker, Boston M. and 8. J., 1849, xl., pp. 409, 439.
5 See Winkel, Jahresb. d. Gesettsch. f. Natur- und Heilk. in Dresden, Sitzung,
December 6, 1873.
6 Bernard, L., Zur Auscultation des Abdomens, Inaugural-Diss., Wiirzburg,
1879. There is evidence that Bernard is mistaken in his first statement ; he
may be mistaken also in his second statement.
7 Hurthle, Arch. f. d. ges. Physiol., 1895, lx., p. 264.
8 Moritz, Ztschr. f. Bid., 1895, xxxii., p. 353.
9 Hertz, Guy's Hosp. Rep., 1907, IxL, p. 402.
10 Cannon, Am. J. PhysioL, 1902, vi., p. 259.
11 Hertz, loc. cit.,p. 412.
12 Boldireff, Arch, des Sc. BioL, 1905, xi., p. 1.
13 Hertz, Brit. Med. Jour., 1908, ii., p. 1603.
THE INTRINSIC INNERVATION OF THE GASTROINTESTINAL
THE relative parts played by the intrinsic and extrinsic nerve-
supply of the gastro-intestinal tract can perhaps best be under-
stood by considering first the activities of the canal separated
from the central nervous system, and later attending to the
modifications of these activities through external connections.
The neuromuscular mechanism which underlies peristalsis has
been studied chiefly in the small intestine. As we shall see,
probably no fundamental difference exists between the intrinsic
mechanism in the small intestine and that elsewhere in the
alimentary canal. The peculiarities of the activity in different
parts of the canal, however, make desirable a separate considera-
tion of each part. Thereafter we shall be in a position to deter-
mine to what extent a general statement regarding the entire
canal is justified.
The Small Intestine. Nothnagel pointed out in 1882 that
stimulation of the rabbit's small intestine with a crystal of
sodium chloride results in a contraction which spreads from the
stimulated region upward, whereas complete rest prevails below. 1
After persisting for a variable number of seconds, the contracted
region relaxes, and becomes at once the seat of peristalsis. That
contraction occurs above, and not below the stimulated region
was proved also by Liideritz, who used a somewhat more natural
method the introduction of an inflatable balloon and found
that rapid distension of the rabbit's gut caused an almost exact
repetition of the phenomenon described by Nothnagel. When
the intestine was very irritable, the balloon was driven downward
by the contraction above it, and thus, by successively stimulating
new regions, it caused a downward-moving peristaltic wave.
Since these results occurred after the nerves in the mesentery
were cut, Liideritz concluded that the controlling mechanism
THE INTRINSIC INNERVATION 179
must be present in the intestinal wall. 2 The modern conception
of intestinal peristalsis was, however, not fully stated until Mall
pointed out the significance of Nothnagel's observation on intus-
susception. Nothnagel had reported that the intussuscipiens *
portion of the gut, lying below the point of stimulation, folds back,
and extends upward over the contracted intussusceptum lying
above. 3 Thus contraction above and relaxation below seemed
so related as to be parts of a single act. And Mall concluded that
while a mass in the intestine is causing a contraction above, which
forces the mass downward and thus stimulates fresh regions
above to contract, active dilatation below is at the same time
inviting an easy descent. 4 Peristalsis would thus be another
example of the mutual adjustment of antagonistic muscles
towards efficient action an example which presents in the
simple neuromusculature of the gut the important principles long
ago perceived by Descartes and Bell in the neuromusculature of
the skeleton, which in recent years have been named by Meltzer
and by Sherrington, respectively, " contrary " and " reciprocal "
Although Nothnagel and Liideritz had shown experimentally
the intrinsic control of peristalsis, and Mall had clearly inferred
the nature of the peristaltic wave, Bayliss and Starling made the
first exact demonstration of the process. When they introduced
.a bolus into the dog's intestine, they observed the formation of a
" strong tonic contraction " immediately above the object, which
pressed it downward. And as the bolus moved, the ring of con-
striction followed it. The region of the gut over which the con-
striction ring had just passed was occupied by peristaltic waves,
which repeatedly swept down to the ring. By means of apparatus
which registered the movements of both the longitudinal and the
circular coats, Bayliss and Starling proved that the descending
bolus was preceded by an area of relaxation. The two effects,
contraction and inhibition, could be produced by pinching the
gut above and below the recording apparatus ; a pinch 1 or 2 centi-
metres below caused the registering of an increased contraction ;
a pinch much farther above even 30 centimetres or more
resulted in cessation of contraction or relaxation. These results
appeared after exclusion of cerebrospinal reflexes. " Excitation
.at any point of the gut excites contraction above, inhibition
below. This is the law of the intestine." Such was the con-
clusion of Bayliss and Starling. 5 Since this co-ordinated action
180 THE MECHANICAL FACTOKS OF DIGESTION
could not conceivably be performed by muscles alone, they
inferred that it was controlled by Auerbach's plexus, possibly by
short augmentor paths extending upwards, and long inhibitory
paths reaching downwards.
After injecting nicotine, Bayliss and Starling found that
rhythmic contractions of a stretched ring of gut continued, but
that the waves of constriction, which ran over the gut, now
passed as often in one direction as in the other. 6 A pinch caused
a local contraction which was not propagated in .either direction ;
a bolus placed anywhere in the gut remained unmoved. The
same results followed painting the intestine with cocaine, or
injecting muscarine. They concluded that the rhythmic move-
ments were myogenic, but capable of travelling as a wave from
muscle fibre to muscle fibre. Usually these waves moved in a
downward direction, an effect which they suggested might result
from higher excitability at the duodenal end. True peristalsis
they regarded as not like these waves, but as a co-ordinated
reflex, consisting of combined contraction and relaxation, de-
pendent on the proper functioning of the local nervous system. 7
More detailed work on the functions of the local nervous
system of the intestine was done by Magnus, and has been
reported in a series of valuable papers. 8 Using 0. Cohnheim's.
method, 9 he studied excised pieces of cat's intestine, kept alive
in oxygenated, warm Ringer's solution. Thus, Magnus was
able to secure records of contraction above and relaxation below
the stimulated point in isolated loops The reflex persisted after
removal of the mucous and sub mucous layers, including Meissner's
plexus. It is therefore mediated through Auerbach's plexus a
conclusion which has been inferred by Bayliss and Starling.
Bayliss and Starling's evidence that the rhythmic contractions
of the gut are myogenic is not conclusive. That the short aug-
mentor paths and the long inhibitory paths assumed by these
investigators are in fact superintending fibres in the wall of the
canal, normally affecting subordinate nervous activities in a.
positive or negative manner, is easily conceivable. Indeed,
Dogiel has found histologically that an axon, on leaving a ganglion,
frequently passes through several neighbouring or more remote
ganglia, and gives off collaterals to the nerve cells lying in them. 10
Nicotine might, then, block conduction between superintending
and subordinate neurons, and still leave unaffected the subordi-
THE INTRINSIC INNERVATION 181
Experimental evidence against Bayliss and Starling's con-
clusion that the rhythmic movements are myogenic was brought
forward by Magnus. His first argument against their contention
was based on the distinction between the local motor centres for
muscular action and the conducting paths uniting these centres.
He had found in the marine worm, Sipunculus, that atropin
paralyzes conducting paths, but not the centres, whereas cocaine
paralyzes the motor centres before stopping conduction. 11 It
was possible, therefore, that the drugs used by Bayliss and
Starling, although destructive to the machinery of the local
reflex, did not seriously injure the immediate nerve-supply.
The rhythmic contractions therefore might result from rhythmic
The second argument of Magnus was supported by more direct
proof. He found that when the longitudinal and circular
muscular layers are pulled apart, Auerbach's plexus, which lies
between, adheres to the longitudinal layer. Under these cir-
cumstances the longitudinal muscle alone manifests sponta-
neous rhythmic contractions. The circular muscle, deprived
of the plexus, although capable of responding to a single
mechanical stimulus by a single contraction, never shortens
The objection has been raised 12 that the circular muscle must
be seriously injured by separation from the longitudinal coat and
the nerve net, and is therefore inert. As Magnus has pointed
out, however, removal of the submucosa with Meissner's plexus
is, in relation to the circular coat, a similar operation, but it
causes no alteration of the activities of that coat ; and, further-
more, the longitudinal coat, which is about one-seventh as thick
as the circular, and consequently much more liable to injury,
is precisely the part that shows the peculiar rhythmic con-
tractions. 33 This contention of Magnus has been supported by
Sick, who succeeded in separating from the stomach pieces of
longitudinal muscle without the nerve plexus, and in observing
that they then no longer contracted spontaneously. 14
According to Magnus's careful observations, there are other
important differences between intestinal muscle when controlled
by the plexus and the same muscle when freed from that control.
The independent muscle can be tetanized ; it gives superposed
contractions, has no refractory period, and manifests no rhythmic
response to continued stimulation. On the other hand, good
182 THE MECHANICAL FACTORS OF DIGESTION
preparations with the plexus attached cannot be tetanized, are
clearly refractory to weak stimulation during the period of
shortening and the first part of the period of relaxation, and with
continued stimulation exhibit rhythmic contractions.
Of these activities of smooth muscle connected with its
intrinsic nervous system, the most significant, in relation to bodily
functions, is the refractory period. Given the refractory period,
the rhythmic response to continued stimulation necessarily
follows. The rhythmic nature of many of the activities of the
alimentary canal might thus receive explanation. The con-
tention of Schultz, 15 that Magnus's " refractory period " was due
to defective methods of stimulation, Magnus has met by repeating
the experiments under better conditions, and finding again that
weak stimulation does not affect the intestinal neuromusculature
while it is contracting, and becomes effective again only gradually
as the muscle relaxes. 16 Magnus was able furthermore to show
the refractory period by mechanical stimulation ; by this method
I also have obtained evidence of the phenomenon, and can
therefore confirm Magnus's statement.
The question now arises as to the conditions under which the
two typical movements of the small intestine appear. The
simplest movement to explain is that which causes segmentation.
It is only necessary to attach a writing lever to a narrow ring of
the intestine to secure a record of rhythmic contractions. The
ring may be only a few millimetres wide ; the rhythmic response
therefore is local. It can best be explained as a resultant of the
stretching. This mechanical stimulation causes contraction ; as
soon as the contraction begins, the ring becomes refractory, and
is not again subject to the stimulus until it is relaxing. Thus
the constant pull results in a rhythmic response. The extent and
force of the contractions are increased within limits by an in-
creased distending force, or, if absent, they may be induced in
the same way. 17
In harmony with the foregoing explanation is Bayliss and
Starling's observation that the contractions of the gut, when a
distending balloon is introduced, are most marked in the region
of greatest tension. 18 In harmony with that explanation also is
the observation that, as a mass of food is being pushed along the
gut, the back end is likely to be cut off by a constriction ring
(see p. 137). The violent segmenting activity in cases of obstruc-
tion (see p. 141) also points to distension of the gut as a cause of
THE INTRINSIC INNERVATION 18S
rhythmic contractions. Indeed, rhythmic segmentation itself is
an excellent example of the response of the gut to stretching, for
the contraction occurs each time in the bulging region about
midway between two previous contractions. Experimental evi-
dence to the same effect I have secured by seizing the active,
exposed intestine between the fingers at two points a few centi-
metres apart, and placing the enclosed contents under pressure
sufficient to distend the gut. The distension was followed by the
contraction of a narrow ring of the circular coat ; and when the
finger pressure was repeated rhythmically, as rapidly as a con-
tracted ring relaxed, a new contraction occurred, not where one
had just appeared, but in a fresh region. Now here, now there,
the gut responded to the distending contents, a shifting perhaps
associated with lessened irritability in the region just recovering
from activity. Since these rings of constriction press the mucosa
into the midst of the food, the requirement of fresh neuro muscu-
lature for contraction results, of course, in the utilization of fresh
mucosa for absorption.
Why peristalsis of the small intestine starts and why it stops
is not known. Certainly nutriment is not pushed onward con-
tinuously from stomach to colon. Even in the active small
intestine of the rabbit the food-masses can be seen in different
loops lying for some time undisturbed by any movement of the
wall. In the less active gut of the cat this stasis of the contents
is even more marked. Yet from this quiet state, or even after
segmentation has been for some time in process, a peristaltic
wave will appear, force the mass forward for a short distance,
and then stop. Under experimental conditions mechanical
stimulation will cause contraction above and relaxation below.
Magnus, for example, after removal of all the mucous lining that
normally comes in contact with the food, could still demonstrate
the reflex by pinching. But the reflex, and the progression of the
reflex along the intestine, are not the same phenomenon. Peri-
stalsis implies an advancing wave, and although food containing
cellulose seems to be carried through the gut rapidly because of
the mechanical effects induced by it, nevertheless the chemical
state of the contents is probably of first importance for the
moving contraction. Bayliss and Starling found that cotton
coated with soft soap was an efficient stimulus for peristalsis of
the small intestine. Nothnagel and others used strong salt
solutions to evoke it. I have observed energetic peristalsis after
184 THE MECHANICAL FACTORS OF DIGESTION
the injection of soapy enemata, and after introducing into the
lumen of the gut a small cylinder of alkaline soap. Meltzer and
Auer produced rushing peristalsis by administering drugs in
stimulating and depressing combinations ; the cathartics are
irritants of vegetable origin, or salts only slightly absorbable.
Most of these agencies would affect the gut not so much by
distension as by chemical stimulation. The observation of
Bokai, 19 that products of decomposition carbon dioxide, marsh-
gas, hydrogen peroxide, and skatol cause powerful movements
of both the small and large intestines, and Koger's testimony 20
that peptones and glucose stimulate peristaltic activity, are to
the same effect. If we consider, furthermore, the other functions
of the small intestine which peristalsis subserves the functions
of further digestion and absorption then the forwarding of the
chyme seems required, not because the chyme is bulky, but
rather because fresh regions for digestion and absorption are
desirable. In an orderly mechanism, therefore, we might
reasonably regard the degree of digestion, or the status of the
mucosa, or some relation between these two, as a basis for
explaining the peculiarities of intestinal peristalsis.
That some regulatory arrangement for the advancement of
material through the small intestine exists is suggested by the
fact that the different foodstuffs do not pass through the small
intestine with the same speed (see p. 145), and yet when the
end of the ileum is reached, practically all of the serviceable
stuff is absorbed. The work of London and his associates indi-
cates also that foodstuffs are absorbed at different rates at
different parts of the tube meat most in the upper part, starch
and fat most in the lower part 21 and that in each portion of
the tract, in the case of any particular food, a constant per-
centage amount is absorbed, quite independent of the amount
fed. 22 Nutriment when given in small bulk (50 c.c.) was dis-
tributed in the small intestine quite as it was when given in
large bulk (500 c.c.), so that the entire tract is forced into service. 23
These results can best be explained, I believe, as a response of
the canal to the nature and state of the intestinal contents,
rather than as a response to mechanical stretching. In this
connection the control of the sphincters of the stomach by
chemical agencies is perhaps significant. The manner in which
the chemical character of the chyme may affect intestinal peri-
stalsis, however, is still quite hypothetical, and the whole ques-
THE INTRINSIC INNERVATION 185
tion will require much more investigation before a decisive
answer can be given.
Further discussion of the mechanisms governing segmentation
and peristalsis in the small intestine will be necessary, but we
shall be able to look on these processes from a new point of view
after considering the intrinsic nervous control in the large intes-
tine and the stomach.
The Large Intestine. The same region in the colon may mani-
fest both peristalsis and antiperistalsis. In my observations, 24
and in those of Elliott and Barclay- Smith, 25 antiperistalsis
was seen in the middle and distal thirds of the large intestine,
from which regions the contents are normally driven by peri-
stalsis. The English investigators have reported further that in
the rat the proximal colon, which is commonly worked over by
antiperistaltic waves, exhibits the peristaltic reflex if the material
it receives, instead of being soft and moist, is stiff and dry.
Since the antiperistaltic waves are not affected by large doses
of nicotine, 26 they are like the rhythmic segmenting movements
of the small intestine. And again like the segmenting move-
ments, these waves not only utilize the same muscles as the
downward-moving constrictions, but, if we may transfer Magnus's
evidence to this final region, they probably utilize also the same
intrinsic nerve centres that are involved in the local reflex.
The local reflex in the large intestine was first demonstrated
by Bayliss and Starling. 27 They found, by using the methods
employed in studying the small intestine, that both in the dog
and in the rabbit pinching above the recording balloon caused
an inhibition of the activities below, and pinching below caused
contraction above. The ascending excitation in the dog and the
descending inhibition in the rabbit were more difficult to demon-
strate than the reciprocal activities. At most the descending
inhibition in the rabbit extended not more than 2 or 3 centi-
metres below the stimulated spot. In both dog and rabbit the
activity of the local mechanism diminished from the ileo-colic
valve to the anus, thus throwing the evacuation of the distal
colon more and more into the control of extrinsic nerves. The
local reflex in the rabbit's colon Langley and Magnus were able
to demonstrate after degeneration of the post-ganglionic sympa-
thetic fibres. 28 That the cat's colon also is the seat of the co-
ordinated reflex was shown by Elliott and Barclay- Smith, who
found that distension in the middle third of the large intestine
186 THE MECHANICAL FACTOKS OF DIGESTION
of this animal causes constriction above the distended area, and
relaxation below. 29
Thus far I have used the terms " peristalsis " and " antiperi-
stalsis," as if descriptive of the same activity, and merely
opposed in direction. The only difference between them that
has been suggested is the failure of nicotine to stop antiperistalsis,
whereas in the small intestine nicotine at once abolishes peri-
stalsis and the reflex on which that activity rests. Antiperi-
stalsis is peculiar in a number of other ways, however, which
clearly distinguish it from the propulsive wave.
The chief peculiarity of antiperistalsis is the absence of a
region of inhibition projected before the moving ring of con-
striction. As" a result, these rings continue passing over the,
proximal colon in a close series, each succeeding constriction
never checking or interfering in any way with those already
started and progressing before it.
A second and important characteristic of the antiperistaltic
waves to which I have called attention 30 is their origin. In my
first paper on the movements of the intestine, I reported that
these waves were seen starting from the " nearest tonic constric-
tion." 31 Elliott and Barclay-Smith also noted that the waves
began at " the anal limit of a distended area," " from the upper
limits of a ring of constriction," " from a deep constriction which
formed and remained with slight oscillations as a starting-point." 32
Although we reported thus our observations, we did not realize
the significance of the tonus ring as th, source of antiperistalsis.
By producing a tonus ring in the proximal colon, however, by a
pinch or by applying a weak solution of barium chloride, I have
been able to cause the waves to appear at will. By making the
ring at the caecum, repeated downward-running waves may be
set going ; by making a new ring now at the terminus of these
waves, reversed waves appear, and meet the downward waves
progressively nearer the caecum until only reversed waves are
running. Furthermore, a tonus ring made midway in the
proximal colon I have seen giving rise to repeated waves which
passed away in both directions. 33 The origin of antiperistalsis,
therefore, is the tonus ring.
A third feature of antiperistaltic activity in the colon is its
rhythmicity. The waves appear one after another at regular
intervals. These rhythmic waves must have a source that is
rhythmically active. Careful inspection of the tonus ring shows
THE INTRINSIC INNERVATION 187
that at regular intervals it pulsates. Each pulsation sends away
a ring of constriction.
A fourth characteristic of this antiperistalsis is its dependence
on a state of tension. If a tube is tied into the colon, and as
fluid is introduced a tonus ring is made, antiperistaltic waves are
usually started by the ring. If now the fluid is largely with-
drawn, the waves cease. Reintroducing the fluid starts them
again. The observation that antiperistalsis begins as soon as new
food enters the colon from the ileum, and Elliott and Barclay-
Smith's method of starting the waves by injecting air or gruel,
agree completely with the idea that distension is the condition
under which the waves originate.
Mechanical extension has long been known as the most efficient
stimulus for bringing smooth muscle into activity. The exten-
sion, however, must not be merely the elongation of non- elastic
substance. When smooth muscle is flaccid or already much
relaxed, extension calls forth no response. Only when shortened
and resilient i.e., in a state of tonus does the pull evoke con-
According to Schultz, 34 smooth muscle, when much contracted,
is extended more by a given weight than when less contracted
and loaded with the same weight. The tonus ring is a region
contracted more than the neighbouring regions. We may
assume, therefore, that at the tonus ring the neuromusculature
is in a condition especially favourable to extension by any
internal pressure, and, further, that it will respond to extension
In thus responding to an extending force, the smooth muscle
of the colon, like that of the small intestine, is, during the entire
period of shortening, relatively refractory to stimulation. It
begins again to be subject to the stimulus just after reaching its
most contracted state i.e., when again most extensible. Now,
by being extended, it is stimulated, and again responds. In
explaining the rhythmic pulsation of the tonus ring in response
to a constant pull, therefore, the same factors are involved as
in the rhythmic contractions of the small intestine.
The movement of a wave of constriction from the pulsating
ring towards the csecum can best be regarded as another instance
of the passage of the state of excitation from an active to a less
active region in a simple neuromuscular structure a phenomenon
which v. Uexkiill has so frequently observed in the nerve net
188 THE MECHANICAL FACTORS OF DIGESTION
of invertebrates that he has based upon it a general law. 35 Thus
would be explained the departure of waves from a pulsating ring
backwards or forwards, or in both directions simultaneously, as
described above. In my experience, this progress of a wave does
not occur if the wall expands sharply at the edge of the ring.
The wall must taper from the expanded to the narrow region
before the pulsations will send off the moving constrictions. It
is a corollary from the above discussion of the effect of extension
on contraction that the expanded region must itself be in a
condition to be extended i.e., possess some degree of tonus in
order to be in a state to respond. If the gut is quite relaxed, the
arousing of antiperistaltic waves from a pulsating ring is usually
The wave departing from the contracting ring leaves a refrac-
tory region behind, and is itself a moving refractory state of the
neuromusculature. The only direction in which the wave can
make progress, therefore, is away from its origin. As soon as
the region of the colon next to the ring has contracted, it begins
to relax. Thus between moving rings of constriction are moving
regions of relaxation. When the region next the tonus ring is
relaxed, it is, of course, again subject to an impulse coming to it
from the pulsating ring. What is true of this region is true also
of all regions lying beyond. Thus, just as in cardiac contraction
the pulsations of the sinus set the pace for the rest of the heart,
so here in ths colon the pulsations of the tonus ring determine
the rate at which waves shall appear.
A tonic constriction is itself refractory to the stimulus that
comes to it in the form of a constriction wave. My own observa-
tions and those of Elliott and Barclay-Smith on antiperistaltic
waves observable between the natural tonic constrictions of the
colon illustrate the definite boundary set by the state of tonus.
The blocking of the waves started at tonus ring b by the nearly
relaxed ring a (Fig. 32) offers another illustration of the same
The dependence of pulsations on an adjustment between locally
increased tonus and the internal pressure is also illustrated in
Fig. 32. The colon is filled with fluid ; ring 6, which is deep, is
pulsating and sending forth waves ; ring a, which has relaxed,
no longer pulsates. The two rings are exposed to approximately
the same internal pressure. This is adequate as a stimulus for
the deeper ring, but not for the less deep. Under such circum-
THE INTRINSIC INNERVATION
stances, I have been able to renew rhythmic activity in the
quiet ring merely by increasing the internal pressure. In all
probability this is what occurs when new food enters the large
intestine from the ileum, and starts a fresh series of antiperi-
staltic waves. And once started, the waves can be augmented
by increase of internal pressure. For example, if they are
shallow depressions, they can be made much deeper by a series
of slight momentary pressures on the gut, which cause repeated
slight distensions of the wall where the waves are passing.
The precise relation between the degree of tonus and the
internal pressure, which results in rhythmic contraction, is
difficult to define. When
a tonus ring is first made,
either by a pinch or by
applying barium chloride,
it is a deep and strong con-
traction, and shows no evi-
dence of pulsations. Only
when it has relaxed to some
extent does it begin to beat
rhythmically. On the other
hand, if the pressure within
is sufficiently increased, the
waves moving along the
gut will disappear, and then
can only be seen again
when the distension is re-
duced. Both the tonus and the distending force, therefore,
can be too great for rhythmic action.
From the foregoing discussion we can understand that, given
the state of tonus and a locally increased tonic contraction, anti-
peristalsis of the colon can be explained. The conditions for the
establishment of tonus rings, however, are still undetermined.
Since the rings persist after destruction of the spinal cord, they
must be maintained by the gut itself. Henderson's observation
that the movements of the alimentary canal appear if the carbon
dioxide content of the blood is kept normal or increased 36 can
be explained as due to the well-known effect of this gas in aug-
menting my enteric tonus. Probably both the general tonic state
of the proximal colon, and also the tonus rings, are of local origin,
and possibly directly dependent on the character of the blood-
Em. 32. PHOTOGRAPH OF A COLON EX-
POSED UNDER WARM SALT SOLUTION.
Tonus ring b is sending forth antiperistal-
tic waves, which are stopped by the
nearly relaxed tonus ring a.
190 THE MECHANICAL FACTORS OF DIGESTION
supply. More than this we are not at present warranted in
Just as we were not able to determine the normal occasion for
peristalsis in the small intestine, so likewise we are ignorant of
what causes the appearance of peristalsis in the region where
antiperistalsis usually prevails. As already stated, change in
the nature of the contents may change the direction of the
waves. Magnus has found that, when senna is mixed with the
food, it causes an evacuation as soon as it enters the colon. He
was unable to note the occurrence of antiperistalsis in any of ten
animals thus treated. 37 Possibly, as seems to be true in the
small intestine, the peristaltic wave of the colon is related to
other activities of the region, and is reserved for pushing onward
waste material from which all good has been removed or which
has dried and hardened, or for quick discharge of irritant and
harmful substances. In this activity the mechanism of de-
fsecation is, of course, a distinct aid. This mechanism, however,
will be considered in relation to the extrinsic inner vation.
The Stomach. The characteristic activities of the stomach, so
long as gastric digestion persists, are the repeated peristaltic waves
running over the pyloric end, and the tonic contraction of the
cardiac end. The fact that the waves of the stomach, like those
of the colon, follow one another in a series indicates that the
extensive forerunning inhibition, such as is seen in the dog's
small intestine, is absent. Moreover, when nicotine is given,
even in large doses, the gastric waves are not stopped. 38 The
peristaltic activity of the stomach, therefore, is by this evidence
placed in the same class with antiperistalsis of the colon and the
segmenting movements of the small intestine.
The first waves of gastric peristalsis are usually seen in the
pyloric region ; later they begin nearer the cardiac end. This
observation proves that there is no special and peculiar region
for the origin of the waves. Indeed, I have recently found that
by gradually increasing intragastric pressure the waves can be
made to start progressively nearer the pylorus ; or, as the pres-
sure is decreased, step by step nearer the fundus. Our con-
sideration of rhythmic antiperistalsis in the colon has shown
that the waves start at a pulsating ring. In the stomach also
the rhythmically recurring waves must have a rhythmically
pulsating source. The conditions in the colon indicate further
that whether a ring pulsates or not depends on the relation
THE INTRINSIC INNERVATION
between the degree of tonus and internal pressure. The same
factors I have found operative in the stomach. If the resting
organ is contracted, the introduction of fluid at once starts
peristaltic waves ; if, on the contrary, the organ is flaccid and
relaxed, the introduction of material usually has no effect.
During the process of gastric digestion the stomach maintains
its contractions with a considerable tonic tightening always
existent. The intragastric pressure, 6 to 16 centimetres of water,
is a measure of the tonus of the muscle. If while intragastric
pressure is being recorded the animal is given adrenalin, the
pressure at once falls to zero. Simultaneously peristalsis ceases,
and does not begin again until
the pressure has to some
extent been restored (see
The stomach when first
filled has roughly a conical
shape. The circumference is
large at the cardiac end, and
progressively smaller as the
FIG. 33. RECORDS OF INTRAGASTRIC
PRESSURE AND THE CONTRACTIONS
OF PYLORIC END OF THE STOMACH
AFTER GIVING ADRENALIN.
Peristalsis of the pyloric end (upper
curve) begins again after pressure
(lower curve) has begun to rise. Time,
pylorus is approached. If
the contents are fluid or semi-
fluid, and are subjected to the
tension of the gastric muscu-
lature, the pressure through-
out the contents (gravity
aside) will be uniform. Every unit area of the wall will be support-
ing the same pressure. Obviously, then, a circumference of given
width in the larger cardiac end will be subjected to greater total
stress than a circumference of equal width in the smaller pyloric
end. Since the forces in the inactive stomach are in equilibrium,
however, the circular muscle of the cardiac end necessarily has
to exert stronger tension than that in the pyloric end. And,
furthermore, since the muscular wall of the cardiac sac is thinner
than that of the vestibule, there are fewer muscle fibres in equal
cross-sections. The greater circumference and the weaker mus-
culature both tend to place the cardiac region at a disadvantage.
The tension of the muscle in this region must therefore deter-
mine the pressure in the stomach.
With the conditions of pressure and tonus in the stomach
known, how can gastric peristalsis be explained ? There is
192 THE MECHANICAL FACTORS OF DIGESTION
evidence that the observations already reported on the factors
governing activity in the proximal colon can be applied here.
As we noted in considering antiperistalsis in the colon, the
internal pressure may be too slight to evoke a response in the
tonically contracted muscle, or it may be too great. On the
basis of these observations, we may assume that at first the
muscles of the cardiac end are too much distended to respond,
and that those of the pyloric end are too little distended. Be-
tween the large cardiac end and the small pyloric end, however,
the relations of internal pressure and tonus will be intermediate.
At some point the relations will be such that the neuromuscula-
ture responds by contraction. The material displaced by this
contraction is probably accommodated in the cardiac region
where the weakest muscles are working against greatest obstacles.
As the contracted circumference relaxes, however, the tonic
pressure from the cardiac end again stretches the ring. Thus
the contraction will be repeated rhythmically at this point, for
the same reasons that were given for the rhythmic response of
the small intestine and the colon.
Each pulsation will send off a wave, just as in the colon, but
this wave will travel only towards the pylorus. This direction is
not taken because antiperistaltic waves cannot occur. If a frog's
stomach is distended with water, tied at the two ends, and
removed from the body, peristaltic or antiperistaltic waves will
run over it, according to the end having a pulsating tonus ring.
Similarly in the cat : a tonus ring made near the pylorus will send
waves backward over the vestibule.* 39 The failure of peristalsis
to move from the pulsating ring in the stomach backwards over
the cardiac sac is due to the sac meeting too much pressure to-
be able to respond. If it were not so, it would itself be the pul-
sating region. The sac therefore exerts only a tonic grasp on
its contents, and the waves move only towards the pylorus.
Probably the greater internal pressure in the vestibule which
results from peristalsis is a factor in bringing this region, where
the muscle rings are small and the muscles themselves are strong,
into more powerful activity.
In harmony with the preceding argument is the observation
already mentioned, that, when peristaltic waves are running on
* I have never seen these reverse waves traverse the conically-shaped
mid-region, though reversal over the more tubular mid-region of man haa
been reported in clinical cases (Rautenberg, Deutsches Arch. f. klin. Med., 1903,
Ixxvii., p. 308).
THE INTRINSIC INNERVATION 193
the stomach, their place of origin can be shifted close to the
vestibule by increasing internal pressure, or almost to the
fundus by decreasing that pressure. In the first procedure the
overstretched region is extended, and the pulsating circum-
ference, having to meet a greater distending force, is moved to
a region where the muscles are stronger and in a smaller ring.
In the second procedure precisely the opposite occurs the
muscles of the cardiac end, gradually less stretched beyond their
responding power, begin to contract, and in consequence the
pulsatile source of the waves is moved farther towards the area
of weakest musculature and largest circumference.
In the stomach, as in the colon, a local neuromuscular mechan-
ism is present for causing a contraction above the stimulated
region. Evidence for this conclusion I presented in 1907, 40 and
by use of chemical instead of mechanical stimulation Sick has
obtained results leading to the same conclusion. 41 Inhibition
below the stimulated point is either very slight or extends only
a short distance. The local reflex may assure the origin of
gastric waves as near the cardia as possible. But that it prob-
ably has little effect in the management of gastric peristalsis I
have shown by cutting rings through both muscular coats to the
submucous connective tissue, thus entirely severing Auerbach's
plexus. In one instance six rings were thus cut between the
cardiac end of the stomach and the pylorus, and after three
weeks the waves were seen passing with perfect regularity, much
as in a normal stomach. When a wave approached in an upper
section, it stretched the muscles in the next lower section, and
they responded by contracting. The contraction passed on
rather than back, because the neuromusculature above, still in
the active phase, was refractory, 42 whereas that below, relaxed,
was ready for contraction in response to extension.
As the stomach empties, the mid- region becomes narrow (see
p. 49). The waves then originate at the upper end of this
gastric tube at a tonus ring separating the tube from the cardiac
sac. The ring forms a depression which has been repeatedly
noted in X-ray photographs of the human stomach, 43 and is
observable also in the exposed stomach of lower animals. X-ray
workers have called this persistent constriction the " incisura
cardiaca." The activity of the deepened ring can best be under-
stood in terms of the activity of tonus rings in the large intes-
tine. Since the stomach when full has a conical shape, the
194 THE MECHANICAL FACTORS OF DIGESTION
formation of a gastric tube of fairly uniform diameter requires a
greater contraction at the cardiac end than at the pyloric end.
Because the cardiac incisure, at the extreme cardiac end of the
tube, is therefore more contracted than any other part of the
stomach, it, like the tonus ring in the colon, is probably more
easily distended than any other part. Distension by the internal
pressure causes the ring to respond rhythmically. Each con-
traction sends off a wave towards the pylorus. And as the food
is forced on into the intestine the cardiac sac, by tonically pressing
on its contents, provides more material for the waves, while
helping to maintain the internal pressure necessary for the con-
tinuance of gastric peristalsis. Only after the means of exercising
internal pressure i.e., the contents have disappeared does the
peristalsis normally cease.
The origin of tonus in the gastric neuromusculature we shall
consider in connection with the extrinsic innervation of the
stomach. The continuance of the tonic state, when once estab-
lished, can be seen in the excised stomach. I have tied the
digesting stomach at the two ends, removed it from the body,
placed it in warm oxygenated Ringer's solution, introduced a
glass tube which rose above the gastric level, and observed for
a half-hour peristaltic waves passing over the organ, and the
contents being gradually discharged as the volume diminished.
Possibly the slow decrease in size (increase in tonic contraction),
especially where the pulsations occur, is due to the " contraction
remainder " of smooth muscle. This phenomenon, to which
Schultz has called special attention, 44 is due to the failure of the
muscle to relax fully before the occurrence of another contraction.
Evidently, if such a remainder were left as a heritage to each
successive shortening, a process of building up would occur.
The muscles would become more and more contracted i.e.,
the circumference of the stomach would be slowly diminished.
The possibility (see p. 60) that the smaller size of the stomach
is the result of the muscle fibres slipping by one another, and
rearranging themselves in an increased number of layers, should
also be kept in mind. For the present we must, therefore,
accept the facts of the tonic state, though we are unable to define
exactly its nature.
The Myenteric Reflex. We have now reviewed the activities of
the stomach and intestines in relation to their intrinsic nervous
control. Each of these regions, and the oesophagus as well, 45
THE INTRINSIC INNERVATION 195
possesses an intrinsic arrangement whereby a stimulus causes
a contraction above and a relaxation below. The relaxation
below may be extensive and marked, as in the small intestine
of the dog, or may be close and slight, as in the small and large
intestine of the rabbit, and in the stomach and oesophagus.
We have seen that throughout the alimentary canal the smooth
muscle is disposed in an outer longitudinal and an inner circular
coat, with Auerbach's plexus between. In the new nomencla-
ture this nerve net is called the " myenteric plexus." Since the
local reflex, which acts, as we have seen, in the cardiac and
pyloric sphincters, and everywhere else in the wall of the canal
to assure orderly progression of the contents, is mediated by the
myenteric plexus, I have suggested that it be called the " myen-
teric reflex." 46
Although more or less extensive inhibition below a stimulated
point is characteristic of the myenteric reflex in the small intes-
tine, abolishment of this inhibition by nicotine does not stop the
passage of rings of constriction along the gut. Such rings or
" waves of constriction " were described by Bayliss and Starling
as moving in either direction regularly and powerfully along the
intestine after the administration of nicotine had destroyed the
local reflex. The usual source of the rhythmic waves in the dog,
they found, was in a slight persistent " ring of constriction "
immediately above the dilating balloon. 47
The conditions in the small intestine appear to be true also
of other parts of the canal. Although the myenteric reflex is
present and capable of taking control of the musculature, yet
it is not always in control. It does not govern the rhythmic
contractions of the small intestine, the rhythmic peristalsis and
antiperistalsis of the colon, and probably not the rhythmic
waves of the stomach. In each of these cases there is no exten-
sive forerunning inhibition. The source of the moving waves is
a pulsating tonus ring, and from this ring waves can pass off in
either direction. For these activities the tonic contraction of
the wall of the canal is all-important.
1 Nothnagel, Arch. /. path. Anat., 1882, Ixxxviii., p. 4.
2 Liideritz, Arch. f. path. Anat., 1889, cxviii., p. 33.
3 Nothnagel, Beitr. z. Physid. u. Pathol. d. Darmes, Berlin, 1884, p. 48.
4 Mall, Johns Hopkins Hosp. Rep., 1896, i., p. 71.
5 Bayliss and Starling, J. Physiol., 1899, xxiv., p. 110
196 THE MECHANICAL FACTORS OF DIGESTION
6 Bayliss and Starling, loc. c',t., p. 115.
7 Bayliss and Starling, loc. cit., p. 116.
8 Magnus, Arch. f. d. ges. Physid., 1904, cii., pp. 123, 349, ciii., pp. 515,
525 ; 1906, cxi., p. 152.
9 Cohnheim, Ztschr. /. BioL, 1899, xxxviii., p. 420.
10 Dogiel, Arch. f. Anat., 1899, Suppl., p. 137.
11 Magnus, Arch. f. exper. Path. u. Pharmakd., 1903, i., pp. 97, 103.
12 Lewandowsky, Die Functionen des Zentral-Nervensystems, Jena, 1907, p. 92.
13 Magnus, Ergeb. d. Physiol., 1905, vii., p. 45.
14 Sick, Deutsches Arch. f. Uin. Med., 1908, xcii., p. 422.
15 Schultz, Arch. f. Physid., 1905, Suppl., p. 23.
16 Magnus, loc. cit., 1906, cxi., p. 152.
17 Bayliss and Starling, J. Physiol., 1899, xxiv., p. 105.
18 Bayliss and Starling, J. Physid., 1901, xxvi., p. 134.
19 Bokai, Arch. /. exper. Pathol. u. Pharmakd., 1887, xxiii., p. 209; xxiv.,
20 Roger, Compt. rend. Soc. de Bid., 1905, Ivii., p. 312.
21 London and Sivre, Ztschr. f. physiol. Chem., 1909, lx., p. 201.
22 London and Sandberg, Ztschr. f. physid. Chem., 1908, Ivi., p. 402.
23 London and Dobrowolskaja, Ztschr. f. physid. Chem., 1909, lx., p. 273.
24 Cannon, Am. J. Physid., 1902, vi., p. 269.
25 Elliott and Barclay-Smith, J. Physid., 1904, xxxi., p. 278.
26 Elliott and Barclay-Smith, loc. cit., p. 304.
27 Bayliss and Starling, J. Physid., 1900, xxvi., p. 107.
23 Langley and Magnus, /. Physiol., 1905, xxxiii., p. 50.
29 Elliott and Barclay-Smith, loc. cit., p. 281.
30 Cannon, Am. J. Physid., 1909, xxiii., p. xxvii.
si Cannon, Am. J. Physid., 1902, vi., p. 265.
32 Elliott and Barclay-Smith, loc. cit., pp. 280, 281, 284, 285.
33 Cannon, Am. J. Physid., 1909, xxiii., p. xxvii.
34 Schultz, Arch. /. Physiol., 1903, Suppl., p. 1.
35 v. Uexkiill, Ergeb. d. Physid., 1904, III. 2 , p. 1.
36 Henderson, Am. J. Physiol., 1909, xxiv., p. 70.
37 Magnus, Arch. f. d. ges. Physid., 1908, cxxii., p. 258.
38 Cannon, Am. J. Physid., 1909, xxiii., p. xxvii.
39 Cannon, Am. J. Physid., 1909, xxiii., p. xxvii.
40 Cannon, Am. J. Physid., 1908, xxi., p. xx.
41 Sick, Deutsches Arch. f. Uin. Med., 1908, xcii., p. 431.
42 Ducceschi, Arch. p. la Sc. Med., 1897, xxi., p. 167.
43 Kaestle, Rieder and Rosenthal, Arch. Rontgen Ray, 1910, xv., pp. 21-24.
44 Schultz, loc. cit., p. 124.
45 Cannon, Am. J. Physid., 1908, xxi., p. xx.
46 Cannon, Am. J. Physid., 1909, xxiii., p. xxvi.
47 Bayliss and Starling, J. Physid., 1899, xxiv., pp. 104, 115.
THE EXTRINSIC INNERVATION OF THE GASTRO-INTESTINAL
THE stomach and intestines receive their extrinsic innervation
from three regions of the central nervous system from the bulb,
from the sacral cord, and from the thoracico-lumbar origin of the
sympathetic. Both the bulbar and the sacral systems of nerves
are in general motor. The bulbar system, through the vagi,
innervates the canal from the oesophagus to the end of the
ileum, diminishing in influence as it descends ; the sacral system,
starting at the anal end, reaches upwards along the colon, with
diminishing influence as it ascends. Opposed to these two motor
systems is the sympathetic, distributed to the same areas which
they innervate, and acting in the main to inhibit what they
stimulate. 1 Through these opposed systems the automatic
activities of the gastro-intestinal tract can be modified, not, to
be sure, voluntarily, but to an important degree by the general
bodily state and by emotional conditions. The way in which
the extrinsic nerves produce their effects we shall consider in
relation to the different parts of the canal the stomach, small
and large intestine taken separately.
The Extrinsic Innervation of the Stomach. Connecting the
bulb with the stomach are the two vagus nerves. Only one is
required to give the entire surface of the stomach a motor supply.
Ducceschi has shown that this fact is not due to the transmission
of impulses through the myenteric plexus ; for if one of the vagus
trunks is cut at the cardia, the corresponding part of the stomach
does not respond to vagus stimulation. The capacity of one of
the cervical vagi to innervate the whole stomach is, therefore,
probably due to the interweaving of fibres from the two nerves
in their course down the oesophagus. 2
The vagus fibres distributed to the heart connect with the
198 THE MECHANICAL FACTORS OF DIGESTION
intrinsic nerve cells of that organ, and the connection is readily
interrupted by nicotine. Although the endings of the vagus
fibres in the stomach have not been traced, probably they do
not impinge directly on the smooth muscle, but affect it through
nerve cells embedded in the gastric wall. The observation of
Bayliss and Starling, that nicotine permanently abolishes the
action of vagus impulses on the gut, 3 may be interpreted in this
manner. For reasons which we shall consider in discussing the
innervation of the colon, Langley is inclined to believe that these
outlying nerve cells are not part of the my enteric plexus. 4
The action of the vagus impulses can be shown by recording
alterations of gastric pressure as a result of vagus stimulation.
The first effect of moderate stimulation is a lessening of the tonus
of the muscle. The cardiac sac markedly relaxes ; and although
the pyloric waves may continue, they are diminished in ampli-
tude. The inhibitory action may last in some instances during
sixty or seventy seconds of stimulation ; in other instances it
continues only ten or fifteen seconds. The inhibition is followed
by an augmentor effect indicated by increased tonus and greater
amplitude of the rhythmic waves than normal. This stage in
turn is followed by the subsidence of both tonus and waves to
the initial state. When a vagus nerve is repeatedly stimulated,
however, the tonus increases more permanently after each stimu-
lation, and in some instances may remain continuously high. 5
The bulbar supply, therefore, may have not only an augmentor,
but also an inhibitory effect, and the evidence from stimulation
indicates that the inhibitory effect appears after a shorter latent
period, and has less permanence than the augmentor.
The function of the vagus impulses can be inferred also from
the effects of severing the nerves. These effects have been
studied in a series of experiments by means of the X rays. 6 The
right vagus was severed below the origin of the recurrent laryngeal
branch, and in a second operation the left nerve was severed in
the neck. When both nerves were thus sectioned, the first
effect was often total suppression of peristalsis. In two instances
in which the second vagus was cut immediately after the animals
had voluntarily eaten boiled lean beef, no gastric peristalsis was
observed for four hours ; and in another instance in which this
operation was done the day previous, no gastric peristalsis was
seen during the first three hours after feeding. This depression
of function was observed also when the splanchnic nerves had
THE EXTRINSIC INNERVATION 199
been previously severed. In every instance of vagus section,
however, the peristaltic waves, even when restored and running
with normal rhythm, were characterized at first by being extra-
ordinarily shallow. Sometimes they were hardly visible ; at other
times they could be seen distinctly only on the vestibule. But
the period during which the movements of the stomach were
late in commencing and were notably weak did not long con-
tinue. As days passed, these abnormalities largely disappeared,
and the waves started at the usual time and had much of their
The similarity between the effects of vagus section on the
stomach and on the oesophagus is noteworthy. As we have
learned (see p. 28), the immediate effect on the oesophagus of
severing the vagi is paralysis. The food stagnates in the
tube for hours, distending its walls, but the toneless structures
make no response. In time the part composed of smooth muscle
recovers its power. Then distension, it will be recalled, becomes
the efficient stimulus. At first, however, a slender mass has no
effect ; the addition of a second mass is required to call forth a
constriction. As time goes on, however, even a slender mass
becomes effective. The neuromusculature has recovered by
itself the state which the vagi formerly maintained the tonic
state which makes it resilient when stretched.
That the restoration observed in the oesophagus is duplicated
in the stomach is shown by what occurs when all extrinsic nerves
are cut. The stomach develops in itself a remarkable degree of
tonus. As I pointed out in 1906, the diameter of the organ in
the cat may under these circumstances be only 1-5 or 2 centi-
metres a smallness of size almost incredible. 7
We are now in a position to consider the normal function of
the vagus nerves with reference to the musculature of the
stomach. We have seen that repeated stimulation of these
nerves causes an increased and more permanent tonic contraction
of the gastric wall, and that as the tonus increases the peristaltic
constrictions increase, and vice versa. We have seen also that
when the nerves are cut the activities are for some time in abey-
ance, and even when peristalsis reappears the constrictions at
first are shallow. We may conclude, therefore, that the function
of the vagi is that of setting the muscles in a tonic state, of
making them exert a tension, so that in relation to the gastric
contents thev are as if stretched by those contents.
200 THE MECHANICAL FACTORS OF DIGESTION
The prime importance of the tonic state for normal functioning
of the gastric neuromusculature has already been emphasized
in the discussion of intrinsic innervation. The evidence there
adduced is strengthened by the observation that, when all
extrinsic nerves are cut, the oesophagus and the stomach develop
in themselves a tonic state. Whether the extrinsic nerves are
present or not, the muscles of the gastric wall must be in tonus,
and must be placed in tension by the contents before response
will occur. In all probability the extrinsic nerves (the vagi)
adapt the size of the organ to the varying amount of food taken
in. Thus, if the stomach were relaxed, these nerves might set
the muscles into tension about a small amount of food which
otherwise would not produce any tension whatever. After these
nerves are severed, however, the intrinsic tonus which appears
compensates by rendering the stomach so contracted that, even
if only a small amount is swallowed, the muscles are stretched,
and peristaltic activities are at once started.
The question now arises as to the stage in the digestive process
at which the vagus influences affect gastric tonus. That during
the mastication and ingestion of food impulses pass down these
nerves to the stomach was proved by Pawlow's observations on
the psychic secretion of the gastric juice. 8 As already stated,
repeated stimulation of the vagi results in an increased tonic
state, which is much more persistent than that which follows
single stimulation. Since a tonic state is necessary for gastric
peristalsis, and since peristalsis does not appear if the vagi are
cut shortly before the ingestion of food, the inference is sug-
gested that just as there is psychic secretion, so likewise there
is psychic tonus. At present, however, no direct evidence has
been. secured for this inference.
After digestion is well started, the vagus nerves can be severed
without altering either the nature of gastric peristalsis or the
rate at which the stomach empties itself. This statement is
supported both by observations with the X rays, and by inspec-
tion and records of intragastric pressure when the digesting
stomach was exposed under salt solution. Psychic tonus, like
psychic secretion, would be aroused while food was being ingested,
and might continue for a period of some minutes thereafter.
Then the tonic state must be continued by other agencies. As
the above evidence and also observations on the excised stomach
show (see p. 194), the tonic state, once established at the be-
THE EXTRINSIC INNERVATION 201
ginning of gastric digestion, is self-supporting, and, again like
the psychic secretion, maintains itself by some local mechanism.
The inhibitory impulses along the vagi have their function
after gastric tonus has developed a considerable pressure in the
stomach. By introducing a balloon into the cardiac end of the
stomach through an oesophagotomy opening in the neck, the
alterations of intragastric pressure and volume can be recorded.
If now the animal swallows, the food does not pass down the
03sophagus, but emerges through the upper opening. Using this
method, C. W. Lieb and I have shown 9 that after each separate
swallow intragastric pressure drops almost to zero ; and if the
balloon pressure is 3 or 4 centimetres of water, the volume of the
stomach may increase by 8 or 10 c.c. The fall of pressure begins
between two and five seconds after the larynx rises, and the
greatest volume change is reached between six and ten seconds
after the bolus leaves the mouth. The admirable character of
this receptive relaxation of the stomach can be appreciated if
we recall that the time required for a bolus to be carried through
the cat's oesophagus varies between seven and ten seconds.
Thus, whenever a tonic state of the gastric musculature has
raised intragastric pressure, an automatic mechanism exists for
lowering that pressure while the oesophagus is pushing new food
into the stomach. If the vagi are cut, the phenomenon does
Stimulation of the splanchnic nerves, most observers have
reported, causes diminished tonus of the gastric musculature and
weakening of the rhythmic contractions. Again we note the
concomitant variation of tonus and rhythmic response to tension.
A maximum loss of tone and total disappearance of pulsations
and peristalsis occur when adrenalin is administered (see Fig. 33,
p. 191). The presence and action of inhibitory sympathetic
nerves 10 was thus demonstrated by Elliott. That these nerves
exert a constant influence is made probable by the observation
that, when all extrinsic nerves to the stomach are cut, gastric
peristalsis and the rate at which the stomach empties are more
nearly normal than when the vagi alone are cut, and the splanch-
nics left intact. The abnormality of functioning after vagus
* The recent observation by Joseph and Meltzer (Am. J. Physid., 1911,
xxvii., p. xxxi), that in the rabbit contraction of the pyloric portion of the
stomach is accompanied by inhibition of duodenal contractions, may be a
phenomenon similar to the receptive relaxation of the stomach. Tho
mechanism of the duodenal inhibition has not been reported.
202 THE MECHANICAL FACTORS OF DIGESTION
section, therefore, is due, not only to the absence of vagus
impulses, but also in part to the depressive effect of the
Whether sensory impressions arise in the stomach itself is still
in question. From clinical experience, surgeons have reported
that the stomach, and the intestine also, can be cut, crushed, or
burned, in operations on the conscious human subject without
any experience of discomfort. According to Lennander's studies,
no sensations of pain, touch, heat, or cold, arise in the viscera of
the abdomen which are innervated only by the vagi and the
sympathetic nerves. This is true either in normal conditions or
during inflammation. The pain not infrequently referred to the
abdomen is explained as the result of disturbances in the serous
membrane and the subserous connective tissue of the abdominal
wall, which are innervated by the phrenic, the lower six inter-
costal, the lumbar and sacral nerves. This parietal surface, like
the cornea, seems, when stimulated, to originate only sensations
of pain. It may be stimulated by rubbing, especially when
inflamed, or by stretching any mesenteric attachment or patho-
logical adhesion between the viscera and the abdominal wall. 12
In support of the contention that the abdominal viscera are
not sensitive to heat and cold, Hertz, Cook, and Schlesinger, have
reported that if care is taken to introduce hot or cold water into
the stomach through the inner of two tubes, no temperature
sensation is experienced. The temperature sensations usually
ascribed to the stomach they attribute to stimulation of the
oesophagus ; for if the water is introduced when the tubes are
withdrawn until slightly above the cardia, the subject can tell
whether it is hot or cold. Hydrochloric acid, even 0-5 per
cent., poured into a normal empty stomach produces no sensa-
tion whatever, but strong alcohol (48 per cent.) injected through
a gastric fistula causes a burning sensation. Conceivably, how-
ever, the alcohol is in part regurgitated into the oesophagus. 13
The distressing effect of a foreign object in the stomach,
such as a thermometer-tube or a balloon, has been recorded by
Beaumont and by Moritz (see p. 52). The two conditions
most commonly associated with gastric pain are liberation and
cramp. Observations on patients with gastric ulcer have shown
that even weak acid introduced into the stomach causes pain. 14
The pain from ulcer in the stomach or intestine is explained by
Lennander as a result of inflammation of the lymphatic vessels
THE EXTRINSIC INNERVATION 203
and glands which drain the affected region. The painful cramp
is attributed to a strong contraction of a part of the alimentary
canal which stretches the parietal serosa either directly or through
mesenteric connections. In man the duodenum and the colon,
because of their relations to the abdominal wall, are especially
capable of causing pain, both by inflammations and by powerful
The clinical evidence of the insensitivity of the viscera has
been criticized by Kast and Meltzer. Experimental observations
on dogs and cats indicated to them that the operation of opening
the abdominal cavity may have an inhibitory effect on sensory
impulses, especially in states of bodily weakness. Unmistakable
signs of pain can be evoked, they declare, if after a small
opening is made in the body wall a short loop of intestine is
withdrawn and immediately investigated. In their experience,
inflammation increases the irritability. 16 According to Duc-
ceschi, stimulation of the gastric wall with thermal, mechanical,
or chemical agencies causes characteristic changes in the rhythm
and frequency of respiration, like those attending stimulation of
sensory nerves. These effects are produced by way of either
the vagus or splanchnic paths. The afferent fibres of the vagi,
like the efferent, are distributed from each nerve trunk at the
cardia to only one side of the stomach, whereas the fibres in one
cervical vagus are sent to all parts of the organ. Likewise the
afferent fibres in each splanchnic nerve are connected through
filaments from the coeliac plexus with the entire surface of the
stomach. Thus only one cervical vagus or one splanchnic nerve
would be necessary to carry afferent impulses from any part of
the gastric wall to the central nervous system. 17 These observa-
tions on the sensitivity of the gastro-intestinal canal, quite apart
from irritation of the abdominal wall, have been corroborated
by Ritter, 18 whose results correspond to those obtained by Kast
and Meltzer. More recently Miller has shown that irritation of
the gastric mucosa with mustard evokes salivation, rapid respira-
tion, and the vomiting reflex. All these effects are absent if the
vagi have been previously cut. He was unable to demonstrate
that the splanchnics transmit sensory impulses of any kind from
the gastric mucosa. 19
From the above brief review it is clear that important unex-
plained discrepancies exist among investigators, so that a
definite decision as to the immediate origin of pain sensations in
204 THE MECHANICAL FACTOKS OF DIGESTION
the walls of the stomach and intestines cannot as yet be made.
There is no doubt that disturbances in these structures result in
sensations of one sort or another. Aches, pains, vague feelings
of heaviness, are all experienced in pathological conditions of the
tract below the diaphragm. The question is as to the possibility
of these conditions affecting the central nervous system immedi-
ately and not by way of spinal nerves.*
The Extrinsic Innervation of the Small Intestine. Most ob-
servers have attributed to the vagus nerves motor effects on the
small intestine. After section of the splanchnic nerves and in-
terruption of inhibitory impulses to the heart, Bayliss and
Starling found that repeated stimulation of the vagus in the
neck gave consistent results. A very brief inhibitory phase was
followed by a rise of tonus and a gradual increase of the rhythmic
contractions to an extent above the normal, and, as soon as the
stimulation was stopped, by an immediate and considerable
increase of tonus and augmentation of the beat. The return to
the original state is slow and gradual. The vagus nerves appear,
therefore, to convey both motor and inhibitory fibres to the
small intestine, although the inhibitory effect is conceivably due
to the direct nervous stimulation of a region above the recording
The splanchnic nerves were shown by Pfliiger many years ago
to have an inhibitory influence on the movements of the intes-
tine. 21 Although other investigators have since described motor
effects from stimulation of sympathetic fibres, and still others
have believed that the effects are opposite on the longitudinal
* Among the sensations referred rather indefinitely to the abdomen is that
of hunger. Either directly or through an effect on the parietal peritoneum
gastric conditions may give rise to this sensation. In studying auscultation of
the abdominal sounds I had occasion to note repeatedly that the sensation of
hunger was not continuous, but recurrent, and that its disappearance was
commonly associated with a rather loud gurgling sound as heard through the
stethoscope. Since then I have paid occasional attention to the matter, and
have experienced disappearance of the sensation as gas was gurgling upward
through the cardia. That the gas was rising rather than being forced down-
ward was shown by its regurgitation immediately after the sound was heard.
As a suggestion I venture to state that hunger is due to contraction of the
nearly empty stomach. The contracted stomach in fasting animals has been noted
(His, Arch. f. Anat., 1903, p. 345). In the cat, after forty-eight hours of
fasting, the organ may be so small as to look like a slightly enlarged duodenum
(Wolff, Dissertation, Giessen, 1902, p. 9). Of course, the hungry stomach, thus
contracted, is ready at once to begin rhythmic pulsations on being stretched
by food. In this connection it is of interest to note that the disagreeable
sensation of hunger, in my experience, is momentarily abolished a few seconds
after swallowing, a result which can be explained as due to the inhibitioa of
gastric contraction by vagus influences, in the manner above described.
THE EXTRINSIC INNERVATION 205
and circular muscle, the careful work of Bayliss and Starling
has demonstrated only inhibition of activity in each muscular
Since the splanchnic nerves bear vasoconstrictor impulses to
the bloodvessels of the intestines, and since the primary result
of anaemia is cessation of intestinal activity, the inhibitory effect
these nerves produce might be due to a diminished blood-supply.
This interpretation of the results of sympathetic impulses Bayliss
and Starling were able to exclude by causing the usual effects
immediately after the death of the animal, when the circulation
was no longer present. 22
The normal functions of the two sets of nerves seem to be
exercised continuously. After complete severance of the splanch-
nic nerves, for example, I found that the rate of passage of lean
beef through the small intestine was much accelerated, whereas
after total vagus section the passage was slower than normal. 23
Probably the vagus nerves act on the intestine, just as they act
on the stomach, to produce a tonic condition of the neuromuscu-
lature. Magnus has reported that it is advisable, in studying
isolated pieces of the intestine, to take them from a normally
fed animal, since the intestine of a fasting animal is less active.
If, however, the animal has been without food for three days,
the intestine begins activity as soon as placed in Ringer's solu-
tion. The condition in the last instance seems not unrelated to
the readiness for activity in the highly tonic fasting stomach.
The Extrinsic Innervation of the Large Intestine. Whether
vagus fibres reach the large intestine is still in doubt. Bayliss
and Starling were unable to demonstrate that vagus stimulation
affected any part of the large intestine. 24 On the other hand,
Meltzer and Auer observed that vagus stimulation caused strong
contraction of the caecum in the rabbit. 25 Apart from this
possible vagus innervation, the large intestine receives, as already
stated, a motor supply through the sacral visceral nerves, and
an inhibitory supply from the lumbar cord through the sympa-
thetic system by way of the inferior mesenteric ganglion. The
sacral nerves (from sacral roots ii. and iii., and occasionally i., in
the cat) do not pass directly from the spinal cord to the colon,
but end in ganglia at the side of the rectum and the neck of the
bladder. After nicotine has abolished conduction through these
ganglia, stimulation of the post-ganglionic fibres still causes
contraction. There exist, consequently, in relation to the colon.
206 THE MECHANICAL FACTORS OF DIGESTION
peripheral neurons of the motor path which are quite distinct
from the my enteric plexus. 26
Although results have been reported indicating a " crossed
innervation " of the two muscular coats i.e., contraction or
inhibition of the circular coat by impulses that simultaneously
inhibit or contract the longitudinal coat 27 Bayliss and Starling
in their careful observations found that sympathetic stimulation
caused pure inhibition, while sacral stimulation after a momen-
tary inhibition called forth contraction of both the circular and
longitudinal coats. 28 These observations Elliott and Barclay-
Smith have confirmed, but they found that the pelvic nerves are
distributed only to that part of the colon which is involved in
the act of defaecation. For example, these nerves supply all but
the caecum in the dog, and the distal two-thirds of the colon in
the cat. The region where antiperistalsis prevails does not,
therefore, receive motor impulses. Stimulation of the pelvic
nerves first increases the tonus of the mid-region, whence then
antiperistaltic waves may arise ; but continued stimulation
causes the distal half of the colon to shorten, and thereafter a
strong contraction of the circular coat to spread downward in
the manner already described for natural evacuation. 29
The normal functioning of the two sets of nerves is indicated
by the results of sectioning, as well as by the results of stimulating
them. Severance of the sympathetic fibres supplying the large
intestine causes in the cat and the rabbit no lasting disturbance
of the motor functions. After removal of the motor impulses,
however, by destruction of the spinal cord or by cutting the
nerves, the functions of the colon in the rat and the rabbit are
evidently disturbed. Faeces accumulate, and the contractions
of the gut are sluggish and weak. 30 Langley and Anderson's
observations on the cat with sacral nerves cut indicate a similar
defect of function. 31 These functional defects are not the tem-
porary result of motor nerve section, like the inactivity of the
stomach after severance of the vagi, for they were observed in
the rat and rabbit six weeks after operation. They may be due
in part, however, to the continuance of inhibitory sympathetic
impulses acting in the absence of their usual opponents. This
suggestion is supported by the observation of Goltz and Ewald,
that, although removal of both sets of nerves by destruction of
the lumbar and sacral cord results in a diarrhoea lasting several
days, yet recovery occurs, and after a few weeks the dog exhibits
THE EXTRINSIC INNERVATION 207
normal activity of the colon, with faeces of usual consistency
discharged at customary intervals. After defaecation the rectum
is found empty. 32
As already stated, defsecation is a reflex initiated by the
presence of faeces in the rectum. The section of sensory roots
of the sacral nerves supplying the rectal mucosa causes an aboli-
tion of the normal co-ordination. 33
The Innervation of the Sphincters. Although the cardiac and
pyloric sphincters are affected by local conditions, they are, like
the rest of the canal, subject also to the central nervous system.
The extrinsic innervation of the cardia has been considered. At
the pylorus the usual result of vagus stimulation is contraction, 34
but Langley observed also at times dilatation. 35 According to
Openchowski, the same stimulation of the vagus that produces
relaxation of the cardia simultaneously produces closure of the
pylorus, a co-ordination that is evidently serviceable in vomiting.
The splanchnics cause in the rabbit contraction of the pyloric
sphincter, and when adrenalin is given the same result is to be
seen. 36 In dogs, splanchnic stimulation is said to relax or open
a closed pylorus. 37
The ileo-colic sphincter was unaffected, in Elliott's experience,
by vagus stimulation. Its tonic closure is due to impulses from
the central nervous system by way of the splanchnics. If these
nerves are stimulated, the tonus of the sphincter increases ; if
they are cut or the spinal cord destroyed, the sphincter becomes
toneless and permits material to pass back from the colon. 38
Both the internal and external anal sphincters are normally
in a state of tonic contraction. Although the external sphincter
is composed of striated muscle, its connection with extrinsic
nerves is not interrupted by curare. Destruction of the spinal
cord, 39 or removal of the ganglia between the cord and the
viscera, 40 causes a loss of tonus of the sphincters, from which,
however, they soon recover. Stimulation of the sympathetic
nerves in the cat causes contraction of the internal sphincter,
and in the rabbit and dog at times contraction, and at other times
relaxation. 41 The sacral nerves, when artificially excited, cause
closure of this sphincter in the dog, relaxation in the rabbit, and
both effects in the cat.
The diverse results reported as the result of stimulating the
sphincters are perhaps due to the artificial character of the
excitation. In physiological conditions they co-operate with
208 THE MECHANICAL FACTORS OF DIGESTION
other processes ; the orderliness of their action then is probably
produced through nervous connections. In the case of the cardia,
Kronecker and Meltzer showed the manner in which the physio-
logical relaxation is associated with the passage of a bolus into
the stomach. Further observations on the sphincters with refer-
ence to physiological stimuli will be necessary before the func-
tions of the extrinsic nerves can be clearly denned. Meanwhile
the only generalization which has been offered is that of Elliott,
who has stated that " If the quiet lodgment of the contents be
facilitated by the presence of sympathetic inhibitor nerves to the
body of the viscus, there will also be sympathetic motor nerves
to the sphincter closing the exit." 42 Thus adrenalin, which
stimulates as sympathetic impulses stimulate, causes relaxation
of the entire gastro-intestinal tract, except at the pyloric, ileo-
colic, and internal anal sphincters.
1 Langley, Ergeb. d, Physiol., 1903, ii. 2 , p. 832.
2 Ducceschi, Arch, di Fisiol., 1905, ii., p. 52.
3 Bayliss and Starling, J. Physiol. , 1899, xxiv., p. 143.
4 Langley, loc. cit., p. 853.
5 May, J. Physiol., 1904, xxxi., pp. 262, 264.
6 Cannon, Am. J. Physiol., 1906, xvii., p. 431.
7 Cannon, Am. J. Physiol., 1906, xvii., p. 432.
8 Pawlow, The Work of the Digestive Glands, London, 1902, p. 50.
9 Cannon and Lieb, Am. J. Physiol., 1911, xxvii., p. xiii.
10 Elliott, /. Physiol., 1905, xxxii., p. 420.
11 Cannon, Am. J. Physiol., 1906, xvii., p. 441.
12 Lennander, Arch. f. Verdauungskr., 1907, xiii., p. 467.
13 Hertz, Cook, and Schlesinger, J. Physiol., 1908, xxxvii., p. 481.
14 Bonninger, Berl. klin. Wchnschr., 1908, xlv., p. 396.
15 See Lennander, loc. cit., also J. Am. Med. Ass., 1907, xlix., p. 836 ; Wilms,
Mitth. a. d. Grenzgeb. d. M. u. Chir., 1906, xvi., p. 609.
16 Kast and Meltzer, Mitth. a. d. Grenzgeb. d. M. u. Chir., 1909, xix., p. 616.
17 Ducceschi, Arch, di Fisiol., 1905, ii., p. 525.
18 Ritter, Zentralbl. f. Chir., 1908, xxxv., p. 611.
19 Miller, J. Physiol., 1910, xli., p. 410.
20 See Starling, Ergeb. d. Physiol., 1902, i. 2 , p. 460.
21 Pfiiiger, U. d. Hemmungsnervensystem f. d. peristalt. Beweg. d. Gedarme,
22 Bayliss and Starling, loc. cit., p. 124.
23 Cannon, Am. J. Physiol., 1906, xvii., p. 438.
24 Bayliss and Starling, J. Physiol., 1900, xxvi., p. 114.
25 Meltzer and Auer, Proc. Soc. Exper. Biol. H., New York, 1907, iv.,
26 Langley and Anderson, J. Physiol., 1895, xviii., p. 67, xix., pp. 71, 372 ;
1896, xx., p. 372.
27 Ehrmann, Wien. med. Jahrb., 1885, p. 115 ; Fellner, Arch. f. d. ges. Physiol.,
1894, Ivi., p. 542 ; Courtade and Guyon, Arch, de Physiol., 1897, xxix., p. 881.
J8 Bayliss and Starling, J. Physiol., 1900, xxvi., p. 107.
29 Elliott and Barclay-Smith, J. Physiol., 1904, xxxi., pp. 282, 283.
30 Elliott and Barclay-Smith, loc. cit., p. 288.
THE EXTRINSIC INNERVATION 203
31 Langloy and Anderson, J. Physiol., 1896, xix., p. 380.
52 Goltz and Ewald, Arch. f. d. ges. Physiol., 1896, Ixiii., p. 331.
13 Merzbaoher, ^rcfe. /. d. ges. Physiol., 1902, xcii., p. 597.
34 See Openchovvski, loc. tit., p. 4.
35 Langley, /. Physiol., 1898, xxiii., p. 414.
36 Elliott, J. Physiol., 1905, xxxii., p. 420.
3r Oser, Ztschr. /. Idin. Med., 1892, xx., p. 291.
38 Elliott, J. Physiol., 1904, xxxi., p. 166.
39 Goltz and Ewald, loc. tit., p. 399.
40 Frankl-Hochwart and Frohlich, Arch. f. d. ges. PhytioL, 1900, Ixxxi.,
41 Langley and Anderson, J. Physiol., 1895, xviii., p. 104 ; Frankl-Hochwart
and Frohlich, loc. tit., p. 462.
42 Elliott, J. Physiol., 1905, xxxii., p. 422.
DEPRESSIVE NERVOUS INFLUENCES AFFECTING GASTRO-
THUS far our review of the extrinsic innervation of the alimentary
canal has shown that two influences are affecting its movements
depressive influences through the sympathetic, and augmentor
influences through the bulbar and sacral nerves. It is clear that
absence of activity may be due either to a failure of the impulses
which establish the necessary tonic state of the musculature, or
to the predominance of the impulses which depress. In these
relations the phenomena attending a condition of general bodily
weakness are of interest.
The Influence of General Asthenia. When the nervous con-
nections between the alimentary canal and the central nervous
system are intact, nothing is more remarkable than the respon-
siveness of the canal to general asthenia. I have had repeated
opportunity to examine the movements of the stomach and
intestines in animals suffering from " distemper," with purulent
inflammation of the nose and eyes, with soft toneless muscles,
and every appearance of debility. Under these circumstances,
food will lie in the stomach or intestine all day without the
slightest sign of a peristaltic wave affecting it. There is total
stoppage of the motor activity of the digestive organs.
The result is quite different when the canal is disconnected
from the spinal cord and brain. In such a state the stomach
and small intestine have been observed exhibiting their normal
activities, although the animal was to the last extremity feeble
and toneless. 1
The absence of activity in states of bodily depression is prob-
ably due in greatest measure to the lack of necessary tonus in
the gastro-intestinal musculature. The animals manifest no signs
DEPRESSIVE NERVOUS INFLUENCES 211
of appetite, and do not eat spontaneously. There is, conse-
quently, no occasion for the establishment of the " psychic
tonus " which I have suggested as a resultant of the eager
taking of food. It is possible, however, that when all nerves
are intact inhibitory influences through the splanchnics may also
play a part in maintaining the quiet state, for fairly normal
activities have been observed in two cases of asthenia when only
splanchnic nerves had been severed and the vagi were still
Post-operative Paralysis. One of the most distressing instances
of inactivity of the bowel is that seen occasionally after surgical
operations on the abdomen. From what we have learned of
the controlling factors, we should expect that this inactivity
might be due either to general causes working through the
central nervous system, or to local factors, such as the inefficiency
of the myenteric plexus or the muscles subject to it. With the
hope of determining the relative importance of the modifiable
procedures in surgical operations, F. T. Murphy and I under-
took to learn the effects of etherization, and of exposing,
cooling, and handling the alimentary canal, on the passage of
food from the stomach and through the small intestine. 2
The effect of etherization was tested by etherizing one half-
hour or one hour and a half, and feeding about a half-hour there
after 25 c.c. of the standard potato and bismuth subnitrate
mixture. By the method already described the aggregate length
of the food-masses in the intestine was determined at regular
intervals after feeding. The results are shown in Fig. 34.
Clearly, anaesthesia alone, compared, for example, with high
intestinal operation accompanied by anaesthesia (see p. 126),
has relatively slight effect. The initial passage of food from
the stomach was delayed and the outgo was slow. The passage
through the small intestine was also slow. Material reached the
colon, not after two or three hours, as in normal conditions, but
only after four, five, and six hours. But etherization, neverthe-
less, did not cause inactivity of the canal.
The effect of exposure was tested by displaying the stomach
and small intestine as much as possible without manipulation,
during a half-hour's anaesthesia. The visible serosa became dry
and lustreless. At the end of the half-hour the abdomen was
closed, and when the animal had recovered from the ether the
standard food was fed. Fig. 35 represents graphically the
THE MECHANICAL FACTORS OF DIGESTION
differences between the normal condition and that following
exposure. As long ago as 1872 v. Braam Houckgeest 3 noted
the disturbing effect of exposure on the action of the intestines,
Sp % <
*S A 1 V 6 4 6 b 7
The continuous line represents the normal condition ; the dash-line the typical
condition after etherization for a half -hour ; and the dot-line the typical
condition after etherization for an hour and a half.
and to avoid it he devised the warm saline bath as the medium
in which to retain the normal conditions when the abdomen is
opened. The inhibitory effect of exposure might be expected to
exert a disturbing after-effect. That seems not to be the case.
*S 4 1 -A 5 4 o b ' 7
The continuous line represents the normal condition ; the dash-line the typical
condition following etherization, with exposure of the stomach and
intestines to the air for a half -hour.
The passage of the food through the canal was hardly different
from that which followed etherization alone.
Cooling the body causes a cessation of the movements of the
DEPRESSIVE NERVOUS INFLUENCES
alimentary canal. 4 It was possible that a temporary cooling of
the stomach and intestines, without drying, would stop the
movements of these organs. To test this possibility, sterile
normal salt solution at 20 C. was poured repeatedly' into the
opened abdominal cavity for ten minutes during the usual half-
hour of etherization. The procedure reduced the body tem-
perature to nearly 33 C. About forty minutes after the abdo-
men had been closed and the etherization discontinued, the animal
was given the standard food. Fig. 36 represents graphically the
results. The discharge from the stomach again started some-
what slowly, but the passage through the small intestine was
surprisingly rapid. The sharp drop in the curve between the
re i 1 2 3 4 5 b 7
The continuous line represents the normal condition ; the dash-line the typical
condition after etherization and cooling of the abdominal cavity with
sterile normal salt solution at 20 C. The early drop in the dash-line is
due to the rapid passage of the food into the large intestine.
second and third hours is thus explained. Although the degree
of cooling was excessive, the departure of food from the stomach
was about as rapid as when etherization alone disturbed the
normal state. And the rapid passage of the food through the
small intestine certainly lends no support to the idea that cooling
causes enteric paresis.
Handling the stomach and intestines may have different effects
according to different degrees of manipulation, and these degrees
are difficult to express. In the most severe treatment the organs
were stripped between the thumb and first finger with consider-
able pressure, as would be done in forcing out the contents ; in
the less severe treatment the organs were fingered gently in air,
or in a trickling stream of warm normal salt solution, with the
THE MECHANICAL FACTORS OF DIGESTION
parts protected from the fingers by absorbent cotton wet with
the solution, or run through the bare fingers within the peritoneal
cavity. About an hour after stopping the anaesthetic the animals
were fed as in former experiments, and the observations were
taken at the usua] intervals. The relation of typical cases to the
normal condition is shown graphically in Fig. 37. In examining
these curves, we should remember that since neither etherization
alone, nor such cooling and drying as the viscera in some cases
suffered, cause a delay in the passage of food from the stomach,
the delay must have been due to the manipulation. Even when
the stomach and intestines were handled most gently, either
The heavy, continuous line represents the normal condition ; the light, con-
tinuous line the typical condition after har dling the stomach and intestine
gently under warm normal salt solution ; the dash-line the typical con-
dition after handling the organs gently in the peritoneal cavity ; the dash-
and-dot line after handling them gently in the air ; and the dot-line after
handling them severely in the air.
under warm normal salt solution or within the peritoneal cavity,
no movements of the stomach were seen, and no discharge into
the intestine, for three full hours after the feeding. Even after
the first departure of food from the stomach the discharge con-
tinued very slowly, as shown by the sloping of the curve. The
passage through the small intestine was also retarded. In only
one case did food appear in the large intestine before the end of
the seven hours of observation.
When the organs were removed from the abdomen and handled
gently in air, the movement of the food was retarded to a greater
degree than when they were fingered in the peritoneal cavity or
under warm normal salt solution. So great was the retardation
DEPRESSIVE NERVOUS INFLUENCES 215
in one case that not all the food had passed into the large
intestine from the ileum twenty-six hours after the feeding.
Indeed, the condition then was that reached normally in about
With rougher treatment in air food was first passed from the
stomach only after four hours. Thenceforward it departed very
slowly, and, as shown by the permanence of position from
observation to observation, was carried through the small
intestine with extreme sluggishness. In one case of severe
manipulation no food had left the stomach at the end of seven
hours, and in another case the food had not yet reached the
large intestine twenty-four hours after the feeding (the food
used begins to appear there normally at the end of two or three
hours). Only a slight amount of food was in the small intestine,
and the stomach was still well filled. Manipulation of the
stomach and intestine, therefore, even gently and under most
favourable circumstances, produced in our experiments much
greater effect in the direction of post- operative inactivity
than any other of the factors concerned in the manner of
Whether manipulation acted locally on the neuromusculature
of the alimentary canal or indirectly through reflex inhibitions
from the central nervous system remained to be determined.
The observation of Bayliss and Starling that manipulation of
the intestine at one point inhibits activities at other points 6
was suggestive of reflex inhibition.
In order to test the source of the post-operative inactivity,
Murphy and I undertook a further series of experiments. 6
Evidently, if the inactivity is due to reflex inhibition, handling
after the splanchnic nerves are cut ought to have no effect,
since the pathway for inhibitory impulses is destroyed. If
after severance of the splanchnics, however, manipulation still
produces inactivity, th.e result can be attributed to local dis-
Animals in which the splanchnic nerves had been severed
aseptically several days before were treated in the same manner
as the normal animals on which the earlier observations were
made. During the half-hour of etherization the abdomen was
opened, and the stomach and intestines, under aseptic precau-
tions, were stripped between the fingers i.e., roughly handled.
Within an hour after etherization ceased the animals were given
216 THE MECHANICAL FACTOKS OF DIGESTION
the standard food, and observed at the regular intervals after
In one animal there was no discharge from the stomach during
seven hours of observation, though the next day the stomach
was largely empty. Another animal vomited the gastric con-
tents after the first hour. In a third case nothing left the
stomach during the first six hours, and then the outgo was slow.
In still another instance food began fco pass the pylorus at the
end of an hour, but the exit was very slow, and at the end of
seven hours no food had reached the large intestine. These
results correspond closely to the results following manipulation
of the stomach and intestines of normal animals. In both there
was a marked retardation of the discharge of food from the
stomach, and a sluggish condition of the small intestine. The
effects of handling, therefore, are not necessarily the consequence
of reflex inhibitions from the spinal cord, but can be explained
as disturbances of the local mechanisms in the wall of the gut.
The observation of Meltzer and Auer that destruction of the
spinal cord in the rabbit does not prevent the direct inhibition
of peristalsis, observed when the abdomen is opened, 7 and our
observation of local inhibition, are in perfect agreement.
Lasting inactivity of the gastro-intestinal tract can also be
produced reflexly. Thus Meltzer and Auer found that dissec-
tion of the skin over the abdomen produced reflex inhibition of
peristalsis, and Murphy and I found that trauma of the testicles
during the half-hour of etherization retarded the exit from the
stomach for four or five hours, and caused the exit thereafter to
be characteristically slow. The movement through the small
intestine was likewise very sluggish ; in only one case out of ten
did the potato reach the colon within six hours. If the splanchnic
nerves have been previously severed, trauma of the testicle has
no effect whatever ; indeed, the results observed in these cases
compare favourably with those from animals in quite natural
The animals used in these experiments were vigorous and
normal. The trauma to which they were subjected was done
under anaesthesia when nervous conduction may be much
depressed. The intestine of these animals also may be less
sensitive to manipulation than is the human intestine. It is
probable, therefore, that if the experimental conditions were
superposed on a state of bodily weakness, or were performed
DEPRESSIVE NERVOUS INFLUENCES 217
without anaesthesia, or were long continued, as in states of in-
flammation thus simulating common conditions in human
beings the results would have been even more pronounced.
From the foregoing evidence it is clear that in any case of
adynamic ileus a distinction must be made between the inactivity
due to local disturbances in the gastro-intestinal wall and in-
activity due to inhibitory impulses from the central nervous
system. In any case of unnatural quiescence the first considera-
tion is to determine its source. If the inhibition is extrinsic,
any agent that will stop the delivery of inhibitory influences
from the spinal cord will permit the stomach and intestines to
resume the functions of which they are independently capable.
If, on the other hand, the inactivity is the immediate effect of
local disturbance, this same agent will have no effect in pro-
moting the restoration of peristalsis. Thus, in our experiments
we found that physostigmine salicylate produced a marked, but
temporary, increase of peristalsis in cases of reflex inhibition of
the alimentary canal, but that tincture of aloes, which is particu-
larly effective in promoting peristalsis in the cat, was quite in-
effective after such manipulation of the gut as results in paralysis. 8
The various conditions that affect the alimentary canal locally
or reflexly have not yet been experimentally studied, but mani-
festly on such a study depends the possibility of rational judg-
ment in any particular case.
The Influence of Emotions. In my earliest observations on the
stomach 9 I had difficulty, because in some animals peristalsis was
perfectly evident, and in others there was no sign of activity.
Several weeks passed before I discovered that this difference in
response to the presence of food in the stomach was associated
with a difference of sex. The male cats were restive and excited
on being fastened to the holder, and under these circumstances
gastric peristalsis was absent ; the female cats, especially if
elderly, submitted with calmness to the restraint, and in them
peristaltic waves took their normal course. Once a female with
kittens turned from her state of quiet contentment to one of
apparent restless anxiety. The movements of the stomach im-
mediately stopped, and only started again after the animal had
been petted and had begun to purr. I later found that by
covering the cat's mouth and nose with the fingers until a slight
distress of breathing occurred the stomach movements could be
stopped at will. Thus, in the cat any sign of rage, or distress,
218 THE MECHANICAL FACTORS OF DIGESTION
or mere anxiety, was accompanied by a total cessation of the
movements of the stomach. I have watched with the X rays
the stomach of a male cat for more than an hour, during which
time there was not the slightest beginning of peristaltic activity,
and yet the only visible indication of excitement in the animal
was a continued to-and-fro twitching of the tail.
What is true of the cat has been proved true also of the rabbit,
dog, and guinea-pig. Even slight psychic disturbances were
accompanied by stoppage of peristalsis. 10 My observations on
the rabbit have been confirmed by Auer, 11 who found that the
handling of the animal incident to fastening it gently to a holder
stopped gastric peristalsis for a variable length of time ; and if
the animal was startled in any way, or struggled, peristalsis was
again abolished. The observations on the dog also have been
confirmed. Lommel 12 found that small dogs in strange sur-
roundings might have no movements of the stomach for two or
three hours. And whenever the animals showed any indications
of being uncomfortable or distressed, the movements were in-
hibited and the discharge from the stomach checked.
Since the extrinsic innervation of a large part of the intestinal
tract is the same as that of the stomach, it is interesting to note
the effect of emotional states on the movements of the intestines.
Esselmont, 13 in a study of the dog's intestine, noted constantly
after signs of emotion a marked increase of activity lasting for
only a few moments. Fubini 14 also observed that fear occa-
sioned more rapid peristalsis. The increase of activity in the
large intestine during excitement may cause uncontrollable
voiding of the gut. 15 There is no doubt that many emotional
states are a strong stimulus to peristalsis, but it is equally true
that other emotional states inhibit peristalsis. In the cat the
same conditions which stop the movements of the stomach stop
also the movements of the intestines. A female cat, that ordi-
narily lies quietly on the holder, and makes no demonstration,
will occasionally, with only a little premonitory restlessness,
suddenly fly into a rage, lashing her tail from side to side,
pulling and jerking with every limb, and biting at everything
near her head. During such excitement, and for some momenta
after the animal becomes pacified again, the movements both of
the large and small intestine entirely cease. Such violence of
excitement is not necessary to cause the movements to stop.
A cat wMch was restless and continually whining while confined
DEPRESSIVE NERVOUS INFLUENCES 219
to the holder showed no signs of intestinal movements during
any period of observation (one period lasted more than an hour),
although the changes in the distribution of the food observable
from one period to the next proved that movements were going
on during the quiet intermissions. In another cat, uneasy and
fretful for fifty minutes, no activity was seen ; then she became
quiet for several minutes, and peristalsis of the small intestine
When the segmentation process in the small intestine is
stopped by excitement, the segments unite and return to the
form of a solid strand. In the large intestine antiperistalsis of
the proximal portion is abolished by excitement, possibly because
the pulsating tonus ring is inhibited.
Since the effects of impulses coming to the alimentary canal
along extrinsic nerves have been studied mainly by artificial
stimulation, it was of interest to observe the results of physio-
logical stimulation during emotion after different nervous con-
nections had been destroyed. 16 Under these circumstances, such
nerves as were left received impulses normally and delivered them
normally to the peripheral organ. The conditions, therefore,
were highly favourable for determining the course of inhibitory
paths. When the vagus nerves were severed, and the splanchnic
nerves alone remained, respiratory distress caused the usual total
cessation of the movements of the stomach and small intestine.
Impulses along the splanchnic nerves, therefore, physiologically
inhibit not only the intestines, but the stomach as well. When
the splanchnic nerves were cut, and the vagi alone remained,
respiratory distress had no effect on the movements of the small
intestine ; but when the distress was prolonged until the animal
began to toss about, gastric peristaltic waves became very
shallow or momentarily stopped. From this evidence it would
appear that the inhibitory impulses of the vagi, which are
physiologically active after deglutition, are capable of acting
also in states of turbulence, although they are not nearly so
efficient in stopping gastric peristalsis as are the impulses delivered
by the splanchnics. When the splanchnic and vagus nerves are
all cut, the movements of the alimentary canal cannot be stopped
by respiratory distress. The stoppage in theforniejL^ases
not, therefore, be attributed to any other *j&jjfr . .
influence-as, for example, to asphyxia. >f^^^^|||J^^f/}
In Pawlow's investigations of the wo
220 THE MECHANICAL FACTORS OF DIGESTION
the importance of pleasurable psychic states for the first secretion
of the gastric juice, on which so many processes in the stomach
and intestines depend, was strongly emphasized. It is probable,
also, as I have indicated, that the initial tonus of the stomach is
likewise dependent on the satisfaction of appetite. These results
are produced through nervous influences passing down the vagi.
The opposing influences, reaching the alimentary canal by way
of the sympathetic system during emotional excitement, can
totally destroy both the secretory 17 and the motor activities
which have been started by the bulbar system. The importance
of avoiding so far as possible the states of worry and anxiety,
and of not permitting grief and anger and other violent emotions
to prevail unduly, is not commonly appreciated, for the subtle
alterations wrought by these emotional disturbances are unknown
to consciousness, and have become clearly demonstrated solely
through physiological studies. Only as the consequences of
mental states favourable and unfavourable to normal digestion
are better understood can the good results be sought and the
bad results avoided, or, if not avoided, regarded and treated
1 Cannon and Murphy, J. Am. Med. Ass., 1907, xlix., p. 840.
2 Cannon and Murphy, Ann. Surg., 1906, xliii., p. 528.
3 v. Braam Houckgeest, Arch. f. d. ges. Physiot,.; 1872, vi., p. 266.
: 4 Liideritz, Arch. f. path. Anat., 1889, cxvi., p. 53.
5 Bayliss and Starling, J. Physid., 1899, xxiv., p. 127.
6 Cannon and Murphy, J. Am. Med. Ass., 1907, xlix., p. 840.
7 Meltzer and Auer, Proc. Soc. Exper. Bid. and M., New York, 1907, iv.,
8 Cannon and Murphy, J. Am. Med. Ass., 1907, xlix., p. 842.
9 Cannon, Am. J. Physid., 1898, i., p. 380.
10 Cannon, Am. J. Physid., 1902, viii., p. xxii.
11 Auer, Am. J. Physid., 1907, xviii., p. 356.
12 Lommel, Munchen. med. Wchnschr., 1903, i., p. 1634.
13 Esselmont, Rep. Brit. Ass. Adv. of Sc., 1899, p. 899.
14 Fubini, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1892, xiv., p. 528.
15 See Darwin, Expression of Emotions in Man and Animals, New York, 1873,
16 Cannon, Am. J. Physid., 1905, xiii., p. xxii; Am. J. Med. Sc., 1909,
cxxxvii., p. 485.
17 See Bickel and Sasaki, Deutsche med. Wchnschr., 1905, xxxi., p. 1829.
FROM THE LABORATORY OF PHYSIOLOGY OF HARVARD
UNIVERSITY, BEARING ON THE MECHANICAL
FACTORS OF DIGESTION
" The Movements of the Stomach Studied by Means of the Rontgen Rays."
By W. B. Cannon. American Journal of Physiology, 1898, i., pp. xiii-xiv,
" The Movements of the Food in the (Esophagus." By W. B. Cannon and
A. Moser. American Journal of Physiology, 1898, i., pp. 435-444.
" The Movements of the Intestines Studied by Means of the Rontgen Rays."
By W. B. Cannon. American Journal of Physiology, 1902, vi., pp. 251-277.
" Observations on the Mechanics of Digestion." By W. B. Cannon. Journal
of the American Medical Association, 1903, xl., pp. 749-753.
" Further Observations on the Movements of the Stomach and Intestines."
By W. B. Cannon. American Journal of Physiology, 1903, viii., pp. xxi-
" Salivary Digestion in the Stomach." By W. B. Cannon and H. F. Day.
American Journal of Physiology, 1903, ix., pp. 396-416.
" The Emptying of the Human Stomach." By W. B. Cannon. American
Journal of Physiology, 1904, x., p. xix.
" The Passage of Different Foodstuffs from the Stomach and through the
Small Intestines." By W. B. Cannon. American Journal of Physiology,
1904, xii., pp. 387-418.
" Gastro-enterostomy and Pyloroplasty : an Experimental Study." By W. B.
Cannon and J. B. Blake. Annals of Surgery, 1905, xli., pp. 868-911.
" Auscultation of the Rhythmic Sounds Produced by the Stomach and Intes-
tines." By W. B. Cannon. American Journal of Physiology, 1905, xiv.,
" Recent Advances in the Physiology of the Digestive Organs bearing on
Medicine and Surgery." By W. B. Cannon. The American Journal of
the Medical Sciences, 1906, cxxxi., pp. 563-578.
" The Movements of the Stomach and Intestines in some Surgical Conditions."
By W. B. Cannon and F. T. Murphy. Annals of Surgery, 1906, xliii.,
" The Motor Activities of the Stomach and Small Intestines after Splanchnic
and Vagus Section." By W. B. Cannon. American Journal of Physiology,
1906, xvii., pp. 429-442.
" Gastric Peristalsis in Rabbits under Normal and some Experimental Condi-
tions." By John Auer. American Journal of Physiology, 1907, xviii.,
222 THE MECHANICAL FACTORS OF DIGESTION
" (Esophageal Peristalsis after Bilateral Vagotomy." By W. B. Cannon.
American Journal of Physiology, 1907, xix., pp. 436-444.
" Physiologic Observations on Experimentally Produced Ileus." By W. B.
Cannon and F. T. Murphy. Journal of the American Medical Association,
1907, xlix., pp. 840-843.
" The Acid Control of the Pylorus." By W. B. Cannon. American Journal
of Physiology, 1907, xx., pp. 283-322.
" Some Observations on the Neuro muscular Mechanism of the Alimentary
Canal." By W. B. Cannon. American Journal of Physiology, 1908, xxi.,
" The Acid Closure of the Cardia." By W. B. Cannon. American Journal
of Physiology, 1908, xxiii., pp. 105-114.
*' Further Observations on the Myenteric Reflex." By W. B. Cannon. Ameri-
can Journal of Physiology, 1909, xxiii., pp. xxvi-xxvii.
" The Influence of Emotional States on the Functions of the Alimentary
Canal." By W. B. Cannon. The American Journal of the Medical
Sciences, 1909, cxxxvii., pp. 480-487.
'"Some Conditions Affecting the Discharge of Food from the Stomach." By
C. A. Hedblom and W. B. Cannon. The American Journal of Medical
Sciences, 1909, cxxxviii., pp. 504-521.
" The Physiological Aspects of Gastroenterostomy." By W. B. Cannon.
Boston Medical and Surgical Journal, 1909, clxi., pp. 720-722.
" The Correlation of the Digestive Functions." By W. B. Cannon. Boston
Medical and Surgical Journal, 1910, clxii., pp. 97-101.
" The Effect of Severing the Vagi or Splanchnics or Both upon Gastric Motility
in Rabbits." By John Auer. American Journal of Physiology, 1910,
xxv., pp. 335-344.
" Some Observations on the Nature of Gastric Peristalsis." By W. B. Cannon
American Journal of Physiology, 1911, xxvii., pp. xii-xiii.
" The Receptive Relaxation of the Stomach." By W. B. Cannon and C. W.
Lieb. American Journal of Physiology, 1911, xxvii., p. xiii.
ABDOMEN : adaptation of capacity of,
to increased gastric contents, 60; hy-
draulic relations of contents of, 48
Acid, hydrochloric : effect of, in
stomach in closing cardia, 39-42 ;
in opening pylorus, 102-106 ; in
duodenum in closing pylorus, 107-
110 ; gastric discharge of, 119
Albumin from white of egg, gastric
discharge of, 118-119
Alimentary canal, activity of, when
isolated from central nervous sys-
Alkaline contents of stomach, effect
of, on peristalsis, 56
Amylolysis in stomach, 71-74
Anaesthesia, effect of : on cesophageal
peristalsis, 23 ; on gastric discharge,
Anastomosis, intestinal, results of
end-to-end and lateral, 137-140
Antiperistalsis : of stomach, 57, 192 ;
of small intestine, 141-143 ; of large
intestine, 149-156, 185-190; rela-
tion of, to tonus ring, 186
Anxiety, effect of, on peristalsis, 218
Apomorphine, use of, for intestinal
Asthenia, general, effect of, on move-
ments of gastro-intestinal canal, 210
Auerbach's plexus. See Myenteric
Auscultation: of stomach, 166-170,
177; of small intestine, 170-173;
of large intestine, 173-176
Beer, gastric discharge of, 119
Bile, effect of elimination of, on
gastric discharge, 108
Bismuth salts in X-ray observation
on alimentary canal, 5
Caecum : functions of, 148 ; effect of
irritation of, on gastric discharge,
Carbohydrate : gastric discharge of,
90 ; when mixed with protein, 93 ;
when mixed with fat, 94 ; effect of
dilution of, on gastric discharge,
Cardia : rhythmic contraction of, 32,
35; tonic closure of, 32-34; after
vagotoiny, 29 ; relaxation of, 33 ;
conditions affecting, 24-35 ; vagus
inhibition of, 34 ; action of, in
eructation, 35 ; periodic relaxation
of, 36 ; closure of, by acid gastric
Cardiac sac of stomach, 50 ; salivary
digestion in, 72
Cellulose, effect on passage of food,
Chyme, circulation of, after gastro-
Cold, effect of, on gastric discharge,
Colon. See Intestine, large
Consistency of food, effect of: on
deglutition, 16-18; on gastric dis-
charge, 120-123; after gastro-
Cramps, intestinal, 174
" Crossed innervation " of colon, 206
Defalcation, 158-162 ; innervation of,
Deglutition : mass of bolus in, 9 ;
movements of, 11 ; buccal pressure
in, 12 ; discharge theory of, 13 ;
sounds of, 14 ; in different animals,
15-18 ; rates of, with different con-
sistencies of food, 16-18 ; effect of,
on cardia, 33 ; on gastric tonus,
Deglutition reflex : sensitive spots for,
21 ; afferent nerves of, 21 ; resist-
ance of, to fatigue, 21; efferent
nerves of, 22 ; centre for, 22 ; in-
hibition of, 25; as affected by
stimulation of glosso-pharyngeus
THE MECHANICAL FACTOKS OF DIGESTION
nerve, 25 ; in relation to relaxation
of stomach, 201
" Digestibility " tables, objections to,
Digestion : functions of mechanical
factors of, 1 ; correlation of gastric
and duodenal, 112-120
Distress, effect of, on peristalsis, 217
Duodenum, effects on gastric dis-
charge: of acid in, 107 ; of absence
of bile and pancreatic juice from,
107-108 ; of destroying continuity
of, with stomach, 108-109
Egg-albumin, rate of gastric dis-
charge of, 118
Emotions : inhibition of gastrointes-
tinal movements by, 217-220 ;
nervous pathways for the inhibi-
Enemata, passage of, into small in-
Eructation of gas, 35
Etherization, effect of, on gastric
Excitement, effect of, on peristalsis,
Exposure of gastro -intestinal tract,
effect of, on gastric discharge, 211
Fats : gastric discharge of, 88-90 ;
when mixed with protein, 94 ;
when mixed with carbohydrate,
94 ; explanation of slow passage,
Fear, effect of, on peristalsis, 218
Food, effect on gastric discharge :
of consistency of, 119-122; of hot,
125 ; of cold, 125 ; mechanical
treatment of, in small intestine, 144;
rate of passage of, through small
Foodstuffs, mixed, gastric discharge
of, 93-95, 114
Gas in stomach : effect of, on gastric
discharge, 123, 124 ; in large intes-
Gastric tube, 50
Gastro - enterostomy : gastric peri-
stalsis after, 75 ; passage of food
through pylorus after, 77-79 ; cir-
culation of chyme after, 79 ; effect
of gastric distension on stoma in,
79-80; kinks after, 80; effect of,
on pancreatic digestion, 81
Glosso-pharyngeus nerves, inhibitory
to deglutition, 25
Haustra, 157, 158
Hydrochloric acid : effect of, on cardia,
when in stomach, 39-42 ; on pylorus,
when in stomach, 102-106 ; on py-
lorus, when in duodenum, 107-110 ;
gastric discharge of, 119
Hyperacidity, effect of, on gastric
Ileo -colic sphincter, innervation of,
Incisura angularis of stomach, 46
Incisura cardiaca, 193
Inhibition : of gastric tomis, 201 ;
reflex, of gastro -intestinal move-
Innervation, extrinsic : of oesophagus,
22-23; of stomach, 197-204; of
small intestine, 204-205 ; of large
intestine, 205-207 ; of sphincters,
207-208 ; " contrary " and " recip-
rocal," 179 ; " crossed," 206
Innervation, intrinsic : of oesophagus,
26 ; of small intestine, 178-185 ; of
large intestine, 185-190 ; of sto-
Internal anal sphincter, innervation
Intestinal pain, 203
Intestine, law of, 179
Intestine, small : effect of injury of,
on pylorus, 126 ; effect of irritation
*of caecum on passage of food
through, 127 ; length of, 130 ;
rhythmic segmentation in, 131-
135, 182; peristalsis in, 135-137,
183 ; effects of end-to-end and
lateral suture of, 137-140; activi-
ties of, when obstructed, 140-141 ;
antiperistalsis in, 141-143 ; effect
of severing segments of, 142 ;
"peristaltic rush" in, 143; mechani-
cal treatment of contents by, 144 ;
passage of food through, 145-146 ;
regurgitation into, from large in-
testine, 155-156 ; rhythmic sounds
produced by, 170-173 ; intrinsic
innervation of, 178-185; local
reflex in, 180 ; rhythmic contrac-
tions of, 181 ; neuromuscular re-
fractory period of, 182 ; effect on,
of vagus stimulation, 204 ; of
splanchnic stimulation, 204 ; of
vagotomy, 205 ; of splanchnic
Intestine, large : consistency of con-
tents of, 149 ; size of, in different
animals, 152 ; antiperistalsis in,
149-156, 185-190; tonic constric-
tions in, 149, 157 ; passage of con-
tents through, 157-158 ; haustra
of, 157, 158 ; peristalsis in, 158,
162, 185 ; delayed discharge from,
162 ; sounds produced by, 173-1 7> ;
local reflex in, 185 ; effect on, of
stimulation of sacral nerves, 206 ;
of sympathetic nerves, 206 ; of
cutting sacral nerves, 206 ; of cut-
ting sympathetic nerves, 206
Kinks, intestinal, after gastro-enter-
Laryngeus nerves, recurrent, distribu-
tion of, to oesophagus, 22
Law of intestine, 179
Manipulation of gastro-intestinaltract,
effect of, on passage of food, 213-
Mastication : duration of, under vari-
ous conditions, 8 ; effects of, on
food, 8 ; on salivary flow, 9 ; on
subsequent digestion, 10 ; dental
pressures in, 9
Methods of investigating movements
of the alimentary canal, 4-7, 84-87
Milk, gastric discharge of, 115
Mouth-pressure in deglutition, 12
Muscle : smooth, characteristic ac-
tivities of, when intrinsically inner-
vated, 2, 181 ; nature of tonus
changes in, 60 ; action when de-
prived of my enteric plexus, 181
Myenteric plexus : of small intestine,
178-185 ; of large intestine, 185-
190 ; of stomach, 193
Myenteric reflex, 195
Nicotine, effect of : on peristalsis of
small intestine, 180 ; on anti-
peristalsis of large intestine, 186 ;
on gastric peristalsis, 190
Obstruction, intestinal, effects of, 011
intestinal movements, 140-141
(Esophagus : functional divisions of,
14, 18, 20 ; innervation of, 22 ;
effects of anaesthesia on, 23 ;
primary peristalsis of, 24 ; second-
ary peristalsis of, 24, 36 ; paralysis
of, with later recovery, after vag-
otomy, 25-29 ; tertiary paralysis of,
30 ; regurgitation into, 36, 43
Pain, intestinal : 174,203; gastric, 202
Pancreatic digestion, after gastro-
Paralysis : oesophageal, after vag-
otomy, with later recovery, 25-29 ;
post-operative, 211-215; gastro-
intestinal, from manipulation, after
splanchnic nerves cut, 216
" Pendulum movement " in small
Peristalsis, 3; inhibited by i-moti'i-i I,
217-220 ; <K8o)ilin<j,nl, V. ,/
20 ; primary, of central origin, -J3,
24 ; secondary, of peripheral origin,
23, 24, 36; effects of anaesthesia
on, 23 ; after vagotomy, 26 et seq. ;
tertiary, under local control, 30 ;
gastric, 51 et seq., 190-194 ; rate of,
54-55 ; with different gastric con-
tents, 55 ; dependence of, on tonus
of musculature, 56 ; churning func-
tion of, 67 ; after gastro-enteros-
tomy, 75 ; passage of waves of,
192, 193 ; in small intestine, 135 et
seq., 178 et seq., 183 ; combined
with segmentation, 137 ; rushing,
136, 143 ; regulation of, 184 ; in
large intestine, 158, 162 ; passage
of waves of, 187, 188 ; regulation of,
" Peristaltic rush," 136, 143
Physostigmine, effect of. on paralyzed
Post-operative paralysis, 211
Pressure : intragastrtc, in eructation,
35, 38 ; normal degree of, 60-61 ;
effect of, in pyloric vestibule, after
gastro-enterostomy, 77 ; effect of,
on gastric peristalsis, 190, 191,
192-193 ; intra-abdominal, unifor-
mity of, with varying abdominal
contents, 60 ; effect of voluntary
increase of, on position of viscera,
Proteins : rate of gastric discharge of,
91-92 ; when mixed with carbo-
hydrates, 93 ; when mixed with
fats, 94 ; explanation of slow pas-
sage, 113, 114 ; effect of dilution of,
on gastric discharge, 121, 122
Psychic tonus, 200
Pyloric canal of stomach, 46
Pyloric portion of stomach, 49
Pyloric vestibule of stomach, 46
Pylorus : selective action of, 69 ; dis-
charge through, after gastro-enter-
ostomy, 77-79 ; relaxation of, occa-
sional, 96 ; mechanical agencies
affecting, 97 ; chemical agencies
affecting, 98 ; theory of acid control
of, 100-101 ; opened by acid on
stomach side, 102-106 ; closed by
acid in duodenum, 107-110; corre-
lating functions of, 112-120; tonus
of, 115; conditions affecting, 120-
128 ; closed by intestinal injury,
126 ; relaxation in absence of acid,
127, 128 ; innervation of, 207
THE MECHANICAL FACTORS OF DIGESTION
Rage, effect of, on peristalsis, 217, 218
Rectum, accommodation to contents,
Refractory period of gastro-intes-
tinal neuromusculature, 182
Regurgitation : from stomach to oeso-
phagus, 36, 43 ; conditions for it,
37, 38 ; from large to small intes-
Rhythmic segmentation, 131-135,
182 ; sounds produced by, 170-173
" Rollbewegung " of small intestine,
Sacral nerves: supply of, to colon,
205 ; effect of severance of, on
colon, 206 ; effect of, on internal
anal sphincter, 207
Saliva, flow of, stimulated by mastica-
Salivary digestion in stomach, 71-74
Segmentation : rhythmic, in small
intestine, 131-135, 182; combined
with peristalsis, 137 ; in proximal
colon, 151 ; haustral, in colon, 157,
158 ; sounds produced by, 170-
173 ; inhibition of, by emotions,
Solids: passage of, through pylorus,
69 ; effect of, in gastric contents,
on gastric discharge, 122
Sounds produced: during digestion,
165 ; by stomach, 167-168 ; by small
intestine, 170-173 ; by large in-
Sphincter : pyloric, 96 et seq. ; ileo-
colic, 154 ; innervation of, 207-208
Splanchnic nerves : effect of, on gastric
tonus, 201 ; on small intestine, 204,
205 ; on pylorus, 207 ; on ileo-colic
sphincter, 207 ; as pathways of
emotional inhibition, 219
Starch, digestion of, in stomach, 71-74
Stomach : mechanical functions of, 45 ;
form of, 45-47 ; musculature of, 46,
47 ; position of, 47 ; " drainage "
of, 48 ; two parts of, 49 ; as reser-
voir, 50 ; transverse band in, 51,
52; peristalsis of, 51-56, 190-194;
rate of peristalsis in, 54, 55 ; with
different contents, 56 ; movements
of, in vomiting, 57 ; antiperistalsis
of, 57 ; adaptation of, to amount
of contents, 59 ; change in muscle
fibres of, as organ fills, 60 ; pres
sures in, 60, 61 ; difference in con
tents in two ends of, 62 ; theory o
circulating contents of, 62, 64
stratification of contents, 63, 64
movements of contents of, 63-67
immobility of contents of cardiac
end of, 64 ; absence of acid from
these contents, 65 ; churning
function of peristalsis of, 67 ; secre-
tion of and absorption by, fa-
voured by churning peristalsis,
68 ; salivary digestion in, 71-74 ;
movements of, after gastro -enter -
ostomy, 75 ; discharge from, after
gastro - enterostomy, 77-79 ; dis-
charge of different foodstuffs from,
84-95 ; discharge of fats from, 88-90,
115-117 ; carbohydrates, 90, 91, 92 ;
proteins, 91-92, 113-114; mixtures
of foodstuffs, 93-95 ; factors con-
cerned in discharge from, 99 ;
discharge from, delayed by delay
of acid reactions of contents of,
102 ; discharge from, hastened by
hastening acid reaction, 103 ; dis-
charge from, preceded by acidula-
tion of chyme, 104 ; acid in, opens
pylorus in excised organ, 105 ;
discharge of milk from, 115 ; water,
117 ; egg-albumin, 118 ; hydro-
chloric acid, 119 ; beer, 119 ; effects
of hyperacidity on gastric dis-
charge from, 119-120; of food
consistency, 120-122 ; of gas in
stomach, 123-124 ; of hot and cold
food, 125 ; of irritation of caecum,
127 ; sounds produced by, 167-168 ;
innervation of, by vagus nerves,
197 ; by splanchnic nerves, 201 ;
tonus of, from vagus impulses,
199 ; inhibition of, by splanchnic,
201 ; relaxation of, after swallow-
ing, 201 ; question whether source
of sensations of heat, cold, and
pain, 202-203 ; size of fasting, 204 ;
discharge from, after etherization,
211 ; after exposure to air, 211-
212 ; after cooling, 213 ; after
manipulation, 213-214 ; after mani-
pulation with splanchnics cut, 216
Sympathetic nerves, distribution to
colon, 205 ; effect of severance of,
206 ; effect of, on internal anal
Temperature, effect of, on gastric
Tension : importance of, for oesopha-
geal peristalsis, 28 ; as a condition
favourable to contraction, 182, 187,
188-189, 191, 192
Tonus : importance of, for movements
of colon, 188 ; of stomach, 191,
200-201 ; of small intestine, 195 ;
of alimentary tract, 210 ; in digest-
ing stomach, 191, 194 ; relation of
gastric, to vagus impulses, 199
Tonus ring : in large intestine, 149,
157 ; pulsations of, 186 ; as source
of antiperistalsis in large intestine,
186 ; refractory to stimulation,
188 ; origin of, 189 ; as source of
gastric peristalsis, 193-194
Transverse band of stomach, 51, 52
Vagotomy : effects of, on oesophagus,
26 et seq. ; effects on cardia, 29,
34 ; effect on stomach, 199
Vagus nerves : distribution of, to
oesophagus, 22 ; to stomach, 198 ;
effects of, on cardia, 33-34 ; effect
of stimulation of, on gastric ton us.
198 ; function of, in relation to
stomach, 199, 201 ; effect on small
intestine of stimulation of, 204 ; of
severance of, 205 ; effect of, on
pylorus, 207 ; as pathway for
emotional inhibition, 219
Vomiting, 56, 57 ; faecal, 142
Water, gastric discharge of, 117
X-ray methods of studying move-
ments of the alimentary tract,
5-7, 84-87 ; consideration of objec-
tions to, 86, 87
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