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Full text of "The mechanical factors of digestion"

INTERNATIONAL MEDICAL MONOGRAPHS 

rDR. LEONARD HILL, F.R.S. 
General Editors | DR WlLUAM BULLOCH 



THE 

MECHANICAL FACTORS 
OF DIGESTION 



BY 

WALTER B. CANNON, A.M., M.D. 

GEORGE HIGGINSON PROFESSOR OF PHYSIOLOGY 
HARVARD UNIVERSITY 



ILLUSTRATED 



LONDON 

EDWARD ARNOLD 

NEW YORK : LONGMANS, GREEN & CO. 

1911 

(A II rights res erred 



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TO THE MEMORY OF 

PROFESSOR HENRY PICKERING BOWDITCH 

IS GRATEFULLY DEDICATED 

THIS ACCOUNT OF RESEARCHES BEGUN 

UNDER HIS INSPIRATION 



V 



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 

Medicine. 

LEONARD HILL, 
WILLIAM BULLOCH. 

October, 1911. 



PREFACE 

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 
Physiological Society. 

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 

attained. 

WALTER B. CANNON. 

BOSTON, MASSACHUSETTS, 
July, 1911. 




CONTENTS 



CHAPTER I 

GENERAL FEATURES OF THE MOVEMENTS OF THE ALIMENTARY 
CANAL, AND METHODS OF INVESTIGATION 

PAGES 

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 



CHAPTER II 
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 

CHAPTER III 
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 

CHAPTER IV 
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 

vii 



Vlll CONTENTS 

CHAPTER V 
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 

CHAPTER VI 
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 



CHAPTER VII 

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 



CHAPTER VIII 

THE PASSAGE OF DIFFERENT FOODSTUFFS FROM THE 
STOMACH 

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 



CONTENTS IX 

PAGES 

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 

CHAPTER IX 
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 

CHAPTER X 

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 

CHAPTER XI 
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 



CHAPTER XII 
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 



CONTENTS 

PAGES 

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 



CHAPTER XIII 
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 

CHAPTER XIV 

THE INTRINSIC INNERVATION OF THE GASTRO- 
INTESTINAL TRACT 

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 

CHAPTER XV 

|,'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 



CONTENTS XI 

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 



CHAPTEE XVI 

DEPRESSIVE NERVOUS INFLUENCES AFFECTING GASTRO- 
INTESTINAL MOVEMENTS 

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 
DIGESTION 



CHAPTER I 

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 

1 



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 
chemical changes. 

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 
processes. 

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 
operation. 

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. 

REFERENCES. 

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. 



CHAPTEE II 

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 
swallowed. 1 

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 

8 



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 
proceses. 

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 
food onward. 

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- 
vented. 

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 
acid. 

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 

2 



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 
thoracic portion. 

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. 

REFERENCES. 

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. 



CHAPTER III 
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 

20 



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 
peculiarly interesting. 

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 
results. 

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 
anaesthesia. 



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 
stomach. 

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. 



REFERENCES. 

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, 
p. 132. 

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. 



CHAPTER IV 

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 
coughing. 5 

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 
relaxation. 

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 
escape. 

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 : 

Out. In. 

3-4114 3-4127 

4226 4242 

4345 4359 

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 
reached. 

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 
contraction weakens. 

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 
regurgitations. 

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 
digestion. 

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 



32 42 

46 57 

57 8 5718 



5930 40 

(cat excited) 
3-0035 3-01 2 



(cat excited) 

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 : 

Out. In. 

3.13 45 3-1353 

1417 1439 



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 
animal. 

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 
GASTRIC CONTENTS. 

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- 
minute intervals. 

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 
are fed. 

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 
most favourable. 

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& 



R 

^2^*&tMWffii, 1 1 (V '<e 

4fe^ 



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. 



REFERENCES. 

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. 



CHAPTER V 

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 

45 




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- 
stalsis. 

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 



48 



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 



49 



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- 
372. 



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- 
tive conditions. 



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 



55 



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 



- 


Number of 
Observations. 


Average Rate 
per Minute. 


Most Frequent 
Rate. 


Extreme 
Variations. 


Fats 
Proteins 
Carbohydrates 


23 
16 
13 


5-0 
5-2 
5-5 


5-2 

5 to 5-4 

5-8 


4 to6 
4-8 5-8 
5 6 



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. 



REFERENCES. 

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, 
i.,p. 14. 

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. 



CHAPTER VI 

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 
itself. 

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 

59 



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 
explained. 

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 
judged. 

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 
stomach. 

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, 

5 



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 
in animals. 

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 
zoetrope. 



70 THE MECHANICAL FACTORS OF DIGESTION 



REFERENCES. 

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. 



CHAPTER VII 

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 

71 



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 
reducing action. 

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 
other part. 

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, 



GASTROENTEROSTOMY 75 

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. 



GASTKO-ENTEROSTOMY 77 

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 
feeding. 

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 



GASTRO-ENTEROSTOMY 79 

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. 



80 



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- 




v 

/ 



FIG. 5. DIAGRAM SHOW- 
ING HOW STRETCHING 

THE STOMACH IN GASTRO- 
ENTEROSTOMY MAY 
CAUSE THE ATTACHED 
PART OF INTESTINE TO 

BECOME ALMOST CON- 
TINUOUS WITH THE GAS- 
TRIC WALL, AND THE 



BE CHANGED TO MERE 
SLITS. 

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 



GASTEO-ENTEROSTOMY 81 

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, 

6 



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. 

REFERENCES. 

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. 



GASTROENTEROSTOMY 83 

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. 



CHAPTER VIII 

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 

84 



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 



89 



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 
large intestine. 

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 




FIG. 7. 

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 
cases each. 

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 
amount. 

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. 



92 



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 
fundus. 

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 



Ml 

60 
20 
10 

Box 










^ 


^ 












/ 














/ 




\ ' 










/ 


'/ 






f . 


~'~~ f 


;-- 




// 






^^ 


',*' 








// 




/ 










/ 


/,, 


' / 















'..- 


' 












ITS i 1 2 3 

FIG. 8. 



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 



93 



40 



30 



20 



10 



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 

Hours 

FIG. 9. 

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 
each). 



94 



THE MECHANICAL FACTORS OF DIGESTION 



20 



" >, 1 2 3 4 

Hours 

FIG. 10. 

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- 



40 



20 



10 



/\ 






Hours 
FIG. 11. 

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. 



REFERENCES. 

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., 
p. 364. 

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. 



CHAPTER IX 
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 

96 



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 
peristaltic constrictions. 

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. 

7 



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 
gastric evacuation. 

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 
were pathologic. 

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 
pressure. 

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 



103 



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 
state. 

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 
FIG. 12. 

The continuous line i 
the curve after feeding 
potato, rice, an< 



crackers (four 
each) moistened with 
water, and the dot-line 
the same, moistened 
with 1 per cent. 
NaHC0 3 . 



104 



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 
hastened. 

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 




10 



Hours 



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 



108 



THE MECHANICAL FACTOKS OF DIGESTION 



cm. 



30 



20 



10 



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 
hours. 

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 
the pylorus. 

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 
FIG. 14. 

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 



109 



cm. 



20 



10 



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- 
sions. 

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 
rapid rate. 

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 
aside. 



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 



REFERENCES. 

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., 
p .214. 

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. 



CHAPTER X 

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. 
112 



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 

8 



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 
pyloric passage. 

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 
egg-white. 

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 
rapidly. 16 

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 
stomach.* 

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 
explained.* 

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 
this food. 

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. 



Centimetres 
S g 8 g g 




\ 


1 / 






/ 










i 


' 


/ 




i 


_J' 




i 


' 








/ 




/ 


i 






V 


i 






I/ 
























1 

Tlours 
FIG. 16. 

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 
cent, acidity. 



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 




Z 



2 



FIG. 17. 

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 
varying consistencies. 

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 
stomach. 



122 THE MECHANICAL FACTORS OF DIGESTION 



40 



30 



20 



10 



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 
potato. 

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 



Hours 

FIG. 18. 

The heavy line is the 
normal curve for 
potato ; the light 
line, the curve when 
hard particles are 
present in the food 
10 cases. 



CORRELATING FUNCTIONS OF THE PYLORUS 123 



s 20 

O 
10 



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 

Hours 

FIG. 19. 

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 
temperature. 

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 



cm. 





30 
20 
10 

Hou] 








/ 


\ 
























/ 


/ 


\ 
























/ 






\ 




















/ 








\ 




















/ 










^ 


^ 
















/ 














X 


s 












/ 


















^ 


x^ 






/ 






















. 


>^ 


^- 
























. 






8 4 1 2 3 4 5 6 

FIG. 20. 



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 
half-hour. 

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 



40 



,30 



I 20 
I 
10 



\ 



" >2 1 2 3 4 5 6 78 

Hours 

FIG. 21. 

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 
and explained. 

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. 



REFERENCES. 

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. 



CHAPTER XI 

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 
nourishment. 

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 

130 



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 
SEGMENTATION. 

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 constrictions. 

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 
unaffected. 

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 
slower segmentation. 

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. 



134 



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 
established. 

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- 
tion. 

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 
SMALL INTESTINE. 

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 



140 



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 
satisfactorily. 

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 



A 



FIG. 25. DIAGRAM 
SHOWING EFFECT OF 
Too GREAT OVER- 
LAPPING OF LOOPS 
IN LATERAL UNION. 

Proximal loop (A) im- 
pacted, distal loop 
(B) invaginated. 



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 
rest. 

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 
peristaltic waves. 

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 
large intestine. 

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. 

10 



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 
surroundings. 37 

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. 



REFERENCES. 

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. 



CHAPTER XII 

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 
disappears. 

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. 

148 



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- 
peristalsis. 

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 
tonic constriction. 

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 

watched. 

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 

CONSTRJCTION. 




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 
wall. 

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 sacculi." 

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 
developed. 13 

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 
body. 

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 
them. 

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 
pressed forward. 

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, 

11 



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 
suppressed. 

REFERENCES. 

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., 
p. /i. 

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. 




CHAPTER XIII 

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 

164 



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 
ring. 

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 
dinner : 

19 20 

38=19+19 19 

18 19 

19 20 
59=19+20+20 38=19+19 
19 20 



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 
NERVE-MUSCLE PREPARATION. 

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 
determined. 

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 
a second. 

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 8 

8 15 = 7 + 8 

6 9 

8 6 

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 
INTESTINE. 

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 
contractions : 

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 
the bowel. 

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 
clinician. 

REFERENCES. 

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. 



12 



CHAPTER XIV 

THE INTRINSIC INNERVATION OF THE GASTROINTESTINAL 

TRACT 

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 

178 



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 " 
innervation. 

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- 
nate neurons. 



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 
nervous discharges. 

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 
rhythmically. 

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- 
traction. 

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 
by contraction. 

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 
impossible. 

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 
fact. 

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 



189 



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 
saying. 

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 



191 



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 
Fig. 33). 

The stomach when first 
filled has roughly a conical 
shape. The circumference is 
large at the cardiac end, and 
progressively smaller as the 




t 



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, 
half-minutes. 



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 

13 



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. 

REFERENCES. 

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., 
p. 166. 

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. 



CHAPTER XV 

THE EXTRINSIC INNERVATION OF THE GASTRO-INTESTINAL 

TRACT 

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 

197 



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 
normal vigour. 

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 
not occur.* 

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 
splanchnics. 11 

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 
contractions. 15 

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 
ring. 20 

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 
layer. 

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. 



REFERENCES. 

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, 
Berlin, 1857. 

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., 
p. 39. 

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., 
p. 474. 

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. 



14 



CHAPTER XVI 

DEPRESSIVE NERVOUS INFLUENCES AFFECTING GASTRO- 
INTESTINAL MOVEMENTS 

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 

210 



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 
intacfc. 

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 



212 



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, 



40 
3C 
20 
10 

Houi 








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*S A 1 V 6 4 6 b 7 

FIG. 34. 



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. 

cm. 



40 
3C 
2( 
10 

Hou] 


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FIG. 35. 



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 



213 



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 



cm. 



40 
30 
20 
10 

Hou 








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re i 1 2 3 4 5 b 7 
FIG. 36. 



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 



214 



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 



cm 



40 



\ 









Houra 



FIG. 37. 



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 
five hours. 

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 
operating. 

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- 
turbance. 

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 
the feeding. 

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 
conditions. 

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 
appeared. 

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 
with intelligence. 



REFERENCES. 

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., 
p. 39. 

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, 
p. 77. 

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. 



PUBLICATIONS 

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, 

359-382. 
" 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- 

xxii. 
" 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., 

pp. 339-353. 
" 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., 

pp. 512-536. 
" 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., 

pp. 347-361. 

221 



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., 

p. xx. 
" 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. 



INDEX 



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- 
tem, 210 

Alkaline contents of stomach, effect 
of, on peristalsis, 56 

Amylolysis in stomach, 71-74 

Anaesthesia, effect of : on cesophageal 
peristalsis, 23 ; on gastric discharge, 
211 

Anastomosis, intestinal, results of 
end-to-end and lateral, 137-140 

Animal-holder, 6 

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 
paralysis, 57 

Asthenia, general, effect of, on move- 
ments of gastro-intestinal canal, 210 

Auerbach's plexus. See Myenteric 
plexus 

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, 
127 



Carbohydrate : gastric discharge of, 
90 ; when mixed with protein, 93 ; 
when mixed with fat, 94 ; effect of 
dilution of, on gastric discharge, 
121 

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 
contents, 39-42 

Cardiac sac of stomach, 50 ; salivary 
digestion in, 72 

Cardiospasm, 35 

Cellulose, effect on passage of food, 
146 

Chyme, circulation of, after gastro- 
enterostomy, 79 

Cold, effect of, on gastric discharge, 
124-126, 212 

Colon. See Intestine, large 

Consistency of food, effect of: on 
deglutition, 16-18; on gastric dis- 
charge, 120-123; after gastro- 
enterostomy, 77-78 

Cramps, intestinal, 174 

" Crossed innervation " of colon, 206 

Defalcation, 158-162 ; innervation of, 
206-207 

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, 
201 

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 



223 



224 



THE MECHANICAL FACTOKS OF DIGESTION 



nerve, 25 ; in relation to relaxation 
of stomach, 201 

" Digestibility " tables, objections to, 
87 

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- 
tion, 219 

Enemata, passage of, into small in- 
testine, 155-156 

Eructation of gas, 35 

Etherization, effect of, on gastric 
discharge, 211 

Excitement, effect of, on peristalsis, 
218 

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, 

115-117 

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 

intestine, 145-146 
Foodstuffs, mixed, gastric discharge 

of, 93-95, 114 

Gas in stomach : effect of, on gastric 
discharge, 123, 124 ; in large intes- 
tine, 176 

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 
Hunger, 204 



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 
discharge, 119 

Ileo -colic sphincter, innervation of, 
207 

Incisura angularis of stomach, 46 

Incisura cardiaca, 193 

Inhibition : of gastric tomis, 201 ; 
reflex, of gastro -intestinal move- 
ments, 261 

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- 
mach, 193 

Internal anal sphincter, innervation 
of, 207 

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 
section, 205 

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, 



INDEX 



225 



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- 
ostomy, 80 

Laryngeus nerves, recurrent, distribu- 
tion of, to oesophagus, 22 
Law of intestine, 179 

Manipulation of gastro-intestinaltract, 
effect of, on passage of food, 213- 
214 

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- 

enterostomy, 81 

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, 
190 

" Peristaltic rush," 136, 143 

Physostigmine, effect of. on paralyzed 
intestine, 217 

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, 
161 

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 

Pyloroplasty, 82 

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 



226 



THE MECHANICAL FACTORS OF DIGESTION 



Rage, effect of, on peristalsis, 217, 218 

Rectum, accommodation to contents, 
162 

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- 
tine, 155-156 

Rhythmic segmentation, 131-135, 
182 ; sounds produced by, 170-173 

" Rollbewegung " of small intestine, 
143 

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- 
tion, 9 

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, 
219 

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- 
testine, 173-176 

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 
sphincter, 207 

Temperature, effect of, on gastric 
discharge, 125 

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 



INDEX 



227 



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 



THE END 



BILLING AND SONS, LIMITED, PRINTERS, GDILDFORD 



UNIVERSITY OF CALIFORNIA 
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UNIVERSITY OF CALIFORNIA MEDICAL SCHOOL LIBRARY