THE NATURE OF HUNGER
On the same plane with pain and the dominant emotions of fear
and anger, as agencies which determine the action of organisms,
is the sensation of hunger. It is a sensation so peremptory, so
disagreeable, so tormenting, that men have committed crimes in order
to assuage it. It has led to cannibalism, even among the civilized.
It has resulted in suicide. And it has defeated armies--for the
aggressive spirit becomes detached from larger loyalties and turns
personal and selfish as hunger pangs increase in vigor and insistence.
In 1905, while observing in myself the rhythmic sounds produced by
the activities of the alimentary tract, I had occasion to note that
the sensation of hunger was not constant but recurrent, and that
the moment of its disappearance was often associated with a rather
loud gurgling sound as heard through the stethoscope. This and other
evidence, indicative of a source of the hunger sensations in the
contractions of the digestive canal, I reported in 1911.[171] That
same year, with the help of one of my students, A. L. Washburn, I
obtained final proof for this inference.
Appetite and Hunger
The sensations of appetite and hunger are so complex and so
intimately interrelated that any discussion of either sensation is
sure to go astray unless at the start there is clear understanding
of the meanings of the terms. The view has been propounded that
appetite is the first degree of hunger, the mild and pleasant stage,
agreeable in character; and that hunger itself is a more advanced
condition, disagreeable and even painful--the unpleasant result
of not satisfying the appetite.[172] On this basis appetite and
hunger would differ only quantitatively. Another view, which seems
more justifiable, is that the two experiences are fundamentally
different.
Careful observation indicates that appetite is related to previous
sensations of taste and smell of food. Delightful or disgusting
tastes and odors, associated with this or that edible substance,
determine the appetite. It has, therefore, important psychic elements
in its composition. Thus, by taking thought, we can anticipate the
odor of a delicious beefsteak or the taste of peaches and cream,
and in that imagination we can find pleasure. In the realization,
direct effects in the senses of taste and smell give still further
delight. As already noted in the first chapter, observations on
experimental animals and on human beings have shown that the
pleasures of both anticipation and realization, by stimulating the
flow of saliva and gastric juice, play a highly significant rôle
in the initiation of digestive processes.
Among prosperous people, supplied with abundance of food, the
appetite seems sufficient to ensure for bodily needs a proper
supply of nutriment. We eat because dinner is announced, because
by eating we avoid unpleasant consequences, and because food is
placed before us in delectable form and with tempting tastes and
odors. Under less easy circumstances, however, the body needs are
supplied through the much stronger and more insistent demands of
hunger.
The sensation of hunger is difficult to describe, but almost
everyone from childhood has felt at times that dull ache or gnawing
pain referred to the lower mid-chest region and the epigastrium,
which may take imperious control of human actions. As Sternberg
has pointed out, hunger may be sufficiently insistent to force the
taking of food which is so distasteful that it not only fails to
rouse appetite, but may even produce nausea. The hungry being gulps
his food with a rush. The pleasures of appetite are not for him--he
wants quantity rather than quality, and he wants it at once.
Hunger and appetite are, therefore, widely different--in
physiological basis, in localization and in psychic elements. Hunger
may be satisfied while the appetite still calls. Who is still hungry
when the tempting dessert is served, and yet are there any who
refuse it, on the plea that they no longer need it? On the other
hand, appetite may be in abeyance while hunger is goading.[173]
What ravenous boy is critical of his food? Do we not all know that
“hunger is the best sauce”? Although the two sensations may thus
exist separately, they nevertheless have the same function of leading
to the intake of food, and they usually appear together. Indeed,
the coöperation of hunger and appetite is probably the reason for
their being so frequently confused.
The Sensation of Hunger
Hunger may be described as having a central core and certain more
or less variable accessories. The peculiar dull ache of hungriness,
referred to the epigastrium, is usually the organism’s first strong
demand for food; and when the initial order is not obeyed, the
sensation is likely to grow into a highly uncomfortable pang or
gnawing, less definitely localized as it becomes more intense.
This may be regarded as the essential feature of hunger. Besides
the dull ache, however, lassitude and drowsiness may appear, or
faintness, or violent headache, or irritability and restlessness
such that continuous effort in ordinary affairs becomes increasingly
difficult. That these states differ much with individuals--headache
in one and faintness in another, for example--indicates that they
do not constitute the central fact of hunger, but are more or less
inconstant accompaniments. The “feeling of emptiness,” which has
been mentioned as an important element of the experience,[174] is
an inference rather than a distinct datum of consciousness, and can
likewise be eliminated from further consideration. The dull pressing
sensation is left, therefore, as the constant characteristic, the
central fact, to be examined in detail.
Hunger can evidently be regarded from the psychological point of
view, and discussed solely on the basis of introspection; or it can
be studied with reference to its antecedents and to the physiological
conditions which accompany it--a consideration which requires the
use of both objective methods and subjective observation. This
psycho-physiological treatment of the subject will be deferred till
the last. Certain theories which have been advanced with regard to
hunger, and which have been given more or less credit, must first
be examined.
Two main theories have been advocated. The first is supported by
contentions that hunger is a general sensation, arising at no special
region of the body, but having a local reference. This theory has
been more widely credited by physiologists and psychologists than
the other. The other is supported by evidence that hunger has a
local source and therefore a local reference. In the course of our
examination of these views we shall have opportunity to consider
some pertinent new observations.
The Theory That Hunger is a General Sensation
The conception that hunger arises from a general condition of the
body rests in turn on the notion that, as the body uses up material,
the blood becomes impoverished. Schiff[175] advocated this notion,
and suggested that poverty of the blood in food substance affects
the tissues in such manner that they demand a new supply. The nerve
cells of the brain share in this general shortage of provisions,
and because of internal changes, give rise to the sensation. Thus
is hunger explained as an experience dependent on the body as a
whole.
Three classes of evidence are cited in support of this view:
1. “Hunger increases as time passes”--a partial statement. The
development of hunger as time passes is a common observation which
quite accords with the assumption that the condition of the body
and the state of the blood are becoming constantly worse, so long
as the need, once established, is not satisfied.
While it is true that with the lapse of time hunger increases as the
supply of body nutriment decreases, this concomitance is not proof
that the sensation arises directly from a serious encroachment on the
store of food materials. If this argument were valid we should expect
hunger to become more and more distressing until death follows from
starvation. There is abundant evidence that the sensation is not thus
intensified; on the contrary, during continued fasting hunger, at
least in some persons, wholly disappears after the first few days.
Luciani,[176] who carefully recorded the experience of the faster
Succi, states that after a certain time the hunger feelings vanish
and do not return. And he tells of two dogs that showed no signs of
hunger after the third or fourth day of fasting; thereafter they
remained quite passive in the presence of food. Tigerstedt,[177]
who also has studied the metabolism of starvation, declares that
although the desire to eat is very great during the first day of
the ordeal, the unpleasant sensations disappear early, and that at
the end of the fast the subject may have to force himself to take
nourishment. The subject, “J. A.,” studied by Tigerstedt and his
co-workers,[178] reported that after the fourth day of fasting, he
had no disagreeable feelings.
Carrington,[179] after examining many persons who, to better their
health, abstained from eating for different periods, records
that “habit-hunger” usually lasts only two or three days and, if
plenty of water is drunk, does not last longer than three days.
Viterbi,[180] a Corsican lawyer condemned to death for political
causes, determined to escape execution by depriving his body of
food and drink. During the eighteen days that he lived he kept
careful notes. On the third day the sensation of hunger departed,
and although thereafter thirst came and went, hunger never returned.
Still further evidence of the same character could be cited, but
enough has already been given to show that after the first few days
of fasting the hunger feelings may wholly cease. On the theory that
hunger is a manifestation of bodily need, are we to suppose that,
in the course of starvation, the body is mysteriously not in need
after the third day, and that therefore the sensation of hunger
disappears? The absurdity of such a view is obvious.
2. “Hunger may be felt though the stomach be full”--a selected
alternative. Instances of duodenal fistula in man have been carefully
studied, which have shown that a modified sensation of hunger
may be felt when the stomach is full. A famous case described by
Busch[181] has been repeatedly used as evidence. His patient, who
lost nutriment through a duodenal fistula, was hungry soon after
eating, and felt satisfied only when the chyme was restored to the
intestine through the distal fistulous opening. As food is absorbed
mainly through the intestinal wall, the inference is direct that
the general bodily state, and not the local conditions of the
alimentary canal, must account for the patient’s feelings.
A full consideration of the evidence from cases of duodenal fistula
cannot so effectively be presented now as later. That in Busch’s
case hunger disappeared while food was being taken is, as we shall
see, quite significant. It may be that the restoration of chyme
to the intestine quieted hunger, not because nutriment was thus
introduced into the body, but because the presence of material
altered the nature of gastro-intestinal activity. The basis for
this suggestion will be given in due course.
3. “Animals may eat eagerly after section of their vagus and
splanchnic nerves”--a fallacious argument. The third support for
the view that hunger has a general origin in the body is derived
from observations on experimental animals. By severance of the vagus
and splanchnic nerves, the lower esophagus, the stomach and the
small intestine can be wholly separated from the central nervous
system. Animals thus operated upon nevertheless eat food placed
before them, and may indeed manifest some eagerness for it.[182]
How is this behavior to be accounted for--when the possibility of
local stimulation has been eliminated--save by assuming a central
origin of the impulse to eat?
The fallacy of this evidence, though repeatedly overlooked, is easily
shown. We have already seen that appetite as well as hunger may lead
to the taking of food. Indeed, the animal with all gastro-intestinal
nerves cut may have the same incentive to eat that a well-fed man
may have, who delights in the pleasurable taste and smell of food
and knows nothing of hunger pangs. Even when the nerves of taste are
cut, as they were in Longet’s experiments,[183] sensations of smell
are still possible, as well as agreeable associations which can be
roused by sight. More than fifty years ago Ludwig[184] pointed out
that, even if all the nerves were severed, psychic reasons could
be given for the taking of food, and yet because animals eat after
one or another set of nerves is eliminated, the conclusion has been
drawn by various writers that the nerves in question are thereby
proved to be not concerned in the sensation of hunger. Evidently,
since hunger is not required for eating, the act of eating is no
testimony whatever that the animal is hungry, and, after the nerves
have been severed, is no proof that hunger is of central origin.
Weakness of the Assumptions Underlying the Theory
That Hunger is a General Sensation
The evidence thus far examined has been shown to afford only shaky
support for the theory that hunger is a general sensation. The
theory, furthermore, is weak in its fundamental assumptions. There
is no clear indication, for example, that the blood undergoes or has
undergone any marked change, chemical or physical, when the first
stages of hunger appear. There is no evidence of any direct chemical
stimulation of the gray matter of the cerebral cortex. Indeed,
attempts to excite the gray matter artificially by chemical agents
have been without results;[185] and even electrical stimulation,
which is effective, must, in order to produce movements, be so
powerful that the movements have been attributed to excitation
of underlying white matter rather than cells in the gray. This
insensitivity of cortical cells to direct stimulation is not at
all favorable to the notion that they are sentinels set to warn
against too great diminution of bodily supplies.
Body Need May Exist Without Hunger
Still further evidence opposed to the theory that hunger results
directly from the using up of organic stores is found in patients
suffering from fever. Metabolism in fever patients is augmented,
body substance is destroyed to such a degree that the weight of
the patient may be greatly reduced, and yet the sensation of hunger
under these conditions of increased need is wholly lacking.
Again, if a person is hungry and takes food, the sensation is
suppressed soon afterwards, long before any considerable amount of
nutriment could be digested and absorbed, and therefore long before
the blood and the general bodily condition, if previously altered,
could be restored to normal.
Furthermore, persons exposed to privation have testified that hunger
can be temporarily suppressed by swallowing indigestible materials.
Certainly scraps of leather and bits of moss, not to mention clay
eaten by the Otomacs, would not materially compensate for large
organic losses. In rebuttal to this argument the comment has been
made that central states as a rule can be readily overwhelmed by
peripheral stimulation, and just as sleep, for example, can be
abolished by bathing the temples, so hunger can be abolished by
irritating the gastric walls.[186] This comment is beside the point,
for it meets the issue by merely assuming as true the condition
under discussion. The absence of hunger during the ravages of fever,
and its quick abolition after food or even indigestible stuff is
swallowed, still further weakens the argument, therefore, that the
sensation arises directly from lack of nutriment in the body.
The Theory That Hunger is of General Origin Does Not
Explain the Quick Onset and the Periodicity
of the Sensation
Many persons have noted that hunger has a sharp onset. A person
may be tramping in the woods or working in the fields, where
fixed attention is not demanded, and without premonition may feel
the abrupt arrival of the characteristic ache. The expression
“grub-struck” is a picturesque description of this experience. If
this sudden arrival of the sensation corresponds to the general
bodily state, the change in the general bodily state must occur with
like suddenness or have a critical point at which the sensation is
instantly precipitated. There is no evidence whatever that either
of these conditions occurs in the course of metabolism.
Another peculiarity of hunger, which I have already mentioned, is
its intermittency. It may come and go several times in the course
of a few hours. Furthermore, while the sensation is prevailing,
its intensity is not uniform, but marked by ups and downs. In some
instances the ups and downs change to a periodic presence and absence
without change of rate. In my own experience the hunger pangs came
and went on one occasion as follows:
Came Went
12--37--20 38--30
40--45 41--10
41--45 42--25
43--20 43--35
44--40 45--55
46--15 46--30
and so on, for ten minutes longer. Again in this relation, the
intermittent and periodic character of hunger would require, on the
theory under examination, that the bodily supplies be intermittently
and periodically insufficient. During one moment the absence of
hunger would imply an abundance of nutriment in the organism, ten
seconds later the presence of hunger would imply that the stores
had been suddenly reduced, ten seconds later still the absence of
hunger would imply a sudden renewal of plenty. Such zig-zag shifts
of the general bodily state may not be impossible, but from all
that is known of the course of metabolism, such quick changes are
highly improbable. The periodicity of hunger, therefore, is further
evidence against the theory that the sensation has a general basis
in the body.
The Theory That Hunger is of General Origin Does Not
Explain the Local Reference
The last objection to this theory is that it does not account for
the most common feature of hunger--namely, the reference of the
sensation to the region of the stomach. Schiff and others[187]
who have supported the theory have met this objection by two
contentions. First they have pointed out that the sensation is
not always referred to the stomach. Schiff interrogated ignorant
soldiers regarding the local reference; several indicated the neck
or chest, twenty-three the sternum, four were uncertain of any
region, and two only designated the stomach. In other words, the
stomach region was most rarely mentioned.
The second contention against the importance of local reference is
that such evidence is fallacious. An armless man may feel tinglings
which seem to arise in fingers which have long since ceased to be
a portion of his body. The fact that he experiences such tinglings
and ascribes them to dissevered parts, does not prove that the
sensation originates in those parts. And similarly the assignment
of the ache of hunger to any special region of the body does not
demonstrate that the ache arises from that region. Such are the
arguments against a local origin of hunger.
Concerning these arguments we may recall, first, Schiff’s admission
that the soldiers he questioned were too few to give conclusive
evidence. Further, the testimony of most of them that hunger
seemed to originate in the chest or region of the sternum cannot
be claimed as unfavorable to a peripheral source of the sensation.
The description of feelings which develop from disturbances within
the body is almost always indefinite. As Head[188] and others
have shown, conditions in a viscus which give rise to sensation
are likely not to be attributed to the viscus, but to related skin
areas. Under such circumstances we do not dismiss the testimony as
worthless merely because it may not point precisely to the source
of the trouble. On the contrary, we use such testimony constantly
as a basis for judging internal disorders.
With regard to the contention that reference to the periphery is
not proof of the peripheral origin of a sensation, we may answer
that the force of that contention depends on the amount of accessory
evidence which is available. Thus if we see an object come into
contact with a finger, we are justified in assuming that the
simultaneous sensation of touch which we refer to that finger has
resulted from the contact, and is not a purely central experience
accidentally attributed to an outlying member. Similarly in the
case of hunger--all that we need as support for the peripheral
reference of the sensation is proof that conditions occur there,
simultaneously with hunger pangs, which might reasonably be regarded
as giving rise to those pangs.
With the requirement in mind that peripheral conditions be adequate,
let us examine the state of the fasting stomach to see whether,
indeed, conditions may be present in times of hunger which would
sustain the theory that hunger has a local outlying source.
Hunger Not Due To Emptiness of the Stomach
Among the suggestions which have been offered to account for a
peripheral origin of the sensation is that of attributing it to
emptiness of the stomach. By use of the stomach tube Nicolai[189]
found that when his subjects had their first intimation of hunger
the stomach was quite empty. But, in other instances, after lavage
of the stomach, the sensation did not appear for intervals varying
between one and a half and three and a half hours. During these
intervals the stomach must have been empty, and yet no sensation
was experienced. The same testimony was given long before by
Beaumont,[190] who, from his observations on Alexis St. Martin,
declared that hunger arises some time after the stomach is normally
evacuated. Mere emptiness of the organ, therefore, does not explain
the phenomenon.
Hunger Not Due to Hydrochloric Acid in the Empty Stomach
A second theory, apparently suggested by observations on cases
of hyperacidity, is that the ache or pang is due to the natural
hydrochloric acid of the stomach but secreted while the organ is
empty. Again the facts are hostile. Nicolai[191] reported that the
gastric wash-water from his hungry subjects was neutral or only
slightly acid. This testimony confirms Beaumont’s statement, and
is in complete agreement with the results of gastric examination
of fasting animals reported by numerous experimenters. There is no
secretion into the empty stomach during the first days of starvation.
Furthermore, persons suffering from absence of hydrochloric acid
(achylia gastrica) declare that they have normal feelings of hunger.
Hydrochloric acid cannot, therefore, be called upon to account for
the sensation.
Hunger Not Due to Turgescence of the
Gastric Mucous Membrane
Another theory, which was first advanced by Beaumont,[192] is
that hunger arises from turgescence of the gastric glands. The
disappearance of the pangs as fasting continues has been accounted
for by supposing that the gastric glands share in the general
depletion of the body, and that thus the turgescence is relieved.[*]
This turgescence theory has commended itself to several recent
writers. Thus Luciani[193] has accepted it, and by adding the idea
that nerves distributed to the mucosa are specially sensitive
to deprivation of food he accounts for the hunger pangs. Also
Valenti[194] declared a few years ago that the turgescence theory
of Beaumont is the only one with a semblance of truth in it. The
experimental work reported by these two investigators, however, does
not necessarily sustain the turgescence theory. Luciani severed
the previously exposed vagi after cocainizing them, and Valenti
merely cocainized the nerves; the fasting dogs, eager to eat a few
minutes previous to this operation, now ran about as before, but
when offered food, licked and smelled it, but did not take it.
This total neglect of the food lasted varying periods up to two
hours. The vagus nerves seem, indeed, to convey impulses which
affect the procedure of eating, but there is no clear evidence
that those impulses arise from distention of the gland cells. The
turgescence theory, moreover, does not explain the effect of taking
indigestible material into the stomach. According to Pawlow, and to
others who have observed human beings, the chewing and swallowing of
unappetizing stuff does not cause any secretion of gastric juice (see
p. 8). Yet such stuff when swallowed will cause the disappearance
of hunger, and Nicolai found that the sensation could be abolished
by simply introducing a stomach sound. It is highly improbable that
the turgescence of the gastric glands can be reduced by either of
these procedures. The turgescence theory, furthermore, does not
explain the quick onset of hunger, or its intermittent and periodic
character. That the cells are repeatedly swollen and contracted
within periods a few seconds in duration is almost inconceivable.
For these reasons, therefore, the theory that hunger results from
turgescence of the gastric mucosa can reasonably be rejected.
*[Footnote: A better explanation perhaps is afforded by Boldireff’s
discovery that at the end of two or three days the stomachs of
fasting dogs begin to secrete gastric juice and continue the
secretion indefinitely. (Boldireff, Archives Biologiques de St.
Petersburg, 1905, xi, p. 98.)]
Hunger the Result of Contractions
There remain to be considered, as a possible cause of hunger pangs,
contractions of the stomach and other parts of the alimentary
canal. This suggestion is not new. Sixty-nine years ago Weber[195]
declared his belief that “strong contraction of the muscle fibres
of the wholly empty stomach, whereby its cavity disappears, makes
a part of the sensation which we call hunger.” Vierordt[196] drew
the same inference twenty-five years later (in 1871), and since
then Ewald, Knapp, and Hertz have declared their adherence to this
view. These writers have not brought forward any direct evidence for
their conclusion, though Hertz has cited Boldireff’s observations on
fasting dogs as probably accounting for what he terms “the gastric
constituent of the sensation.”
The Empty Stomach and Intestine Contract
The argument commonly used against the gastric contraction theory
is that the stomach is not energetically active when empty. Thus
Schiff[197] stated, “The movements of the empty stomach are rare
and much less energetic than during digestion.” Luciani[198]
expressed his disbelief by asserting that gastric movements are
much more active during gastric digestion than at other times, and
cease almost entirely when the stomach has discharged its contents.
And Valenti[199] stated (1910), “We know very well that gastric
movements are exaggerated while digestion is proceeding in the
stomach, but when the organ is empty they are more rare and much
less pronounced,” and, therefore, they cannot account for hunger.
Evidence opposed to these suppositions has been in existence
for many years. In 1899 Bettmann[200] called attention to the
contracted condition of the stomach after several days’ fast. In
1902 Wolff[201] reported that after forty-eight hours without food
the stomach of the cat may be so small as to look like a slightly
enlarged duodenum. In a similar circumstance I have noticed the same
extraordinary smallness of the organ, especially in the pyloric
half. The anatomist His[202] also recorded his observation of the
phenomenon. In 1905 Boldireff[203] demonstrated that the whole
gastro-intestinal tract has a periodic activity while not digesting.
Each period of activity lasts from twenty to thirty minutes, and
is characterized in the stomach by rhythmic contractions ten to
twenty in number. These contractions, Boldireff reports, may be
stronger than during digestion, and his published records clearly
support this statement. The intervals of repose between periodic
recurrences of the contractions lasted from one and a half to two
and a half hours. Especially noteworthy is Boldireff’s observation
that if fasting is continued for two or three days, the groups of
contractions appear at gradually longer intervals and last for
gradually shorter periods, and thereupon, as the gastric glands
begin continuous secretion, all movements cease.
Observations Suggesting that Contractions Cause Hunger
The research, previously mentioned, on the rhythmic sounds produced
by the digestive process, I was engaged in when Boldireff’s paper
was published. That contractions of the alimentary canal on a
gaseous content might explain the hunger pangs which I had noticed
seemed probable at that time, especially in the light of Boldireff’s
observations. Indeed, Boldireff[204] himself had considered hunger
in relation to the activities he described, but solely with the idea
that hunger might _provoke_ them; and since the activities dwindled
in force and frequency as time passed, whereas, in his belief, they
should have become more pronounced, he abandoned the notion of any
relation between the phenomena. Did not Boldireff misinterpret
his own observations? When he was considering whether hunger might
cause the contractions, did he not overlook the possibility that
the contractions might cause hunger? A number of experiences have
led to the conviction that Boldireff did, indeed, fail to perceive
part of the significance of his results. For example, I have noticed
the disappearance of a hunger pang as gas was heard gurgling upward
through the cardia. That the gas was rising rather than being forced
downward was proved by its regurgitation immediately after the sound
was heard. In all probability the pressure that forced the gas from
the stomach was the cause of the preceding sensation of hunger.
Again the sensation can be momentarily abolished a few seconds
after swallowing a small accumulation of saliva or a teaspoonful
of water. If the stomach is in strong contraction in hunger, this
result can be accounted for, in accordance with the observations of
Lieb and myself,[205] as due to the inhibition of the contraction
by swallowing. Thus also could be explained the prompt vanishing of
the ache soon after we begin to eat, for repeated swallowing results
in continued inhibition.[*] Furthermore, Ducceschi’s discovery[206]
that hydrochloric acid diminishes the tonus of the pyloric portion
of the stomach may have its application here; the acid would be
secreted as food is taken and would then cause relaxation of the
very region which is most strongly contracted.
*[Footnote: The absence of hunger in Busch’s patient while food
was being eaten (see p. 239) can also be accounted for in this
manner.]
The Concomitance of Contractions and Hunger in Man
Although the evidence above outlined had led me to the conviction
that hunger results from contractions of the alimentary canal, direct
proof was still lacking. In order to learn whether such proof might
be secured, Washburn determined to become accustomed to the presence
of a rubber tube in the esophagus.[*] Almost every day for several
weeks Washburn introduced as far as the stomach a small tube, to
the lower end of which was attached a soft-rubber balloon about
8 centimeters in diameter. The tube was thus carried about each
time for two or three hours. After this preliminary experience the
introduction of the tube and its presence in the gullet and stomach
were not at all disturbing. When a record was to be taken, the
balloon, placed just within the stomach, was moderately distended
with air, and was connected with a water manometer ending in a
cylindrical chamber 3.5 centimeters wide. A float recorder resting
on the water in the chamber permitted registering any contractions
of the fundus of the stomach. On the days of observation Washburn
would abstain from breakfast, or eat sparingly; and without taking
any luncheon would appear in the laboratory about two o’clock. The
recording apparatus was arranged as above described. In order to
avoid any error that might arise from artificial pressure on the
balloon, a pneumograph, fastened below the ribs, was made to record
the movements of the abdominal wall. Uniformity of these movements
would show that no special contractions of the abdominal muscles
were made. Between the records of gastric pressure and abdominal
movement, time was marked in minutes, and an electromagnetic signal
traced a line which could be altered by pressing a key. All these
recording arrangements were out of Washburn’s sight; he sat with
one hand at the key, ready whenever the sensation of hunger was
experienced to make the current which moved the signal.
*[Footnote: Nicolai (_loc. cit._) reported that although the
introduction of a stomach tube at first abolished hunger in his
subjects, with repeated use the effects became insignificant.]
Sometimes the observations were started before any hunger was noted;
at other times the sensation, after running a course, gave way to a
feeling of fatigue. Under either of these circumstances there were
no contractions of the stomach. When Washburn stated that he was
hungry, however, powerful contractions of the stomach were invariably
being registered. As in my own earlier experience, the sensations
were characterized by periodic recurrences with free intervals,
or by periodic accesses of an uninterrupted ache. The record of
Washburn’s introspection of his hunger pangs agreed closely with
the record of his gastric contractions. Almost invariably, however,
the contraction nearly reached its maximum before the record of
the sensation was started (see Fig. 37).
[Illustration: Figure 37.--One-half the original size. The top
record represents intragastric pressure (the small oscillations
due to respiration, the large to contractions of the stomach); the
second record is time in minutes (ten minutes); the third record
is W’s report of hunger pangs; the lowest record is respiration
registered by means of a pneumograph about the abdomen.]
This fact may be regarded as evidence that the contraction precedes
the sensation, and not _vice versa_, as Boldireff considered it.
The contractions were about a half-minute in duration, and the
intervals between varied from thirty to ninety seconds, with an
average of about one minute. The augmentations of intragastric
pressure in Washburn ranged between eleven and thirteen in twenty
minutes; I had previously counted in myself eleven hunger pangs in
the same time. The rate in each of us was, therefore, approximately
the same. This rate is slightly slower than that found in dogs by
Boldireff; the difference is perhaps correlated with the slower
rhythm of gastric peristalsis in man compared with that in the
dog.[207]
Before hunger was experienced by Washburn the recording apparatus
revealed no signs of gastric activity. Sometimes a rather tedious
period of waiting had to be endured before contractions occurred.
And after they began they continued for a while, then ceased (see
Fig. 38). The feeling of hunger, which was reported while the
contractions were recurring, disappeared as the waves stopped. The
inability of the subject to control the contractions eliminated
the possibility of their being artifacts, perhaps induced by
suggestion. The close concomitance of the contractions with hunger
pangs, therefore, clearly indicates that they are the real source
of those pangs.
[Illustration: Figure 38.--One-half the original size. The same
conditions as in Fig. 37. (Fifteen minutes.) There was a long
wait for hunger to disappear. After x, W. reported himself “tired
but not hungry.” The record from y to z was the continuance, on
a second drum, of x to y.]
Boldireff’s studies proved that when the empty stomach is manifesting
periodic contractions, the intestines also are active. Conceivably
all parts of the alimentary canal composed of smooth muscle share
in these movements. The lower esophagus in man is provided with
smooth muscle. It was possible to determine whether this region in
Washburn was active during hunger.
To the esophageal tube a thin-rubber finger-cot (2 centimeters
in length) was attached and lowered into the stomach. The little
rubber bag was distended with air, and the tube, pinched to keep the
bag inflated, was gently withdrawn until resistance was felt. The
air was now released from the bag and the tube farther withdrawn
about 3 centimeters. The bag was again distended with air at a
manometric pressure of 10 centimeters of water. Inspiration now
caused the writing lever, which recorded the pressure changes, to
rise; and a slightly farther withdrawal of the tube changed the
rise, on inspiration, to a fall. The former position of the tube,
therefore, was above the gastric cavity and below the diaphragm. In
this position the bag, attached to a float recorder (with chamber
2.3 centimeters in diameter), registered the periodic oscillations
shown in Fig. 39. Though individually more prolonged than those of
the stomach, these contractions, it will be noted, occur at about
the same rate.
[Illustration: Figure 39.--One-half the original size. The top
record represents compression of thin rubber bag in the lower
esophagus. The pressure in the bag varied between 9 and 13
centimeters of water. The cylinder of the recorder was of smaller
diameter than that used in the gastric records. The esophageal
contractions compressed the bag so completely that, at the summits
of the large oscillations, the respirations were not registered.
When the oscillations dropped to the time line, the bag was about
half inflated. The middle line registers time in minutes (ten
minutes). The bottom record is W’s report of hunger pangs.]
This study of hunger, reported by Washburn and myself in 1912, has
since been taken up by Carlson of Chicago, and in observations
on a man with a permanent gastric fistula, as well as on himself
and his collaborators, he has fully confirmed our evidence as to
the relation between contractions of the alimentary canal and the
hunger sensation. In a series of nearly a score of interesting
papers, Carlson and his students[208] have greatly amplified our
knowledge of the physiology of the “empty” stomach. Not only are
there the contractions observed by Washburn and myself, but at times
these may fuse into a continuous cramp of the gastric muscle. The
characteristic contractions, furthermore, continue after the vagus
nerve supply to the stomach has been destroyed, and, therefore, are
not dependent on the reception of impulses by way of the cranial
autonomic fibres. Recently Luckhardt and Carlson have brought
forward evidence that the blood of a fasting animal if injected into
the vein of a normal animal is capable of inducing in the latter
the condition of cramp or tetanus in the gastric muscle mentioned
above--an effect which does not occur when the blood of a well-fed
animal is injected. It seems _possible_ that a substance exists in
the blood which acts to excite the gastric hunger mechanism. But
this point will require further investigation.
With these demonstrations that contractions are the immediate cause
of hunger, most of the difficulties confronting other explanations
are readily obviated. Thus the sudden onset of hunger and its
peculiar periodicity--phenomena which no other explanation of hunger
can account for--are at once explained.
In fever, when bodily material is being most rapidly used, hunger
is absent. Its absence is understood from an observation made
by F. T. Murphy and myself,[209] that infection, with systemic
involvement, is accompanied by a total cessation of all movements
of the alimentary canal. Boldireff observed that when his dogs were
fatigued the rhythmic contractions failed to appear. Being “too
tired to eat” is thereby given a rational explanation.
A pathological form of the sensation--the inordinate hunger
(bulimia) of certain neurotics--is in accordance with the well-known
disturbances of the tonic innervation of the alimentary canal in
such individuals.
Since the lower end of the esophagus, as well as the stomach,
contracts periodically in hunger, the reference of the sensation
to the sternum by the ignorant persons questioned by Schiff was
wholly natural. The activity of the lower esophagus also explains
why, after the stomach has been removed, or in some cases when the
stomach is distended with food, hunger can still be experienced.
Conceivably the intestines also originate vague sensations by their
contractions. Indeed, the final banishment of the modified hunger
sensation in the patient with duodenal fistula, described by Busch,
may have been due to the lessened activity of the intestines when
chyme was injected into them.
The observations recorded in this paper have, as already noted,
numerous points of similarity to Boldireff’s observations[210] on
the periodic activity of the alimentary canal in fasting dogs.
Each period of activity, he found, comprised not only widespread
contractions of the digestive canal, but also the pouring out of
bile, and of pancreatic and intestinal juices rich in ferments.
Gastric juice was not secreted at these times; when it was secreted
and reached the intestine, the periodic activity ceased. What is
the significance of this extensive disturbance? I have elsewhere
presented evidence[211] that gastric peristalsis is dependent on the
stretching of gastric muscle when tonically contracted. The evidence
that the stomach is in fact strongly contracted in hunger--i. e.,
in a state of high tonus--has been presented above.[*] Thus the
very condition which causes hunger and leads to the taking of food
is the condition, when the swallowed food stretches the shortened
muscles, for immediate starting of gastric peristalsis. In this
connection the observations of Haudek and Stigler[212] are probably
significant. They found that the stomach discharges its contents more
rapidly if food is eaten in hunger than if not so eaten. Hunger, in
other words, is normally the signal that the stomach is contracted
for action; the unpleasantness of hunger leads to eating; eating
starts gastric digestion, and abolishes the sensation. Meanwhile
the pancreatic and intestinal juices, as well as bile, have been
prepared in the duodenum to receive the oncoming chyme. The periodic
activity of the alimentary canal in fasting, therefore, is not solely
the source of hunger pangs, but is at the same time an exhibition
in the digestive organs of readiness for prompt attack on the food
swallowed by the hungry animal.
*[Footnote: The “empty” stomach and esophagus contain gas (see
Hertz: Quarterly Journal of Medicine, 1910, iii, p. 378; Mikulicz:
Mittheilungen aus den Grenzgebieten der Medicin und Chirurgie,
1903, xii, p. 596). They would naturally manifest rhythmic
contractions on shortening tonically on their content.]
REFERENCES
[Footnote 171: Cannon: The Mechanical Factors of Digestion, London
and New York, 1911, p. 204.]
[Footnote 172: Bardier: Richet’s Dictionnaire de Physiologie, article
Faim, 1904, vi, p. 1. See, also, Howell: Text-book of Physiology,
fourth edition, Philadelphia and London, 1911, p. 285.]
[Footnote 173: See Sternberg: Zentralblatt für Physiologie, 1909,
xxii, p. 653. Similar views were expressed by Bayle in a thesis
presented to the Faculty of Medicine in Paris in 1816.]
[Footnote 174: See Hertz: The Sensibility of the Alimentary Canal,
London, 1911, p. 38.]
[Footnote 175: Schiff: Physiologie de la Digestion, Florence and
Turin, 1867, p. 40.]
[Footnote 176: Luciani: Das Hungern, Hamburg and Leipzig, 1890, p.
113.]
[Footnote 177: Tigerstedt: Nagel’s Handbuch der Physiologie, Berlin,
1909, i, p. 376.]
[Footnote 178: Johanson, Landergren, Sonden and Tigerstedt:
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[Footnote 179: Carrington: Vitality, Fasting and Nutrition, New
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[Footnote 180: Viterbi, quoted by Bardier: _Loc. cit._, p. 7.]
[Footnote 181: Busch: Archiv für pathologische Anatomie und
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[Footnote 182: See Schiff: _Loc. cit._, p. 37; also Ducceschi;
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[Footnote 183: Longet: Traité de Physiologie, Paris, 1868, i, p.
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[Footnote 184: Ludwig: Lehrbuch der Physiologie des Menschen,
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[Footnote 185: Maxwell: Journal of Biological Chemistry, 1906-7,
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[Footnote 186: See Schiff: _Loc. cit._, p. 49.]
[Footnote 187: See Schiff: _Loc. cit._, p. 31; Bardier; _Loc. cit._,
p. 16.]
[Footnote 188: Head: Brain, 1893, xvi, p. 1; 1901, xxiv, p. 345.]
[Footnote 189: Nicolai: Ueber die Entstehung des Hungergefühls,
Inaugural Dissertation, Berlin, 1892, p. 17.]
[Footnote 190: Beaumont: The Physiology of Digestion, second edition,
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[Footnote 191: Nicolai: _Loc. cit._, p. 15.]
[Footnote 192: Beaumont: _Loc. cit._, p. 55.]
[Footnote 193: Luciani: Archivio di Fisiologia, 1906, iii, p. 54.
Tiedemann long ago suggested that gastric nerves become increasingly
sensitive as fasting progresses. (Physiologie des Menschen,
Darmstadt, 1836, iii, p. 22.)]
[Footnote 194: Valenti: Archives Italiennes de Biologie, 1910,
liii, p. 94.]
[Footnote 195: Weber: Wagner’s Handwörterbuch der Physiologie,
1846, iii², p. 580.]
[Footnote 196: Vierordt: Grundriss der Physiologie, Tübingen, 1871,
p. 433.]
[Footnote 197: Schiff: _Loc. cit._, p. 33.]
[Footnote 198: Luciani: _Loc. cit._, p. 542.]
[Footnote 199: Valenti: _Loc. cit._, p. 95.]
[Footnote 200: Bettmann: Philadelphia Monthly Medical Journal,
1899, i, p. 133.]
[Footnote 201: Wolff: Dissertation, Giessen, 1902, p. 9.]
[Footnote 202: His: Archiv für Anatomie, 1903, p. 345.]
[Footnote 203: Boldireff: _Loc. cit._, p. 1.]
[Footnote 204: Boldireff: _Loc. cit._, p. 96.]
[Footnote 205: See Cannon and Lieb: American Journal of Physiology,
1911, xxix, p. 267.]
[Footnote 206: Ducceschi: Archivio per le Scienze Mediche, 197,
xxi, p. 154.]
[Footnote 207: See Cannon: American Journal of Physiology, 1903,
viii, p. xxi; 1905, xiv, p. 344.]
[Footnote 208: See American Journal of Physiology, 1913, 1914.]
[Footnote 209: Cannon and Murphy: Journal of the American Medical
Association, 1907, xlix, p. 840.]
[Footnote 210: Boldireff: _Loc. cit._, pp. 108-111.]
[Footnote 211: Cannon: American Journal of Physiology, 1911, xxix,
p. 250.]
[Footnote 212: Haudek and Stigler: Archiv für die gesammte
Physiologie, 1910, cxxxiii, p. 159.]