Hunger Not Due to Turgescence of the Gastric Mucous Membrane
Another theory, which was first advanced by Beaumont,[22] 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[23] 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[24] 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.
[*] 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[25] 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[26] 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[27] stated, “The movements of the empty stomach are rare and much less energetic than during digestion.” Luciani[28] 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[29] 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[30] called attention to the contracted condition of the stomach after several days’ fast. In 1902 Wolff[31] 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[32] also recorded his observation of the phenomenon. In 1905 Boldireff[33] 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[34] 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,[35] 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[36] 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.