The effect of the emotions on the digestive processes is so important from the standpoint of clinical medicine that I quote the following summary of published observations from Cannon: "Hornborg found that when the boy whom he studied chewed agreeable food a more or less active secretion of the gastric juice was started, whereas the chewing of indifferent material was without influence.
"Not only is it true that normal secretion is favored by pleasurable sensations during mastication, but also that unpleasant feelings, such as vexation and some of the major emotions, are accompanied by a failure of secretion. Thus Hornborg was unable to confirm in his patient the observation of Pawlow that mere sight of food to a hungry subject causes the flow of gastric juice. Hornborg explains the difference between his and Pawlow’s results by the difference in the reaction of the subjects to the situation. When food was shown, but withheld, Pawlow’s hungry dogs were all eagerness to secure it, and the juice at once began to flow. Hornborg’s little boy, on the contrary, became vexed when he could not eat at once, and began to cry; then no secretion appeared. Bogen also reports that his patient, a child, aged three and a half years, sometimes fell into such a passion in consequence of vain hoping for food, that the giving of the food, after calming the child, was not followed by any secretion of the gastric juice.
"The observations of Bickel and Sasaki confirm and define more precisely the inhibitory effects of violent emotion on gastric secretion. They studied these effects on a dog with an œsophageal fistula, and with a side pouch of the stomach which, according to Pawlow’s method, opened only to the exterior. If the animal was permitted to eat while the œsophageal fistula was open the food passed out through the fistula and did not go to the stomach. Bickel and Sasaki confirmed the observation of Pawlow that this sham feeding is attended by a copious flow of gastric juice, a true ‘psychic secretion,’ resulting from the pleasurable taste of the food. In a typical instance the sham feeding lasted five minutes, and the secretion continued for twenty minutes, during which time 66.7 c. c. of pure gastric juice was produced.
"On another day a cat was brought into the presence of the dog, whereupon the dog flew into a great fury. The cat was soon removed, and the dog pacified. Now the dog was again given the sham feeding for five minutes. In spite of the fact that the animal was hungry and ate eagerly, there was no secretion worthy of mention. During a period of twenty minutes, corresponding to the previous observation, only 9 c. c. of acid fluid was produced, and this was rich in mucus. It is evident that in the dog, as in the boy observed by Bogen, strong emotions can so profoundly disarrange the mechanisms of secretion that the natural nervous excitation accompanying the taking of food cannot cause the normal flow.
"On another occasion Bickel and Sasaki started gastric secretion in the dog by sham feeding, and when the flow of gastric juice had reached a certain height the dog was infuriated for five minutes by the presence of the cat. During the next fifteen minutes there appeared only a few drops of a very mucous secretion. Evidently in this instance a physiological process, started as an accompaniment of a psychic state quietly pleasurable in character, was almost entirely stopped by another psychic state violent in character.
"It is noteworthy that in both the positive and negative results of the emotional excitement illustrated in Bickel and Sasaki’s dog the effects persisted long after the removal of the exciting condition. This fact Bickel was able to confirm in a girl with œsophageal and gastric fistulas; the gastric secretion long outlasted the period of eating, although no food entered the stomach. The importance of these observations to personal economics is too obvious to require elaboration.
“Not only are the secretory activities of the stomach unfavorably affected by strong emotions; the movements of the stomach as well, and, indeed, the movements of almost the entire alimentary canal, are wholly stopped during excitement.”[[205]]
So you see that the proverb, “Better a dinner of herbs where love is than a stalled ox and hatred therewith,” has a physiological as well as a moral basis.
Nearly any sensory or psychical stimulus can be artificially made to excite the secretion of saliva as determined by experimentation on animals by Pawlow.
It is probable that all the ductless glands (thyroid, suprarenal, etc.), are likewise under the influence of the emotions. The suprarenal glands secrete a substance which in almost infinitesimal doses has a powerful effect upon the heart and blood vessels, increasing the force of the former and contracting the peripheral arterioles. The recent observations of Cannon and de la Paz have demonstrated in the cat that under the influence of fear or anger an increase of this substance is poured into the circulation.[[206]] Cannon, Shohl and Wright have also demonstrated that the glycosuria which was known to occur in animals experimented upon in the laboratory is due (in cats) to the influence of the emotions, very probably discharging through the sympathetic system on the adrenal glands and increasing their secretion.[[207]] The glycosuria is undoubtedly due to an increase of sugar in the blood. It is interesting to note, in this connection, that there is considerable clinical evidence that indicates that some cases of diabetes and glycosuria have an emotional origin. The same is true of disease of the thyroid gland (exophthalmic goiter).