Continued secretion of gastric juice in the absence of food in the alimentary tract, and in the absence of cerebral processes relating to appetite ("psychic" stimulation), is a well-known phenomenon in certain types of gastric disorders, but it is generally assumed by physiologists that, in the absence of psychic stimulation, the gastric glands cease to secrete almost as soon as the stomach is emptied of chyme, and that the glands remain quiescent up to the next feeding. The quiescence is supposed to be sufficiently complete to render the surface of the stomach alkaline, due to the continued secretion of alkaline mucus.. To the extent that this view is anything more than an assumption, it is based essentially on the studies by Pavlov and his pupils on dogs. Pavlov frequently emphasizes the fact that not a drop of gastric juice flows from the stomach unless there is food or other stimuli in the stomach or unless the appetite is called into play. Later Boldyreff reported that on continued starvation the gastric glands exhibit periodic activity, and if the starvation is maintained for more than three or four days the secretion of the gastric gland becomes continuous. In gastric-fistula cases of normaj persons no specific study has been made of the continuous secretory activity of the empty stomach, but in some instances (Kaznelson, Hornborg) there are indications of a slow, continued secretion even when the stomach had been free from food for hours.
Most of our observations on Mr. V. were made between 10:00 a.m. and 4:00 p.m., the usual breakfast of coffee, milk, and biscuits being taken at 7:00 a.m. A few tests were made between 9:00 a.m. and 12:00 m., and on such occasions Mr. V. did not take any breakfast. The rate of the continuous secretion of gastric juice in the empty stomach of Mr. V. varies from a few cubic centimeters up to 60 c.c. per hour.
In general more gastric juice is obtained from the empty stomach if the stomach is emptied (through the fistula) every 5 or 10 minutes than if it is emptied every 30 or 60 minutes. It is therefore likely that some of this secretion passes into the intestines or is actually reabsorbed in the stomach itself. It does not seem probable that the presence of a certain amount of this juice in the stomach would tend to inhibit further secretion.
If the secretion rate is low the acidity is usually not over 0.20 to 0.25 per cent, but the pepsin concentration is nearly as great as that of the appetite gastric juice. If the secretion rate is moderate the acidity is greater and the pepsin concentration may even exceed that of the appetite secretion. When the secretion rate is low the juice is very thick and opalescent, owing to the great amount of ropy mucin.
What constitutes the stimulus to the continuous gastric secretion ? Wc think it can be shown that it is not an appetite secretion. To be sure, in the case of normal and vigorous persons, periods of hunger and appetite are present almost as soon as the stomach is emptied of food. And it is obviously difficult so to control the cerebral processes of a person that the thoughts are not diverted to food and eating, especially if the usual meal time has passed and one's attention is at the time on the stomach. This is especially true if the gastric juice is collected every 10 minutes. If the stomach is emptied every 30 or 60 minutes and the person is kept very-busy with matters not pertaining to food and eating, we think this factor is entirely eliminated. This was done every day for two weeks at a stretch, so as to make it a mere incident or routine in the day's work. Nevertheless, the continued secretion persisted with the usual fluctuations in character and quantity.
Is the secretion due to a subconscious secretory vagus tonus ? The vagi carry secretory fibers to the gastric glands. But we know next to nothing about the reflex or tonus control of this neurosecretory mechanism. We know that the vagi send tonus impulses to the gastric motor mechanism. But it does not follow that this is also the situation in regard to the gastric gland.
The presence of food in the intestine may be partly responsible for this continued secretion, by reflex action from the intestinal mucosa (Pavlov), or by absorptions of gastric secretins into the blood. In a thirty-nine-year-old man with gastric fistula Umber obtained some secretion of gastric juice on rectal feeding with milk, sugar, and eggs. Umber explains the secretion as a reflex effect from the mucosa of the large intestine. We are not convinced that kpurely psychic factors are excluded in his experiments. If a person is hungry it is likely he will be led to think of food and eating by the mere act of rectal feeding. Moreover, Umber's experiments were not numerous enough really to establish the point.
Gastric juice itself contains mucins and proteins that are digested by the pepsin-hydrochloric of the gastric juice. It is highly probable that the products of this digestion yield gastric secretagogues, just as in the case of some of the digestion products of the food proteins. According to Bickel amino-acids given by mouth cause secretion of gastric juice. Absorbed slowly in tfce stomach or passed into, the intestines to be absorbed there, the products of the auto-digestion of the gastric juice probably furnish chemical stimuli for a slow but continuous gastric secretion. Which one of these factors is of prime importance in the continuous secretion of gastric juice by the empty stomach must be determined by other lines of work, especially in disease conditions where the continuous secretion is greatly increased.