1. The mere act of chewing indifferent substances attd the stimulation of nerve-endings in the mouth by substances other than those directly related to food cause no secretion of gastric juice. On this point our results on Mr. V. are in complete accord with those obtained from dogs by Pavlov and his school, and contrary to those of a number of observers on man.

In a woman with gastric fistula and esophageal stenosis Richet reports secretion of gastric juice from acid stimulation in the mouth. He also states that the introduction of food or sapid substances into the stomach via the fistula caused salivation. This must have been a purely psychic effect, unless the procedure caused nausea. The subject was evidently a hypersensitive woman. We have never observed any of these effects in Mr. V.

Table I. Gastric Juice In C.c. (Mr. V.)

In 1896 Schiile introduced the method of obtaining pure appetite gastric juice in man by emptying the stomach by means of a stomach tube, then chewing food for 15 minutes, and again emptying the stomach with the tube. He claims that the mere act of chewing and the tasting of such sapid substances as oil of peppermint, slices of lemon, and mustard cause secretion of gastric juice even in the absence of appetite. Troller, using Schule's method, also reports that slices of lemon, mustard, etc., in the mouth, as well as the mere act of chewing, cause secretion of gastric juice. In the majority of his experiments the secretion thus obtained was very slight (only about one-fourth that obtained on chewing bread), and in some of the experiments recorded in detail the acidity of the juice is so low that it must have been mixed with swallowed saliva. It is probably very difficult for the average person to avoid swallowing some saliva with mustard or citric acid in the mouth for 10 to 15 minutes. Troller did not adequately control the rate of the continuous secretion in the empty stomach when the persons had nothing in particular in the mouth. Riegel cites the case of a professional cook, in whom chewing of food (beefsteak) or slices of lemon caused no secretion of gastric juice. This man showed chronic digestive disorders, however. But Riegel suggests that the absence of appetite secretion was due to a kind of permanent fatigue of the taste-secretory mechanism in consequence of his duties as cook. Horn-borg, working on a five-year-old boy with gastric fistula and nearly complete cicatricial stenosis of the esophagus, concluded that chewing indifferent, badly tasting, or strongly tasting (lemon) substances did not induce secretion of gastric juice. Umber obtained no gastric secretion by chewing indifferent substances (pieces of rubber), but in one experiment alcohol in the mouth gave a slight secretion. It must be noted that Umber's subject was a man fifty-nine years old, who might have been in the habit of taking alcoholic beverages with his meals.

Kaznelson and Bickel, working on a twenty-three-year-old girl with gastric fistula and complete cicatricial esophageal stenosis, report that all sapid substances (quinine, asafoetida, etc.) in the mouth, even those that give rise to disgust, initiate or augment the gastric secretion/ Kaznelson cites one experiment with quinine (control experiment with water), from which she concludes that bitter substances in the mouth augment the secretion of gastric juice, but her actual figures show, if anything, the reverse. The total secretion of gastric juice for 80 minutes with the water control (sham drinking) was 43.7 c.c., while the quinine experiment yielded only 37.6 c.c. for the corresponding time.

How are these contradictory findings to be accounted for ? In view of the consistently negative results of Pavlov and his students on dogs, and of Hornborg, and the writer on man, it is our belief that the investigators who report that mechanical chewing and general stimulation of the nerve-endings in the mouth cause secretion of gastric juice have not eliminated the factors of appetite, swallowed saliva, and variations in the rate of the continuous secretion of the empty stomach. In man the appetite factor is not easily controlled, except by a long series of tests in which the experimental procedure becomes a mere routine to the subject. There appears to be no direct or unconditional reflex pathway from the mouth to the gastric gland. Unless the stimuli in the mouth initiate or augment the central processes that constitute the sensation of appetite, there is no innervation of the secretory nerve-fibers to the gastric gland.

2. The relatively slight and inconstant secretion of gastric juice produced by seeing, smelling^ or thinking of food.-Bringing a tray of palatable food into the room in sight of Mr. V. has never yet caused secretion of gastric juice, no matter what the degree of hunger and appetite. It is probable that under these conditions the primary and normal effects of seeing and smelling the food are inhibited by the consciousness of the experiment, or possibly his main interest was not the food, but the expiration of the experiment so that he might partake of the food. In order more closely to approximate normal conditions, Mr. V. was sent out to the near-by cafeteria to select the lunch that he knew he would eat shortly after returning with it to the laboratory. The rate of his gastric secretion was measured for 10-minute periods before going for the food, during the selection of, and after returning to the laboratory with it. In the majority of these tests the act of selecting the ingredients for the noonday meal caused a slight and temporary augmentation of the secretion rate of the empty stomach. On the whole this augmentation was greater the greater the rate of the continuous secretion. But on some days the augmentation was absent, although Mr. V. was in good health, felt hunger, and the cafeteria displayed the usual variety of food.

Pavlov reports that there are great individual variations in dogs in the amount of gastric secretion induced by seeing and smelling food. This, in all likelihood, is true of man, and we suspect that Mr. V. belongs to the group of individuals in whom the taste of the food is the all-important factor in the psychic secretion of gastric juice. We have not been able appreciably to augment the continuous secretion in Mr. V. by inducing the thought of food, for example, during a test while he is busy with other work, by arresting his attention casually, and by discussing with him the taste and ingredients of his favorite dishes.

Schiile states that seeing or smelling food causes no secretion of gastric juice in normal persons. This is directly contradicted by Bulawinzew. This investigator emptied the stomach by means of the stomach tube, then let the subject see or smell food, and again emptied the stomach. The gastric juice thus obtained had such low acidity (0.2 per cent HCl) that it must either have been in the continuous gastric secretion or the appetite gastric juice mixed with saliva. There is nothing in the review to indicate that he controlled the continuous gastric secretion. Hornborg obtained no secretion of gastric juice from a five-year-old boy on his seeing or smelling food, probably because the child always became angry when not permitted to eat the food shown him. Cade and Latarjet report secretion of gastric juice was induced by talking to the subject about her favorite food. This subject (a young woman) is exceptional in that she virtually had an accessory stomach, but the mucosa of the isolated stomach portion was directly exposed so that the collection of the secretions was rather difficult. Kaznelson and Bickel, working with a twenty-three-year-old girl with gastric fistula and stenosis of the esophagus, reached the remarkable conclusion that anything which stimulated the olfactory sense induced secretion of gastric juice in the resting stomach. Thus they claim that smelling ammonia, acidic acid, and aromatic oils causes secretion of gastric juice. This we are absolutely unable to confirm on Mr. V. It is possible that in this young woman every gustatory and olfactory stimulus when manipulated by the investigators led to thoughts of food through idea associations.