In 1846 Weber suggested that the sensation of cold or warmth in the epigastrium, after drinking ice-cold or very warm water, originates in the skin of the abdomen over the stomach and not in the stomach mucosa. According to Weber sufficient conduction takes place through the walls of the stomach and abdomen to stimulate the temperature nerves of the skin. Becher swallowed a single rubber tube and through it injected water of different temperatures into the stomach. He did not experience any heat or cold sensation before the heat or cold had passed through the walls of the tube and stimulated the mucosa of the esophagus. Mueller concluded that ice water produced no sensation in the stomach. Zimmerman irrigated his stomach with hot or cold water through a thick rubber tube. He claims that hot or cold sensations were felt only when the lower end of the tube was 30 to 25 cm. distant-hence not far from the lower end of the esophagus. He therefore concludes that the sensation is projected from the esophageal mucosa. MacKenzie believes that the temperature sensations induced by hot and cold water entering the stomach is due to reflex vasomotor changes in the skin of the abdomen.' Nystrom reports that touching the gastric mucosa of a man having gastric fistula with a hot piece of metal or piece of ice, does not call forth any definite temperature sensations. According to Hertz the hot or cold sensations felt in the epigastrium, upon swallowing hot or cold water, come from the lower end of the esophagus. The water accumulates here before the cardiac orifice opens, and that part of the esophagus is thus stimulated more than the parts above. He defends his conclusion by this observation: by auscultation over the epigastrium after swallowing a mouthful of very hot or cold water, one will find that immediately after the second deglutition sound, which occurs after the last trace of food has entered the stomach, the hot or cold sensation disappears. He also states that upon injecting hot or cold water through a double rubber tube, no temperature sensation was noticed before 3 or 4 ounces had passed into the stomach. An ill-defined temperature sensation was then experienced, but he concludes that this was due to the conduction of heat or cold to the esophageal wall. Hence, according to Hertz, the stomach mucosa is not endowed with heat or cold nerve-endings. Quincke introduced hot and cold water into the stomach of a boy with a gastric fistula and reports that the patient experienced vague heat or cold sensations. Neumann and Roux, injecting hot and cold water into the stomach through a double rubber tube, experienced hot and cold sensations in the stomach, the cold sensations being the more pronounced. Head, Rivers, and Sherren injected water at different temperatures into the colon of a patient, upon whom a colostomy had been performed, and found that water at 200 to 400 C. produced no sensation at all, but water at 50° C. and very cold water did give rise to temperature sensations, but that these sensations were by no means as pronounced and as easily localized as those produced by applying water at the same temperatures to the skin. Head concludes that the viscera is endowed with "protopathic" temperature sensibility only.
Boring reports that water at 400 C. produces a sensation of warmth, and water at 300 C. a sensation of cold referred to the stomach. In his first paper Boring inclined to the view that these sensations originate not in the stomach but in the abdominal wall; in the second paper he concludes that they arise either in the stomach itself or in tissues closer to the stomach than the abdominal wall and the esophagus.
It is thus evident that by far the majority of those who have investigated this problem have experienced a vague hot or cold sensation, in the region of the epigastrium, upon stimulating the stomach mucosa with hot or cold water. Those who do not believe that the sensations arise in the stomach mucosa explain its origin in one of the following ways: (i) It is due to conduction to the skin of the abdomen. (2) It is due to reflex vascular changes of the skin of the abdomen. (3) It is projected from the esophagus. (4) It arises in the lower part of the esophagus.
Our own experiments on Mr. V. and on ourselves go to show that the above-mentioned theories are untenable. That is to say, we find that the gastric mucosa is endowed with protopathk temperature sensibility.
The first series of experiments was on Mr. V. He was blindfolded and was not told the nature of the experiments. The water, 40 to 60 ex., was injected through a small rubber tube which was passed through the large permanent tube of the fistula. With water at 500 C. he said that he felt a hot sensation in the stomach, after a latent period of about 5 seconds. When the same amount of water at 10° C. was injected, a cold sensation was felt after a slightly shorter latent period. A metal rod 5 mm. in diameter, heated to about 500 C, was passed down through the fistula catheter until the end touched the mucosa of the dorsal wall of the stomach. A longer latent period elapsed here before any sensation of heat was noticed. When, however, a small piece of ice, held by a pair of forceps, was brought into contact with the stomach mucosa, the latent period was not much longer than when cold water had been injected. A cold sensation was distinctly felt. These experiments were repeated over and over again, and Mr. V. was invariably able to recognize whether the mucosa was being stimulated with hot or cold media, provided the media was 45 to 550 C. and the cold at least 13° C.
The temperature sensations initiated by touching the gastric mucosa directly with hot or cold solids cannot come from the stimulation of the esophageal mucosa. The latent period is too short to allow temperature conductions to the skin of the abdomen. But since it is possible that the cardia and the lower end of the esophagus of Mr. V. are patent, water injected through the fistula may reach the lower end of the esophagus. This possibility was guarded against in a second series of experiments, where we injected the hot and cold water into a very delicate rubber balloon previously introduced into the stomach. The hot and cold water was correctly recognized as hot or cold, just as in the test with the water touching the mucosa directly, the only difference being a somewhat longer latent period. It is clear from the above that the gastric mucosa of Mr. V. is endowed with protopathic temperature sense.