CONTRIBUTIONS TO THE PHYSIOLOGY OF GASTRIC SECRETION. I: GASTRIC SECRETION BY LOCAL (MECHANICAL AND CHEMICAL) STIMULATION

¹ Hull Physiological Laboratory, the University of Chicago

1. Mechanical distension of the stomach stimulates gastric secretion in man and dog, in the latter with and without vagi intact. The latent period is from five to fifteen minutes. This substantiates the opinion of the older physiologists, particularly Magendie, Beaumont, and Heidenhain. Pavlov would have come to this conclusion if he had divided the vagi, as he made similar observations to ours but assumed that the stimulation was psychic.

2. The application of certain substances, such as raw meat juice, -alanine, and histamine when applied to the gastric mucosa in quantities insufficient to cause distension, excites gastric secretion. Strong NaCl solutions, glucose (50 per cent.) solution, and Liebig's meat extract stimulate, but not to the extent that the above substances do, the formation of mucus being markedly augmented. Cane-sugar, starch, and fats do not stimulate when applied. Water stimulates when used in a quantity sufficient to cause adequate distension. This specific chemical excitation substantiates the observations of Pavlov and others.

3. Water is absorbed from the stomach of unanæsthetised animals if permitted to remain for a half to one hour.

4. The stimulation of gastric secretion by mechanical distension, or by the sub-maximal application of certain chemicals, is inhibited by the hypodermic administration of 1 mg. of atropine and by the introduction of fats into the intestine, which agents are known to inhibit the secretion that occurs after the ingestion of a meal. Fat applied to the gastric mucosa only slightly inhibits the action of the above excitants.

5. Various preparations of animals used in our work are described, including a preparation with a pouch of the entire stomach with vagi cut and an anastomosis of the sophagus to the intestine, which has made possible many of our observations and makes more possible the experimental solution of many important problems in gastro-intestinal physiology.

6. The mechanism concerned in gastric secretion is discussed and a working hypothesis is suggested, which is as follows: All stimuli that excite gastric secretion act essentially by increasing the active blood-flow through the gastric glands; the means by which this is accomplished may be quite varied, the motility of the stomach being in some way involved. We do not hold this view to the exclusion of others; for example, we believe that the enteric reflex may play an important role; but since this mechanism does not suffice to explain the secretion to meals in the denervated pouch, and since all attempts up to date have failed to prove a hormone or humoral mechanism, we believe it is better to adopt a hypothesis which offers a common mechanism. We realise that this hypothesis runs counter to the accumulated evidence on the mechanism concerned in the secretion of saliva, but it must be kept in mind that the nature of the two secretions differs radically.

7. Our observations offer a satisfactory explanation for at least a part of the hypernormal gastric secretion ("hypersecretion") that is observed to occur in cases of pyloric obstruction.

8. Our analysis of the factors concerned in the excitation of gastric secretion is as follows: (1)The cephalic phase, heretofore referred to as the "psychic secretion" demonstrated by Pavlov, which is excited chiefly by the taste, smell, and mastication of palatable food, and by sight or hypnotic suggestion of palatable food. The term "psychic secretion" is rejected because it is not necessarily psychic, as it has been shown to occur in the absence of the cerebral cortex (65). (2)The gastric phase, in which mechanical and chemical stimuli are effective, as shown by the observations recorded in this paper. (3)The intestinal phase, in which the stimuli are certain chemical substances acting in the intestine, as recently demonstrated by Ivy and M'Ilvain (27) and proven without question of doubt by the observations to be recorded in a succeeding article.