Professor Pawlow is one of the Board of Scientific Assessors mentioned in the REPORT of a PLAN for an International Inquiry into the subject of Human Nutrition.
In one of the lectures, not here reprinted, Professor Pawlow gives merited recognition of the early statements of the French physiologist Blondlot relative to psychic influence on the digestive secretions made some half century ago, but discredited by physiologists since that time, owing to insufficiency of evidence brought forward in support of the statements.
Professor Pawlow’s acknowledgment is so gracefully rendered that it is here given as a model of scientific courtesy.
“I have depicted the work of the gastric glands as we have seen it in our experiments, and as it has developed under our hands. Is the picture a new one? In its details, yes; but not in its fundamental features. However singular it may appear, the sketch of this picture was more than fifty years ago outlined by physiology. May this constitute another reason for our science relinquishing its characteristic shyness of new things and for its conversion to our interpretation of the phenomena under consideration!
“The talented author of the Traité Analytique de la Digestion—Blondlot—spoke in plain words of the importance of taking food, and of the specific excitability of the gastric mucous membrane. The facts adduced in the working up of his theory were naturally insufficient, but we must not forget that the first experiments on dogs with artificial gastric fistulæ had only just been performed. It is truly incomprehensible that the researches of Blondlot and his views upon the secretion of gastric juice have experienced during the past fifty years no completion, no additions, but, on the contrary, have passed out of sight, thanks to the faulty experiments and erroneous representations of later authors. Only in the works of a few writers—and those mostly French—has Blondlot’s theory survived. Of other investigators we must give mention to Heidenhain, who has enriched the physiology of absorption in general, but more especially, in connection with the secretory work of the stomach, has discovered many important facts and has given birth to many fruitful ideas. From him proceed the subdivision of the secretory process according to periods and exciting agencies, as well as the suggestion that it would be important to investigate the individual food-stuffs in relation to the work of the stomach. Heidenhain’s results are contained in his well-known article on the secretion of the cardiac glands of the stomach, published in the year 1879 in Pflüger’s Archives. The work of Blondlot and the additions of Heidenhain comprise almost everything of importance which was accomplished by physiology in fifty years concerning the conditions and mechanism of the secretory work of the stomach during digestion. Full of moment, however, for our subject was the obvious error that mechanical stimulation constituted an effective excitant of the gastric glands, and this error was in its turn a result of faulty methods.”—Horace Fletcher.]
LECTURE IV
GENERAL SCHEME OF AN INNERVATION MECHANISM—THE WORK OF THE NERVOUS APPARATUS OF THE SALIVARY GLANDS—APPETITE, THE FIRST AND MOST POTENT EXCITER OF THE GASTRIC SECRETION
Constituent parts of a complete innervation mechanism—The special duty of the peripheral terminations of afferent nerves—The specific qualities of nerve cells—Analogy between the innervation mechanism of the salivary glands and that of the deeper-lying glands of digestion—The exciting agencies of the nervous mechanism of the salivary glands; their particular properties—Differences between the exciting agencies of the different salivary glands—Discussion of the sham feeding experiment—Mechanical and chemical stimulation of the cavity of the mouth has no effect on the gastric glands—The experiment of Bidder and Schmidt relative to psychic excitation of the gastric secretion—Conditions for success in this experiment—The passionate longing for food—the appetite—alone brings on the secretory effect in the sham feeding experiment.
Gentlemen,—As you have learned in the last lecture, and also in part have seen by direct experiment, the nervous system can influence the work of our glands in the most diverse ways. The vagus nerve, already burdened with many duties, has, in addition, proved itself to be an undoubted exciter of the gastric glands and of the pancreas. But we must also assign to the sympathetic nerve a similar rôle. This is a matter which cannot be doubted, so far as the pancreas is concerned, and is highly probable as regards the stomach. We also saw good reason for believing that these two nerves contained two different classes of fibres, secretory and trophic, a condition which had already been proved to exist by Heidenhain for the nerves of the salivary glands. As a hypothesis we might even have proceeded a step farther and have divided Heidenhain’s trophic nerves into separate classes of secretory fibres. Lastly, we advanced important experimental evidence to show the existence of special inhibitory fibres to the glands, and these fibres also run in the vagus, the list of whose functions seems almost interminable.
We obtained these results by division and artificial excitation of the nerves which run to the glands. But when, how, and by what means these nerves are thrown into activity during the normal course of physiological events remains a question.