Functional Dyspepsia (Atonic Dyspepsia, Indigestion).
To difficulty in the physiological process of digestion the familiar name of dyspepsia has been given, while to a merely disturbed condition of the function the term indigestion is more frequently applied. This distinction, difficult at all times to make, may appear more arbitrary than real; and inasmuch as it involves no important practical point, the author of the present article will use the terms interchangeably as indicating functional disturbance of the stomach—i.e. disturbance of the digestive process not associated with changes of an inflammatory character, so far as we know.
Since it is one of the most common of all complaints from its association with various other morbid conditions, the term is not unfrequently vaguely employed. It is difficult, of course, to define a disease whose etiology is so directly related to so many distinct morbid conditions. Indeed, there are few diseases, general or local, which are not at some time in their history associated with more or less derangement of the digestive process. For purposes of limitation, therefore, it will be understood that we now refer to chronic functional forms of indigestion which depend largely, at least, on a purely nervous element, and for this reason are not infrequently described as sympathetic dyspepsia. Doubt has been expressed as to whether such forms of disease ever exist, but that we encounter purely functional forms of dyspepsia, corresponding to the dyspepsia apyretica of Broussais, would appear to be a well-recognized clinical fact.
What the precise relation is between digestive disturbances and the nervous system we may not fully understand, no more than we understand how a healthy condition of nervous endowment is essential to all vital processes. Even lesions of nutrition are now known to depend upon primary disturbance of nervous influence. This is seen in certain skin diseases, such as herpes zoster, which closely follows the destruction of certain nerves. And it is well known that injury of nerve-trunks is not unfrequently followed by impaired nutrition and failure in reparative power in the parts to which such nerves are distributed. Indeed, so marked is the influence of the nervous system over the nutritive operations that the question has been considered as to whether there are trophic nerves distributed to tissue-elements themselves whose special function is to keep these elements in a healthy state of nutrition. The proof, at least, that the digestive process is, in some unexplained way, under the immediate influence of the nervous system, either cerebro-spinal or trophic, is both varied and abundant. The digestive secretions are known to be the products of living cells which are abundantly supplied with nerve-fibres, and we can readily believe that the potential energy of this cell-force is probably vital and trophic. At any rate, it is unknown in the domain of ordinary chemistry. The digestive ferments, as clearly pointed out by Roberts, are the direct products of living cells. Their mode of action, he claims, bears no resemblance to that of ordinary chemical affinity. It has a distinctly physiological character. Nor do they derive their vital endowments from material substances. "They give nothing material to, and take nothing from, the substances acted on. The albuminoid matter which constitutes their mass is evidently no more than the material substance of a special kind of energy—just as the steel of a magnet is the material substratum of the magnetic energy, but is not itself that energy" (Roberts). That this living cell-force is partly, at least, derived from the nervous system is clear from the well-known effects of mental emotion, such as acute grief, despair, etc., in putting an immediate stop to the digestive process. Experiments on the lower animals have also shown the direct influence of the nervous system over gastric secretion. Wilson Philip showed by various experiments on rabbits and other animals that if the eighth pair of nerves be divided in the neck, any food which the creatures may afterward eat remains in the stomach undigested, and after death, when the nerve has been divided, the coats of the stomach are not found digested, however long the animal may have been dead. Bernard also excited a copious secretion by galvanization of the pneumogastric, and by section of the same nerve stopped the process of digestion and produced "pallor and flaccidity of the stomach." Recently doubt has been thrown on these statements of Bernard and Frerichs. Goltz concludes, from observations made on frogs, that nerve-ganglia, connected by numerous intercommunicating bundles of nerve-fibres, exist in the walls of the stomach, the irritation of which gives rise to local contractions and peristaltic movements of the stomach, and that these ganglia influence the gastric secretion. However this may be, it still remains true that these gastric ganglia are in connection, through the vagi, with the medulla oblongata, and are thus influenced by the cerebro-spinal nerve-centres. And clinical observation confirms what theoretical considerations would suggest. Thus, strong mental impressions are known to produce sudden arrest of secretion, and that which arrests secretion may, if continued, lead to perversion of the same.
Impressions made upon the nerves of special sense are also known to affect the salivary and gastric secretions. The flow of saliva is stimulated by the sight, the smell, the taste, and even thought, of food. Bidder and Schmidt made interesting experiments on dogs bearing upon this point. They ascertained by placing meat before dogs that had been kept fasting that gastric juice was copiously effused into the stomach. Other secretions are known to be similarly affected. Carpenter by a series of well-observed cases has shown the direct influence of mental conditions on the mammary secretion. The nervous association of diabetes and chronic Bright's disease is interesting in this connection, and the direct nervous connection betwixt the brain and the liver has been shown by numerous experiments. It is maintained by modern physiologists that "the liver—indeed each of the viscera—has its representative area in the brain, just as much as the arm or leg is represented in a distant localized area" (Hughlings Jackson). And in harmony with this view Carpenter long since pointed out the fact that if the volitional direction of the consciousness to a part be automatically kept up for a length of time, both the functional action and the nutrition of the part may suffer. It has been described by him as expectant attention, and it has, as we shall see, important practical bearings on the management of gastric affections. Sympathetic disturbance of the stomach is also connected with direct disease of the brain. This is seen in cases of concussion. The almost immediate effects of a blow are nausea and vomiting, and the same thing is observed in local inflammation of the meninges of the brain.
Many forms of functional dyspepsia due to nervous disturbance of a reflex character will be pointed out when discussing the etiology of the disease.
ETIOLOGY.—Among the agencies affecting the digestive process in atonic forms of dyspepsia may be mentioned—
First, predisposing causes;
Second, exciting causes.