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the saliva and gastric juice. Many circumstances combine to modify the extent and quality of the secretion furnished by these several glands, i. e., the character and extent of the stimulation, so that constant fluctuation, within certain limits, may be expected in the volume and concentration of the fluids from day to day, and hence in their physiological activity likewise. Thus, influences which affect the volume and character of the blood flowing through the glands, local blood-pressure, etc., as well as the character and amount of the ingested food, all have an effect upon the volume and composition of the secretions.

The digestive power of these several secretions is dependent mainly upon the presence of specific ferments or enzymes, manufactured in the glands, which, acting upon the foodstuffs under suitable conditions, render them soluble and diffusible and so capable of being absorbed. The saliva is a slightly alkaline fluid, and in virtue of the enzyme (ptyalin) it contains acts upon starchy or farinaceous foods, transforming them into soluble dextrins and sugars, a process which commences in the mouth and continues for a brief time in the stomach, until the enzyme is finally destroyed by the increasing acidity of the gastric juice. This starch-digesting action of the saliva is frequently spoken of as amylolytic action, while the active agent may be described as an amylolytic ferment or enzyme. The gastric juice is an acid-reacting fluid containing normally about two tenths per cent. of hydrochloric acid, the enzyme pepsin and a milk-curdling enzyme known as rennin. The main action of the gastric juice, in virtue of the contained pepsin-hydrochloric acid, is upon the proteid or albuminous foods transforming them into a number of products, chiefly proteoses and peptones, characterized especially by their solubility and diffusibility. This proteid-digesting power is described as proteolytic action, and the enzyme which accomplishes the transformation of the proteid is known as a proteolytic enzyme. When the acid chyme, i. e., the semi-digested mass in the stomach, leaves the latter organ, it passes through the pyloric orifice into the small intestine, where it is exposed to the double action of the bile and pancreatic juice. The latter is a powerful digestive fluid of strong alkaline reaction, containing three distinct enzymes. One of these is an amylolytic or starch-digesting enzyme essentially identical with the enzyme of saliva and converts any unchanged

starch into soluble dextrins and sugar. The second ferment is a powerful proteolytic enzyme known as trypsin which in a neutral or alkaline-reacting fluid transforms proteid matter into a row of soluble products different in nature from those formed in acid gastric digestion. The third ferment is an adipolytic or fat-splitting enzyme which transforms at least a portion of the fats of the food into soluble forms. This threefold action of the pancreatic juice may continue for some time in the small intestine, but as the peristaltic or wave-like contraction of the intestinal walls tends to push the contents of the tube onward toward the large intestine, and as absorption is quite rapid at this point, the conditions gradually become unfavorable for further digestive action.

From the foregoing, it is plain that digestion, broadly speaking, may be modified in a variety of ways, notably through the influence of agencies affecting the nervous system, thereby modifying the rate and character of the secretions coming from the digestive glands. Thus, agents introduced with the food, as well as the food itself, may after their absorption into the circulation lead to changes in the rate of flow and composition of the blood passing through the glands, modifying thereby the amount of material available for the manufacture of the several digestive secretions. Further, these agents may exert a specific influence upon the nerves which directly govern secretion, thereby directly affecting the manufacture and flow of the individual digestive fluids. Again, the mere presence of substances introduced with the food may exert an influence upon the digestive or solvent action of the secretions, thus modifying the rate of digestion. For example, the presence of salt in the stomach-contents may lead to an acceleration of gastric digestion through a simple acceleration of ferment action, while larger quantities of the same salt in the stomach may retard gastric digestion through inhibition of ferment action. Obviously, the duration of this acceleration or retardation of gastric digestion would depend primarily upon the length of time the salt remained in the stomach, i. e., upon the rapidity of its absorption and consequent removal from the alimentary tract. Still again, the rate of digestion may be modified by agents which, absorbed. into the blood, act upon the nerves, controlling the motor functions of the stomach and intestine. Thus, normally the latter

organs are constantly in motion, producing a more or less constant agitation or churning of the respective contents which serves to intimately mingle the food particles with the digestive juices, thereby accelerating digestion. Hence, everything else being equal, anything which tends to accelerate peristalsis will in turn accelerate the rate of digestion, while, on the other hand, retardation of peristalsis may be accompanied by inhibition of digestion. Lastly, the rate of absorption from the alimentary tract exercises an influence upon the speed of digestion; consequently any agent which, for example, modifies the flow of blood along the gastro-intestinal tract, thus influencing the rate of absorption, may indirectly affect the speed of digestion. It is thus plainly evident that what we term digestion may be influenced through a variety of channels, but the two more important ways in which digestion may be modified are through changes in the rate of flow and composition of the digestive fluids, i. e., changes in secretion, and through changes (either acceleration or retardation) in the rate of digestive action caused by the mere presence of some substance in the digestive mixture, i. e., through a direct influence upon the purely chemical processes of digestion. Moreover, it is obvious likewise that a substance may exercise an inhibitory influence in one direction, as upon the chemical process of digestion, while leading to an acceleration in another direction, as on secretion. Further, a given agent may produce one effect on salivary digestion and quite a different effect on gastric digestion. Obviously, therefore, in studying the influence of alcoholic beverages on digestion, there are many lines of inquiry which must receive attention.

II.

GENERAL CONCLUSIONS AS TO THE INFLUENCE OF ALCOHOL AND ALCOHOLIC BEVERAGES ON DIGESTION.

As already indicated, digestion may be influenced by alcoholic fluids in several ways, notably by influencing the rate of secretion of the digestive fluid, either increasing or diminishing the rate of flow and thereby increasing or decreasing the volume of digestive fluid available, and also by modifying either favorably or unfavorably the chemical composition of the secretion. Further, the presence of the alcoholic fluid, in the stomach for example, may exercise a direct influence upon the chemical processes of digestion, either augmenting or retarding the natural solvent or digestive action of the secretion. Again, digestion may be influenced indirectly by the action of an alcoholic fluid upon the rate of absorption and upon the peristaltic movements of the intestine, since both of these factors exert an influence upon the rapidity of digestion.

1. GASTRIC DIGESTION.

a. Influence of alcohol and alcoholic beverages on the secretion of gastric juice. The results of the experiments carried out by the writer and his assistants on the influence of alcohol and alcoholic beverages on the secretion of gastric juice lead to some very definite conclusions. The data obtained and presented in detail in the subjoined report tend to show that when alcohol and alcoholic fluids are taken into the stomach there is a marked increase in the flow of gastric juice accompanied by an increase in the content of the essential constituents, pepsin and hydrochloric acid, as well as in the content of total solid matter. Moreover, this stimulating effect of alcohol and alcoholic beverages upon the secretion of gastric juice is not limited to a direct action dependent upon the presence of the alcoholic fluid in the stomach, but is exerted likewise indirectly through the influence of alcohol absorbed from the intestine. Thus, if the

intestine is entirely shut off from the stomach by a ligature at the pylorus, the introduction of an alcoholic fluid into the intestine is followed by a stimulation of the gastric glands accompanied by an outpouring of the gastric secretion. Whiskey, brandy, sherry, claret, beer, and porter, as well as pure alcohol, all agree in producing direct and indirect stimulation of gastric secretion, increasing both the rate of flow of the gastric juice and the concentration of the fluid.

Of special importance in this connection is the fact, brought out by experiment, that when alcohol and alcoholic beverages are introduced into the alimentary tract there is a very rapid absorption of the alcohol into the circulation. The alcohol quickly leaves the stomach and intestine passing into the blood, this act being accompanied by an inrush of acid gastric juice in large quantity. Even from the stomach, where absorption is ordinarily comparatively slight, the absorption of alcohol goes on with considerable rapidity. Thus, the introduction of two hundred c. c. of thirty-seven per cent. alcohol into the stomach of a dog with the intestine ligated at the pylorus may be followed by the nearly complete disappearance of the alcohol in three hours by absorption through the stomach walls into the blood. When the outlet from the stomach into the intestine is open, then the rate of absorption of alcohol is greatly increased. Alcohol unquestionably disappears from the alimentary tract quite rapidly. Thus, in one experiment, fifty c. c. of twenty per cent. alcohol were introduced into the stomach of a dog with a gastric fistula, and on withdrawal of the stomach-contents half an hour later no alcohol whatever was found in the forty c. c. of fluid obtained. In view of this rapid disappearance of alcohol from the alimentary tract it is plain that alcoholic fluids cannot have much, if any, direct influence upon the secretion of either pancreatic or intestinal juice. Further, it is equally clear that the rapid removal of alcohol from the stomach by absorption must tend to diminish considerably any influence the presence of alcohol might exert upon the solvent or digestive action of the gastric juice in the stomach.

The conclusion is therefore obvious that when alcoholic fluids are taken into the stomach there is first a direct stimulation, leading to the rapid secretion of a powerful gastric juice. This is followed by a more or less rapid absorption of the alcohol

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