The physiology of digestion, considered with relation to the principles of dietetics / [Andrew Combe] ; edited, and adapted to the present state of physiological and chemical science, by James Coxe.

  • Combe, Andrew, 1797-1847
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: The physiology of digestion, considered with relation to the principles of dietetics / [Andrew Combe] ; edited, and adapted to the present state of physiological and chemical science, by James Coxe. Source: Wellcome Collection.

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    during sleep, as to spread over the neighbouring integuments five or six inches in circumference, fairly exhi- biting the natural ruge and mucous coat lining the gastric cavity. This appearance was almost invariably ex- hibited in the morning before rising from bed. Dr Beaumont found far- ther, that on pushing back the pro- truded part, and placing St Martin op- posite to a strong light, the interior of the stomach became visible to a consi- derable extent. Taking advantage of this fact, Dr Beaumont proceeded to examine, by means of a magnifying-glass, the changes which occurred on the intro- duction into the stomach ofa well-mas- ticated morsel of food, either through the external opening, or through the natural channel of the gullet. The moment the food came into contact with the villous coat, the action of the neighbouring bloodvessels increased, and their branches dilated so as to ad- mit the red blood much more freely than before. The colour of the mem- brane consequently changed from a pale pink to a deep red, the vermicular or wormlike motions of the stomach be- came excited, and innumerable minute lucid points and very fine nervous and vascular papille could be seen arising from its surface. These papille dis- tilled a pure, colourless, and slightly viscid fluid, which first collected in drops on the very points of the pa- pille, and then trickled down the sides of the stomach till it mingled with the food. This afterwards proved to be the gastric juice ; and the mucous fluid se- ereted by the follicles, which is found in the stomach in the absence of food, and which some have mistaken for it, not only is more viscid, but wants al- together the acid character by which | gastric juice is always distinguished. | Gastric juice, in its purest form, | and unmixed with any thing except the small portion of mucus from which it can never be obtained entirely free, | is described by Dr Beaumont to be a clear, transparent fluid, without smell, slightly saltish (probably from the ad- mixture of mucus), and very percep- tibly acid. Its taste, he says, resem- 45 bles that of thin mucilaginous water, slightly acidulated with muriatic acid. Itisreadily diffusible in water, wine, or spirits, and effervesces slightly with al- kalies—a direct proof of its acid nature. The grand distinguishing property of the gastric juice is the remarkable power which it possesses of dissolving or reducing to a soft, thickish, fluid mass, certain aliments submitted to its action. It acts with much greater en- ergy upon animal than upon vegetable substances, and its most characteristic power may therefore be more strictly described as that of converting into a soluble form all albuminous or protein articles of food, whether these be de- rived from the animal or vegetable kingdom. The gastric juice thus acts with peculiar energy in dissolving flesh, eggs, and similar alimentary sub- stances ; while its action on potatoes, starch, and such articles, is compara- tively feeble. The stomach, no doubt, has the power of reducing farinaceous substances, such as rice, and also well- boiled vegetables, to a pulp, and of dissolving and absorbing the albumi- nous principles which they contain; but the principal changes which vegetable aliment undergoes in digestion take place in the duodenum and the small intestines generally. When dextrine and sugar are detected in the stomach, as derived from starch, they probably owe their origin to the action of the saliva, as already explained ; for the gastric juice does not appear to have any peculiar action on farinaceous sub- stances, beyond exciting, after some time, acetous fermentation. The gastric juice has no power over living animal matter. Had the case been otherwise, it would have at once attacked and destroyed the stomach it- self which produces it. It is owing to this want of power over living animal matter, that certain worms are able to exist in the stomach of man and other animals; and, accordingly, if it were possible for an oyster, swallowed di- rectly from the shell, to continue to live, it also would effectually resist every attempt at digestion. But it, in common with most other animals, soon perishes in circumstances so foreign to