A manual of health science ... / by Andrew Wilson.

  • Wilson, Andrew, 1852-1912.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: A manual of health science ... / by Andrew Wilson. Source: Wellcome Collection.

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    free hydrochloric acid, and pepsin. Its specific gravity is about 1002*5. The solids amount to over 990 parts per 1000, the remainder being water. The pepsin is seen to be the special constituent of this fluid, as was ptyalin of saliva. Before food enters the stomach, the lining or mucous mem- brane of the organ is pale-coloured. After the entrance of food, the mucous membrane becomes reddened, from the increased flow of blood which takes place to the walls of the stomach, to afford material for the secretion of the gastric juice, which is secreted in quantity varying from ten to twenty pints in twenty-four hours, and is poured out in drops on the food. The stomach, contrary to popular opinion, does not exercise digestive power equally in all kinds of food- substances. Thus gastric juice is powerless to digest oils and fats^ while starch is also unaffected in the stomach. On which foods, then, does the stomach specially act ? is a question answered by the statement that the albuminous or nitrogenous compounds of the food are affected and digested in this organ. Such substances as the albu?nen of meat juice, white of egg, &c., casein of milk, gluten of flour, gelatin of bones and horns, are digested by the stomach. These sub- stances, through the action of the gastric juice, and specially by the pepsin and acid, are chemically changed into matters called peptones. The result of this change is to cause these highly important food-stuffs to become soluble, and thus to enable them to be readily absorbed into the blood, of which they are destined to form an important part. In the stomach, the fibres of meat, softened by cooking, are broken up and dissolved, and their nutritive matters extracted. Milk is first curdled in the stomach, and is then dissolved. The nitrogenous food-elements thus seized upon and modified by the stomach, pass through its walls, are probably con- veyed to the liver, therein modified, and thence sent onward with the blood-circulation, to assist in the renewal and repair of the tissues at an early period of digestion.