The physiology of digestion, considered with relation to the principles of dietetics / by Andrew Combe.
- Andrew Combe
- Date:
- 1860
Licence: Public Domain Mark
Credit: The physiology of digestion, considered with relation to the principles of dietetics / by Andrew Combe. Source: Wellcome Collection.
51/224 (page 27)
![smooth, glistening, whitish membrane, which is familiar to all who have ever seen an animal opened. It is a fold of the tough shining membrane called the peritoneum (from ■;rs^iTuiia),pcriteino, i I extend round], which lines the abdo- men, and constitutes the outer covering of all the abdominal organs. Its use is obviously to strengthen the substance of the stomach, to assist in binding ' down it and the other organs in their re- ', spective situations, and, by the smooth- ness and constant moisture of their 1 surfaces, to enable them to move upon each other, and adapt themselves freely to their different states of emptiness and distention. The second, middle, or muscidar coat consists of fleshy fibres, one layer of which, running longitudinally from one end of the stomach to the other, seems to be a continuation of the longitudi- nal muscular fibres of the gullet; while another runs in a circular direction, embracing the stomach from one curva- ture to the other, and constituting what are called the transverse fibres. The uses of the muscidar coat have, as we shall afterwards see, a direct refer- ence to the special function of diges- I tion. By the joint action of its longi- li tudinal and circular fibres, the stomach ! is enabled to contract, and shorten its diameter in every direction, so as to adapt its capacity to the volume of its contents; while, by their successive action, or alternate contraction and re- laxation, a kind of churning motion is produced, which contributes greatly to digestion by the motion which it im- parts to the food, and the consequent exposure which it effects of every por- tion of it in its turn to the contact of the gastric juice. The force and rapidity of these mus- cular contractions are modified by the I more or less stimulant nature of the I food, the state of health, exercise, and other circumstances; but, according to ' Dr Beaumont, the ordinary direction ; in which they take place, and the course which they impart to the food, are as follows. The alimentary holus or morsel, on entering the cardiac orifice, turns to the left, follows the line of the great curvature of the stomach towards the pylorus, returns in the line of the smaller curvature, makes its appear- ance again at the cardia, and then de- scends as before to the great curvature, to undergo similar revolutions till di- gestion be completed. Each revolu- tion occupies about from one to three minutes, and its rapidity increases as chymification advances. In treating of muscular action in my Principles of Physiology, I pointed out (Chap. VI.) the necessity of the co-ope- ration of a nervous stimulus to produce the result; and remarked that there are two kinds of muscles, one called the voluntary, which contract at the command of the ivill, and the other the involuntary, over which the will has no control, and which act only in obe- dience to their own peculiar stimuli. Of the latter description are the mus- cular fibres of the stomach. They con- tract when the stimulus of food is ap- plied to them, but we can neither con- tract nor relax them by aii effort ol the wiU, nor are we even conscious of their existence. It is, indeed, fortunate for us that the necessary motions of the stomach are not entrusted to oar guidance, like those of the hand or foot. Supposing that we were to eat three meals a-day, the digestion of each requiring three or four hours,—and that its manage- ment depended entirely upon our su- perintendence,—our whole attention would be required to the process, to the exclusion of every other duty, for ten or twelve hours a-day; and every time that our thoughts wandered for a few minutes, digestion would stand stili, and the stomach be disordered by the chemical decomposition of the food which would ensue, so that it would be impossible for us to dedicate any time either to business or to social en- joyment. . But from all these inconve- niences we are entirely freed by the stomach being placed under the domi- nion of the involuntary nerves, and so constituted as to perform its functions without any aid from our will. The third and innermost coat, called the mucous or villous, is that smooth, unequal, velvety membrane, of a red-](https://iiif.wellcomecollection.org/image/b20404542_0051.jp2/full/800%2C/0/default.jpg)
