This section is from the book "Health", by W. H. Coefield.
So we see that the presence of the food in the mouth, and the exercise of the tongue and cheeks, cause the salivary fluid to flow from the glands into the mouth; that fluid is mixed up with the food that has been minutely subdivided by the teeth, the whole thing together forming a ball The fluid, in the first place, moistens, and, in the second place, it aerates it, as of course there are bubbles of air in the saliva. This soft ball of food is gradually passed backwards to the hinder part of the mouth between the tongue and palate, and so it comes to the soft palate, and there the soft palate ordinarily hangs downwards; and as soon as the ball of food touches it, the muscles of which the soft palate is composed and the adjacent muscles tilt it upwards across the cavity behind the mouth, which is called the pharynx. You will see the importance of this; the soft palate, by being tilted upwards, and forming a roof to the pharynx, prevents the food from going upwards and backwards into the nose, and it prevents the fluid also from going into some other tubes, which I shall mention presently. The food then is, as you see, just at the entrance of the pharynx, the soft palate being over it, and the root of the tongue being below it When it gets to this place, the ball of food is seized by some muscular bands, which pass down from the soft palate towards the roof of. the tongue on each side.
It is seized by these bands; there are two pairs of them, one on each side of each tonsil Tou all know where the tonsils are, at the back of the mouth; at any rate, all who have suffered from quinsy know whereabouts the tonsils are. These muscular bands which run down on each side of the tonsils seize hold of the ball of food; at the same time the tongue rises a little upwards and backwards, and the root of the tongue presses down the epiglottis or lid of the larynx. Now you remember that over the larynx, or box in which the voice is formed, there is this cartilaginous lid called the epiglottis, because it is over the glottis, the glottis being the aperture leading into the larynx, and so into the windpipe. So we see that when the tongue rises backwards with the ball of food on it, it pushes down the epiglottis, and then the muscular columns contract upon the ball of food and push it over the lid of the larynx into the pharynx or cavity behind the mouth, and so into the continuation from the pharynx, which is called the gullet or swallow, and that is how the food is prevented from going the wrong way; however, food and liquids do sometimes go the wrong way when we are talking while we are swallowing. You can see exactly how it happens: when we are talking the air is coming out and that lid cannot be shut properly, and so some of the food gets into the larynx.
I want to make you understand what the pharynx is, by mentioning to you the different tubes which open into its cavity; no less than seven tubes lead into or out of it. I have mentioned all. but two.
In the first place, the mouth leads into it; in the second place, the two cavities of the nose lead into it; and in the third place, two tubes, not mentioned before, forming part of the apparatus of hearing, called, from the name of their discoverer, the Eustachian tubes, lead into it. Then the windpipe is connected with it, and so is the gullet or swallow, and that makes the seven.
When the soft palate is raised up so as to prevent the food or drink from getting into the nose-and in all people who have cleft palates, until a particular operation is performed, some of the fodd goes back into the nose, and the same thing happens with people who have had their palates destroyed by disease-it also prevents the food from getting into the two Eustachian tubes, so the food gets into the gullet or swallow, called, in anatomical language, the oesophagus. This tube h&s soft, compressible walls; it is strong and fibrous, and has on its outside two muscular coats, and so it is capable of contracting. It has also a coat which carries bloodvessels to supply it with blood, and it has lastly, of course, a mucous membrane. It passes down through the neck, close in front of the bodies of the vertebrae, and close behind the windpipe, and you will remember I told you that the incomplete cartilaginous rings of the windpipe, which nearly surround it and keep it wide open, have their ends joined together at the back by a fibrous membrane, and this membrane is closely attached to the fibrous coat of the oesophagus or gullet, and it is because that membrane is there that the windpipe does not offer any resistance to the food which is being swallowed.
The oesophagus then passes downwards through the neck and chest, and through a hole in the diaphragm into a bag that we call the stomach. As soon as the food gets from the pharynx and over the lid of the larynx into the oesophagus, the fibres of the oesophagus, which are round it and which are called circular fibres, contract upon the ball of food and hold it, and then the fibres running lengthwise down that part of the gullet contract and pull up the next bit of the gullet, the circular fibres of which at once contract upon the ball of food, so that the latter is continually caught hold of by each piece of gullet, and then by the next piece, and squeezed farther down. That action is peculiar to the whole of the intestinal canal, including the gullet, and goes by the name of the peristaltic action.
The food does not fall down this tube into the stomach, for the simple reason that the gullet id not wide open like the windpipe; each part is only open when the food is going down, and it is opened by the food, for as soon as it gets to one part, that part contracts upon it, and, as it were, squeezes it to the next, and so on; and this peristaltic action does not merely happen with food, but with drink also. When you take drink into your mouth and swallow it, it does not fall down the gullet; it is swallowed in precisely the same manner as the solid food, and that is illustrated by the fact that when a horse drinks the drink cannot fall up his neck into his stomach, he'swallows it up his neck. We need not go to horses; there are some persons who can stand on their heads, and drink while standing on their heads; it is a common feat of jugglers.