The Mouth and the Stomach

Erasistratus neglected everything else except for digestion.

He at least tried to prove that digestion in animals differs from boiling carried on outside.

In regard to the question of deglutition, however, he did not go even so far as this.

The stomach has 2 coats which extend as far as the mouth.

1. The internal one stays similar to what it is in the stomach.
2. The other one has a more fleshy nature in the gullet.

These coats have their fibres inserted in contrary directions.

Erasistratus did not explain why they are like this.

The inner coat has its fibres straight, since it exists for traction.

The outer coat has its fibres transverse, for peristalsis.

In fact, the movements of each of the mobile organs of the body depend on the setting of the fibres.

Test this first in the muscles themselves.

In these, the fibres are most distinct, and their movements visible due to their vigour.

After the muscles, pass to the physical organs, and you will see that they all move in correspondence with their fibres.

This is why the fibres throughout the intestines are circular in both coats—they only contract peristaltically, they do not exercise traction.

The stomach has some of its fibres:

• longitudinal for the purpose of traction
• transverse for the purpose of peristalsis

The movements in the muscles happen when each of the fibres becomes tightened and drawn towards its origin.

The same also happens in the stomach.

When the transverse fibres tighten, the width of the cavity contained by them becomes less.

When the longitudinal fibres contract and draw in on themselves, the length is curtailed.

This curtailment of length is seen in the act of swallowing.

The larynx rises upwards to exactly the same degree that the gullet is drawn downwards.

After swallowing:

• the gullet is released from tension
• the larynx can be clearly seen to sink down again.

This is because the inner coat of the stomach has the longitudinal fibres which also lines the gullet and the mouth.

• These fibres extend to the interior of the larynx.

This makes it impossible for it to be drawn down by the stomach without the larynx being involved in the traction.

Erasistratus’s writes that the circular fibres (by which the stomach as well as other parts performs its contractions) do not curtail its length, but contract and lessen its breadth.

He says that:

• the stomach contracts peristaltically around the food during the whole period of digestion.
• But if it contracts, without in any way being diminished in length, this is because downward traction of the gullet is not a property of the movement of circular peristalsis
• when the upper parts contract, the lower ones dilate.

This is seen happening even in a dead man, if water be poured down his throat.

This symptom results from the passage of matter through a narrow channel.

It would be extraordinary it the channel did not dilate when a mass was passing through it.

Then the dilatation of the lower parts along with the contraction of the upper is common both to dead bodies, when anything whatsoever is passing through them, and to living ones, whether they contract peristaltically round their contents or attract them.

Curtailment of length, on the other hand, is peculiar to organs which possess longitudinal fibres for the purpose of attraction.

But the gullet was shown to be pulled down; for otherwise it would not have drawn upon the larynx.

Thus, the stomach attracts food by the gullet.

In vomiting, the mere passive conveyance of rejected matter up to the mouth will suffice to keep open those parts of the oesophagus which are distended by the returned food; as it occupies each part in front [above], it first dilates this, and of course leaves the part behind [below] contracted.

Thus, the condition of the gullet is precisely similar to what it is in the act of swallowing.

But there being no traction, the whole length remains equal in such cases.

This is why it is easier to swallow than to vomit.

• Deglutition results from both coats of the stomach being brought into action, the inner one exerting a pull and the outer one helping by peristalsis and propulsion, whereas emesis occurs from the outer coat alone functioning, without there being any kind of pull towards the mouth.

The swallowing of food is preceded by a feeling of desire on the part of the stomach.

There is in the case of vomiting no corresponding desire from the mouth-parts for the experience; the two are opposite dispositions of the stomach itself; it yearns after and tends towards what is advantageous and proper to it, it loathes and rids itself of what is foreign.

Thus, the actual process of swallowing occurs very quickly in those who have a good appetite for such foods as are proper to the stomach.

This organ obviously draws them in and down before they are masticated.

Whereas in the case of those who are forced to take a medicinal draught or who take food as medicine, the swallowing of these articles is accomplished with distress and difficulty.

The inner coat of the stomach (that containing longitudinal fibres) exists for the purpose of exerting a pull from mouth to stomach, and that it is only in deglutition that it is active, whereas the external coat, which contains transverse fibres, has been so constituted in order that it may contract upon its contents and propel them forward.

This coat functions in vomiting no less than in swallowing.

This is seen in the channae and synodonts.

The stomachs of these animals are sometimes found in their mouths, as also Aristotle writes in his History of Animals.

He says that this is due to their voracity.

In all animals, when the appetite is very intense, the stomach rises up.

People say that their stomach “creeps out” of them.

In others, who are still masticating their food and have not yet worked it up properly in the mouth, the stomach obviously snatches away the food from them against their will.

Some animals are naturally voracious. They have a large mouth cavity which is close to their stomach, as in the case of the synodont and channa.

When they are hungry and are about to catch smaller animals, the stomach should, under the impulse of desire, spring into the mouth.

This cannot possibly take place in any other way than by the stomach drawing the food to itself by means of the gullet, as though by a hand.

When we want to grasp more quickly something lying before us, sometimes we stretch out our whole bodies along with our hands.

Likewise, the stomach stretches itself forward along with the gullet, which is its hand.

Thus, these 3 factors exist in these animals:

1. An excessive propensity for food
2. A small gullet
3. Ample mouth proportions

This allows any slight tendency to move forward to bring the whole stomach into the mouth.

Now the constitution of the organs might itself suffice to give a naturalist an indication of their functions.

For Nature would never have purposelessly constructed the oesophagus of two coats with contrary dispositions; they must also have each been meant to have a different action.

The Erasistratean school, however, are capable of anything rather than of recognizing the effects of Nature.

Take an animal.

Lay bare the structures surrounding the gullet, without severing any of the nerves, arteries, or veins which are there situated.

Next divide with vertical incisions, from the lower jaw to the thorax, the outer coat of the oesophagus (that containing transverse fibres).

Then give the animal food and you will see that it still swallows although the peristaltic function has been abolished.

If, again, in another animal, you cut through both coats with transverse incisions, you will observe that this animal also swallows although the inner coat is no longer functioning.

The animal can also swallow by either of the 2 coats, although not so well as by both.

During deglutition, the gullet becomes slightly filled with air which is swallowed along with the food, and that, when the outer coat is contracting, this air is easily forced with the food into the stomach, but that, when there only exists an inner coat, the air impedes the conveyance of food, by distending this coat and hindering its action.

But Erasistratus said nothing about this.

Nor did he point out that the oblique situation of the gullet clearly confutes the teaching of those who hold that it is simply by virtue of the impulse from above that food which is swallowed reaches the stomach.

The only correct thing he said was that many of the long-necked animals bend down to swallow.

Hence, the observed fact does not show how we swallow but how we do not swallow.

For from this observation it is clear that swallowing is not due merely to the impulse from above; it is yet, however, not clear whether it results from the food being attracted by the stomach, or conducted by the gullet.

I have proved that:

• the inner coat exists for attraction
• the outer for the purpose of propulsion.

This book is tasked to demonstrate that the retentive faculty exists in every one of the organs, just as in the previous book we proved the existence of the attractive, and, over and above this, the alterative faculty.

Thus, in the natural course of our argument, we

I have thus demonstrated these 4 faculties in the stomach:

1. The attractive in swallowing
2. The retentive with digestion
3. The expulsive with:

• vomiting
• the descent of digested food into the small intestine

4. Digestion as a process of alteration.