Then comes eating and drinking which are ingestion, an operation which begins as soon as the food is in the mouth, and enters the oesophagus.

During its passage, through a space of a few inches much takes place.

The teeth divide solid food, the glands which line the inside of the mouth moisten it, the tongue mingles the food, presses it against the palate so as to force out the juice, and then collects the elements in the centre of the mouth, after which, resting on the lower jaw, it lifts up the central portion forming a kind of inclined plane to the lower portion of the mouth where they are received by the pharynx, which itself contracting, forces them into the oesophagus.

One mouthful having thus been treated, a second is managed in the same way, and deglutition continues until appetite informs us that it is time to stop.  It is rarely, though, that it stops here, for as it is one of the attributes of man to drink without thirst, cooks have taught him to eat without hunger.

To ensure every particle of food reaching the stomach, two dangers must be avoided.

It must not pass into the passage behind the nose, which luckily is covered by a veil.

The second is that it must not enter the trachea.  This is a serious danger, for any particle passing into the trachea, would cause a convulsive cough, which would last until it was expelled.

An admirable mechanism, however, closes the glottis while we swallow, and we have a certain instinct which teaches us not to breathe during deglutition.  In general, therefore, we may say, that in spite of this strange conformation, food passes easily into the stomach, where the exercise of the will ceases, and digestion begins.

Duty of the stomach.

Digestion is a purely mechanical operation and the digestive apparatus, may be considered as a winnowing mill, the effect of which is, to extract all that is nutritious and to get rid of the chaff.

The manner in which digestion is effcted has been so long a question for argument, and persons have sought to ascertain if it were effected by coction, fermentation, solution, chemical, or vital action.

All of these modes have their influence, and the only error was that many causes were sought to be attributed to one.

In fact food impregnated by all fluids which fill the mouth and oesophagus, reaches the stomach where it is impregnated by the gastric juices, which always fill it.  It is then subjected for several hours to a heat of 30 [degrees] Reaumer; it is mingled by the organic motion of the stomach, which their presence excites.  They act on each other by the effect of this juxtaposition and fermentation must take place.  All that is nourishing ferments.

In consequence of all of these operations, chyle is elaborated and spread over the food, which then passes the pylorus and enters the intestines.  Portion after portion succeeds until the stomach is empty, thus evacuating itself as it was filled.