When the fluid has passed the two arcs, the arcus palatoglossus and the arcus palatopharyngeus, the latter contract and close the way back to the front, while the soft palate or uvula closes up the cavity of the nose by the action of the M. levator veli palatini (facialis) and the M. tensor veli palatini (trigeminus).
The fluid or the morsel is thus confined in the head of the pharynx. The larynx is now drawn upward and forward by the Mm. geniohyoideus, digastricus and mylohyoideus. In this way the root of the tongue presses the epiglottis down upon the orifice of the larynx, and prevents the food from entering into the lungs.
The food enters now the oesophagus which by a peristaltic movement presses the same down into the stomach.
Arrived in the stomach, the epithelia of the latter begin to secrete hydrochloric acid and pepsin by which the albumen of the food is changed successively into syntonin, propeton, and pepton. By a peristaltic movement of the stomach, the solution is then forwarded into the duodenum.
At the arrival there the pancreas sends its ferments, trypsin, to dissolve the still unchanged albuminates, and the fat-ferment to break up the fatty substances (the diastatic ferment for changing the carbohydrates into sugar is not found yet in the infant). At the same time the liver sends in its secretion, the bile, which serves to effect an emulsion of the fatty substances. The other intestinal glands also contribute their secretions to effect all these necessary changes, so that the chyle can now be imbibed by the intestinal villi, by a kind of osmosis, and forwarded into the lymphatic current to serve as nourishment for the new-born individual.
Now, all these organs, the nerves, muscles, and glands, must work in coördination and perfect harmony to accomplish the task of the preparation of the young animal’s food. It would take a physicist and chemist years of hard study to be able to accomplish all the different tasks, just described, which the new-born baby is able to effect, without any effort, in the first hours of its new existence.
This wonderful instinct of hunger for food and its satisfaction is really awe-inspiring. It is an inexplicable mystery as life itself. In fact, it is, as Bergson truly says, the prolongation of the life-principle. The author is unable to agree with the last named philosopher, who claims that intellect is the highest in men and instinct in the hymenoptera. It seems to the author that the instinct of taking in food and its preparation into chyle by man is no less wonderful than the knowledge of the digger-wasp to sting the caterpillar just in the right place to ensure paralysis without death.
The objection that all these actions are merely reflex-actions does not detract an iota from the marvel. Then the coördination of all these reflexes is miraculous. It only changes the name of instinct into reflex, just as the change of the name of the creative power from the old name of God into that of the atheist’s “Nature,” or of Plato’s “idea,” or Nietzsche’s “Wille zur Macht,” or Bergson’s “Élan vital,” or Shaw’s “Life force,” etc., does not in the least change the nature of the creative power.
[U] Hegar says that in civilized men we can not speak at all of an instinct of propagation. For with them so many reflexions and considerations enter into play that to speak of anything impulsive is to ignore the state of mind of the society of our days.
[V] The old German law punished adultery or granted a divorce only when intermissio penis in vaginam has been witnessed.