Physiologus: On the Natures of Twelve Animals

...draws them to do the same. ¶ Also, the eagle is said to be named from aquilos in Greek original: "aquilos", which is acucies meaning "sharpness" or "keenness"; original: "acucies" in Latin, because it sharpens its beak by removing its curvature. Whence it is said: No bird is there that flies higher than the eagle.

¶ Concerning the serpent

Large red rubricated initial I I now, the old serpent, rejoices to be made new,
And by fasting, it shudders at its lean body;
The worn-out skin trembles, emptied out,
Only bones and sinews remain.
It seeks a narrow hole in the stone,
Hardly moving itself, it comes there at last.
It passes through and sheds its old flesh,
Seeking out living waters anywhere.
To drive away thirst, it first vomits out its poison;
Therefore in the waters you will fear it less, being without its venom.
If it sees any man without clothing,
The serpent retreats far away as if from fire;
But seeing one who wears a garment, it rises up against him.
Whom the man pursues much to overcome it,
Gathering its body, it makes of it a shield;
It truly takes care of its head, lest it die.

¶ In this third distinction distinction: a formal division or chapter in a medieval academic text, he shows the natures of the serpent. And it is divided into two: for first he sets down the historical sense historical sense: the literal or natural-history level of the text, and second he sets down the allegorical sense or allegory allegory: the deeper spiritual or symbolic meaning. The second part begins at: in the sacred fountain. He says here first, therefore, that the serpent has four natures.

The first nature is that when the serpent grows old through excessive age, its eyes grow dim. And when it wishes to become young, it fasts for forty days and thus becomes so lean that its skin becomes wrinkled and is loosened by the wasting away. After this, it seeks a narrow hole and passes through it, and thus allows the skin to remain in the hole so that it becomes young again.

The second nature of the serpent is that when it suffers great thirst, to drive it away it goes to the water; before it enters the water, however, it vomits out all the venom it has in its body.

The third nature of the serpent is that while it sees a man...