Quote 4
They were all shouting: "At Filippo Argenti!"
At this, the Florentine, gone wild with spleen,
began to turn his teeth against himself. (Inf. VIII, 61-63)
After being violently rejected by Dante and called a "dog" by Virgil, Filippo Argenti goes mad and, unable to contain his rage, turns his wrath upon himself. His behavior seems distinctly bestial because only animals turn to as visceral a punishment as biting when enraged; for the most part, humans do not.
Quote 5
And at the edge above the cracked abyss,
there lay outstretched the infamy of Crete,
conceived within the counterfeited cow;
and, catching sight of us, he bit himself
like one whom fury devastates within.
Turning to him, my sage cried out:…
"Be off, you beast; this man who comes has not
been tutored by your sister; all he wants
in coming here is to observe your torments."
Just as the bull that breaks loose from its halter
the moment it receives the fatal stroke,
and cannot run but plunges back and forth,
so did I see the Minotaur respond; (Inf. XII, 11-25)
Not only is the Minotaur the unnatural spawn of man and animal, a "counterfeited cow," but it acts on animal impulses, biting itself, rearing in rage, and charging its offenders. It is no coincidence that Dante describes its movements as those of a haltered bull.
Quote 6
Then Chrion wheeled about and right and said
to Nessus: "Then return and be their guide;
If other troops disturb you, fend them off."
Now with our faithful escort, we advanced
along the bloodred, boiling ditch’s banks,
beside the piercing cries of those who boiled.
I saw some who were sunk up to their brows,
and that huge Centaur said: "These are the tyrants
who plunged their hands in blood and plundering.
Here they lament their ruthless crimes; here are
both Alexander and the fierce Dionysius,
who brought such years of grief to Sicily." (Inf. XII, 97-108)
Here in the circle of the violent, the beastly figures (Centaurs – half man, half horse) prove to be more human than the human sinners. While the Centaurs speak coherently, the sinners only give out "piercing cries." Surprisingly, the Centaurs – despite their reputation of senseless violence – show mercy to Dante and Virgil, even providing them with a guide to protect them.