Neither Greek literature, nor Greek art, however, really seems to fix
either the shape or nature of Kerberos; it was left to the Roman poets
to say the last word about him. They finally settle the number of his
heads, or the number of his bodies fused in one. He is _triceps_
"three-headed," _triplex_ or _tergeminus_ "threefold," _triformis_ "of
three bodies," or simply Tricerberus. Tibullus says explicitly that he
has both three heads and three tongues: _cui tres sint linguæ
tergeminumque caput_. Virgil, in the _Æneid_, vi. 417, has huge Cerberus
barking with triple jaws; his neck bristles with serpents. Ovid in his
_Metamorphoses_, x. 21, makes Orpheus, looking for dear Eurydice in
Tartarus, declare that he did not go down in order that he might chain
the three necks, shaggy with serpents, of the monster begotten of
Medusa. His business also is settled for all time; he is the terrible,
fearless, and watchful janitor, or guardian (_janitor_ or _custos_) of
Orcus, the Styx, Lethe, or the black Kingdom.[9] And so he remains for
modern poets, as when Dante, reproducing Virgil, describes him:[10]
"When Cerberus, that great worm, had seen us
His mouth he opened and his fangs were shown,
And then my leader with his folded palms
Took of the earth, and filling full his hand,
Into those hungry gullets flung it down."
Or Shakespeare, _Love's Labor Lost_, v. ii: "Great Hercules is presented
by this imp whose club killed Cerberus, the three-headed _canis_."