Excerpted from De proprietatibus rerum 18.37

The dragon is the largest of all serpents, as Isidore says [Etymologies 12.4]. The Greeks call it “dragon,” since often, when it has been dragged out of its cave, it is borne into the air, and the air is moved because of it; similarly the sea rises at its arrival. It is crested, with a small face, and it draws its breath through narrow tubes, and stretches and sticks out its tongue. It has sharp serrated teeth, but its strength is not in its teeth but rather in its tail, and it does more harm by beating than by stabbing. It does not have as much poison as other serpents, since poisons are not necessary for it to bring death upon anything, since if it binds anything, it kills it. Therefore even an elephant is not safe because of the size of its body, for it hides around the paths where elephants walk, ties and knots its tail around their legs, and destroys and kills them by suffocation.

Original Latin

Non habet autem tantum de veneno quantum et alii serpentes, quia ad mortem alicui inferenda non sunt illi necessaria venena, quia si quem ligaverit, occidit; a quo nec elephas tutus est corporis sui magnitudine. Nam circa semitas delitescens per quas elephantes gradiuntur, crura cauda sua alligat et innodat, et suffocatos perimit atque necat.

Item, capite 13: Inter elephantes et dracones perpetua est dimicatio. Nam draco cauda constringit elephantem, et elephas pede et promuscide prosternit draconem. Draco autem nexu caudae innodat pedes elephantis et cadere eum facit, sed non impune, quia dum interficit elephantem, interficitur casu eius.

Item, capite 13: Elephas vides draconem super arborem, nititur eam frangere ut percutiat draconem, draco autem insilit in elephantem, et captat eum mordere inter nares, et impetit oculos elephantis, et quandoque excaecat eum, quandoque insilit super eum a tergo et mordet eum et sugit sanguinem eius. Tandem post longum conflictum elephas ex subtractione sanguinis debilitatur in tantum, quod cadit super draconem et moriens interficit suum occisorem.

Item, dicit idem quod Aethiopes utuntur sanguine draconis contra fervorem aestus, et vescuntur eius carnibus contra diversos morbos. Sciunt enim separare venenum ab eius carne, nam solum habet venenum in lingua et in felle, et ideo amputant eis linguas et fella, quae receptiva sunt veneni, et sic abstracto veneno utuntur corpore reliquo, tam in medicina quam in cibo. Et hoc videtur tangere David, ubi dicit, “dedisti eum escam populis Aethiopum.”

In mari quandoque habitat, quandoque in fluminibus natat, in speluncis et antris latitat, raro dormit, immo vero semper vigilat, aves et bestias devorat. Acutissimum habet visum, unde in altissimis montibus manens, a remotis videt praedam suam, morsu et ictu pugnat, de oculis et naribus animalis in pugna maxime captat, unde dicit Plinius lib. 8 quod ita laedit in oculis et ore elephantes, quod quandoque caeci inveniuntur, nec possunt comedere et ita moriuntur.