
In the Middle Ages, the understanding of the natural world was not based on scientific observation but on utility and moral applicability. This was particularly so for plants and animals: if they could be eaten (or could produce eggs, milk etc for human consumption) then they fitted into the scheme of things and were farmed or domesticated accordingly. However, many plants and animals defied ready explanation and represented, instead, a source of such wonder and (often) fear that their very existence could only be accommodated if they were regarded as serving a moral purpose. Enter the bestiary, a book that was a sort of compendium of beasts and animals, real and mythical, accompanied by a symbolic interpretation and a moral lesson, particular to each beast.
Although the bestiary had originated in the ancient world (with the volume known as Physiologus bringing together insights about animals from such authors as Aristotle and Herodotus), it was later Christian writers like Isidore of Seville and St Ambrose who gave the stories a moral and religious focus. Because the majority of the medieval populace was illiterate, the imparting of the Christian message in stories and allegories was an essential part of the Church’s teaching method. Nevertheless, the creatures presented in the medieval bestiaries were usually so exotic that their descriptions were often considered to be factual in many respects. Griffins, dragons, and unicorns featured along with lions and elephants.
Even in early times, the lion was considered to be the king of the beasts, and as such, generally is the first beast described in the bestiaries. Two types of lions are described: a timid lion which has a short body and curly hair (think, the Cowardly Lion in L. Frank Baum’s The Wizard of Oz); and a fierce lion with a longer body and straight hair. Both types were understood to have three particular attributes: the practice of erasing their tracks with their tail; always sleeping with eyes open; and giving birth to dead cubs which the mother brings to life on the third day by breathing into them.
The Christian association of Jesus with the lion is relatively straightforward: the lion as King of the Beasts = Jesus Christ the King. (In this aspect, such writers as C.S. Lewis with his character Aslan in The Lion, the Witch and the Wardrobe can be seen to be drawing directly on the medieval parallel). And the three attributes are similarly associated: the lion’s erasing of its tracks was representative of Jesus’s hidden divinity; its sleeping with eyes open represented Jesus’s (and all Christians) physical death to the world but spiritually alive and alert; and the lion cubs being brought to life after three days is, of course, allegorically standing for Jesus’s death and three days in his tomb before his resurrection.
The bestiaries’ lion could be injured by a scorpion but it was only serpents that could kill it. And supreme among the serpents was the dragon, with its strength in its tail and not its teeth. Its thrashing, coiling tail enabled it to kill any animal – even one as large as the elephant – by suffocation. Thus, the dragon stood for the Devil, with his ability to squeeze the (holy) breath of life out of souls, suffocating them with sin. Further, with his fiery breath, the dragon could make the air shine and so he would sometimes appear to be an angel of light, tricking and luring the unsuspecting to their spiritual demise.

The dragons of today’s literature (for children in particular) are generally quite placid, with their mythic quality overtaking their earlier ‘evil’ connotations.
I have a harmless dragon, myself, in my garden.
(Well, I hope he’s harmless!).