Evil as something physically present in our world is one of the main themes of the poem. The girl has always had fears and suspected that they would be manifested in some kind of being. The bull, which represents the devil to her – the physical incarnation of all the ills of the world – merely confirms what she knew all along – that evil lives amongst us.
The encounter with the bull causes the girl to look at the world in a different way. She starts to see chaos and destruction all around her. As she runs in terror from the bull she passes
the big boys. It is unclear whether she sees them committing the sadistic acts she ascribes to them or whether, having encountered physical evil, she feels that they must have done or will do these terrible things. Either way, for the girl, the world is now a scary place full of people, specifically males, who mean harm to her and others.
The symbols of life, growth, innocence in the poem are all female:
These are contrasted with the evil of the world which Lochhead characterises as male. The bull, straining at his tether to inflict anarchy on the world, is male, as are the boys in the lane who the girl imagines are torturing animals. Lochhead is suggesting that masculinity is a destructive force whereas femininity is a nurturing one.