Its ambiguous portrayal of the two protagonists seamlessly blends their animal and human characteristics in a way that allowed the makar to satirise new social classes in the rising burous touns of his day with subtle and philosophical irony.
His expansion creates fully fleshed scenes from each of the elements and heightens the drama in a number of different ways while remaining essentially concise.
Henryson's fabill describes the two mice as sisteris and presents the difference in their lifestyles using human and economic terms that lend them ambiguous overtones.
By contrast, the Burges Mous in town has it easy and lives a privileged life like a gild brother able to move freely all year but custum mair or les (i.e. without paying tax) among the cheis in ark and meill in kist.
When the Burges Mous decides to look for her sister, she sets out barefute, allone, with pykestaf in hir hand/ as pure pylgryme, and the image is of a lost figure in rugged terrain of uncertain vastness.
Their journey back to town even has unlawful overtones (though quite natural for a mouse) as the pair sleep by day and move by night as if in violation of a curfew.
After the spencer passes, the Burges persuades her reluctant sister to return to the burde, but (lines 325-6) This time the Uponlandis Mous is lucky to escape with her life.
The simple (generally unprocessed) foods associated with the rural existence are: This list ends with candill insteid of spyce (perhaps also involving a pun with Scots cannel).
The foods associated with the urban setting, on the other hand, are effectively household produce: Once again, the list is completed with quhyte candill to gust thair mouth withall.
When the Burges Mous ventures forth to seek her rural cousin beyond the confines of city, the picture of her as a figure in a landscape (created in a very few words) produces a highly ambiguous sense of scale: