The poem re-enchants the bull by setting imaginary walls and thresholds around it.

[…] like a sexton delving into a grave, possibly in quest of a jewel that had been buried on the dead man’s bosom, but likely to find nothing save mortality and corruption.

He laughed again, plummily. Sounds as though he'd committed the murder himself.

One person says that there is more to it: The guyascutus Ieadeth the wangdoodle wheresoever he willeth.