The metamorphosis of the demons into serpents has been censured as grotesque; but it was imperatively necessary to manifest by some unmistakable outward sign that victory did not after all remain with Satan, and the critics may be challenged to find one more appropriate.

The bridge built by Sin and Death is equally essential.

Satan's progeny must not be dismissed without some exploit worthy of their parentage.

The one passage where Milton's taste seems to us entirely at fault is the description of the Paradise of Fools (iii., 481-497), where his scorn of-- "Reliques, beads, Indulgences, dispenses, pardons, bulls," has tempted him to chequer the sublime with the ludicrous.
No subject but a Biblical one would have insured Milton universal popularity among his countrymen, for his style is that of an ancient classic transplanted, like Aladdin's palace set down with all its magnificence in the heart of Africa; and his diction, the delight of the educated, is the despair of the ignorant man.

Not that this diction is in any respect affected or pedantic.