They shut me up in Prose — Roebuck

A roebuck is a male roe-deer but called girl in its second year, so Girl and Himself both indicate the roebuck in this poem.

People kept a roebuck in a small room alone for its treason in the pound. The roebuck's mind left its body and escaped like a bird. Dickinson was the girl, and the society the pound.

They shut me up in Prose-1
As when a little Girl
They put me in the Closet-
Because they liked me "still"-

Still! Could themself have peeped-5
And seen my Brain-go round-
They might as wise have lodged a Bird
For Treason-in the Pound-

Himself has but to will 9
And easy as a Star
Abolish his Captivity-
And laugh-No more have I-
(F.445/J.613)
[1] prose:: dull, tedious;
[2] girl:: a roebuck in its second year (OED 3).
[3] Closet:: any small room; the den or lair of a wild beast (OED 5).
[4] still:: calm, motionless;
[5] Still:: nevertheless;
[6] Brain go round:: this roebuck was kept in a small pound for the keeper thought the animal was mad (treason in line eight).
[8] pound:: a shelter for domestic animals. Treason:: the roebuck acted abnormally like mad.
[9] Himself:: the roebuck's mind left its body and became the third party.
[11] Captivity:: a hint on pound, a shelter.
[12] no more have I:: the roebuck's mind left its body.

A kid is the name which the roe bears the first year, the second a girl, the third a pemuse, the fourth a roebuck of the first head, and lastly a fair roebuck. ─ A Treatise on the Laws of Game and Inland Fisheries in Ireland (1827)