By 1840, the collapsed sleeve was…

.. much narrower, but still had the dropped shoulder.  The bodice of a gown in the Early Victorian era was tight fitting and pointed in front; much longer and with a small, tight fitting waist.

It was accomplished through restrictive corsets and extensive boning in the bodice itself.  They also directed all decoration and boning vertically to look slim and smooth, and to keep bodices from bending over or folding.

The whole focus of fashion in 1840 was a teeny tiny waist.

(Photos of real garments: note the sleeves getting smaller and the waist getting longer and sharply pointed as the late 1830’s turn into the 1840’s of Victoria’s early reign)