e distortion of the surrounding parts:

"The wonderful duck-like mandibles into which the head is prolonged
are sadly misrepresented in the stuffed specimens which we generally
see, and are black, flat, stiff, and shrivelled, as if cut from shoe
leather. The dark colour is unavoidable, at all events in the present
state of taxidermy. Bare skin invariably becomes blackish-brown by
lapse of time, no matter what the previous colour may have been, so
that the delicate tints of an English maiden's cheek and the sable hue
of the blackest negro would in a few years assume the same dingy
colour, and become quite undistinguishable from each other.

But there is no excuse now-a-days for allowing the bare skin to become
shrivelled. The colours we cannot preserve, the form we can and ought
to reproduce. No one would conceive, after inspecting a dried
specimen, how round, full, and pouting were once those black and
wrinkled mandibles, and how delicately they had been coloured while
the animal retained life. Their natural hue is rather curious, the
outer surface of the upper mandible being very dark grey, spotted
profusely with black, and its lower surface pale flesh-colour. In the
lower mandible the inner surface is flesh-coloured, and the outer
surface pinky white, sometimes nearly pure white."

All this could easily be avoided by the taxidermist first skinning the
beak and lips to their farthest extent, and then filling them with
clay or composition, and afterwards waxing and colouring the parts in
question.

Small birds having black feet or bills, which permanently retain their
colour, need only to have them slightly brushed with oil, before
casing up, to give them proper freshness.

HOLLOW EYES.--I have for a great number of years discarded the
conventional glass eyes--glass buttons I have heard them irreverently
termed!--for all fishes, reptiles, birds, and mammals, excepting the
smallest, using, in their stead, hollow half-globes rather more oval
than round; these are hand-painted on the inside with either water or
oil-colours, and when dry are varnished, filled in with wadding and
putty, or modelling-wax, not clay, and fixed in the orbits with wax,
see ante. These, properly coloured, and, in the instance of fishes,
gilded inside, are wonderful representations of the natural eye, and
when properly inserted, the cornea in mammals reproduced by wax, and
the eyelids properly managed, give a most life-like and natural
appear