The womb of birds has the lower and tubular portion fleshy and
firm, and the part close to the midriff membranous and exceedingly
thin and fine: so thin and fine that the eggs might seem to be outside
the womb altogether. In the larger birds the membrane is more
distinctly visible, and, if inflated through the tube, lifts and
swells out; in the smaller birds all these parts are more indistinct.