Formation of an Image on the Eyeball
In passing through the crystalline, the rays cross each other, so that those rays which pass from the lower part of an object are presented uppermost in the bottom of the eye and the reverse, so that the images of object are always inverted, or bottom side upwards. Labels: a, the aqueous; c, the crystalline; v, the vitreous humor.
Lee, Charles A. Human Physiology for the Use of Elementary Schools, 11th ed. (Buffalo: J. C. Derby & Co., 1847) 207