In von Helmholtz's "Treatise on Physiological Optics,"1 Gullstrand, prefacing the description of his investigations of the actual imagery of the eye, made the following statement:
. . . The theory of collinear imagery applied to objects of finite extent and stops with finite apertures, which is the basis of the expositions still to be found in modern text-books, constitutes . . . an essentially arbitrary extension of the region of validity of these laws, inasmuch as a system of fictions had to be introduced in place of the ideal undiscovered law.
A misunderstanding of what Gullstrand meant seems to have caused considerable concern among some ophthalmologists. For instance, Lancaster,2 concerning Gullstrand's statement, said :
. . . Then a prophet appeared and proclaimed the errors that permeated the current belief and practice. . . . I believe the time is ripe for teaching ophthalmologists the truth about the formation of images . . . the present methods of teaching that subject have been a