Fig. 7 Inhibitory character within angled oval of an expanding fortification spectrum. Outside the limiting line, vision is preserved; within it, vision is lost. This occurs at first over the whole area; afterwards, when the sphere is broken and has become oval, loss is most intense close to the limiting line and becomes less toward the middle. (Gowers WR: Visual sensations in migraine. In: Subjective Sensations of Sight and Sound: Abiotrophy and Other Lectures. London: Churchill, 1907)