TORSION has been described by Donders1 in 1847, by Listing2 in 1854 and by Duke-Elder3 and many others; yet the subject of torsion remains unclear.
Of the two types, false and real, false torsion has become a controversial subject. In its demonstration, the projection obliquely of after-images on a flat wall caused distortion, a phenomenon which was finally explained by Le Conte4 in 1881. Donders' and Listing's laws do not permit actual turning about the anteroposterior axis of the eye in moving from a primary position obliquely to a tertiary position, but Márques5 quotes Helmholtz as believing that such turning does occur. Davson6 feels the terms rolling, or real, torsion and false torsion can be used indifferently. Duke-Elder3 draws a clear distinction between them.
The present paper is an attempt to clarify the picture. It consists, first, of a description of false torsion,