All that is known about the clinical features and pathology of accommodation rests on Helmholtz' explanation of the physiologic mechanism, and any abnormality encountered can really be explained by this theory. It is true that one is still unable mechanically or physically to record the function of the ciliary muscle and the change of the curvature of the crystalline lens proper to accommodation, but the physico-optical observations and physiologic conclusions do not permit refutation of the theory that Helmholtz set up so objectively. According to this theory, the increase of the refractive power of the lens, due to the increase in the convexity of the anterior surface of the lens so that the images of near objects may form on the retina during accommodation, is produced by contraction of the ciliary muscle and relaxation of the zonule. This old theory, ingeniously erected and thus far unshaken, gives a